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ISSN 1454-8518

ANNALSOF THE UNIVERSITY OF

PETROŞANIELECTRICAL ENGINEERING

VOL. 9 (XXXVI)

UNIVERSITAS PUBLISHING HOUSEPETROŞANI - ROMANIA 2007

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ISSN 1454-8518

EDITOR OF PUBLICATIONProf.dr.eng. Ioan-Lucian BOLUNDUŢ: Email: [emailprotected]

ADVISORY BOARD

Prof. Dr. Eng. Pop Emil - University of Petroşani, Romania; Acad. Prof. Dr.Pivnyak Ghenadi – National Mining Uninersity of Ukraine; Prof. Dr. Eng.Munteanu Radu - Tehnichal University of Cluj-Napoca, Romania; Acad. Prof. DrEng. Dašić Predrag - High Technological Technical School, Krusevac, Serbia andMontenegro, Prof. Dr. Eng. Cierpisz Stanislaw – Silesian University ofTechnology, Poland; Prof. Dr. Eng. Bitoleanu Alexandru - University of Craiova,Romania; Prof. Dr. Eng. Păsculescu Mihai - University of Petroşani, Romania;Acad. Prof. Dr. Eng. Coloşi Tiberiu - Tehnichal University of Cluj-Napoca,Romania; Prof. Dr.Eng. Szabo Willibald – “Transilvania” University of Braşov,Romania; Prof. Dr. Eng. Poantă Aron - University of Petroşani, Romania; Prof.Dr. Eng. Manolea Gheorghe - University of Craiova, Romania; Prof. Dr. Eng.Vasilievici Alexandru - Politechnical University of Timişoara, Romania; Assoc.Prof. Dr. Dubois Daniel - University of Liège, Belgium; Assoc. Prof. Dr.Eng.Kovács Ernö - University of Moskolc, Hungary; Prof. Dr. Eng. KlepikovVladimir Borisovich – National Technical University of Kharkov, Ukraine; Prof. Dr.Eng. Truşcă Vasile - University “Politechnica” of Bucharest, Romania; Prof. Dr.Eng. Fotău Ion - University of Petroşani, Romania

EDITORIAL BOARD

Editor-in-chief:Prof. Dr. Eng. Fotău Ion University of PetroşaniAssoc.Prof. Dr.Eng Marcu Marius University of Petroşani

Associate Editors: Prof. Dr. Eng. Poantă Aron University of PetroşaniAssoc.Prof. Dr.Eng Uţu Ilie University of PetroşaniAssoc.Prof. Dr.Eng. Pătrăşcoiu Nicolae University of Petroşani

Editor Secretary:Assistant Eng. PhD Student Dobra Remus University of Petroşani

Editorial office address:

University of Petroşani, 20 University Street, 332006 Petroşani, Romania,Phone: (40) 254/54.29.94; 54.25.80; 54.25.81; 54.33.82;Fax: (40) 254/54.34.91; 54.62.38, Telex: 72524 univp, E-mail: [emailprotected]

This publication is with international distribution. It is sending in 28th countries.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) -3-

CONTENTS

Dašić Predrag, Nedeff Valentin, Curčić Srećko, Analysis and evaluation of software tools forlife cycle assessment ………………………………………….………………………………....6Dumitru Cazacu., Constantin Stanescu, Aspects concerning the computation of microstriplines parameters ……………………………………………………………………………….16Gabriel Nicolae Popa, Iosif Popa, Sorin Deaconu, Classical power supply sollutions for lowpressure mercury lamps...............................................................................................................22Susana Arad, Victor Arad, Bogdan Bobora, Mihaela Bobora, Coal/petco*ke conversion likeauxiliary fuel at S.C. carpatcement holding S.A Deva branch ………………………………...28Liviu Blanaru, Sorin Cureleanu, Anghel Stoichitoiu, Coal-main basic resource in the energyproduction ……………………………………..……………………..……………………….. 34Sorin Burian, Ionescu Jeana, Daire Marius, Moldovan Lucian, Comparative study on thetypes of protection for the electric apparatus intended for use in explosive atmospheres …… 37Tiberiu Csaszar, Sorin Burian, Marius Darie, Conditions for interconnecting intrinsic safetycircuits supplied by linear and non-linear sources intended for use in potentially explosiveatmospheres ………………………………………..…………………………………………..43Miltiade Cârlan, Horia Goia, Simona Dziţac, Consideration viewing the optimaldimensioning of the maintenance team from thermo-electric power plants ...……....................49Ioan Felea, Horia Goia, Simona Dziţac, Contributions to implement the reliability centeredmaintenance at the thermo-electric plants ………………….…………………………….……55Teodor Tabacaru-Barbu Diagnostic testing for asynchronous motors....................................61Dragoş Pasculescu, Constantin Brindusa, Electric frames with linear induction motorpropulsion systems electric traction scheme …………….......................................................…67Andrei Ceclan, Dan Doru Micu, Dan Micu, Emil Simion, Electromagnetic device designsynthesis ………………..............................................................................................................72Iosif Popa, Gabriel Nicolae Popa, Sorin Deaconu, Electronic time relays with differentfunctions with T.T.L. integrated circuits……………………….…………………………….…77Corina Cunţan, Ioan Baciu, Establishing of the effects produced by the passive filters of rctype on the sinusoidal voltage source..........................................................................................83Leonard Lupu, Nicula Vatavu, Florin Paun, Improvement methods and technical tests fortechnical equipment intended for use in area with combustible dusts…………………………87Doru Visan,Daniela Mardare,Adriana Busoniu,Ileana Marcu Increase of energeticefficiency at S.E.Paroseni plant concerning of environmental European rules………………….91Dan Stoia, Mihai Cernat, Integrated starter-generator machines for hybrid automotivevehicles………………………………………………………………………………………….….…..…97Sorin Deaconu,Gabriel Nicolae Popa, Iosif Popa, Ioan Rodean, Modern system formonitoring and diagnosis of the mechanical and electrical defects for high capacity inductionmotors……………………………………………………………………………………....….107Mircea Risteiu, Adrian Tulbure, Moise Achim, Cosmin Covaciu, New approach inmeasurement-based power network modeling by using smart sensors.....................................111Sorin Burian, Jana Ionescu, Marius Darie, Possibilities to protect against explosion the lowcurrent circuits made of micro-drivings…………….…………………….…………………..120Piotr Gawor, Sergiusz Boron, Power supply and design problems of longwall installations ofrated voltage above 1 kV in underground coal mines……………............................................126Maria Orban, Cristinel Popescu, Sorin Cureleanu, Liviu Blanaru, Problem viewing thedrive of large power machines from coal extraction industry………………………………...133Victor Vaida, Reflections on the qualification of the generation units for providing the serviceconsisting in reactive power within the voltage secondary control range……………….…...138

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Analysis and evaluation of software tools for life cycle assessment-4-

Niculina Vătavu, Adrian Jurca, Florina Muntean Berzan, Researches on the risk factorswhen using electro-insulating materials in construction of technical equipment intended for usein areas with explosion hazards……………………………………………………………….147Marius Marcu, Ilie Utu, Florin Popescu, Leon Pană, Simulation software for static switchcontrollers……………………………………………………………………………………...153Nicolae Dan, Visalon Dan, Some results in solving field engineering problems using finiteelement method………………………………………………………………………………..160Florin Adrian Păun, Leonard Lupu, Florina Muntean Berzan, Standardization test methodsused at assessment of product conformity with the requirements of preventing the explosiveatmosphere ignition by electrostatic discharges…………………………………………..…..164Leon Pană, Ion Fotău, Horia Şerban Stochastic models for reliability analysis of protectionsystems…………………………………………………………………...................................168Jenica Ileana Corcău, Study dynamic of a synchronous generator with electronicload………………………………………………………………………………………….…174Constantin Brînduşa, Mihai Păsculescu, Dragoş Păsculescu Tensions invertors withcommutation on three levels. Mathematical modeling; structural diagram…………………..183Constantin Brînduşa, Mihai Păsculescu, Dragoş Păsculescu Tensions invertors withcommutation on two levels. Mathematical modeling; structural diagram……………………188Ioan Baciu, Corina Cunţan, The analysis of the lc-type passive filters’ influence upon thepower supply network of a rezistive consumer using the LabViewprogram.....................................................................................................................................192Sorin Cureleanu, Liviu Blanaru, Anchel Stoichitoiu The lignite role as the primary source inthe electrical energy supply in Romania……………………………………………...……….196Adrian Marius Jurca, Mihaela Părăian, Emilian Ghicioi, Nicula Vătavu The new Europeanconcept of explosion protection for the non–electrical equipment intended for use in explosiveatmospheres……………………………………………………………………………………199Ioan Vasiu, The optimal operating ranges of the steam generators with natural circulationworking on powdwred coal in the romanian power plants………………………………........205Visalon Dan, Nicolae Dan Theoretical aspects in solving field engineering problems usingfinite element method……………………………………………………………………..…...211Andreea Brînduşa, Iosif Kovacs, Adriana Bociat Thermoenergetic block on coal pollutionvector water hydroconveyer for ashes………………………………………………………...…215Andreea Brînduşa, Iosif Kovacs Thermoenergetic block on coal pollution vector: burninggas………………………………………………………………………………………………218Constantin Brînduşa, Mihai Păsculescu, Marius Popescu, Urban frame with static converterand asynchronous motors. Direct field orientation……………………………………………222Visalon Dan, Carol Zoller, Using graphical programming vee pro 6 software for functionsimmulation of the grinding aggregates to maintain optimuum specific energyconsumption…………………………………………………………………………………...226Jenica Ileana Corcău, Voltage electronic regulator for aircraft………….............................232Dragoş Pasculescu, Constantin Brindusa Wear valuation of braking activ material at urbanelectric frames brake regime………………………………...…………………………………..237Remus Dobra PC to CY8C29466 microcontroller serial communication method…………..242Corneliu Mândrescu, Olimpiu Stoicuţa, Analysis of the luemberger extended estimator usedwithin a vectorial type electrical driving system with an inductionmotor………………………………………………………………………………..................246Monica Leba, Emil Pop, Petre Vamvu, Approach on distributions for control systems withrelay type nonlinearities…………………………………………………………………….…254Gabriela Bucur, Liviu Bucur, Automatic wig welding control using feedforward neuralnetwork………………………………………………………………………………………...260

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) -5-

Roxana-Adina Irimia, Alina-Nicoleta Vlăsceanu, Electronic government–reflections over thedesign of a regional development strategy…………………………………………..……..…266Adrian Tulbure, Mircea Risteiu, Embedded-system zur steuerung leistungselektronischermodule…………………………………………………………………………………....……272Aron Poanta, Dan Dojcsar, Bogdan Sochirca, Equipment used in priming of the blastingcartridge with cypress microcontroller………………………………………………….……..278Luminiţa Popescu,Florin Grofu,Marian Popescu,Experimental model for predictive controlof the pumping aggregates used for water drain in roşia mining pit……………………...….286Luminiţa Popescu, Olaru Onisifor Florin Grofu, Experimental model for monitoring apumping aggregate used for water drain in roşia mining pit...................................................292Cristina Popa, Cristian Patrascioiu, FCC Model predictive control.....................................298Nicolae Pătrăşcoiu, Adrian Marius Tomuş, Gas monitoring system based on Modbusprotocol and virtual instrumentation………………………………………………………….309Popescu Marius-Constantin, Hybrid neural network for prediction of process parameters ininjection moulding....................................................................................................................312Otilia Cangea, Informatic viruses detection using heuristic algorithms…………………….320Egri Angela, Sirb Vali Chivuţa, Modeling for industrial and manufacturingsystems…………………………………………………………….………………………..…326Cristina Popescu, Neural network techniques for mobile robot navigation……………...….332Valentin Casavela, Program conceived in the visual studio.net mediu, for a capitaldevaluation calculation and displaying…………………………………………………..…..338Emil Pop, Ioana Camelia Tabacaru Barbu, Maria Pop, Renewable energy resourcesposibilities use in jiu valley……………………………………………………………….…...343Nicolae Pătrăşcoiu, Adrian Marius Tomuş, Resistive bridge controled by virtualinstrumentation………………………………………………………………………………..351Laurenţiu Alboteanu, Gheorghe Manolea, Florin Ravigan, Adrian NourStrategies of control for solar panels positioning systems........................................................357Corneliu Mândrescu, Olimpiu Stoicuţa, Synthesis of the luemberger extended estimator usedwithin a vectorial-type electrical driving system with an inductionmotor…………………………………………………………………………………………..365Mircea Rîsteiu, Adrian Tulbure, Zigbee development setup for measurement-based webmodeling and simulation............................................................................................................373Andreea Brînduşa, Iosif Kovacs, Thermoenergetic block on coal. Pollution vector: Evacuatedwater…………………………………………………………………………………………..381Dašić Predrag,, Ječmenica Ratomir, Šerifi Veis One classification example ofdecision support systems……………………………………………………………..385Liviu Dumitraşcu, Gabriel Marcu, Dorel Dusmanescu Implementing within anobject-oriented language (java) the UML modelling concepts………………………392

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 6-15

ANALYSIS AND EVALUATION OF SOFTWARE TOOLSFOR LIFE CYCLE ASSESSMENT

PREDRAG DAŠIĆ, VALENTIN NEDEFF, SREĆKO ĆURČIĆ

Abstract: Life-cycle assessment (LCA) is a methodology for analyzing andsystematic evaluation of environmental aspects of a product or service system through all stagesof its life cycle. LCA was chosen to be worldwide used tool in the 1990s for environmentalmanagement in the form of ISO 14040 series. There is a large number of developed softwaretools for LCA nowadays in the world. This paper analyzes and evaluates software tool: GaBi,KCL-ECO, LCAiT, PEMS, SimaPro and TEAM for product and process LCAs.

Keywords: LCA (Life-Cycle Assessment), LCE (Life-Cycle Engineering), LCI (Life-Cycle Inventory), LCIA (Life-Cycle Impact Assessment), software tools

1. INTRODUCTION

Life cycle is consecutive and interlinked stages of a product system, from rawmaterial acquisition or generation of natural resources to the final disposal.Product and process life cycle topics are 7, 12-13: LCA (Life-Cycle Analysis), LCA (Life-Cycle Assessment), LCC (Life-Cycle Cost), LCD (Life-Cycle Design), LCI (Life-Cycle Inventory), LCIA (Life-Cycle Impact Assessment), LCM (Life-Cycle Management), LCS (Life-Cycle Strategy), SCM (Supply Chain Management) etc.

High Technological Technical School, Kosanciceva 36, 37000 Krusevac, Serbia andMontenegro University of Bacău Technical Faculty Cacak, Svetog Save 65, 32000 Cacak, Serbia and Montenegro

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Dašić P., Nedeff V., Curčić S. -7-

All listed topics for life-cycle incorporate all scientific areas called LCE (Life-Cycle Engineering).

Methodology for the life-cycle and sustainability analysis of manufacturingprocesses is given in paper 6.LCA (Life Cycle Assessment) is a methodology used to evaluate the potentialenvironmental impact of a product, process or activity throughout its entire life cycleby quantifying the use of resources ("inputs" such as energy, raw materials, water) andenvironmental emissions ("outputs" to air, water and soil) associated with the systemthat is being evaluated.

The most important applications are: Analysis of the contribution of the life cycle stages to the overall environmental

load, usually with the aim to prioritise improvements on products or processes and Comparison between products for internal or external communications.

The first predecessor of LCA was the REPA (Resource and EnvironmentalProfile Analysis) in the 1960s and 1970s. First studies that were performed by REPAwere for Coca Cola Company and Mobil Corporation. Interest studies continuedthrough the 1980s as more sophisticated analysis 2.Modern LCA methodology is root in the development of standards through the 1990s.The SECAT (Society for Environmental Toxicology and Chemistry, available on Website: http://www.setac.org/) in 1991 published A Technical Framework for Life CycleAssessments 3 as a first international LCA standard. Detailed LCA methodologieswere specified in 1995 by Nordic Council of Ministers.ISO (International Organization for Standardization or International StandardsOrganization, available on Web site: http://www.iso.org/ or http://www.iso.ch/)released for the first time a general introductory framework on LCA (ISO 14040standard) in 1997, and the ISO 14040 to 14043 standard series in late 1990s and early2000s.A partnership was launched in 2002 between UNEP (United Nations EnvironmentProgramme, available on Web site: http://www.unep.org/) and SETAC in order toform the UNEP/SETAC Life-Cycle Initiative to evaluate products using practical toolsand services to achive sustainable development (available on Web site:http://www.uneptie.org/pc/sustain/lcinitiative/home.htm) and other initiatives 8.In June 1992 a society for LCA called SPOLD (Society for Promotion of LCADevelopment) was established, which is available on Web site: http://www.spold.org/or http://lca-net.com/spold/.

Application of LCA is given in paper 1, LCA in industry and business inpaper 10, evaluation of environmental impacts in LCA 9 and integrating LCAanalysis and LCA in paper 25.

Structure of the life cycle assessment (LCA) is show in figure 1 5, 6.

2. STANDARDIZATION OF LCA

According to ICS (International Classification for Standards), LCA iscategorized in the 13th field for Environment, health protection and safety and 020th

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Analysis and evaluation of software tools for life cycle assessment-8-

group (ICS=13.020) for Environmental protection and 60th subgroup(ICS=13.020.60) for Product life-cycles.The international ISO standards in frame subgroup Product life-cycles(ICS=13.020.60) specifically designed for LCA applications are 14-20, 24: ISO14040:1997, ISO 14041:1998, ISO 14042:2000, ISO 14043:2000, ISO/TR14047:2003, ISO/TS 14048:2002 and ISO/TR 14049:2000.

Fig.1 Structure of the Life Cycle Assessment (LCA)

The ISO 14040 to 14043 standards describes the method presenting thedifferent options for the release of LCA. The ISO 14040 standards are a generalstandard for the LCA area and were issued in 1997 from ISO subcommittee ISO TC207/SC 5 (available on Web site: http://www.tc207.org/). Based on a goal and scopedefinition, the environmental impacts of the important elements are scrutinized in a so-called inventory analysis 14. After that, the impacts are assessed and interpreted inorder to improve the sustainability and the environmental friendliness of the analyzedproduct. According to ISO 14040, the general framework of LCA is illustrated infigure 2 14, 24.

The ISO 14040:1997 standard outlines the principles and the conduct of LCAstudies and how to reduce the overall environmental impact of products and services14.

The ISO 14041:1998 standard in conjunction with ISO 14040 specifiesrequirements and procedures to define the goal and scope for life cycle assessment,performing, interpreting and reporting a LCI (Life-Cycle Inventory) analysis 15.The ISO 14042:2000 standard provides guidance on a general framework for the LCIA(Life-Cycle Impact Assessment) phase of LCA, and the key features and inherentlimitations of LCIA 4, 16.

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Dašić P., Nedeff V., Curčić S. -9-

The ISO 14043:2000 standard summaries the final phase of the LCAprocedure, including the LCI (Life-Cycle Inventory) analysis and LCIA (Life-CycleImpact Assessment) 17.

The ISO 14047:2003 standard provides examples of application of ISO 1404218 and ISO 14049:2000 standard provides examples of application of ISO 1404120.

The ISO 14048:2002 standard provides the requirements and a structure for adata documentation format, to be used for transparent and unambiguous documentationand exchange of LCA (Life-Cycle Assessment) and LCI (Life-Cycle Inventory) data19.

Fig.2 The framework of LCA with four interrelated phases, according to the ISO 14040standard 13

3. SOFTWARE TOOLS FOR LCA

Today there is a large number of developed software tools for LCA, whosereview is given in book 3 and paper 4. The list of the most important software toolsfor product and process LCAs given in alphabetical order is as follows 5, 7-8, 21-22,26-30, 32-34: ACE (Active Community / Stakeholder Engagement Software), available on Web

site: http://www.acttiv.com/, AME (A Modeling Environment), available on Web site:

http://helios.bto.ed.ac.uk/ierm/ame/, ATHENA, available on Web site:

http://www.athenasmi.ca/ath_model/model_main.htm, Boustead Model, available on Web site: http://www.boustead-consulting.co.uk/, BeCost, available on Web site: http://pim.vtt.fi/becost/html/index.htm, CLEAN (Comprehensive Least Emissions Analysis),

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Analysis and evaluation of software tools for life cycle assessment-10-

CMLCA (Chain Management by LCA), available on Web site:http://www.leidenuniv.nl/interfac/cml/ssp/ software/cmlca/index.html,

CMSS (Compliance Management Software Solutions), available on Web site:http://www.amadeussolutions.com/,

CUMPAN (Computerunterstützte umweltorientierte Produktbilanzierung),available on Web site: http://www.debis.de/debis/systemhaus/,

DEEDS (Design for Environment Decision Support), available on Web site:http://sun1.mpce.stu.mmu.ac.uk/ pages/projects/dfe/deeds/deeds.html,

ECO-it (Ecological - Indicator Tool), available on Web site: http://www.pre.nl/eco-it.html,

EcoLab (Ecological - Lab), available on Web site:http://www.port.se/ecolab/default.htm,

EcoMan (Ecological - Manager), available on Web site:http://www.fal.com/software/ecoman.html,

EcoPack (Ecological - Package), EcoPro, available on Web site:

http://www.sinum.com/htdocs/e_software_ecopro.shtml, Eco-Quantum (Ecological Quantum), available on Web site:

http://www.ecoquantum.nl/, EcoScan (Ecological - Scan), available on Web site: ;

http://www.ind.tno.nl/en/product/ecoscan/ or http://www.luna.nl/turtlebay/, EcoSoft (Ecological - Software), available on Web site:

http://www.ibo.at/ecosoft.htm, EcoSys (Ecological - Systems), EDIP (Environmental Design of Industrial Products), available on Web site:

http://www.mst.dk/activi/08030000.htm, EMS (Environmental Management Software), available on Web site:

http://www.esp-net.com/, ENVEST II, available on Web site: http://www.bre.co.uk/envest/ or

http://envest2.bre.co.uk/account.jsp, EPS 2000 (Environmental Priority Strategies 2000), available on Web site:

http://www.assess.se/software.htm, EUKLID, available on Web site: http://www.ivv.fhg.de/sysana_soft.html, GaBi (Ganzheitliche Bilanzierung), available on Web site: http://www.gabi-

software.de/software.html or http://www.pe-consulting-group.com/software_gabi.html or http://www.ikpgabi.uni-stuttgart.de/deutsch/gabi_soft.html,

GBA (Green Building Advisor), available on Web site:http://www.greenbuildingadvisor.com/,

GDM (Green Design and Manufacturing), available on Web site:http://greenmfg.me.berkeley.edu/green/Home/Index.html,

IDEA (International DataBase for Eco-profile Analysis), available on Web site:http://www.iiasa.ac.at/,

IdeMat (Identification Materials), available on Web site:http://www.io.tudelft.nl/research/dfs/idemat/ index.htm,

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Dašić P., Nedeff V., Curčić S. -11-

IRIS (Integrated Risk Information System), available on Web site:http://www.epa.gov/iris/intro.htm,

JEM-LCA (Japan Environment Management - LCA), KCL-ECO (Keskuslaboratorio – Centrallaboratorium Ab - Ecology), available on

Web site: http://www.kcl.fi/eco/softw.html, LCAdvantage (LC Advantage), available on Web site: http://www.battelle.com/, LCAiT (LCA Inventory Tool), available on Web site:

http://www.lcait.com/01.html, LCAPIX, available on Web site: http://www.kmlmtd.com/pas/index.html, LCASys (LCA Systems), LCE (Life Cycle Explorer), available on Web site: http://www.sylvatica.com/, LEGEP, available on Web site: http://www.legep.de/, LIMS (Life Cycle Interactive Modeling System), LISA (LCA in Sustainable Architecture), available on Web site:

http://www.lisa.au.com/, MIET (Missing Inventory Estimation Tool), available on Web site:

http://www.leidenuniv.nl/cml/ssp/ software/miet/index.html, OGIP (Optimisation of Global Demands in Terms of Costs, Energy and

Environment within an Integrated Planning Process), available on Web site:http://www.the-software.de/BauenUmwelt.html,

PEMS (Pira Environmental Management System), available on Web site:http://www.pira.co.uk/pack/ environmental.htm,

PHASETS (Phases in the Design of a Model of a Technical System), PIA (Product Improvement Analysis), available on Web site:

http://www.pira.co.uk/, POEMS (Product Oriented Environmental Management Systems), available on

Web site: http://www.ecobalance.com/uk_m_poems.php, RAVEL (Rail Vehicle Eco-efficient Design), REGIS, available on Web site:

http://www.sinum.com/htdocs/e_software_regis.shtml, REPAQ (Resource and Environmental Profile Analysis Query), available on Web

site: http://www.fal.com/software/REPAQ.html, SEEA (System of Integrated Environmental and Economic Accounting), available

on Web site: http://unstats.un.org/unsd/environment/software.htm, SimaPro (System for Integrated Environmental Assessment of Products), available

on Web site: http://www.pre.nl/simapro/, SimaTool (System for Integrated Environmental Assessment of Tool), SoFi (Software for Sustainability Reporting of Financial Service Providers),

available on Web site: http://www.sofi-software.com// or http://www.pe-consulting-group.com/software_sofi.html,

SWAMI (Strategic Waste Minimization Initiative), available on Web site:http://www.er.doe.gov/epic/html/SWAMI.stm,

TCAce (Total Cost Assessment), available on Web site: http://www.tcace.com/ andhttp://www.sylvatica.com/tcace.htm,

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Analysis and evaluation of software tools for life cycle assessment-12-

TEAM (Tool for Environmental Analysis and Management), available on Web site:http://www.ecobalance.com/uk_team.php,

TEMIS (Total Emission Model for Integrated Systems), TIET (Teleworking Impact Estimation Tool), available on Web site:

http://greenmfg.me.berkeley.edu/green/SoftwareTools/Telework/, Umberto, available on Web site: http://www.umberto.de/en/home/, WISARD (Waste - Integrated Systems Assessment for Recovery and Disposal),

available on Web site: http://www.ecobalance.com/uk_wisard.php, WPC (Web-Based Paper Calculator), available on Web site:

http://www.ofee.gov/recycled/cal-index.htm and etc.

4. EVALUATION OF SOFTWARE TOOLS FOR LCA

Out of a large number of software tools for LCA listed in chapter 3 an analysiswas performed of ten chosen software tools: GaBi, KCL-ECO, LCAiT, PEMS,SimaPro and TEAM (table 1) 11, 26. The following criteria were taken intoconsideration: Functionality, Flexibility, Database, User – friendliness, Softwareproperties, Service and Cost. The evaluation ranges from 1 (very negative) to 5 (verypositive). As this is a very subjective evaluation method we decided to disclose theresults and publish a non-aggregated rating for each tool and criterium. Even theseratings are based on subjective impressions, therefore other individuals may come todifferent findings.

According to evaluation in paper 11, 26 the new releases of software tools:GaBi, KCL-ECO, LCAiT, PEMS, SimaPro and TEAM for LCA are the mostinteresting software tools on the market.

In table 2 is presented a condensed and comparative evaluation of these uniquesoftware tools (GaBi, KCL-ECO, LCAiT, PEMS, SimaPro and TEAM) features forproduct and process LCAs 23.

5. CONCLUSION

All listed topics for life-cycle (LCA, LCC, LCD, LCI, LCIA, LCM, LCS etc.)incorporate all scientific areas called LCE (Life-Cycle Engineering).The general standard for the LCA area is ISO 14040 standards and was issued in 1997by ISO subcommittee ISO TC 207/SC 5.There is a large list of software tools for LCA, for example: BEES, CMLCA,CUMPAN, ECO-it, EcoMan, EcoPro, EDIP, GaBi, KCL-ECO, LCAiT, PEMS,REGIS, REPAQ, SDES, SimaPro, TEAM, TRACI, Umberto etc.New releases of software tools: GaBi, KCL-ECO, LCAiT, PEMS, SimaPro and TEAMfor LCA are the most interesting software tools on the market.

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Dašić P., Nedeff V., Curčić S. -13-

Table 1. Evaluation of the software tools for product and process LCAsCharacteristics GaBi KCL-

ECOLCAiT PEMS SimaPro TEA

MFunctionality 5 4 4 3 2 4Flexibility 3 3 3 3 3 4Database 4 2 4 3 4 5User – friendliness 5 4 3 2 2 3Software properties 3 4 3 3 3 2Service 5 3 4 3 3 5Cost 4 2 3 3 5 2

Table 2. A condensed and comparative evaluation of these unique software tools for LCAfeatures

Characteristics GaBi KCL-ECO

LCAiT PEMS SimaPro TEAM

Graphical Interface Data Protection Unit Flexibility Use of Formulas Uncertainty Analysis Impact Assessment Comparison of Results Graphical Display of Results

REFERENCES

[1] Allen, D. T.: Applications of life-cycle assessment. In: Environmental Life-CycleAssessment. Edited by M. A. Curran. New York (USA): McGraw-Hill, 1996, pp. 5.1-5.17.ISBN 0-07-015063-X.

[2] Assies, J. A.: Life cycle assessment in a historical perspective. In:Environmental Assessment of Products: A Course on Life Cycle Assessment. Edited by B.Pedersen. Helsinki (Finland): UETP – Environmental Engineering Education ( EEE), 1993.ISBN 951-9110-83-6.

[3] A technical framework for life cycle assessments. Pensacola (FL - USA): Societyfor Environmental Toxicology and Chemistry (SETAC), 1991. – 134 pp.

[4] Bare, C. J.; Pennington, W. D. and Udo de Haes, A. H.: Life cycle impactassessment sophistication – international workshop. International Journal of Life CycleAssessment, Vol. 4 (1999), No. 5, pp. 299 – 306. ISSN 0948-3349.

[5] Bruno, P. and Katrien, P.: PRESCO Work Package 2: Inter-comparison andbenchmarking of LCA-based environmental assessment and design tool. Final report,Lozenberg (Belgium): Practical Recommendations for Sustainable Construction (PRESCO),2005. – 74 pp. Available on Web site: http://www.etn-presco.net/generalinfo/PRESCO_WP2_Report.pdf.

[6] Culaba, A. B. and Purvis, M. R. I.: A Methodology for the life-cycle andsustainability analysis of manufacturing processes. Journal of Cleaner Production, Vol. 7(1999), pp. 435 – 445. ISSN 0959-6526.

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Analysis and evaluation of software tools for life cycle assessment-14-

[7] Dašić, P.: Encyclopedia of the Technical and ICT Abbreviations (in preparationin Serbian language). Electronic Edition. Trstenik: High Technical Mechanical School. ISBN86-83803-12-0.

[8] Dašić, P.; Nedeff, V.; Petropoulos G.: Internet resources and software tools forlife cycle assessment. Plenary and Invitation paper. In: Proceedings on CD-ROM of 6th

International Conference Research and Development in Mechanical Industy - RaDMI 2006,Budva, Montenegro, 13-17. September 2006. Edited by Predrag Dašić. Kraljevo: Faculty ofMechanical Engineering and Trstenik: High Technical Mechanical School, 2006, pp. 68-87.ISBN 86-83803-21-X.

[9] Evaluation of environmental impacts in life cycle assessment. Meeting report,Brussels, Belgia, 29-30. November 1998 and Brighton, 25-26. May 2000. Paris: United NationsEnvironment Programme (UNEP), 2003. – 97 pp. ISBN 92-807-2144-5. Available on Website:http://www.uneptie.org/pc/sustain/reports/lcini/UNE.%20P_US%20EPA%20LCIA%20mtg%20report.pdf.

[10] Frankl, P. and Rubik, F.: Life cycle assessment in industry and business.Heidelberg (Germany): Springer, 2000. – 279 pp. ISBN 3-540-66469-6.

[11] Frühbrodt, E.: LCA software review – An up-to-date overview of the Europeanmarket. Workshop on life cycle data for assessment of environmental performance of EEE andEU funded RTD activities on EEE ecodesign. Brussels, 9 October 2002. Available on Web site:http://europe.eu.int/comm/enterprise/ electr_equipment/eee/workshop9-10-02/present/lcasoftwarere.pdf.

[12] Hauschild, M.; Alting, L. and Poll, C.: Life cycle engineering – frommethodology to enterprise culture. Keynote paper. In: Proceedings of 11th International CIRPLife Cycle Engineering Seminar: Product Life Cycle – Quality Management Issues, Belgrade,Serbia and Montenegro, 20 - 22. June 2004. Edited by Leo Alting and Vidosav Majstorović.Belgrade: Faculty of Mechanical Engineering and Association Serbia and Montenegro forQuality and Standardization (JUSK), 2004, pp. 7-15. ISBN 86-903197-3-5.

[13] Herrmann, C.; Mateika, M.: Quality aspects of life cycle strategies. In:Proceedings of 11th International CIRP Life Cycle Engineering Seminar: Product Life Cycle –Quality Management Issues, Belgrade, Serbia and Montenegro, 20 - 22. June 2004. Edited byLeo Alting and Vidosav Majstorović. Belgrade: Faculty of Mechanical Engineering andAssociation Serbia and Montenegro for Quality and Standardization (JUSK), 2004, pp. 57-61.ISBN 86-903197-3-5.

[14] ISO 14040:1997 Environmental management -- Life cycle assessment --Principles and framework. Geneve: International Organization for Standardizations (ISO).

[15] ISO 14041:1998 Environmental management -- Life cycle assessment -- Goaland scope definition and inventory analysis. Geneve: International Organization forStandardizations (ISO).

[16] ISO 14042:2000 Environmental management -- Life cycle assessment -- Lifecycle impact assessment. Geneve: International Organization for Standardizations (ISO).

[17] ISO 14043:2000 Environmental management -- Life cycle assessment -- Lifecycle interpretation. Geneve: International Organization for Standardizations (ISO).

[18] ISO/TR 14047:2003 Environmental management -- Life cycle impactassessment -- Examples of application of ISO 14042. Geneve: International Organization forStandardizations (ISO).

[19] ISO/TS 14048:2002 Environmental management -- Life cycle assessment --Data documentation format. Geneve: International Organization for Standardizations (ISO).

[20] ISO/TR 14049:2000 Environmental management -- Life cycle assessment --Examples of application of ISO 14041 to goal and scope definition and inventory analysis.Geneve: International Organization for Standardizations (ISO).

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Dašić P., Nedeff V., Curčić S. -15-

[21] Life cycle assessment (LCA) – A guide to approaches, experiences andinformation sources. Environmental Issues Series No. 6, Copenhagen: European EnvironmentAgency (EEA), 1998. – 119 pp. Available on Web site: http://reports.eea.eu.int/GH-07-97-595-EN-C/en/Issue%20report%20No%206.pdf.

[22] Life cycle assessment tools to measure environmental impacts: Assessing theirapplicability to the home building industry. Final report, Washington (DC – USA): U.S.Department of Housing and Urban Development (HUD) User, 2001. – 49 pp. Available on Website: http://www.huduser.org/Publications/PDF/lifecycle.pdf.

[23] Menke, M. D.; Davis, A. G. and Vigon, W. B.: Evaluation of life cycleassessment tools. Canada: Hazardous Waste Branch, 1996. – 59 pp. Available on Web site:http://eerc.ra.utk.edu/ccpct/pdfs/LCAToolsEval.pdf.

[24] Nedeff, V.; Dašić, P.; Petropoulos, G.: Standardization of life cycleassessment. U zborniku radova XXXIII Simpozijuma o operacionim istraživanjima - SYM-OP-IS 2006, Banja Koviljača, 03 - 06. oktobra 2006. Editor: Dragan Radojević. Beograd: InstitutMihajlo Pupin, 2006, s. 73-76. ISBN 86-82183-07-2.

[25] Norris G. A.: Integrating life cycle cost analysis and LCA, InternationalJournal of Life Cycle Assessment, Vol. 6 (2001), No. 2, pp. 118-121. ISSN 0948-3349.

[26] Rice, G.; Clift, R. and Burns, R.: LCA software review: comparison ofcurrently available European LCA software. International Journal of Life Cycle Assessment,Vol. 2 (1997), No. 1, pp. 53 – 59. ISSN 0948-3349.

[27] Rizzoli, A. E. and Young, W. J.: Delivering environmental decision supportsystems: software tools and technique. Environmental Modeling & Software, Vol. 12 (1997),No. 2-3, pp. 237-249. ISSN 1364-8152.

[28] SimaPro 6 – Introduction to LCA with SimaPro. Amersfoort (Netherlands): PréConsultants BV, 2004. – 71 pp. Available on Web site:http://www.pre.nl/download/manuals/UserManual.pdf.

[29] SimaPro 6 Tutorial. Amersfoort (Netherlands): Pré Consultants BV, 2004. – 59pp. Available on Web site: http://www.pre.nl/download/manuals/TutorialWood.pdf.

[30] Spatari, S.: Using Gabi 3 to perform life cycle assessment and life cycleengineering. International Journal of Life Cycle Assessment, Vol. 6 (2001), No. 2, pp. 81 – 84.ISSN 0948-3349.

[31] Tan, R. R. and Culaba, A. B.: Sensitivity analysis of the life-cycle inventoriesof electricity and hydrogen as energy vectors for the Philippine automotive transport sector.Asean Journal of Chemical Engineering, Vol. 2 (2002), No. 1, pp. 21-29. ISSN 1655-4418.

[32] Unger, N.; Beigl, P. and Wassermann, G.: General requirements for LCAsoftware tools. In: Proceedings of Complexity and Integrated Resources Management -Transactions of the 2nd Biennial Meeting of the International Environmental Modelling andSoftware Society (iEMSs 2004), Vol. 3. Osnabrück, Germany, 14 - 17. June 2004. Edited byClaudia Pahl-Wostl, Sonja Schmidt, Andrea E. Rizzoli and Anthony J. Jakeman. Manno(Switzerland): International Environmental Modelling and Software Society (iEMSs) andOsnabrück (Germany): University of Osnabrück, Institute of Environmental Systems ResearchResource Flow Management, 2004. pp. 468-473. ISBN 88-900787-1-5. Available on Web site:http://www.iemss.org/iemss2004/pdf/infotech/ungegene.pdf.

[33] Weidema, B. P. and Mortensen, B.: Results of a test of LCA-software withstatistical functionality. Note for the Danish Environmental Protection Agency (EPA), Lyngby:Institute for Product Development, 1997.

[34] Wenzel, H.; Hauschild, Z. M. and Alting, L.: Environmental assessment ofproducts. Vol. 1: Methodology, tools, techniques and case studies in product development.London (UK): Chapman & Hall, 1997. – 576 pp. ISBN 0-412-80800-5.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 16-21

ASPECTS CONCERNING THE COMPUTATION OFMICROSTRIP LINES PARAMETERS

DUMITRU CAZACU, CONSTANTIN STANESCU

Abstract: This paper deals with the computation of the lineical capacity andcharacteristic impedance for a microstrip line configuration using Green functions. Also theinfluence of the artificial boundaries of the computational domain on the surface electric chargedistribution using finite element method was performed. Parametric analysis was performed inorder to evaluate the influence. The results are compared with those from literature and a goodagreement is observed.

Keywords: microstrip, green functions, finite element parametric analysis.

1. INTRODUCTION

Accurately computation of propagation characteristics of the signals is crucialfor designing the integrated circuits and reducing the errors before the manufacturingstage. Determining the propagation parameters is also useful to the design of themultilayer passive electronics devices used in electronics and telecommunications.The importance of the multilayer microstrip lines have increased constantly in the fieldof the high speed integrated circuits for microwaves and millimeters waves. The staticcapacitance of a system is an important parameter in the design of the system. In newdigital electronic system, the trend is toward higher clocking frequencies. The integralequation method implemented numerically by the method of moments [1], the finitedifference method [2], the finite element method [3], the spectral domain Green’sfunction approach [4].One of the factors that influence the computational resourceswhen a finite element analysis is performed is the distance where the artificial fielddomain boundary should be placed, in order to minimize the resources and yet notaffect the parameters of the device. This paper deals with the influence of this factoron the surface charge microstrip line distribution.

Ph.D. at the University of Pitesti , [emailprotected] Ph.D. at the University of Pitesti stancosty@gmailcom

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Cazacu D., Stanescu C. -17-

1 PROBLEM FORMULATION

It was shown in a rigorous way that in the low frequency limit the microstripline can be analyzed as a static field problem and that the propagation constant andcharacteristic impedance are determined by the low frequency distributed capacitanceand inductance.

There are a variety of methods for solving the 2D electrostatic laplacian fields.Considering a Fourier series development of the charge density s of the

form

axnx

ns 2

cos)(,...3,1

(1)

and performing some processing’s the following expression for the potential V is obtained:

'')(

,..3,1

2/

2/ 0

'

)()sinh(

)sinh()cosh()(sin(

)cos()cos(),( dxxeyw

ywhwhwaw

xwxwyxV shywn

n

n

w

w ngnn

nnn

(2)

where 22 )2

(a

nn

, with ax is the distances where the electric walls where

placed.Where the upper term is for hy and the lower is for hy .The factor

multiplying the charge density represents the Green’s function for this problem,).,,,( '' yxyxG

Expressing the integral equation (2) in a form that can be interpreted asrepresenting the capacitance C between a conducting strip in air above a ground planewith spacings eh , eh2 , eh3 , etc. and using the conformal mapping technique, theexpression for the capacitance results [5] :

])1[(1)(1

)(4/1

1 hmCahCa

hCaC M

m

m

g

(3)

The effective dielectric constant for a microstrip line is given by

CaC

ff (4)

where aC is the capacity of the air filled line.Computing the eff using the Schneider-Hammerstaad formula [6] the

characteristic impedance, for a lossless line, can be computed using the followingexpression:

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Aspects concerning the computation of microstrip lines parameters-18-

CZ effc

100 (5)

2 PROBLEM SOLUTION

2.1 Characteristic impedance computation

The characteristic impedance was determined implementing the equations (3),(4), (5). In Table.1 and Table 2 obtained values for different relative permitivitties

.r are compared with the results from the literature. The number in bracketsrepresents the terms number necessary to obtain a numerical convergence of .10 3 Itcan be seen that the results are in good agreement with [7], [8].

Tabel 10.6rw/h

,Z ,]9[Z ,]10[Z0,1 134,790(14) 134,7143 134,72

0,2 112,3435(15) 112,4978 112,500,4 90,1907(15) 90,3807 90,3850,7 72,6731(17) 72,7845 72,7891 61,8295(17) 61,8807 61,8852 42,3945(17) 42,2886 42,2934 26,5168(20) 26,4489 36,45410 12,7164(24) 12,7179 12,726

Table 2

6.9rw/h

,Z ,]9[Z ,]10[Z0,1 108,8966 (25) 109,0053 109,010,2 90,6873 (25) 90,948 90,9520,4 72,6937 (25) 72,9718 72,9750,7 58,4817(27) 58,6731 58,6761 49,6899 (27) 49,8175 49,8212 33,9644(29) 33,9308 33,9344 21,1733(32) 21,1389 21,14310 10,1130(40) 10,1186 10,125

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Cazacu D., Stanescu C. -19-

2.2 Evaluation of boundary influence of the surface charge densitycomputation

In order to study the influence of the positioning on the surface charge densityof a microstrip line (Fig.1) the dimensions and H were parameterized using theparameter p a parametric analysis was performed then with varying from 0.1 to 1 witha constant step of 0.1.

Fig.1 The positioning on the surface charge density of a microstrip line

The geometry used is presented in Fig.1, where geometric initial dimensionsare: the strip width w = 0.2, the substrate thickness h = 0.1, a = 0.1, the outer boundaryheight H = 0.1.

The surface charge distribution was determined performing an parametricelectrostatic analysis with p as a parameter.

2.2.1 Finite element electrostatic analysis

The equation to be solved is:

0V (6)

where V is the electrostatic potential.First the strip was set up to a 1 V potential and the boundary to 0 V (ground).

Because the dielectric is not hom*ogenous at the boundaries between the two media acontinuity boundary condition were set, that specifies that the normal component ofthe electric displacement is continuous across the interior boundary:

0)( 21 DDn (7)

For the initial geometry a 962 second order Lagrange elements mesh wasproduced. Then a electrostatic analysis using a stationary direct solver (UMFPACK)[8] was performed. A number of 1987 DOFs were computed 1.312 s, on a 512M RAM1.1GHz machine and the electrostatic potential distribution has resulted.

B3

Dielectric substrate

r=1

a w a

H

h

BA

D E F C

G H

B2

B4 B6 B7

B6

B9

B1 B5

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Aspects concerning the computation of microstrip lines parameters-20-

2.2.2 Parametric analysis

The implementation of the parametric analysis was in Comsol Multiphysics(Comsol Multiphysics ver.3.2, Copyright(c) 1994-2005 by Comsol AB,www.comsol.com)

A multiphysics coupling between the Parameterized geometry applicationmode and electrostatics was applied [9]. This application mode is used to study howthe physics changes when the geometry changes, as a function of time or of aparameter. The set unknowns are the electrical potential and the dx and dydisplacements. On some boundaries and points some constraints were applied. Theboundaries adjacent to the points with parameterized constraints using a p parameter:B1, B8, B3, B9 and B5 were scaled using similarity transformations.

This option is used when the displacement on the boundaries and points wereprescribed. The software translates, rotates and scales the boundary so that theconstraints at the end points are satisfied.

Also on other boundaries some linear displacement on ox and oy were applied.The point settings for the moving points were parameterized with p.

Then the current solution was used as an initial solution for a parametricanalysis that computed also the dx and dy displacement.

2.2.3 Results

A number of 5961 DOF were solved in 27.33 s on the same machine. Thenumber of DOFs indicates the efficiency of the deformed mesh application mode.

Representing the surface charge distribution for each p value the followingcurves were obtained (Fig.2).

Fig.2 Representing the surface charge distribution

The charge distribution is wider when p increases. It can be noted that thecharacter of the curves meet the analytical character that results from conformalmapping technique. It is known that an isolated infinitely long conducting strip ofwidth w and with total charge Q per meter the charge distribution is given by [5] :

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Cazacu D., Stanescu C. -21-

22 )2//(12)(

wxwQxs

(8)

3 CONCLUSIONS

The characteristics impedance of some microstrip line configurations were computedand the results met those from the literature. Also the influence of the computation domain onthe surface charge distribution was performed and the results are in good agreement with theanalytical results. It seems that for this kind of geometrical variation, by expanding themicrostrip geometry uniformly after ox and oy the surface charge distribution follows theanalytical one. Other types of variations will be considered as well as multilayered structures.

REFERENCES

[1] Wei, C.,Harrington, R.F., Multiconductor Transmission lines in MultilayeredDielectric Media, IEEE Trans. Microwave Theory Techn., MTT-32 (1984), pp.439-449.

[2] Elsherbeni A.Z. et.al., Minimization of the coupling between a two conductormicrostrip transmission line using finite difference method, Progress in ElectromagneticsResearch, PIER 12, 1-35, 1996.

[3] J.K.Lee, D.Sun, Z.Cendes, Full wave analysis of dielectric wave guides usingvector finite elements, IEEE Trans.Magn., vol.39, Nr.8, pp.1262-1271,August 1991.

[4] K.S.Oh , D.Kusnetov, Capacitance computation in a multilayered dielectricmedium using closed form spatial Green’s functions, IEEE Trans.MTT., vol42, pp.1443-1453, 1994.

[5] Collin R., Foundations for microwave engineering, McGraw-Hill, 1992.[6] E.O.Hammerstaad, Accurate models for microstrip computer-aided design, IEEE

MTT-S Int.Microwave Symp.Dig., pp. 407-409, 1980.[7] V.Urbanavicius, R.Martavicius, Model of the microstrip line with a non-uniform

dielectric, Electronics and electrical engineering, ISSN 1392-1215 2006, Nr.3 (67).[8]Cheng K.K.K., Everard K.A. Accurate formulas for efficient calculation on the

characteristic impedance of microstrip lines, IEEE Trans.on Microwave Theory andTechniques, 1991, vol.MTT-39, No.9, pp.1658-1661.

[9] COMSOL Electromagnetics User’s Guide ver.3.2. www.comsol.com

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 22-27

CLASSICAL POWER SUPPLY SOLLUTIONS FOR LOWPRESSURE MERCURY LAMPS

GABRIEL NICOLAE POPA, IOSIF POPA, SORIN DEACONU

Abstract. The world trend in lighting installations is to change the old incandescentlamps with fluorescent lamps. The paper presents the low-pressure mercury lamps study, whensupply through magnetic ballast are and glow starter for different line voltage and improvingpower factor for these lamps.

Keywords: lamps, fluorescent, low-pressure mercury, supply.

1. INTRODUCTION

Each lighting installation is designed to produce a level of illuminationadequate for those working area. Adequate illumination should be maintained to reduceeyestrain, improve moral, increase safety and increase production.

Today, there are neraly 6000 different lamps being manufacturing in sixcategories: incandescent, fluorescent, mercury vapor, metal halide, high pressuresodium and low pressure sodium. The last five categories can be termed as gasdischarge lamps. Fluorescent and low pressure sodium lamps operate on low pressuregaseous discharge and the mercury vapor, metal halide and high pressure sodiumlamps operate on high-pressure gaseous discharge.

Luminous efficacy [lm/W] measure of the lamp’s ability to convert inputelectric power [W] into output luminous flux [lm].

Electric gas discharge lamps convert electrical energy into light by the kineticenergy of moving electrons, which becomes radiation as a result of collision process.The process is collision excitation of atoms in a gas, the electrons take the lowest

Ph.D. Lecturer eng., Electrotechnical Department, Faculty of EngineeringHunedoara, ‘’POLITEHNICA’’ University of Timişoara, Romania Ph.D. Associate professor eng., Electrotechnical Department, Faculty ofEngineering Hunedoara, ‘’POLITEHNICA’’ University of Timişoara, Romania

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Popa, G.N., Popa, I., Deaconu, S. -23-

energy atomic levels and appear the emission of electromagnetic radiation. Thisradiation is not continious, it is consist in a number of separate spectral lines. Throughdifferent gas, the luminous efficacy can be varied.

Compared with incandescent lamps, gas discharge lamps have the followingadvantages: transforming 20-30% of the electric input into light energy output; therated life is up to 20000 h and the lamp characteristics are maintained up to end of life.Fluorescent lamps are more efficient than incandescent lamps of an equivallentbrightness because more of the energy input is converted into light and less into heat.

Sixty percent of all fluorescent lamps contained 10 mg Hg or less and for therest of lamps contained between 10-100 mg Hg [2].

2. FLUORESCENT LAMPS CHARACTERISTICS

In fig.1 is present the structure of low-pressure mercury lamp.

Fig.1. Low-pressure mercury lamp

It is suppose that the lamp is supply at d.c. voltage.In fig.2.a is u-i characteristics when a lamp is alone oprated from a d.c. voltage

source. The slope of the curve has the impedance:

diduZ (1)

Z is negative that cause problem for operating lamps. The starting voltage Us is higherthan the steady-state operation voltage is needed to estabilish ionization in the gas.After the discharge begins, the operating point of the discharge lie to the right of curveand the electron density ne increases continous in time. The discharge current increaseswithout any regulation and the lamp is destroy.

From these reason the gas discharge lamp can not be directly connected to avoltage source and an impedance must be placed between the lamp and the voltagesource to limit the current [1,3].

In fig.2.b is present the effect of series resistance in stabilizing the currentlamp.

LaRAB UUU (2)

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Classical power supply sollutions for low pressure mercury lamps-24-

Fig.2. U-I lamp characteristics for d.c. power supply: a. without ballast; b. with ballast

The operating point of the lamp is the domain of positive dne/dt increase thecurrent until is reaches the point (Iss, Us). The resistor R helps to estabilish the stableoperating point of the lamp and acts as the ballast.

The resistor R increase power loss and the system efficacy reduces.For a.c. voltage supply, the ballast is inductive or capacitance impedance can

be used to provide current limitation and reduce wearing of the two electrodes andmainteins a longer lamp life.

The gas discharge lamps require an auxiliary apparatus called magnetic balastand glow starter.

Fig.3. Voltage and current lamp when operate at 220 V, 50 Hz

The magnetic ballasts operate in 50 Hz line frequency (fig.3). Every half cycle(10 ms) they re-ignite the lamp and limit the lamp current. The magnetic ballasts arelarge and heavy. The time constant of the lamp is arround 1 ms, the arc extinguisheswhen the voltage is zero and then re-ignited. From these reason, the lamp voltagewaveform has a voltage spike that cause the lamp electrode wearing and the flickeringof the lamp.

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Popa, G.N., Popa, I., Deaconu, S. -25-

3. EXPERIMENTAL RESULT

The electric circuit used in experiments is presented in fig.4. In fig.4: AT –autotransformer, A1, A2, V - MY 64 digital multimeter, W - EL 21 wattmeter, C1 =3.75 F, C2 = 5 F, C3 = 8.75 F, H fluorescent lamp 2x20 W with magnetic ballast L.

Fig.4. Experimental circuit

50

100

150

200

250

300

350

400

450

170 180 190 200 210 220 230

U[V]

P[W]I[mA]S[VA]

a. b.Fig.5. Results for 2x20 W fluorescent lamp with magnetic ballast; Uextinction=150 V, Iextinction=50

mA

50

100

150

200

250

300

200 205 210 215 220 225 230

U[V]

P[W]I[mA]S[VA]

a. b.Fig.6. Results for 2x20 W fluorescent lamp with magnetic ballast with C = 3.75F

R

AT

W

**

220V~ V

A1

C1C2

C3

S1

S

A2

L H

S

I1 I2

1 2

0.5

0.55

0.6

0.65

0.7

0.75

0.8

0.85

0.9

0.95

170 180 190 200 210 220 230

U[V]

cosfi [-]

0.920.93

0.940.95

0.960.97

0.980.99

200 210 220 230

U[V]

cosfi[-]

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Classical power supply sollutions for low pressure mercury lamps-26-

Phase between current and voltage, before power factor compensation is:

RLf2

RXtg L

1

(3)

Phase after power factor compensation must be:

2

22

2 coscos1

tg

; 92,0cos 2 (4)

Capacitance that must be connected to the lamp, to obtain cos2=0,92 is:

212a

tgtgUf2

PC

(5)

50

100

150

200

250

300

200 205 210 215 220 225 230

U[V]

P[W]I[mA]S[VA]

a. b.Fig.7. Results for 2x20 W fluorescent lamp with magnetic ballast with C = 5F

50

100

150

200

250

300

350

400

200 205 210 215 220 225 230

U[V]

P[W]I[mA]S[VA]

a. b.Fig.8. Results for 2x20 W fluorescent lamp with magnetic ballast with C = 8.75F

The current lamp is not sinusoidal and from this reason the current and activepower measure (normal measuring devices) are made with error. In fig.6 the lamp isinductive (XL>XC) and in fig.8 the lamp is capacitive (XL<XC).

0.9550.96

0.9650.97

0.9750.98

0.9850.99

0.995

200 210 220 230

U[V]

cosfi[-]

0.550.570.590.610.630.650.670.690.710.73

200 210 220 230

U[V]

cosfi[-]

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Popa, G.N., Popa, I., Deaconu, S. -27-

50

100

150

200

250

300

350

400

190 200 210 220

U[V]

P[W]I[mA]S[VA]

a. b.Fig.9. Results for 2x20 W fluorescent lamp with magnetic ballast supply through variable

alternating voltage (600W/220 V/50 Hz)

If capacitance for improving power factor is too big (5 or 8,75 F, fig.7,8) thecurrent slow down with the increase the voltage and cause lamp unstable. Theimproving power factor with capacitance cause a lot of current harmonics and the lampperformance decrease. From this reason, before improving power factor the currentmust be filtred with pasive or active filters, and then connect the capacitance. If thefluorescent lamp with magnetic ballast supply through variable alternating voltage(with triac), because of current harmonic, the lamp does not work with capacitance.

4. CONCLUSIONS

The fluorescent lamps operate most efficiency and economically at their ratedvoltages. Operating outside their normal operating range is undesirable. Theundervoltage and overvoltage conditions have negative effects on the life, efficiencyand economy of he life sources.

For fluorescent lamps, line voltages greater than the nominal voltages willshorten lamp and ballast life. Line voltages less than the nominal voltages will alsoshorten lamp life, reduce illumination and may cause uncertain starting. Frequentstarting will shorten lamp life.

Fluorescent lamp high frequency operation (with electronic ballast, instead ofmagnetic ballast and glow starter) results in significant ballast volume and weightreduction and improves the performance of the discharge lamp (save energy and longlife).

REFERENCES

[1] Arsenie D., Iluminat, Litografia Universităţii Tehnice Timişoara, 1995;[2] Gendre M., Two Century of Electric Light Source Innovations, Eindhoven

University of Technology, Holland, 2005;[3] Popa G.N., Popa I., Instalaţii electrice, Editura Mirton, Timişoara, 2005.

0.58

0.6

0.62

0.64

0.66

0.68

0.7

0.72

190 200 210 220

U[V]

cosfi[-]

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 28-33

COAL/PETco*kE CONVERSION LIKE AUXILIARY FUELAT S.C. CARPATCEMENT HOLDING S.A DEVA BRANCH

ARAD SUSANA *, VICTOR ARAD , BOBORA BOGDAN ,MIHAELA BOBORA

Abstract: One of the most important cost driver for cement production price is clinkercost and implicit fuel cost. Due to the fact that the price of traditional fuels has greatly increasedat word level, we need to identify and use other types of fuel. These new identified fuels couldbe used to replace, completely or partially, the traditional fuels natural gas and fuel oil. In thepaper it will be presented the use in the future of the coal or petco*ke like auxiliary fuel and thegrinding in a mill of coal designed will be researched. In this paper, different scenario the use inthe future coal or petco*ke will be researched.

Keywords: cement plant, auxiliary fuel, coal mill, energy balance,

1. INTRODUCTION

The cement plant situated near Deva town is one of the three cement plantsthat belong to the HeidelbergCement Group in Romania. Since 2004, this cement plant,along with the cement plants of Fieni and Bicaz form together the company calledCarpatcement Holding S.A. HeidelbergCement has been present in Romania since 1998.They are the market leader in Romania and one of the largest German investors in this country.

The Deva Cement Plant was built among 1972 – 1978 and it wascommissioned in 1977 – 1978. It was projected to have two production lines of 1.9millions tones/year capacity. In 1990 The Cement Plant changed its name and becamea joint stock company called S.C. CASIAL S.A. DEVA. In 2000 HeidelbergCementbecame the main shareholder and started an important investment and restructuringprogram, aiming at:

* Assoc. professor at University of Petrosani ProfessorPhD at University of Petrosani Engineer at S.C. CARPATCEMENT HOLDING S.A -Sucursala Deva

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Susana A., Arad V., Bogdan B., Bobora M. -29-

productivity increase improvement of products quality modernization of the technological flow improvement of environmental quality

The company’s development policy is materialized by reinvestment of theprofit in modernization and technology. During the last years at Deva Cement Plantthere were invested much money in replacement and modernization of the equipmentson one side, and in environmental protection also.

2. GENERAL PROBLEMS

The cement is produced through the following steps: (i) extraction, processingand storage of the raw materials; (ii) grinding of the meal (limestone, clay and pyrite)in the raw mill where the mixture is proportioned according to the fabrication recipe(75-79% limestone, 20-22% clay and 1-3% pyrite); (iii) clinker fabrication, by burningthe raw meal in the clinker kiln; (iv) cement fabrication, by grinding of the clinker inthe cement mills together with the grinding additives (slag, gypsum, fly ash) accordingto the cement type we want to obtain; (v) storage of the cement; (vi) dispatching.

The forecast for the cement market is to increase the cement sales and theclinker production from 377 ths t/y to 550 ths t/y for the next 15 years. The productioncost must be the lowest possible according to the raw material and energy costs.

One of the most important cost’ driver for cement production price is clinkercost and implicit the fuel cost. For clinker fabrication, the rotary kiln uses at this timethe natural gas as main fuel. The clinker kiln burner can use both gaseous fuel, andliquid and solid. The used alternative fuels are old tyre and SAF replacing about 12%from the natural gas.

The electrical energy consumed in the cement making process from the totalused, is presented in Figure 1,where 5% is used in theexcavation crushing andhom*ogenization of raw material,38% kWh/t is the energyconsumption for clinkergrinding, 22% for heating andcooking, 24% for farine grindingand the rest for other operations.

Due to the fact that theprice of traditional fuels hasgreatly increased at word level,we need to identify and use othertypes of fuel. These newidentified fuels could be used toreplace, completely or partially,the traditional fuels natural gasand fuel oil. The possible

Fig.1. The electrical energy consumption graph

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Coal/petco*ke conversion like auxiliary fuel at S.C. carpatcement holding s.aDeva branch

-30-

auxiliary fuels to be used at this time can only substitute up, to about 20% of the basicfuel-assumption for further calculation.

3. THE TECHNICAL AND THEORETICAL ASPECTS

The savings achieved through the replacement of natural gas, which is at thistime the basic fuel, by coal have been calculated considering replacement of naturalgas in proportion of 99%. The alternative fuel equipment for the burning of the solidalternative fuels (ECO-Fuel) will be designed like in Figure 2.

Fig.2. Technological system of the Eco Fuel equipment

In this technological system the most important equipments are: vertical millfor grinding coal, transport and storage system, electrical equipment, dust silos, dosingsystem, deducting unit, air compressor plant, hot gas fan and inertization system. Theflow chart of technological system is shown in Figure 3.

Fig.3. The coal mill flow chart

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Susana A., Arad V., Bogdan B., Bobora M. -31-

The coal mill flow sheet is illustrated in principles in Fig. 4. The coal is fed tothe coal mill through the inlet pipe. The coal is pulverized on the rotating grindingtable by the rollers. The coal mill is a new type medium speed mill, adopting advancedgrinding technology and basing on technology of vertical mill. This equipment isconsist of main engine, speed reducer, casing, grinding device, separator, output,powder-falling pipe, piping device, loading device, controlling box, sealing device, etc.The peripheral equipments are bucket elevator, feeder, storage bin, coal mill filter,electric control cabinet, etc

Fig.4. Coal mill flow sheet

The temperature of the primary air is used to control the temperature in thecoal mill at the classifier. The temperature controller is often required to keep

temperature constant at 100◦C inorder to evaporate the moisturecontent in the coal. A coal mill isa harsh environment in which itis difficult to performmeasurements; this means thatall the variables are notmeasurable. E.g. the actual coalflows in and out of the coal millare not measurable. However, theprimary air flow and temperatureare, as well as the temperature at

the classifier.

Fig.5. An illustration of energy balance in the coalmill

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Coal/petco*ke conversion like auxiliary fuel at S.C. carpatcement holding s.aDeva branch

-32-

A simple energy balance model of the coal mill is illustrated in Fig. 5. In thismodel the coal mill is seen as one body with the mass mm, in which T is thetemperature in the mill, Qair is the energy in the primary air flow, Pmotor denotes thepower delivered by the grinding table, Qcoal is the energy in the coal flow, and Qmoistureis the energy in the coal moisture.

The energy balance is given by (1).

tPtQtQtQtTCm motormoisturecoalairm (1)

Electrical equipment is the major factor in the powering and control of cementplants. The feeding system of the kiln with conventional fuel and the alternative fuelare also monitored. The CemScaner system checks the kiln (shield) temperatures. Theregulation of temperature is done in real time and in the same time the safe operation ofthe equipment is assured.

We ensure good quality and durability of the whole machine, small size, lightweight, small space, low energy consumption, long life of worn out parts, etc.

4. CONCLUSIONS

According to the specific situation of the Deva cement plant, the followingissues have been considered:

- fuel proportion; natural gas 1%, old tyre 10%, SAF 9% and coal 80%,- imported coal through Constanta port,- calorific power assumed; gas 33.7Gj/000 m3 and coal 25.08 Gj/t,- utilization of existing rail road discharge area for rough coal.

At the coal mill, the grinding capacity of 18t/h is enough for the new burning capacityof plant used.

Target intention:- reduction of the specific cost for clinker production- emission under the accepted level of the European law- minimum invested amount- high level of work safety- high level of technology

In the analyses done to now, there have been considered various versionsregarding the storage and grinding of the raw coal. There have also been analyzedversions of grinding in ball mils or vertical mills. There has been chosen as optimumversion the vertical mill, considering the following:

Arrangement of a large-size raw coal silo, Creation of higher capacities for grinded coal storage and implicitly of

loading and unloading equipments for this, Increase of explosion or fire this, Establishing a dependency on the transport system, Additional transport costs, Impossibility of providing the drying air from the hot air recovered.

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Susana A., Arad V., Bogdan B., Bobora M. -33-

Considering the above mentioned, the version with a vertical mill of 15t/h ineach of two cement plants has been chosen.

The vertical mill of 15t/h proposed has the following advantages: low grinding specific energy consumption, possibility of using heat exchanger waste gases for heat recovery reduction of explosion hazard due to the low O2 content in these gases independence of plants operation low grinded coal transport costs.

REFERENCES

[1] Arad, S., Arad, V., Bobora, B.. Cement Production at Deva Cement Factory fromRomania, 23 nd ISARC2006 Tokio, Japan, Proceedings CD, C8 Plant and Dismantling IAARCPubl. Int. Assoc.Aut. Rob.Constr., pg. 806- 809 ISBN 4-9902717-1-8,http://www.iaarc.org/external/isarc_proceedings, 2006

[2] Arad, S.. Tehnologii pentru “cărbune curat” clean coal technology, o provocarepentru cercetare în context european. Revista Minelor, 2/2007, ISSN 1220-2053, 2007

[3] Arad, S., Assesment Environmental Impact from S C Casial SA Deva, M.ScDissertation Thesis, University of Petroşani, Petrosani; 2001

[4] Rees, N.W. and F.Q. Fan. Modelling and control of pulverised fuel coal mills. In:Thermal power plant simulation and control (D. Flynn, Ed.). first ed. Institution of ElectricalEngineers, 2003

[5] Conversie pe carbune/cocs de petrol la S.C. CARPATCEMENT HOLDING S.A.,Contract cercetare C665/2006, CEPROCIM S.A. Consulting and Engineering Devision, 2006

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 34-36

COAL-MAIN BASIC RESOURCE IN THE ENERGYPRODUCTION

LIVIU BLANARU , SORIN CURELEANU ,ANGHEL STOICHITOIU

Abstract. This study is analyzing the trend of the electric energy production oncoal-based power plants.

Key words: lignite, energy, power

1. INTRODUCTION

Nowadays a modern industry, in evolution, cannot survive without an efficientenergetic sector able to provide and sustain with energy various economical branchesand the social development. Due to the economical, political, social and ecologicalimpact the energy problem has became the major imperative of the global economy,preoccupation of all nations being targeted on this matter on the higher degree.

Increasing of population and the diminishing of the economical differencebetween the developed and third world countries is generating the global ascendingrequest of primary energy. In this situation, more, not less energy can solve the globalproblems, especially the social ones, as true as today, about two billions peoples has noaccess at the so called – commercial energy. Under economical and environmentpurpose, there is a continuous and sustained request for the improvement of energeticefficiency, by researching and development of some new energetic technologiesbecause the generation and consumption of energy is a significant indicator ofcivilization degree of any nation, being seldom used in the world hierarchy.

Ph D. Sudent Eng. Professor PhD .eng. University of Petrosani

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Blanaru, L., Cureleanu, S., Stoichitoiu, A. -35-

2. COAL – MAIN PRIMARY RESOURCE ON THE WORLD’SENERGY GENERATION

Demographical prognosis are showing an increase from 6 billions to about 8billions by the year 2010. The Energy World Council is estimating that the energyneeds will be 50% higher until 2020. Assuming this prognosis with precaution, we areconsidering that all countries will reach the developed countries energetically highefficiency level. So in the future, fossil oil and energetic coal together with natural gas willremain the most important energetic resource. The contribution of non-conventionalresources – wind, sun, water and biomass – will increase in absolute value, but it willplay a minor role in the future. A major shift that will overcome the fossil resources, according to the lastWorld Energy Council will be possible not sooner than the second half of this centuryand only if the necessary actions will start on the nearby future. In the mean time, the prognosis implies the fact that all the energetic policyoptions are requesting the assurance of the global energetic resources. Therefore, the coal and nuclear fuel together with the water will form the baseof electric power generation and the future increase of energy request will lead to aglobal increase of coal production. The coal will contribute with over 50% on thepower generation process and will still be the primordial energetic resource all over theworld.

The coal market will run through some structural changes in the future in thesame measure that the third world countries developing rates will overcome theeconomically advanced countries.

For all the countries, the coal represents an attractive economic resource,especially the lignite. Nowadays the European mining industry capacity has adecreasing trend. Asian, Australian, and Latin American mining industry has asensitive growth. In these circ*mstances, is explained the higher quantity of Europeancoal import especially by the continuous decline of the pit coal production in U. E.countries, from 105 Mt. in 2000, to 70 Mt. in 2020.

The situation of global consumption of fuel has the following structure (fig. 1):

1

2

3

4

5

Fig.1

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Coal-main basic resource in the energy production-36-

1 – Oil 38%; 2 – coal 26%; 3 – natural gas 24%; 4 – nuclear 6%; 5 - regenerative6%.

In the European Union, we have the consumption as shown (fig. 2):

12345

Fig. 2

1 - Oil 40%; 2 – coal 15%; 3 – natural gas 24%; 4 – nuclear 15%; 5 –regenerative 6%.

The enlargement of the European Union is bringing the “coal issue” in politicaldebates about redefining of the solid fuel as a long – term energy primary resource.

For implementing the 1997 Kyoto Protocol Resolutions, is necessary to developthe environment protection policies, but without discrimination against the coal.

On the Lignite and Pit Coal European Association, where Romania is alsoaffiliated, the coal power generation Clean Technologies debates has a huge innovationpotential. Today, coal –based power plants can touch efficiency levels of 40% forlignite and 45% for pit coal, so the priority is to create the best conditions forimprovement of the power generating process, especially reducing the CO2 emissionsby investing in modern technologies.

3. CONCLUSIONS

Therefore, it is obvious that the coal will have a great influence on powergeneration and any country development. In the future, will be enforced an activepower saving policy, by revising all technologies implying high-energy consumption.

REFERENCES

[1] European AQUIS Requests;[2] CESCO Consulting Committee Declaration about the role of coal in the XXI

century Europe (July 1999);[3] EUROCOAL Report – PATROMIN Magazine;[4] LEGEA 3 / 2001 – Kyoto Protocol ratification on the United Nation Convention

about Environment and Climate Altering.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 37-42

COMPARATIVE STUDY ON THE TYPES OF PROTECTIONFOR THE ELECTRIC APPARATUS INTENDED FOR USE

IN EXPLOSIVE ATMOSPHERES

SORIN BURIAN*, JEANA IONESCU**, MARIUS DARIE,LUCIAN MOLDOVAN

Abstract: This paper shows the important conditions involved in the selection of aprotective solution on the apparatus intended for use in areas with hazard of explosiveatmospheres. Then, in relation to the operation of the apparatus, one can derive theeconomically eligible variants for the protection of the apparatus intended for use in areas withhazard of explosive atmospheres.

Consequently, this paper intends to be the precursor of a practical guide for theselection and implementation of different types of protection on the apparatus intended for usein areas with hazard of explosive atmospheres, both for designers and manufactures.

Key words: types of protection, comparison

1. INTRODUCTION

Generally speaking, designing and manufacturing of electrical apparatusbenefits lately of special advantages, offered by the appearance of new components(integrated) and technologies, which makes the time that passes from enouncing theidea until physical achievement of the apparatus to be relatively short, and the processinvolved by that to be a monotonous one.

But, when the problem of adapting this apparatus to the particularities of usethem in atmospheres with explosion hazard, the above mentioned process isconsiderably slowed, not by the missing of consecrated components for such processes,but especially by the leak of experience and knowledge regarding the standard

* PhD.Student Eng. at the INSEMEX Petroşani** Ph.D.Eng. at the INSEMEX Petroşani

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Comparative study on the types of protection for the electric apparatusintended for use in explosive atmospheres-38-

requirements, referring to construction and using of electrical apparatus in areas withhazard of explosive atmosphere.

This state of fact is negatively more emphatic because, lately, the groups ofstandards from this field in the world, Europe and Romania have a peculiar dynamiccaused especially by the hom*ogenisation and generalisation process opened andmaintained by IEC.

Considering the above mentioned, this paper proposes to help the designers andmanufacturers of electric apparatus designed to be used in areas with hazard ofexplosive atmosphere by displaying a comparative study regarding definitive aspectsfor apliable types of protection.

2. CLASSIFICATION OF EXPLOSIVE ATMOSPHERES. HAZARD OFEXPLOSION

To have an explosion three factors must exist at the same time and in the samespace. These factors form the triangle of explosion hazard (fig. .1):

Presence of flammable substances in form of gases, vapours, mists;Presence of oxidant substance, air or oxygen, as support for violent combustion

(explosion);Presence of ignition source in form of sparks and hot surfaces.

Flammable substances :

“f lammable gases and powders and

which are in cri tical concentration”

Ignition sources :

- Hot surfaces

- Flames and hot gases

- Mechanical sparks

- Electrical wiring

- Static electrici ty

- Lightning, ul trasounds…

Oxygen sources :

- air (21% oxygen)

- pure oxygen

- oxidant substances (potassium

permanganate etc)

Fig.1 Ignition triangle

3. TYPES OF PROTECTION – SHORT DESCRIPTION

The type of protection represents a technical solution by which at least one ofthe factors represented in the ignition triangle is removed or limited below the criticalvalues.

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Burian S., Jeana I., Marius D., Lucian M. -39-

Flameproof enclosureRepresents a type of protection that permits to have an explosion inside

equipment, but which by the characteristic elements for this type of protection(flameproof joints) makes that explosion not to be transmitted to the explosiveatmosphere that surrounds the enclosure. Generally, it is used for power apparatus, butcan also be used for other kinds of apparatus.

Increased safetyA type of protection which consists in applying some supplementary measures

to avoid producing electric arcs, sparks, or excessive temperatures on any part ofelectrical apparatus (internal or external). These phenomena are not produced even innormal operation.

Non-incendiveRepresents a type of protection which is based on the other types of protection

principles, but it contains less rigorous prescriptions than those contained in thestandards for types of protection eligible in zone 1. This type of protection is onlyeligible for zone 2.

Intrinsic safetyRepresents a type of protection by which electrical parameters are safely

limited so than the ignition source to be limited to a non hazardous value. This is also aconsecrated type of protection for “low currents” applications.

EncapsulationIt is a type of protection by which the small kind apparatus is separated from

hazardous atmosphere by moulding / enclosing in compound.PressurizationIt’s a type of protection by which the apparatus (often) in normal construction

is placed inside an enclosure in which a protective gas is circulated so as in the innerspace the explosive gas concentration is much lower than the lower explosive limit(LEL). Pressurization remains the only available solution for high frame sizesapparatus.

4. COMPARATIVE STUDY FOR THE TYPES OF PROTECTION

AgeThe types of protection showed up like technical punctual solutions of protect

the electrical equipment for use in surface or underground areas which involves theoccurrence of explosive atmospheres.

The oldest types of protection are flameproof enclosure “d”, which appeared atthe end of the 19th century, oil immersion “o”, sand filling “q”, pressurization “p” andintrinsic safety “i” which appeared around 1930, their use and standards occurrence forthem being noticed even from the first half of the 20th century.

Then after the second half of the past century started to be use the types ofprotection increased safety “e” (standardized in 1969) and encapsulation “m”(standardized in 1988).

At the end of the 20th century the types of protection oil immersion (o) andsand (powder) filling (q) were less and less used and leaved the place for a composite

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Comparative study on the types of protection for the electric apparatusintended for use in explosive atmospheres-40-

type of protection which has some “soften” requirements regarding the type ofprotection. This type of protection was called non-incendive (n) and has a few subtypeslike nA, nL, nC, nR.

Incidence on equipmentsRegarding the usage frequency, it is relatively hard to do a documented

(objective) study especially because the information regarding this subject are disparateand the study of certified / tested articles in INSEMEX Petroşani offers a unilateralimage of this issue.

Based on authors experience the following conclusions can be exposed: The type of protection flameproof enclosure (d) is one of the most used

types of protection for electrical apparatus operating in areas with hazard of explosiveatmosphere as well for the power part and low current part. The tendency remarkedregarding the use of this type of protection it’s a low decreasing one especially becausethe appearance and use of other types of protection.

Increased safety (e), pressurization (p), non-incendive (nA and nL)shows an increasing tendency regarding the usage owned especially to the less rigorousrequirements comparative with the type of protection flameproof enclosure “d” andintrinsic safety.

Intrinsic safety (i) keeps and consolidates its position being the directapplicable solution for low currents apparatus and systems.

Encapsulation (m) has a low incidence, but the tendency is to slowlyincrease.

Oil immersion (o) and powder (sand) filling (q) are types of protectionpractically unused.

Eligibility for hazardous zonesAll types of protection are eligible for Zone 1, except the type of protection

non-incendive (n) which is eligible only for Zone 2. Zone 0 necessitates special considerations, and intrinsic safety – level of

protection ia, and encapsulation level of protection ma are (for the moment) the onlytypes of protection eligible to use in such areas.

Requirements regarding mechanical protectionThe requirements regarding normal degree of protection of enclosures varies

from minimum to medium as a function of the types of protection.

Type of protection (symbol) Degree of protectionIntrinsic safety (i) IP 20Pressurization (p) IP 40Increased safety (e) IP 44 (insulated conductive live parts)

IP 54 (bare conductive live parts)IP 20 (rotating electrical machinesinstalled in clean environments andregularly supervised by trained personnel)

Non-incendiv IP 54IP 20 (rotating electrical machinesinstalled in clean environments andregularly supervised by trained personnel)

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Burian S., Jeana I., Marius D., Lucian M. -41-

Creepage distances and clearancesFor the comparative study of those distances the clearance was chosen having

as reference the value imposed by the type of protection increased safety (e).For accomplishing the comparison the downgrade of the regression line was

used.

y = 0,4444xR2 = 0,9467

y = 0,5939x - 0,3098R2 = 0,9861

y = 0,6527x + 1,3547R2 = 0,908

2

4

6

8

10

12

14

16

18

0 5 10 15 20

inAnLLinear (nL)Linear (nA)Linear (i)

Fig.2 Clearance (mm) at different voltages for the types of protection i, nA, nL function of theclearance (mm) imposed by the type of protection increased safety (e)

Taking into account the above mentioned criteria it can say that the type ofprotection increased safety prescribes the largest clearances, being followed by the typeof protection intrinsic safety, non-incendive nA and respectively nL, at approximatelyhalf values.

Maximum voltageThe maximum admitted voltage values for the types of protection are given in

the bellow table.

Type of protection (symbol) Maximum voltage [kV]Intrinsic safety (i) 1,575Non-incendive (nL) 15,6Encapsulation (m) 11Pressurization (p) 11Increased safety (e) 11Flameproof enclosure (d) -Non-incendive (nA) 15,6

Technical protection solutionTaking into account the protection strategy mentioned in the beginning of the

paper four technical solution of protection can be stated, like this: segregation – separates the ignition source (apparatus) from the explosive

atmosphere. The types of protection pressurization (p), encapsulation (m),

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Comparative study on the types of protection for the electric apparatusintended for use in explosive atmospheres-42-

oil immersion (o), powder filling (q) are based on this technical protectionsolution; eliminates the source of ignition. The types of protection increased safety

(e) and non-incendive (nA) are based on this technical protection solution; limitates the energy of ignition source. The types of protection intrinsic

safety (i) and non-incendive (nL) are based on this technical protectionsolution; limitates the deflagration expansion zone. The type of protection

flameproof enclosure (d) is based on this technical protection solution.

5. CONCLUSIONS

By the study made, in this paper were brought out the aspects that recommendsvarious types of protection for one specific application (apparatus).

REFERENCES

[1]. SR EN 60079-14:2004, Electrical apparatus for explosive gas atmospheres. Part14: Electrical installations in hazardous areas (other than mines)

[2]. SR EN 60079-0:2005, Electrical apparatus for explosive gas atmospheres. Part 0:General requirements

[3]. R EN 60079-1:2005, Electrical apparatus for explosive gas atmospheres. Part 1:Flameproof enclosures “d”

[4]. SR EN 60079-2:2005, Electrical apparatus for explosive gas atmospheres. Part 2:Pressurized enclosures “p”

[5]. SR EN 50017:2003, Electrical apparatus for potentially explosive atmospheres.Powder-filling “q”

[6]. SR EN 50015:2003, Electrical apparatus for potentially explosive atmospheres.Part 6: Oil-immersion “o”

[7]. SR EN 60079-7:2004, Electrical apparatus for explosive gas atmospheres. Part 7:Increased safety “e”

[8]. SR EN 60079-10:2004, Electrical apparatus for explosive gas atmospheres. Part10: Classification of hazardous areas

[9]. SR EN 50020:2003, Electrical apparatus for potentially explosive atmospheres.Intrinsic safety “i”

[10]. SR EN 60079-15:2004, Electrical apparatus for explosive gas atmospheres. Part15: Type of protection “n”

[11]. SR EN 60079-18:2004, Electrical apparatus for explosive gas atmospheres. Part18: Encapsulation “m

[12]. SR EN 60079-26:2005, Electrical apparatus for explosive gas atmospheres. Part26: Special requirements for construction and test of electrical apparatus for use in zone “0”

[13]. S. Burian, J. Ionescu, M. Darie, L. Moldovan, ş.a., Aparatură tehnică pentrumedii potenţial explozive. Grupa II, Ediţia a II-a revizuită, Ed. Europrint Oradea, 2006, ISBN973-7735-32-3

[14]. R.STAHL Schaltgeräte GmbH, Ex-Magazine 32/2006-00-en-08/2006, ID-Nr.00 006 24 76 0 S, ISSN 0176-0920, pg. 60-69

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 43-48

CONDITIONS FOR INTERCONNECTING INTRINSICSAFETY CIRCUITS SUPPLIED BY LINEAR AND NON-

LINEAR SOURCES INTENDED FOR USE INPOTENTIALLY EXPLOSIVE ATMOSPHERES

TIBERIU CSASZAR*, SORIN BURIAN, MARIUS DARIE

Abstract: The design and use of non-linear sources need solid knowledge and a richexperience gained in the use of electric apparatus intended for use in potentially explosiveatmospheres. Consequently, after a test house checks the safety level that corresponds to asupply source with intrinsic safety type of protection, the design of a system with intrinsicsafety type of protection is then allowed, but any special condition regarding this type of systemshall be considered.

When analyzing the safety level for a combination of supply sources with non-linearoutputs, then the interaction of the two circuits may lead to a significant increase of energydissipation on the regulating components of the circuit, aspect that shall be considered duringthe evaluation.

Key words: intrinsic safety, non-linear sources

1. INTRODUCTION

This topic has been under analysis for a long period of time and it is still understudy. This paper represents the common opinion of several test houses expert intesting of equipment intended for use in potentially explosive atmospheres and coversthe latest information in this field.

The design and use of non-linear sources need solid knowledge and access tosuitable testing facilities. After the test laboratory checks out the safety level of asystem with intrinsic safety type of protection, it is allowed to design a system withintrinsic safety type of protection but all special conditions with respect to such asystem shall be clearly stated and valuated.

* PhD. Student Eng at the INSEMEX PETROŞANI Ph.D.Eng. at the INSEMEX PETROŞANI

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Conditions for interconnecting intrinsic safety circuits supplied by linear and non-linear sources intended for use in potentially explosive atmospheres

-44-

When analyzing the safety level for a combination of supply sources with non-linear outputs, then the interaction of the two circuits may lead to a significant increaseof energy dissipation on the regulating components of the circuit, aspect that shall beconsidered during the evaluation.

The installation regulations stated by the specific standards allow that theoperator in charge with the hazardous area combines by interconnecting severalcircuits with intrinsic safety. This aspect also includes the situation when there are usedseveral “associated apparatus” (i.e. active in normal operation or in state of failure).When this thing is done, it is no longer necessary to involve a test house whether theintrinsic safety of the interconnection is checked out by calculation or by tests.

It is easy to evaluate interconnection of resistive circuits by means ofcalculation whether the involved sources have an internal linear resistance as shown inFig. 1 Hence the limit ignition curves form the specific standard are being used for thissituation for the intrinsic safety circuits (SR EN 50020).

But the problem gets complicated when the technical equipment is supplied bytwo or several sources. In this case the evaluation should consider the possibility of anaccidental connection of the two sources. The first stage involves the evaluation of theview maximum values for current and voltage, which represent the result of thecombination of the associated apparatus.

Uo

+

U

IR

UUo

R

Io I

a) Circuit with linear characteristics

+

UQ Uo U

IR

Uo

UQ

U

R

Io I

b) Circuit with trapezoidal characteristics

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Csaszar, T., Burian, S., Darie, M. -45-

+

UoU

I

Ik

U

Uo

Io I

c) Circuit with rectangular characteristics

Fig. 1 Equivalent circuit and the output characteristics of resistive circuits

Whether the associated apparatus is combined as shown in Fig. 2 case a), itresults a serial connection. In this situation the maximum values of idle voltages, U0, ofeach subassembly are summed up and there shall be selected the maximum value of theshort-circuit currents, I0, of subassemblies. If the layout is case c) (Fig.2), then we havea parallel connection, it results a summation of the short-circuit currents and there shallbe selected the highest value of the idle voltage.

Even if it is not clearly defined the connecting manner of apparatus withrespect to polarity (Fig. 2, case c)), then we may have a serial or a parallel connectiondepending on the fault condition considered, for this situation both the summation ofvoltage and of current shall be considered for both cases, but separately. Thecalculation shall consider the most unfavourable values.

+

+ – + –

2 UU

Uo1 Uo2

I

1

a) Serial connection with the summation of voltages

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Conditions for interconnecting intrinsic safety circuits supplied by linear and non-linear sources intended for use in potentially explosive atmospheres

-46-

Io1 Io2

Uo1 Uo2

+

I

I

1

U

+ – + –

b) Parallel connection with the summation of currents

Io1 Io2

+

I

I

1

U

+ – + –

+

U

c) Serial or parallel connection with the summation of voltage and current

Fig. 2 Summation of the current and /or voltage for different interconnections

After determining the new maximum values for current and voltage, theintrinsic safety of the mixed circuits shall be checked out with the help of the ignitionlimit curves stated by SR EN 50020; there shall also be considered the safetycoefficient for the resistive circuit and it is compulsory to determine the new maximumadmitted values of the external inductance L0 and the external capacitance C0.Nevertheless, such an approach cannot cover all the situations possible with respect to

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Csaszar, T., Burian, S., Darie, M. -47-

safeness, such as when two or several active sources from inside a circuit display non-liniar characteristics, so the evaluation based only on the idle voltages and short-circuitcurrents is not enough.

Practical applications use mostly “trapezoidal sources” (see Fig. 1, case b)),often with rectangular output characteristics (see Fig. 1, case c)) if one uses currentlimitation electronic devices. The ignition limit curves (SR EN 50020) cannot be usedfor such circuits; the circuit has to be considered vs. one of the above-mentionedpatterns for defining the intrinsic safety parameters of individual circuits or of theassociated apparatus.

For the evaluation of intrinsic safe active circuits, both the internal resistanceand the voltage of the source shall have to be known. For the simplest situation, thesource can be characterized by two electrical values (constants), either voltage U0 orthe internal resistance RI or U0 and the short-circuit current I0 (see Fig. 1, case a)). U0and I0 are the maximum values which can occur in the fault condition stated by thespecific standard for the evaluation of intrinsic safe circuits (SR EN 50020).Consequently, we can take into consideration, for example, a battery equipped with anexternal resistor for current limitation with no constant internal resistance. Similarly,the voltage of the source shall change depending on the charging level. For studyingthe behaviour of these circuits in practical applications, they are being represented bytheir simplest equivalent circuits which obviously shall have to be the least capable toignite compared to the real circuit. For the above said battery, the maximum valuecorresponding to the open circuit shall be considered for U0.

Also, the non-linear circuits can be divided into two basic types shown in Fig1-case b) and case c). Thus, the source with the trapezoidal characteristic (Fig. 1, caseb)) is made of a voltage supply source, a resistance and additional components forlimitation of voltage (for ex. Zenner diodes) and terminals. For the situation shown inFig. 1, case c), the rectangular characteristics has the current limited by an electroniccurrent regulator.

In compliance with the aspect said above, one may say that the availablemaximum power of a voltage supply source with the characteristics as the one shownin Fig. 1- case a) is:

Pmax = ¼ U0 I0 (1)

And for the trapezoidal characteristics (according to Fig. 1, case b), is:

Pmax = ¼ UQ I0 (for U0 > ½ Uq), or (2)Pmax = U0 (UQ – U0)/R (for U0 ½ UQ) (3)

But for a full electrical type description of the source there are necessary twoparameters for the linear and rectangular characteristics and three parameters for thetrapezoidal characteristics (Table 1).

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Conditions for interconnecting intrinsic safety circuits supplied by linear and non-linear sources intended for use in potentially explosive atmospheres

-48-

Table 1 Necessary parameters for describing the output characteristics

Usually, the stated values are as it follows: idle voltage (hereinwith called U0),the short-circuit current (hereinwith called I0) and the maximum available power P0.There is sometimes possible to determine the type of the characteristics even fromthese values.

Nevertheless, in certain circ*mstances even if the values of power, current andvoltage are given, these data are not concluded for a test house because the maximpower is given for the stationary regime (the heating effect of the components that havebeen subsequently connected) and the values of current and voltage for the dynamicregime (ignition by sparks). Whether there are doubts, it is necessary to check outwhich of the characteristics shall be taken as basis for interconnection, with respect tothe evaluation to ignition by spark. Consequently, for the trapezoidal characteristics,the information given by the manufacturer is not enough to determine thecharacteristics because the third parameter is missing (see Table 1), i.e. either UQ or R.

At the end, one can conclude that a certification documentation shall also haveto state the characteristics of non-linear circuits involved in the construction of aintrinsic safety system.

REFERENCES

[1] SR EN 50020:2003, Electrical apparatus for potentially explosive atmospheres.Intrinsic safety “i”

[2] SR EN 60079-25:2006, Electrical apparatus for potentially explosive atmospheres.Systems with intrinsic safety.

Characteristic Necessary parameters

Linear, Fig. 1 a) U0, I0 or U0, R

Trapezoidal, Fig. 1 b) U0, UQ, R or U0, R, I0 or U0, UQ , I0

Rectangular, Fig. 1 c) U0, I0

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 49-54

CONSIDERATION VIEWING THE OPTIMALDIMENSIONING OF THE MAINTENANCE TEAM FROM

THERMO-ELECTRIC POWER PLANTS

MILTIADE CÂRLAN, HORIA GOIA, SIMONA DZIŢAC **

Abstract: Viewing the optimal structure of the maintenance team, the problem of itsdimensioning is very important; in the paper, the proposed optimal criterion is the “maximalengaged degree” of the members. The paper contains general considerations viewing theoptimal component of the maintenance team, presentation of a statistical method – the leastsquares method, adapted to maximize the engage rate of the team, accompanied with a caseanalyze.

Key words: maintenance, engaged degree, work team, thermoelectric plant, statisticsample

1. CONSIDERATIONS VIEWING THE STABILIZING THEOPTIMAL COMPONENT OF OPERATIONAL EQUIPMENT INMAINTENANCE ACTIVITIES

The optimal structure of the maintenance team follows a double scope: it mustdimension for the optimal dimensioning of the work, and on the other part, founds itsoptimal number. For both aspects of the problem, the decisional factor must havecriteria of optimal performance, in the selection of mathematical model but in theobtained efficiency too.

The proposed optimal criteria for the solution of the problems are the maximalengage degree of the team’s member. The engaged degree of a member from the team(maintenance team) is expressed by the relation:

Professor PhD University of Oradea** Eng. PhD Student University of Oradea

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Consideration viewing the optimal dimensioning of the maintenanceteam from thermo-electric power plants

-50-

100MMG e

o (1) where:

oG - engaged grade of the team’s members [-]%;

eM - average number of effective producing staffs (from the productionprocess analyst);

mJm

MM J

e

e

J

,1,

(2)

where:JeM - is the number of executants, observed by the analyst in the m moments of

the days,M – is the number of available staffs from the team

To stabilize of the moments and days when the measurements are performed isused the technique of the Monte Carlo simulation method.Relation (1) has sense only when the executant’s qualification level, the workplaceslogistic for all period of the information collection matches with the requirements ofthe work.Under these conditions, stabilization of a function of dependence MfGop imposes the fulfilling of the following restrictions:

0lim/

0lim/0

oM

om

Gb

Ga (3)

To evaluate of the staffs engaged grade is proposed the following relation:

McMo eAeG 1 (4)

where: A, C represents the regressions coefficients of the function MfGop .Expression (4) satisfies the restriction (3) and represents a point of extreme

(the abscissa of it’s the optimal number of staff).

ccM

dMdG

optimo 1ln0

(5)

Also, the grade of staff engage offers a modality to structure optimal the equipment ofthe maintenance – fig.1. In this fig oZ signs the optimal number of staffs:

supinf , ooo MMZ (6)

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Cârlan, M., Goia, H., Dziţac, S. -51-

Fig. 1. - MfG 0 function graph

To determine the regression coefficient A, c (from relation 4) may be realized throughmany methods, but in this paper we will use the least square method.

2. THE METHOD OF THE LEAST SQUARE METHOD

Let it be Mi the component number of a little group andi

G0 the values ofengaged grade of the group components, table 1.

Table 1. Number of components and the engaged values of the components of groupMi - executants M1 M2 ......................... Mk .................. Mn

i0G [%] 10G 20G .........................k0G ..................

n0G

In the figure 1 are presented the points and results that there is a tendency toform a “group” for a certain shape, the geometrical position of the points.

In concordance with the least square method, the sum of the deviation pointsresulted from the observation, viewing the points located on the regression curve, mustbe minim.This criterion, leads to the regression coefficients evaluation of the function of thegraph.

Fig. 2 - Function G0=f(M); „positioning” of the couples AK (MK,K

G0 )

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Consideration viewing the optimal dimensioning of the maintenanceteam from thermo-electric power plants

-52-

The proposed relation 4 for the applying of this method satisfies the followingrestriction set:

max0

00

0lim

0lim

GMc

Gb

Ga

optim

M

M

(7)

Results that for dimensioning of a work team, the optimal criterion is the maximalengaged grade:

max0GM optim (8)

From the condition: 00 dMdG

is deduced:

ccM optim

1ln (9)

To calculate the regression coefficient, it must take into account the criterion:

2

00~

iii

GGS minim , 20 1

i

McM i

ieAeGS minim (10)

with:i

G0 - are the observed values of the engaged grade of a person Mi;

iG~0 - values of the engaged grade established by the regression relations.

Linearizing the relation, results:

0ln1lnln GecMA M (11)

With the conditions (12)

0cS,0

AS

(12)

There is obtaining the following system of linear equation (13):

i i i i

Miiii

i i i

Mi

ii

ii

eMGMMcMA

eGMcAn

1lnlnln

1lnlnln

02

(13)

Where (n) is the statistic sample volume.A case study: staff for change of the caoutchouc belt rollers upport.

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Cârlan, M., Goia, H., Dziţac, S. -53-

Let be the elements of calculus in the table 2.

Table 2. Elements of calculusi Mi

iG0 [%]

1. 5 702. 7 723. 5 704. 6 705. 7 756. 6 757. 5 658. 7 65

To calculate:o to determine the optimal number of the executants;o maximal engaged grade realized by this team.

In table 3 is presented the synthesis of the regression grade coefficients.

Table 3. Calculus of the regression coefficientsi Mi

iG0

(%)

2iM

iG0ln iMe1 iMe1ln

iGM i 0ln iM

i eM 1ln

1. 5 70 25 4,24849 0,99326 -0,00676 21,24245 -0,033802. 7 72 49 4,27667 0,99909 -0,00091 29,93670 -0,006373. 5 70 25 4,24849 0,99326 -0,00676 21,24245 -0,033804. 6 70 36 4,24849 0,99752 -0,00248 25,49094 -0,014885. 7 75 49 4,31749 0,99909 -0,00091 30,22243 -0,006376. 6 75 36 4,31749 0,99752 -0,00248 25,90494 -0,014887. 5 65 25 4,17439 0,99326 -0,00676 20,87195 -0,033808. 7 65 49 4,17439 0,99909 -0,00091 29,22073 -0,00637

i

48 * 294 34,00540 * -0,02797 204,13259 -0,15027

Starting from the equation system (13) results the coefficients values of theregressions: 85;03,0 Ac .There is reduced the optimal number of the staff: 4;3optimM executants.In some situations the optimal zone is greater.

The correlation rate (coefficient of Pearson) evidences the linear links intensitybut of the curvilinear too (relation adopted for G0).

i

200

i

200

GG

GG~

i

i(15)

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Consideration viewing the optimal dimensioning of the maintenanceteam from thermo-electric power plants

-54-

where:i

G0 - calculus data;

0G - medium value of ”the engaged grade”;

iG0~

- the computed values through the regression relation:

000 GGGii şi 000

~~ GGGii

The correlation rate is: 6,0Due to the reduced volume of the statistic sample, results a medium intensity

correlation rate.

3. CONCLUSIONS

The optimal components of a work team that makes all activities ofmaintenance are stabilized in concordance with the strategy and the maintenanceworks, using the criteria of” maximal engaged degree of the teams’ components”.From the expression of engaged degree the regression coefficients are established byusing one from the following methods: least squares method, the method of doublepoint and the method of interpolation; in this paper we will use the least squaresmethod.

The problem of rational dimensioning of executants team resolves: theefficient utilize of the works time, stabilizing the necessary number of staffs, realizinga complete concordance between the work’s complexity and medium level ofqualifying of the members of the team, squandering the human resources of highquality, realizing a synergy contribution of high level as effect of a cooperation inworks of high productivity of the executant’s team.

REFERENCES:

[1]. Carabulea A., ş.a.- Managementul sistemelor industriale. Probleme, studii de cazşi aplicaţii- E.T.P.Bucureşti, 1995.

[2]. Cârlan M. – Mentenanţa şi disponibilitatea instalaţiilor electrice, RevistaProducerea, transportul şi distribuţia energiei electrice şi termice – nr.12/1994.

[3]. Cârlan M., Goia H. Ştei M. - Posibilităţi privind utilizarea metodei expertonilorcu fundamentarea strategiei de mentenanţă a morilor de cărbune ale unui generator de aburide 420t/h-, Sesiunea anuală de comunicări ştiinţifice, Universitatea din Oradea, 2001.

[4]. Goia H. C., Cârlan M., Goia E., Dziţac S.- Determinarea numărului optim alpersonalului din activitatea de mentenanţă la repararea şi întreţinerea STPCS CET I Oradea,C.I.E., Universitatea din Oradea, Facultatea de Energetică, 2006.

[5]. Ivas D.- Modele de calcul a structurii optime pentru instalaţii energetice şidomeniu de aplicare a acestora – C.I.E., Bucureşti, 1983.

[6]. Kaufmann A.- Metode şi modele ale cercetării operaţionale-Traducere din limbafranceză, E.Ş., Bucureşti, 1968.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 55-60

CONTRIBUTIONS TO IMPLEMENT THE RELIABILITYCENTERED MAINTENANCE AT THE THERMO-

ELECTRIC PLANTS

IOAN FELEA, HORIA GOIA, SIMONA DZIŢAC

Abstract: The paper is structured in three parts. In the first part is presented themethodological considerations viewing the reliability centered maintenance. The second partcontains a synthesis of appliance opportunities of reliability centered maintenance referring onthermo electric plants. There are presented the appliance directions, the approach mode,mathematic models, and the appliance algorithm. The last part of the paper contains two casestudies result and conclusions.

Key words: maintenance, reliability, thermo-electric plants, optimization

1. PRELIMINARIES

A general classification imparts the maintenance politics in two greatcategories: the corrective maintenance (CM), and the preventive maintenance (PM) [1].The combine of the two modalities is named as mixed maintenance. In last few years itwas developed a new direction of preventive maintenance, the proactive maintenance[1,2].

The changing politics (after the age, in blocks, opportunity, stage, and mixed)[1,2] are modalities of PM strategies application. A significant example on scientificmanagement is the reliability centered maintenance (RCM). [2] In RCM concept anefficient maintenance program, plans only that procedures that are necessary to attainthe proposed objective for all operation of the system. The actual practice justifies thefollowing definition for this maintenance strategy: evaluations and actions that leads tothe maintenance works achieve in correlation with a certain reliability level(previsional) or certifiable (operational). To an analytical approach of RCM, is

Professor, Ph.D. at the University of Oradea Eng. PhD Student at the University of Oradea

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Contributions to implement the reliability centered maintenance atthe thermo-electric plants

-56-

necessary to know the real operational reliability level that is obtained from studies,having a good outlined space- temporal localization. For the equipment from the powerengineering systems, the main aspects that are approached and treat and representsRCM actions [1 6] are: establishing the optimal testing frequency, to minimize thetime unavailability, applying the substituting politics after the testing, optimalmanagement of the structures of “k from n” type, optimal, structural and temporalweight, of the works from the two categories (PM+CM), optimizing the stocks level ofthe equipment, materials and subunits.

2. RCM STRATEGIES APPLICATION MODELS IN TERMO -ELECTRIC PLANTS (TEP)

The RCM strategy is utilized to all equipment from the TEP (electric, heating,electro-mechanic). The application with success of RCM strategy implies thecontinuous evaluation and actualization of the operational reliability indicators of theequipment, following the common algorithm [1, 3, 5]. The detailed analysis [7],allowed the application models selection, referring on TEP equipment. The direction ofthe application and the models are synthesized in the followings.

2.1. Substitution politic by stage

This politic supposes the restrictive criterion application [1]:

Prob (t T) RL (1)

where: RL – is a pre-established limit of the probability of good operatingEnjoining the MP works periodicity is obtained: Exponential distribution

LLM lnRλ1-T (2)

Weibull distribution

1

1ln

LLM R

T (3)

where ,,, - parameters of the distribution [1,3,6]

2.2. Selection the maintenance strategy basing on operational availabilitylevel

Hypothesis:HP1: The equipment comes under only action of CM actions;

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Felea, I., Goia, H., Dziţac S. -57-

HP2: The equipment comes under the action of PM action;HP3: The equipment comes under action of predictive maintenance action (PRM), theperiod of testing is 1 year, and the duration of the testing is 1 day.In case of HP1 the time availability of the system may be write as:

CMc

cc TT

TD

(4)

where, TC - time between two replacements [1], TMC - total period of corrective interventions [1].In case of a preventive maintenance politics HP2, the availability of the system is:

D p =Tp

p

TT

(5)

where, TP – continuous operating average timeT the non operating average time for a duration of (0,T):

tRTtRT CMPMT 1 (6)

The availability of the equipment in condition of HP3 for the duration of “n” inspection:

nn

n

nTp

pT T

TD

11

1

1 (7)

where,nPT

1- continuous operating average time for “n” inspection

nT 1

- non operating average time for “n” inspection

2.3. The maintenance of the structure of “k din n”

The structures of „k din n” type, are frequently utilized in thermal heat plants.There are researches and applications that studies the structural optimization (at thedesign) and functional (exploitation) of „k din n” type system [5].

The criteria that is the base of stabilization of the actions moment releasing ofthe PM, is the maximal reliability gain, that justifies the including of such type ofprocedure in category of RCM options. After the release of the PM actions, these willachieve, successively for “n” elements from the investigated structure. The diagram ofequivalent reliability block diagram (RBM) is presented in fig.1.

The time safety of the system with “n” and with “n-j” elements in operating isexplained as:

n

ki

iniinn RRCR )1( (8)

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Contributions to implement the reliability centered maintenance atthe thermo-electric plants

-58-

1 2 k(F)

k+1 n (RZ)

Fig 1. – RBM of the system „k din n” type

The time safety of the system with “n-j” elements in operating is explainedsimilarly:

jn

ki

ijniijnjn knjRRCR ;)1( (9)

The reliability gain between the two stages is explained as:

jnn RRR (10)

To determine the maximal value of the „R” indicator and of Ts indicatorvalue, it is derivate in function with “t” variable of R.

3. THE RESULTS OF THE CASE

For a perfect cooperation between the three entities it were made operationaland previsional reliability, and was established the characteristics of RCM strategy forthe equipment of the transport system structure and for the preparation of solid fuels(STPCS) from CET I Oradea and CTE Mintia.

The complete results of the studies are in [7] and offer for two entities thenecessary dates for the maintenance program.

The obtained results referring on the presented models in chapter 2, applied atcertain equipment from the two plants.

Table 1. The values of TLM parameter for equipment from structure STPCS, al CETI Oradea and CTE Mintia

0,98 0,96 0,94 0,92 0,90Reliability impose (RL)Equipment Values of parameters (TLM) [h]Rotating arms feeder, bands 51 114 117 258 337Machines of delivery – storing of coal 293 426 529 617 714Coal crusher 868 1070 1207 1316 1428Coal mill feeder, CET I 855 1117 1298 1450 1608Coal mill feeder, CTE Mintia 1096 1352 1586 1667 1809Mill grind coal (MV) 974 1230 1410 1553 1701Mill grind coal (MC) 1113 1372 1151 1692 1836

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Felea, I., Goia, H., Dziţac S. -59-

Table 2.The availabilities of time for equipment from STPCS structurethat are supposed to actions

PM actions (Hp2)Nr.crt. Equipment

CMactions(Hp1) RK RT

Predictivemaintenanceactions (Hp3)

1. Feeder with rotating arms (CET I Oradea) 0,9991 0,9455 0,9234 0,9234

2. Machines of delivery – storing(CTE Mintia) 0,9931 0,9877 0,9543 0,9543

3. Transmission bands (CTE Mintia) 0,9940 0,9754 0,9678 0,96784. Crushers (CET I Oradea) 0,9982 0,9865 0,9245 0,92455. Crushers CTE Mintia) 0,9947 0,9890 0,9851 0,98516. Coal Feeder (CET I Oradea) 0,9724 0,9923 0,9678 0,96787. Coal feeder (CTE Mintia) 0,9737 0,9898 0,9489 0,94898. Fan mills (CET I Oradea) 0,9666 0,9843 0,9324 0,9324

9. Hammer mills, with ball crusher(CTE Mintia) 0,9970 0,9264 0,9421 0,9421

The maintenance programThere were analyzed the structures of „2 from 5” type, for the transmission

bands from CET I Oradea, „4 from 5” for the fan mills from CET I Oradea, „2 from4”for the machines of coal delivery and store from CTE Minita (the old stage) and „3from 5” for the transmission bands from CTE Mintia (new stage). Similarly, may betreated other structures with a concrete number of reserve elements from the structureof STPCS.

Structure R R(TS) TS„2 din 5” 0,99768 0,4 3806„4 din 5” 0,8521 0,8 3910„2 din 4” 0,999984 0,5 3080„3 din 5” 0,99943 0,6 1667

For the compute it was utilized the Weibull distribution function, that offersthe best approximation of empirical distribution by the analyzed equipment.

44.. CCOONNCCLLUUSSIIOONNSS

The equipment and transport systems maintenance strategies adequacy as wellthe solid fuels preparation is a solution of action through that are obtained majorfinancial economize by CET and CTE.

The RCM strategy application is the most efficient path with actuality forimplementation of a modern and efficient maintenance system of the equipment fromthe structure of STPCS.

RCM strategy operationalization, from STPCS structure, in principal, is madethrough: the application of substituting politics viewing the stage, the comparativelyevaluation and the availability maximization of the equipment, optimizing the testingfrequency, the maintenance program adequacy by the structures with „k from n” type.

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Contributions to implement the reliability centered maintenance atthe thermo-electric plants

-60-

The substituting politic application viewing the stage of the analyzedequipment, that are made with Weibull distribution of TBF variable, and for the valuesof the reliability function that are in interval of [0,9;0,94].

The obtained values for indicator of “time availability” of the equipment fromthe STPCS structure, reflects the opportunity of mixed maintenance strategy(PM + CM), with the time interval activation between two works of PM in functionwith the operational reliability level of each type of equipment.

The application of the testing optimal frequency optimization model is madeby grouping of the analyzed equipment in “basic installations” category, which impliesthe assurance of characteristic risk level exponential distribution of operating and leadsto conclusion of opportunity of mixed maintenance strategy application by theequipment from structure of STPCS of CET I Oradea and CTE Mintia.

The major of the subsystems from STCPS structure are of „k from n” type. Anessential management aspect of maintenance of structures „k from n” type, is themoment of releasing the maintenance actions, so that, the gain of reliability ismaximum.

Such an approach takes part of strategy of reliability centered maintenance.The indices with interest for management of maintenance systems of „k from n” type,are: the time interval value, after the reliability gain attains the maximal value (Ts), thetime safety [R(Ts)] and the reliability gain [R(Ts)] at Ts moment.

The numerical evaluation of TS parameter (interval of time between twoactions of preventive maintenance) for equipment from STPCS that are of „k from n”,reflects, the main dependency of this parameter from the distribution type and theoperational reliability’s indicator values.

REFERENCES

[1]. Felea, I., Coroiu N.- Fiabilitatea şi mentenanţa echipamentelor electrice, EdituraTehnică, Bucureşti, 2001.

[2]. Monbray I. –Reliability Centered Maintenance, Butterworth, Heinemann, 1991.[3]. Lyonnet P.- La maintenance Mathematiques et Methodes, Tehnique

Documentation, Paris, 1992.[4]. Cârlan M. – Probleme de optim în ingineria sistemelor tehnice, E.A.Române,

Bucureşti, 1994;[5]. Felea I., Coroiu N.,- Recurs la mentenanţa bazată pe fiabilitate în reţeaua de

repartiţie şi distribuţie, Revista Energetica, nr. 3, 2005.[6]. Nitu V. I. – Fiabilitate, disponibilitate, mentenanţă în energetică, E.T. Bucureşti,

1987.[7].Goia H. C.- Contribuţii privind implementarea strategiei de mentenanţă RBM la

echipamentele din structura STPCS, teză de doctorat, 2006

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 61-66

DIAGNOSTIC TESTING FOR ASINCRONOUS MOTORS

TABACARU-BARBU TEODOR

Abstract. Nondestructive diagnostic tests are used to determine the condition of theinsulation and the rate of electrical aging. The description of the recommended diagnostic testsfor the insulation system of motors and the conditions they are designed to detect are discussed.Methods to test stators and rotors of asynchronous motors are presented and their advantages.

Keywords: asynchronous motors, the insulation system

1. INTRODUCTION

The following factors affect the insulation systems in motors: High temperature Environment Mechanical effects such as thermal expansion and contraction, vibration,

electromagnetic bar forces, and motor start-up forces in the end turns Voltage stresses during operating and transient conditions

All these factors contribute to loss of insulation integrity and reliability.These aging factors interact frequently to reinforce one another’s effects.

Nondestructive diagnostic tests are used to determine the condition of the insulationand the rate of electrical aging. The description of the recommended diagnostic testsfor the insulation system of motors and the conditions they are designed to detect arediscussed.

2. STATOR INSULATION TESTS

An electrical test is best suited to determine the condition of electrical insulation.The tests on insulation systems in electrical equipment can be divided into twocategories:

Asoc.Prof.Dr.Eng., University of Petroşani

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Diagnostic testing for asynchronous motors-62-

High-potential (hipot), or voltage-withstand tests Tests that measure some specific insulation property, such as resistance or

dissipation factor.Tests in the first category are performed at some elevated a.c. or d.c. voltage to

confirm that the equipment is not in imminent danger of failure if operated at its ratedvoltage. Various standards give the test voltages that are appropriate to various typesand classes of equipment. They confirm that the insulation has not deteriorated below apredetermined level and that the equipment will most likely survive in service for a fewmore years. However, they do not give a clear indication about the condition of theinsulation.

The second category of electrical tests indicates the moisture content; presenceof dirt; development of flaws, cracks, and delamination and other damage to theinsulation.

A third category of tests includes the use of electrical or ultrasonic probes thatcan determine the specific location of damage in a stator winding. These tests requireaccess to the air gap and energization of the winding from an external source. Thesetests are considered an aid to visual inspection.

3. DC TESTS FOR STATOR AND ROTOR WINDINGS

These tests are sensitive indicators to the presence of dirt, moisture, and cracks.They must be performed off-line with thewinding isolated from ground, as shown in fig. 1.

Suitable safety precautions should be takenwhen performing all high-potential tests.When high-voltage d.c. tests are performed onwater-cooled windings, the tubes or manifoldsshould be dried thoroughly, to remove currentleakage paths to ground and to avoid thepossibility of damage by arcing between moistpatches inside the insulating water tubes. Forgreater sensitivity, these tests can be performedon parts of the windings (phases) isolated fromone another.

The charge will be retained in the insulation system for up to several hours afterapplication of high d.c. voltages. Hence, the windings should be kept grounded forseveral hours after a high-voltage d.c. test to protect personnel from a shock.

Tests using d.c. voltages have been preferred over the ones using a.c. voltagesfor routine evaluation of large machines for two reasons: The high d.c. voltage applied to the insulation during a test is far less damaging

than high a.c. voltages due to the absence of partial discharges; The size and weight of the d.c. test equipment are far less than those of the a.c. test

equipment needed to supply the reactive power of a large winding.

3.1. Insulation Resistance and Polarization Index

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Teodor, B., T. -63-

The polarization index (PI) and insulation resistance tests indicate the presenceof cracks, contamination, and moisture in the insulation. They are commonlyperformed on any motor and generator winding. They are suitable for stator andinsulated rotor windings.

The insulation resistance is the ratio of the d.c. voltage applied between thewinding and ground to the resultant current. When the d.c. voltage is applied, thefollowing current components flow: The charging current into the capacitance of the windings; A polarization or absorption current due to the various molecular mechanisms in

the insulation; A “leakage” current between the conductors and ground. This component is highly

dependent on the dryness of the windings.The first two components of the current are lowering in time. The third

component is mainly determined by the presence of moisture or a ground fault.However, it is relatively constant. Moisture is usually absorbed in the insulation and/orcondensed on the end winding surfaces. If the leakage current is larger than the firsttwo current components, then the total charging current (or insulation resistance) willnot vary significantly with time. Therefore, the dryness and cleanliness of theinsulation can be determined by measuring the insulation resistance after 1 min, andafter 10 min. The polarization index is the ratio of the 10-min to the 1-min reading.

3.2. Test Setup and PerformanceSeveral suppliers offer insulation resistance meters that can determine the

insulation resistance accurately by providing test voltages of 500 to 5000 V d.c. Formotors and generators rated 4 kV and higher, 1 kV is usually used for testing thewindings of a rotor, and 5 kV is used for testing the stator windings.

To perform the test on a stator winding, the phase leads and the neutral lead (ifaccessible) must be isolated. The water must be drained from any water-cooledwinding, and any hoses removed or dried thoroughly by establishing a vacuum.

The test instrument is connected between the neutral lead or one of the phaseleads and the machine frame (fig. 1). To test a rotor winding, the instrument should beconnected between a lead from a rotor winding and the rotor steel. During the test, thetest leads should be clean and dry.

Interpretation

If there is a fault or the insulation is punctured, the resistance of the insulationwill approach zero. The IEEE standard recommends a resistance in excess of VL-L + 1MΩ. If the winding is 13.8 kV, the minimum acceptable insulation resistance is 15MΩ. This value must be considered the absolute minimum since modern machineinsulation is on the order of 100 to 1000 MΩ. If the air around the machine had highhumidity, the insulation resistance would be on the order of 10 MΩ.

The insulation resistance depends highly on the temperature and humidity of thewinding. To monitor the changes of insulation resistance over time, it is essential to

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Diagnostic testing for asynchronous motors-64-

perform the test under the same humidity and temperature conditions. The insulationresistance can be corrected for changes in winding temperature. If the corrected valuesof the insulation resistance are decreasing over time, then there is deterioration in theinsulation.

However, it is more likely that the changes in insulation resistance are caused bychanges in humidity. If the windings were moist and dirty, the leakage component ofthe current, which is relatively constant, will predominate over the time-varyingcomponents. Hence, the total current will reach a steady value rapidly.

Therefore, the polarization index is a direct measure of the dryness andcleanliness of the insulation. The PI is high (>2) for a clean and dry winding. However,it approaches unity for a wet and dirty winding.

The insulation resistance test is a very popular diagnostic test due to itssimplicity and low cost. It should be done to confirm that the winding is not wet anddirty enough to cause a failure that could have been averted by a cleaning and dryingprocedure. The resistance testing has a pass/fail criterion. It cannot be relied upon topredict the insulation condition, except when there is a fault in the insulation.

The high-potential tests, whether d.c. or a.c., are destructive ones. They are notgenerally recommended as maintenance-type tests.

For stator windings rated 5 kV or higher, a partial discharge (PD) test, which inthe past has been referred to as corona, should be done. The level of partial dischargeshould be determined because it can erode the insulation and lead to insulation aging.

4. D.C. HIGH-POTENTIAL TESTING

The d.c. high-potential test is a nondestructive test used to evaluate the dielectricstrength of the groundwall insulation. The voltage applied across the windings is givenby Vdc-hipot = 2V0 + 1000 [V]where V0 is the operating voltage and Vdc-hipot is the voltage applied across the windingsduring the d.c. hipot test. The casing of the motor is maintained at ground voltage. Theleakage current between the windings and the core is measured. The insulationresistance is obtained by dividing the voltage imposed across the windings by theleakage current. The test indicates that the groundwall insulation is able to withstandhigh voltage without being damaged.

Note that this test is different from the destructive a.c. and d.c. high-potentialtests performed by the manufacturer of the motor. These tests are performed todetermine the maximum voltage that the insulation of the motor can withstand. Thevoltage reached during these tests is much higher than the voltage recommended forthe nondestructive d.c. high-potential test. They are performed by a qualified operatorto prevent the destruction of the motor.

4.1. Surge Testing

The d.c. high-potential test confirms the integrity of the insulation. However, itdoes not indicate a failure of the insulation between the turns of the windings (interturnfault). The surge test is used to detect the early stages of insulation failures in the

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Teodor, B., T. -65-

windings such as coil-to-coil failures, short circuits, ground, and misconnections.During the surge test, brief voltagesurges (pulses) are applied across thecoil. These pulses produce a momentaryvoltage stress between the turns of thecoil. Fig. 2 illustrates a typical responseof a coil.

Each coil has a unique signaturewaveform, which can be displayed on thescreen of the equipment during the test.The waveform obtained during the surgetest is directly related to the inductanceof the coil.

A surge test can detect aninterturn fault due to weak insulation. If the voltage spike is greater than the dielectricstrength of the interturn insulation, one or more turns could be shorted out of thecircuit. The number of turns in the coil will drop, leading to a reduction in theinductance of the coil and an increase in the frequency of the waveform produced bythe surge test. If the coil has an interturn fault or a phase-to-phase fault, the waveformproduced during the test could become unstable. It could shift rapidly to the left andright and back to its original position (fig. 3 a).

A comparison is done between the surge tests performed on each of the phases.A healthy three-phase motor should have three identical phases. Therefore, the resultsof the surge tests performed on each of the phases should be identical. Any differencesfound between the three results indicate that there is a fault in the motor (fig. 3 a andb).

4.2. Winding Resistances

This test involves measuring the resistance of each of the three phases. Theresistance unbalance is given by

Resistance unbalance = (Maximum resistance – Minimum resistance)/Averageresistance

For a healthy motor, the resistance unbalance should be less than 10 % if thetest is performed from the motor control center. It should be less than 5 % if the test is

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Diagnostic testing for asynchronous motors-66-

performed at the motor. The larger resistance unbalance (10 %instead of 5 %) isallowed when the test is performed from the motor control center due to the longcables between the motor control center and the motor.

The voltage and current used during the test for 4-kV and 575-V motors are 5V d.c. and 6 A, respectively. This test is used to detect short circuits, ground faults,phase-to-phase faults, looseconnections, open circuits, dirtaccumulation at connections, etc.

5. STATOR CURRENTFLUCTUATION TESTThe stator current fluctuation

test is performed on an operating andloaded motor. The current in one ofthe phases is monitored forfluctuations at twice the slipfrequency (fig.4). An ammeter isobserved, or a current transformeroutput is monitored on a strip chartrecorder or oscilloscope. The resultsshould be interpreted by anexperienced operator.

6. MANUAL ROTATION TEST

The motor is disconnected from its normal three-phase power supply for itsoff-line test. The driven equipment should be uncoupled unless it can be manuallyrotated with the motor. A single-phase a.c. supply is connected across two motorterminals. It has voltage rating of 10 to 25% of rated line-to-line volts and a kVA ratingof 5 to 25% of rated kVA. The rotor is manually turned for one-half revolution whilemonitoring the variations in the current. A broken rotor cage winding is indicated bycurrent fluctuations in excess of 10%. The current fluctuations can also be monitoredon a strip chart recorder connected to the output of a current transformer.

It is important that the test time should not exceed 1 min. due to rapid heating inthe stator and rotor windings. The main limitation of this test is that it can only beconducted off-line. Therefore, breaks in cage windings may not be detected if theyclose up, giving low-resistance connections when centrifugal forces are removed.

REFERENCES

[1]. L. R. Higgins, Maintenance Engineering, 5th ed., McGraw-Hill, New York, 1995.[2]. A. S. Nasar, Handbook of Electric Machines, McGraw-Hill, New York, 1987.[3]. *** , Electrical Equipment Handbook – Troubleshooting and Maintenance,

McGraw-Hill, New York, 2004.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 67-71

ELECTRIC FRAMES WITH LINEAR INDUCTION MOTORPROPULSION SYSTEMS. ELECTRIC TRACTION SCHEME

DRAGOS PASCULESCU, CONSTANTIN BRINDUSA

Abstract: In the case of the electric drive systems which are based on the static convertersand on the traction linear induction motors (LIM), specific to the urban electric frame of subwaytype, it is necessary to establish the traction electric schemes. Their analysis is made on the basis ofsome criteria, among the most important is the travelling transport safety.

Keywords: electric frames, electric traction

1. INTRODUCTION

The subway frames electric drives impose a series of specific conditions and,particularly, a great operation safety and the compulsory introduction of the energyrecovery brake. The mechanico-pneumatic brake has the drawbacks of the clogs wear andthe mechanical dust appearance during the friction.

The traction scheme imposed on the urban electric frames of type VM+VM, withthe feeding from the d.c. network contents, mainly, the following equipments:

-the intermediary circuit, known as network filter FLC-the voltage and frequency static converter CTF;-the braking chopper + the braking resistance + the shunt;-the current captor + the axle contact;-loading contactor + loading resistance;-ultra-rapid automat breaker;-wagons electric couple;-traction motor.

The traction scheme asigure:-the electric energy captation, from:

-the catenary, by the panthograph, inside the depots where it is not allowed the rail

Assistent Drd.Eng., University of Petrosani Professor Dr.Eng., University of Petrosani

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Electric frames with linear induction motor propulsion systems.electric traction scheme-68-

III assembling;-the rail III, by the captors, on the travelling paths; this kind of feeding it is met to

the subway or overhead metro urban transport.- the voltage and current waves level under a admissible level, meaning:

ΔUmax < ( 0,1 – 0,2 ) Ud minΔImax < ( 0,1 – 0,15 ) Is max

- the conversion d.c. - a.c., by a voltage and frequency static converter CTF, whichare supplying the traction motors, at variable voltage and frequency, in concordance withthe adjustment requirements imposed by the assembly CTF-LIM;

- the transformation of the electric energy into the mechanical energy by thetraction linear induction motors (LIM), which are electric connected on the bars RST ofthe CTF; The vehicle propulsion force (the traction force) appears due to the linearinduction motors.

2. ELECTRIC TRACTION SCHEMES. POSSIBLE VARIANTS

The vehicle is an electric frame VM+VM type, meaning that it is formed by twomotor wagons which are elastic coupled. On each motor wagon there are installed tractionlinear induction motors (LIM).

An exemplu of the traction linear induction motors (LIM), made in Romania, isLIM 02.

The linear induction motors LIM 02, with the technical characteristics presentedin Table 1, it is made by S.C. ELECTROPUTERE CRAIOVA S.A., for the urban electricvehicul, class ROM-U-LIM-01.

Table 1Nr. Tip Simbol ML- 021 Rated power ( kW ) Pn 1402 Rated voltage on fase( V ) Un 2253 Rated current ( A ) In 1804 Starting current ( A ) Ip 4205 Rated frequency ( Hz ) fn 606 Nominal speed ( m/s ) v 207 L. primar (m) 2a 0,278 Poles number 2p+1 11

The traction electric frame scheme can be presented in the following variants:

- V1 - defined by the coefficient k=1/4 (Fig.1), meaning that on the vehicle it existsa voltage and frequency static converter which, are supplying the four (4) LIM;

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Pasculescu, , D., Brindusa, C. -69-

Fig.1 Principle traction scheme; k=1/4

- V2 - defined by the coefficient k=2/2 (Fig.2), meaning that on the vehicle thereexist two voltage and frequency static converters, each of them supplying two (2) LIM;

Fig.2 Principle traction scheme; k=2/2

M13~

M23~

M23~

M13~

L1 D1U1

D3U3

D5U5

D2U2

U4D4

U6D6

U2D2

U1D1

U3 D3 U5 D5L1

D4U4

D6U6

a1c

1

c2

c2

c1

a1

R3

R3

R2

R2

R1

R1

U7

U7

D7

D7C

1

C1

VMA VMB

750Vcc

M23~

M13~

M23~

M13~

M13~

M23~

M23~

M13~

L1 D1U1

D3U3

D5U5

D2U2

D4U4

D6U6

a1

c1

c2

a1

R3

R2

R1

U7

D7

C1

VMA VMB

750Vcc

M13~

M23~

M23~

M13~

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Electric frames with linear induction motor propulsion systems.electric traction scheme-70-

In the Table1 there are presented (grouped) the main elements, which are definingthe urban subway traction electric frames schemes, with the structure VM+VM.

Table 1 The urban subway traction electric framesNr. Traction scheme

variant code:

Coefficient K Nr. CS /

Frame

Nr. LIM /

CS

1 V1 1 / 4 1 4

2 V2 2 / 2 2 2

The operation mode of the main traction scheme (Fig.2) for the electric frames itis following:

- the coupling of the captors U1/VMA and U1/VMB at the rail III. This way it isallowed the feeding of the auxiliary services of the urban electric frame, meaning:

- the main compressor feeding at 750 Vd.c., which are supplying the pneumaticenergy to:

-the mechanical brake system;-pneumatic damping system of the frame wagon mechanic waves;- electric-pneumatic line switchers;

-the auxiliary services converter feeding, which can be either a rotating converter ora static one, with power electronic devices (750V/ 3*220V;50Hz;Sn =10KVA);

- the closing of the ultra-rapid breaker a1/VMA, respectively a1/VMB, in function ofthe frame control cabin: A or B. This way it is allowed the vehicle traction supplying;

- the closing of the contactors c1/VMA and c1/VMB. This way it is allowed thecondensator battery loading C1/VMA and C1/VMB under a controlled current slope, under(di/dt)cr, by the loading resistors battery R1/VMA and R1/VMB. The loading time is of *1sorder.

- the closing of the contactors c2/VMA and c2/VMB. This thing it is automaticallyrealized by the control scheme, in the moment when the intermediary circuit voltage it isreaching the 0,85*Udmin value;

- the operation starting command of the invertor on the VMA and of the invertor onthe VMB (composed: Ui+D, where i=1,...,6, with the intermediary circuit L1+C1);

- the feeding of the linear induction motors (LIM), (in concordance with V2defined by the coefficient k=2/2) in the three-phase voltage system with frequency andvoltage variable with modulation PWM.

This is the moment when the frame is able to travel; thus, at the minimum chosenfrequency fmin=sn

*fn (in concordance with the technical literature), the tractionasynchronous motors M1 and M2 / VMA, respectively M1 and M2 / VMB are stacked, andwhen this value it is exceeded the motor it is starting on the linear part of the artificialmechanical characteristic corresponding to the supply minimum frequency. The urbanelectric frame it is accelerating, at the constant traction torque, on the artificialcharacteristics U1/f1 up to fsn, when U1=U1n and then, at the constant power, over fsn.

With a view to the frame electric braking, the traction linear induction motors(LIM) are passing into the generator regime, by the decrease command of the voltage

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Pasculescu, , D., Brindusa, C. -71-

frequency applied to the motors. The traction electric machines are modifying theoperation points on the mechanical characteristics in the dial II, passing into the generatorregime.

In that situation, which is complex from the powers circulation view point, theinvertor (by Ui, where i=1,...,6) it is ensuring the reactive energy necessary to thegenerator regime, by the recovery diodes group (by Di, where i=1,...,6) the machinesupplying the voltage intermediary circuit, as asynchronous generator.

This energy it is taken through recovery by other electric frames situated in travelon the network portion considered or, if the voltage on the intermediary circuit it isincreasing over 1,2 Ud (meaning over 1,2*750=900V), it is commanded the automaticallyoperation of the braking chopper U7 / VMA and U7 / VMB, which are realizing an electricbrake on the braking resistors R2 and D7 / VMA, respectively R2 and D7 / VMB.

The frame disconnection from the network it is realized into the reverse order tothe start, with the exception that at beginning there are disconnected the ultra-rapidbreakers a1 / VMA, respectively a1 / VMB.

3. CONCLUSIONS

The analysis of the variants V1 and V2 must be made taking into account acriteria series, such as:

-the vehicle travelling safety criterium. In concordance with this criterium, the variantV2 it is advantageous, because even after the failure of a CTF, meaning a supplying unit,the vehicle it is able to arrive into a garage point on the travelling path, with 2/4 of theinstalled power;

-the traction scheme reliability criterium. In concordance with this criterium, thescheme realized with the variant V1 it is the most reliable, taking into account the fact thatthe traction scheme operation safety it is decreasing with the number of the powerelectronic devices;

-the traction scheme complexity criterium. The force scheme CTF simplifying it hadbeen realized by using the electronic devices with gate stack, meaning the thyristors withblocking on gate GTO or bipolar transistor with insulated gate IGBT.

From the analysis of the variants of the traction schemes, taking into account thecriteria enunciate as before, it had imposed the variant V2 defined by the coefficientk=2/2, meaning that on the vehicle there are two voltage and frequency static converters(namely, one on each motor wagon), each of them supplying 2 traction bimotors.

REFERENCES

[1] Krause P.C., Wasynczuk O.,Sudhoff S.D., Analysis of Electric Machinnery,IEEE, 1995.

[2] Brînduşa,C.,ş.a., Sisteme electrice de transport neconvenţionale (A23); Rama demetrou acţionată cu motoare asincrone; Execuţie şi experimentare modele (Faza 23.1), Contractcercetare 606C- Anexa A, Institutul naţional de cercetare şi proiectare pentru maşini electrice,echipament electric şi tracţiune, ICMET, Craiova, 1992

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 72-76

ELECTROMAGNETIC DEVICE DESIGN SYNTHESIS

ANDREI CECLAN, DAN DORU MICU, DAN MICU, EMILSIMION

Abstract: We approach the synthesis of a winding configuration with a numericalregularization method. The mathematical model leads to an ill-posed inverse electromagneticproblem. Uniformly textile bands painting use this application for a hom*ogeneous magneticflux density.

Key words: coil, hom*ogeneous, ill-posed, regularization

1. INTRODUCTION

Shape design synthesis of magnetic coils is of great importance inmanufacturing some electromagnetic devices. In this paper we focus on setting theconfiguration of a magnetic device to be used in the efficient painting treatment oftextile bands. We start from imposed performances of the coil and through synthesisreach those magnetic/electric values, or geometrical dimensions that lead to the desiredcharacteristics. [1]

Generally, the synthesis process may be regarded as an inverse and ill-posedelectromagnetic problem. That is, the solution is not unique and very unstable. [2] Theapproach of the problem shall be taken from a special Tikhonov regularizationnumerical procedure. Argues about the numerical results and the method validityconclude the paper.

2. DESIGN PARAMETERS

Engineer, Ms.C. at the Technical University of Cluj-Napoca Lecturer Ph. D. at the Technical University of Cluj-Napoca Professor Ph.D. at the Technical University of Cluj-Napoca

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Ceclan, A., Micu, D., D., Micu, D., Simion, E. -73-

Let us consider the configuration given in fig. 1, and assume the magneticcircuit to be of very high permeability. Also consider the air gap between the poles ofthis electromagnet as a linear, hom*ogeneous and isotropic medium, ofpermeability 0 . The objective is to obtain a constant and hom*ogeneous magneticfield density 0B , generated by an unknown configuration of windings located on theferromagnetic circuit. By rafting across the textile band through this hom*ogeneousfield density, the painting process is assumed to be uniform and economical.

Y

X

Fig. 1 General design of the magnetic device

3. TIKHONOV REGULARIZATION SYNTHESIS

Accounting the symmetry of the device, let us reconsider the winding aslocated only on the main pole. To accomplish the desired hom*ogeneous magnetic fielddensity 0B in the air gap, we have to synthesize a certain configuration of the coil. Inthis situation 0B has to be created by a number of windings kz , all feed with a constantcurrent I , as figure 2, and shows.

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Electromagnetic device design synthesis-74-

-zk I B0 zk I

-zk I zk I

Y

X

Fig. 2 Windings and magnetic images method

If we assume that the magnetic permeability of the medium is almost infinitely,then the magnetic images method can be applied. The four conducting wires, from theabove fig. 2, will generate on the Ox axis a magnetic flux density of:

2k

2k

2k

2k0k

kxsc

xsxsc

xsIzxB (1)

The total magnetic flux density:

n

1kk xBxB (2)

And pass to the integral form:

b

0 22220dssz

xscxs

xscxsxB

Inb

(3)

which is a Fredholm integral equation of the first kind. Generally, this represents an ill-posed mathematical model, with non-unique and unstable solutions. [3]

xudsszs,xKb

0 (4)

If we mesh the x and s domains, the model may be written in a matrix form:uzM , which has a very ill-conditioned coefficient matrix. Therefore, a Tikhonov

regularization procedure has to be applied. On the matrix expression the followingtransformation occurs [4]:

uMzIMM TT (5)

The regularization parameter α, gives the ratio between the stability and theprecision of the solution. Its values are chosen according to the L-curve criterion [5].

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Ceclan, A., Micu, D., D., Micu, D., Simion, E. -75-

Physical achievability and precision of the solution are next to be appreciated. Theerror evaluation formula relates to the attainment of the imposed magnetic flux density:

m

1i

20i Bumax (6)

4. NUMERICAL RESULTS

The initial values for the given geometrical configuration were as below:

Table 1b

[m]c

[m]d

[m]gap[m] B0[mT] I [A]

0.8 0.1 0.4 0.02 0.5 1

A high level of the precision is attained for 16103 in Table 2, but thephysical achievability of the current surface density appears to be impossible. See inTable 3 some of the calculated values:

Table 2B [mT]

Numericalmethodα= 3·10-16

0.5000004 0.499997 0.499994 0.499999

Table 3J [A/mm]Numericalmethodα= 3·10-16

0.0249 -0.6688 9.089·104 4.12·104

Thus, we use a compromise and modify the parameter to 710 so as toreach more appropriate values:

Table 4B [mT]

Numericalmethod

α= 10-7

0.499 0.503 0.504 0.497

Of course, the picked number of values may be extended to an enlargeddomain of meshing. [6] Numerical validation of the achieved solutions is also testedwith a FEM procedure. [7]

5. CONCLUSIONS

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Electromagnetic device design synthesis-76-

Synthesis design of an electromagnetic industrial coil has been proposed. Anoptimal approach from which uses a numerical regularization method, leads toachievable and precise results. Special attention had to be given to the choice of theregularization parameter for Tikhonov regularization numerical method.

REFERENCES

[1]. Micu D., Micu Adriana, Electromagnetic field synthesis (in Romanian),Mediamira, Cluj-Napoca, 2005.

[2]. Tikhonov A. N., Arsenin V. I., Methodes de resolution de problemes mal poses,Edition MIR, Moscou, 1974.

[3]. Micu D. D., Ceclan A., Micu D., Simion E., Synthesis Method of an InductiveSensor using Tikhonov Regularization Procedure, OIPE’06, Sorrento, 2006, pp. 177 – 178.

[4]. Ceclan A., Micu D. D., Micu D., Simion E., Tikhonov Regularization forElectric Field Synthesis, Numelec`06, Lille, 2006, pp. 175-177.

[5]. Hansen C., Analysis of Discrete Ill-posed Problems by Means of the L-curve,SIAM Review, Vol. 34, No. 4, 1992, pp. 561 – 580.

[6]. Micu D. D., Ceclan A., Numerical Methods, Electrical Engineering Applications(in Romanian), Mediamira, Cluj-Napoca, 2007.

[7]. Ţopa V., Optimal Design of electromagnetic Devices, Casa Cartii de Stiinta, Cluj-Napoca, 1998.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 77-82

ELECTRONIC TIME RELAYS WITH DIFFERENTFUNCTIONS WITH T.T.L. INTEGRATED CIRCUITS

IOSIF POPA, GABRIEL NICOLAE POPA , SORIN DEACONU

Abstract. The paper introduces the configurations of electronic devices with T.T.L.integrated circuits performing mains timing functions. These can be used in commandinstallations with T.T.L. static switching elements. In order to be used in command installationswith contact, the analogical time circuits have as an operation element an electro-magneticrelay, whose coil is charge of a logic amplifier. The main element of the electronic time devicesis a T.T.L. monostable, whose work time can be modified with a resistance. The maxim value ofthe work time of those devices is 27,5 s. These circuits perform the main functions: drivetiming, recovery timing and drive and recovery timing, and also used logical NOT, OR andNOR circuits.

Keywords: control relays, protection relays, electronic time relays.

1. INTRODUCTION

The timing circuits used in the command installations using T.T.L. integratedcircuits have as a basic element the CDB 4121 E monostable circuit (CBM) [1], [2],[3]. The T.T.L. monostable multivibrator has the circuit diagram given in fig.1.a,where we also gave the arrangement used to check its functioning. With thisarrangement structure we achieved the timing function, specific to a photographictime-relay. The command part of the monostable multivibrator is made of the logicalcircuits I and II. Signal D, obtained as output of AND circuit II depends on signals A1,A2 and B, according to function:

Ph.D. Associate professor Eng., Electrotechnical Department, Faculty of EngineeringHunedoara, ‘’POLITEHNICA’’ University of Timişoara, Romania Ph.D. Lecturer Eng., Electrotechnical Department, Faculty of EngineeringHunedoara, ‘’POLITEHNICA’’ University of Timişoara, Romania

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Electronic time relays with different functions with T.T.Lintegrated circuits.-78-

BAAD;BAAD;BAD 2121 (1)These values of the output signals are maintained along the period of time:

CR693.0t;2lnCRt ll (2)The time circuit works normally if R = (1.4, …. ,40) k and C = (0,1….,1000)

F. For the maximal values of the parameters of these elements (Rmax = 40 k, Cmax=1000F) a maximal work time is obtained: s5,27t;CR693.0t maxlmaxmaxmaxl .

Fig.1.a. The block diagram using the CDB 4121 E monostable circuit, achieving the function ofa photographic time-relay; b. the block diagram; c. the diagrams of the signals x = f1(t) and y =

f2(t); d. The simplified diagram.

Using the CDB 4121 E monostable as a basic element, one can createelectronic drive-timing circuits, recovery-timing circuits of with timing for bothdriving and recovery.

If signal y at the output of the electronic circuit given in fig.1.a attacks a logicamplifier having as charge an electro-magnetic relay, we obtain a photo-type timeelectronic relay, which can be used in command installations with contacts [2], [4], [5].

2. DRIVE TIMING ELECTRONIC CIRCUITS

The functional diagram of this circuit is given in fig.2.a. For the initial state,when x = 0, E = 1 and F = 1, y will therefore be 0. When, after time t0 the value of

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Popa, I., Popa, G., N., Deaconu, S. -79-

signal x (x = 1) has changed, E = 0, but F keeps its logical value 1 for a very shorttime, depending on the time constant.

111 CRT (3)

Fig.2.a. The functional diagram of the drive timing electronic circuit; b. the block diagram [5];c. the diagrams of the input (x(t)) and output (y(t)) signals.

Along this very short interval of time, CMB switches and Q = 1, so y = 0 evenafter signal F changes its value (F = 0). Signal Q preserves its logic value 1 all alongthe time period tl, calculated by means of (2) and controlled by modifying resistor R.According to the corrected time tl, Q = 0. As signal F = 0 also, it thereby results y = 1.Signal x is kept at the logic value 1 all along the period tx (fig.2.c.). After the value ofsignal x (x = 0) has changed, E = 1, but signal F keeps its logic value 0 for a shortperiod of time, determined by time constant T1, after which F = 1 and y = 0.

3. RECOVERY TIMING ELECTRONIC CIRCUIT

The functional diagram of this circuit is given in fig.3.a. In its initial state,signal x(t) has the logic value 0, therefore A = 0, E = 1, F = 0, B = 0, D = 0, Q = 0,y1(t) = 0 and y2(t) = Q = 0. Changing the value of signal x(t) (x(t) = 1) after time t0(fig.3.d.), A = 0, E = 0, F = 1, B = 1 only after condenser C1 is charged – in a shortperiod of time (R1C1 << RC), therefore D = 0, Q = 0 (y2(t) = 0) and y1(t) = 1 (at thesame time with B = 1). These values of the signals are maintained all along time tx.After this period of time, x(t) passes from logic value 1 to logic value 0 (x(t) = 1 0)and the other signals have the values A = 1, E = 1, F = 0, condenser C1 starts to

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Electronic time relays with different functions with T.T.L. integrated circuits-80-

discharge, but for a short period of time B = 1. As A = 1 also, D = 1 and themonostable switches. It results that Q = 1 (y2(t) = 1), and maintains this value along theperiod tl, given by relation (2). y1(t) = 1 also and therefore y1(t) = 1 in the time intervaltx + tl. Using output y1(t), the circuit performs the function of recovery timing, variant I(the block diagram is given in fig.3.b.) and using output y2(t), the circuit performs thefunction of recovery timing , variant II (fig. 3.c.).

Fig.3.a. The functional diagram of the recovery-timing electronic circuit; b. The block diagramof the recovery-timing electronic circuit, variant I; c. The block diagram of the recovery-timing

electronic circuit, variant II [5]; d. The time modifications of the input output signals.

4. DRIVE AND RECOVERY TIMING ELECTRONIC

The electronic time circuit used in drive and recovery timing (fig.4.a.) is made ofthe ensemble of circuits performing the drive timing (fig.2.a.) and recovery timing(fig.3.a.).

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Popa, I., Popa, G., N., Deaconu, S. -81-

Fig.4.a. The functional diagram of the drive and recovery timing electric circuit; b. the blockdiagram [5]; c. the variation of the input (x(t)) and output signals (y(t)).

In order to perform this function, the output of the drive timing circuit isconnected to the input of the recovery timing circuit.

The CBM 1 monostable multivibrator has the work time:111la CR693.0tt (4)

The CBM 2 monostable multivibrator has the work time:222lr CR693.0tt (5)

5. CONCLUSIONS

The paper establishes the configurations of the main time electronic circuitsbased on the CDB 4121 E monostable and using TTL integrated circuits. These circuitsperform the functions: drive timing, recovery timing and drive and recovery timing,within work times of up to 27,5 s. In order to eliminate a random functioning of thesetime electronic circuits, we used R–C type integrated circuits with low time constants,which do not have a significant influence upon the work time of the time electroniccircuits, as given in relations (2), (4) and (5). These circuits can be used in commandinstallations, which TTL static switching elements, in cable logic.

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Electronic time relays with different functions with T.T.L. integrated circuits-82-

REFERENCES

[1] Morris R.L., Miller J.R., Designing with T.T.L. Integrated Circuits, TexasInstruments Incorporated, U.S.A., 1971.

[2] Pop E., Automatizări în industria minieră, Editura Didactică şi Pedagogică,Bucureşti, Romania, 1983.

[3] Pop V., Popovici V., Circuite de comutare aplicate în calculatoarele electronice,Editura Facla, Timişoara, Romania, 1976.

[4] Popa I., Nekula Fr., Maksay Şt., Releu electronic de timp cu structură variabilă,Invention Patent, RO 106044/30.01.1993, Romania.

[5] Popa I., Popa G.N., Dispozitive electronice cu structură cablată şi programată, deprotecţie a motoarelor asincrone trifazate de joasă tensiune, Editura Mirton, Timişoara,Romania, 2000.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 83-86

ESTABLISHING OF THE EFFECTS PRODUCED BY THEPASSIVE FILTERS OF RC TYPE ON THE SINUSOIDAL

VOLTAGE SOURCE

CORINA CUNŢAN , IOAN BACIU

Abstract: This work is analysing the influence of the passive filters upon theparameters of the single-phase supply line of a resistive consumer using the Lab VIEWprogram. The filter’s model is represented by the mathematical function related to eachharmonic in part, expression which is introduced based on a previously established law. It’saiming the possibility to modify the filter’s expression depending on the power supply line’sparameters.

Keywords: RC filters, power, current, voltage

1. WORK’S PRESENTATION

In order to compensate the harmonics of the currents absorbed from thedistribution networks by different consumers of which supply is made by commutationelements are used passive and/or active power filters of high performance. In the usualcase, the passive filters are influenced by the modification of the own resonancefrequency of the power supply network. This present survey is analyzing the situationwhen the own filter’s frequency is modifying by a sinusoidal law and the network’sfrequency remains unmodified. The operation is emphasized by showing on the samegraphic the input voltage, the current and signal’s power on the load resistance, as wellas by showing the related frequency spectrum, determined with the Fourier

It’s used a signal generator which allows to obtain two dephased outputsignals, with a phase displacement imposed depending on the capacitor’s and coil’svalues, which is the one introduced by the two elements in the circuit. The twoelements are modeled by a mathematical law and which takes into account thesinusoidal shape we want to have the filter’s impedance module.

Ph. D. eng University from Timişoara, Faculty of Engineering from Hunedoara. Dipl. Eng. University from Timişoara, Faculty of Engineering from Hunedoara

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Establishing of the effects produced by the passive filters of rc type onthe sinusoidal voltage source-84-

KR

xn

CCXsin

10

1

where: R and C are values to be imposed for the resistance, respectivelycapacitor.

K is a constant value;n is a weighting factor of capacitor’s value;

xsin signal generated by a sinusoidal signal generator.Considering the two ideal elements, without loss resistance, is obtaining

the RC circuit’s impedance:

xC

nRx

C

nRZ sin10sin10

Having the impedance value, will be obtained the current through the RCcircuit:

1sinsin2sin2 tt

xZUt

ZU

FI ;1t

where: represents the phase displacement introduced by RC for the signalgenerator’s function from the input circuit on the load circuit sR , and is thegenerator’s pulsation.

SRRCX

arctg

Is obained: - the energy stored in the RC filter by the relation:

)sin

102212)(

212

21

xC

nICXICCUnE

- input signal inUtUinU sin2

- signal’s power on the filtration circuit

tUttZUP sin21sin2

- current through the filtration circuit

1sinsin2sin2 tt

xZUt

ZUI

Is applied the Fourier Transformation upon the current and is obtained thespectrum’s module for a sampling sequence of 250Hz.

The circuit’s operation diagram (fig. 1) drawned in LabView allows thevisualization of the connexions between the elements which intervene, as well as themodality to implement the mathematical relations.

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Cunţan, C., Baciu, I. -85-

Thus are obtained the wave shapes of the voltage, current and power (fig. 2), thefrequency spectrum (fig. 3) and the energy stored in the RC filter (fig. 4).

Fig.1

Fig.2

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Establishing of the effects produced by the passive filters of rc type onthe sinusoidal voltage source-86-

2. CONCLUSIONS

The harmonics spectrum emphasizes the existence of the harmonics in theform of the curtent through the filter, harmonics which have a large spectrum andrelatively small values against the fundamental.

For the signal power on the filter is found its double variation frequency, aswell as a shape distorsion at maximum values. Also, one can observe the phasedisplacement imposed between voltage and current.

Interesting is how it’s presenting the shape of the energy stored in the RCfilter, being obtained more simultaneous values, which leads to more sinusoides ofdifferent amplitudes and identical frequency.

REFERENCES

[1] Pop E., Naforniţă I., Tiponuţ V., Toma L., Mihăescu A., - Metode înprelucrarea numerică a semnalelor, Editura Facla, Timişoara 1986;

[2] Cottet F., Ciobanu O., - Bazele programării în LabVIEW , Editura Matrix Rom ,Bucureşti 1998.

Fig.3 Frequency spectrum

Fig.4 Magnetic energy

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 87-90

IMPROVEMENT METHODS AND TECHNICAL TESTSFOR TECHNICAL EQUIPMENT INTENDED FOR USE IN

AREA WITH COMBUSTIBLE DUSTS

LEONARD LUPU*, NICULINA VĂTAVU**, FLORIN PĂUN***

Abstract: In many industrial branches, the technological processes are closely relatedto manufacturing, processing, handling, transportation and storage of the combustible dusts thatgive rise to fire hazards and, in air mixtures, in certain concentrations, and in the presence of aignition source, give rise to explosion hazards.

In the paperwork was carried out a study regarding the explosion and/or fire risk -factors that determine explosion risk occurrence; the safety requirements in order to prevent thatrisk; and technical solutions proposed for the electrical apparatus used in explosive atmosphereswith combustible dusts, taking into account especially the maximum admissible temperature ofthe apparatus surfaces, temperature that should be lesser than the ignition temperature of thedust or layer cloud, so as the normal protection degree IP5X or IP6X is ensured.

Key words: combustible dusts, ignition source, explosion hazard, explosion risk ,normal protection degree

1. GENERALITIES

Many types of dust that are generated, processed, handled and stored, arecombustible. When ignited they can burn rapidly and with considerable explosive forceif mixed with air in the appropriate proportions. It is often necessary to use electricalapparatus in locations where such combustible materials are present, and suitableprecautions must therefore be taken to ensure that all such apparatus is adequatelyprotected so as to reduce the likelihood of ignition of the external explosiveatmosphere. In electrical apparatus, potential ignition sources include electrical arcsand sparks, hot surfaces and frictional sparks.

* D.Eng, research assistant at INSEMEX Petroşani** D.Eng, senior scientific researcher III at INSEMEX Petroşani*** D.Eng, scientific researcher at INSEMEX Petroşani

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Improvement methods and technical tests for technical equipmentintended for use in area with combustible dusts-88-

Areas where dust, flyings and fibres in air occur in dangerous quantities areclassified as hazardous and are divided into three zones according to the level of risk.

Generally, electrical safety is ensured by the implementation of one of twoconsiderations, i.e. that electrical apparatus be located where reasonably practicableoutside hazardous areas, and that electrical apparatus be designed, installed andmaintained in accordance with measures recommended for the area in which theapparatus is located.

Combustible dust can be ignited by electrical apparatus in several ways:– by surfaces of the apparatus that are above the minimum ignition temperature of

the dust concerned. The temperature at which a type of dust ignites is a function ofthe properties of the dust, whether the dust is in a cloud or layer, the thickness ofthe layer and the geometry of the heat source;

– by arcing or sparking of electrical parts such as switches, contacts, commutators,brushes, or the like;

– by discharge of an accumulated electrostatic charge;– by radiated energy (e.g. electromagnetic radiation);– by mechanical sparking or frictional sparking associated with the apparatus.In order to avoid ignition hazards it is necessary that:– the temperature of surfaces on which dust can be deposited, or which would be in

contact with a dust cloud, is kept below the temperature limitation specified.– any electrical sparking parts, or parts having a temperature above the temperature

limit specified. are contained in an enclosure which adequately prevents the ingress of dust, or the energy of electrical circuits is limited so as to avoid arcs, sparks or

temperatures capable of igniting combustible dust;– any other ignition sources are avoided.

2. ELECTRICAL APPARATUS FOR USE IN THE PRESENCE OFCOMBUSTIBLE DUST

In order to select appropriate electrical apparatus for use in a zone 20, 21and 22 hazardous area, the following information is required:a) The classification of the area, i.e. the zone.

The layer ignition temperature of the combustible dust involved or the lowestlayer ignition temperature if more than one combustible material might be present.If the installation is likely to be subjected to excess layers, then the layer ignitiontemperature for the maximum layer depth of the combustible dust(s) will berequired.

b) The cloud ignition temperature of the combustible dust involved or the lowestvalue of cloud ignition temperature if more than one combustible material mightbe present.

c) Where applicable, the minimum cloud ignition energy of the dust involved or thelowest minimum ignition energy if more than one combustible material might bepresent (see 6.3.3).

d) Electrical resistivity (conductivity).

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Lupu, L., Vătavu, N., Păun, F. -89-

Electrical apparatus selected for use in a combustible dust hazardous area shallbe protected by one or a combination of the following types of explosion protection toensure the safety of electrical apparatus:a) dust excluding, ignition-proof enclosures (Ex tD); enclosures complying with

IEC 61241-1;b) encapsulated apparatus (Ex mD); encapsulated apparatus complying with

IEC 61241-18;c) intrinsically safe apparatus (Ex iD) complying with IEC 61241-11;d) pressurized enclosures (Ex pD); pressurized enclosures complying with the

requirements for dust hazardous areas, specified in IEC 61241-2.Electrical apparatus for zones 20, 21 and 22 is intended for use in an ambient

temperature within the range –20 °C to +40 °C, unless marked accordingly. Whereapparatus is installed in an area where the local ambient temperature is likely to beoutside the specified range –20 °C to +40 °C, precautions shall be taken to ensure thatthe apparatus operates within its specified range. Examples of such sources mightinclude solar heating, an electric heater or a boiler.

When apparatus is to be located where its ambient temperature is not within itsspecified range, then the justification for this decision shall be documented. Thisdecision should take into account the rating of components and the possibledeterioration of enclosures and insulation and any other factors which adversely affectthe method of protection. Consultation with the manufacturer and, where appropriate,the certifying authority for the apparatus so as to make an informed decision, willnormally be necessary

Dust layers exhibit two properties as layer thickness increases: a reduction inminimum ignition temperature and an increase in thermal insulation.

The maximum permissible surface temperature for apparatus is determined bythe deduction of a safety margin from the minimum ignition temperature of the dustconcerned, when tested in accordance with the methods specified in IEC 61241-20-1for both dust clouds and layer thickness of up to 5 mm for type of protection “tD”,practice A and all other types of protection, and 12,5 mm for type of protection “tD”practice B.

The maximum surface temperature of the apparatus shall not exceed two-thirdsof the minimum ignition temperature in degrees Celsius of the dust/air mixtureconcerned:

Tmax = 2/3 TCLwhere TCL is the minimum ignition temperature of the cloud of dust.

3. IMPROVEMENT METHODS AND TECHNICAL TESTS FORTECHNICAL EQUIPMENT

Enclosures with the degree of protection IP 5X “Dust protected” do not haveto prevent ingrees of dust totally. However, dust should not penetrate in an amountsufficient to interfere with the satisfactory operation of the equipment enclosed or toimpair safety. In the case of enclosures with degree of protection IP6X “Dust tight” itis necessary to prove that no dust can penetrate into the inside of the enclosure. The

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Improvement methods and technical tests for technical equipmentintended for use in area with combustible dusts-90-

talcum powder must be prepared in such a manner that it will pass through a sieve witha mesh size of 0,075mm. The quantity of talcum given in the regulation is 2 kg percubic of test cabinet volume. The enclosure under test, in the following calledspecimen, is suspended in the test cabinet and – if prescribed – connected to a vacuumpump. This produces inside the specimen a depression of maximum 2 kPa = 20mbar(=approx. 200 mm water column) bellow atmospheric pressure. The test is completedafter 2 hour, if within 2 hours 80 to 120 times the air volume of the specimen has beendrawn through.

Fig.1 Dust test Chamber

1 to 3 dust circulation pumps (12) with transfer pipes (13) and dust distribution out-less(14); 1 pressure equalizing air filter (15); 1 to 3 electric vibrators (16) at the funnels, toremove dust deposition from the walls; 1 to 3 electric heating elements (17) inside ofthe test cabinet to keep the talcum powder dry; 1 vacuum pump (18) to cause adepression inside of the specimen; 1 depression indicator (19); 1 dust filter (20) withremovable insert, to collect the dust, which has been exhausted out of the specimen; 1air volume meter (21) with pointer and counter; 1 vacuum connecting fitting with shut-off valve (22) in the test cabinet behind the door, with hose (23), 2m long, to connectthe specimen; 1 socket outlet (24) inside of the test cabinet for energizing thespecimen, two-pole with side earthing contacts.

4. CONCLUSIONS

As a consequence of these improvements, the assessment and testing level ofthe technical equipment intended for use in area with combustible dusts has increased.

REFERENCES

[1] SR CEI 61241 Aparatură electrică destinată utilizării prezenţa prafuluicombustibil

[2] SR EN 60529 Grade de protecţie asigurate prin carcase (Cod IP)[3] www. Product SafeT.com – Educated, Design and Development Inc.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 91-96

INCREASE OF ENERGETIC EFFICIENCY AT S.E.PAROSENI PLANT CONCERNING OF ENVIRONMENTAL

EUROPEAN RULES

DORU VISAN, DANIELA MARDARE, ADRIANA BUSONIU,ILEANA MARCU

Abstract: The paper present the rehabilitation work at SC Termoelectrica SA –Paroseni Branch, by development the 4th energetic group, which include the setting of a newgenerator and steam boiler, designed and made by Japanese companies.

Keywords: S.E. Paroseni, energetic efficiency, environment, electric and thermalenergy

1. INTRODUCTION

The SC Termoelectrica SA – Paroseni Branch is the first thermoelectric powerplant from Romania. During the activity our plant had the following developmentstages: 1979 – opened the founding to pass from the urban heating to the central

heating, with the unique source at the CET Paroseni. 1980-1983 - accomplish the development 3x50 MW turbine engine from

compression turbine to the heating turbine with controller setting (1,5-2,5 ata) 1999 – putting into service of CAF –100 Gcal/h to assure the peak heating

values.The heating system of Jiu Valey is assured by two transport base-lines which

supply 24 consumers, four of them supply urban consumers from Petroşani, Vulcan,Aninoasa, Lupeni (fig.1). The monitoring of the parameters are made directly from theplant, with some dedicated systems, and the data transmission is made through GSMsystems.

Eng., manager, SC Termoelectrica SA – Paroseni Branch Eng, SC Termoelectrica SA – Paroseni Branch

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Increase of energetic efficiency at S.R. Paroseni plant concerning ofenvironmental European rules-92-

Thermal energy to consummers

42%

2%25%

20%

11%

Petrosani Aninoasa Vulcan Lupeni Others

Fig.1.

Taking into account that the most important factors for the durabledevelopment in Romania are the growth of economy, security of electric and thermalenergy distribution, decrease of pollution due to the energy generation, the presentattention of SC Termoelectrica SA plant (fig.2) is to integrate to the Europeanenvironmental policy and to be a real competitor to the energy market.

Fig.2.

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Visan, D., Mardare, D., Busoniu, A., Marcu, I. -93-

These are possible only with development of technology and equipments,taking into account that the existing equipments are appreciatively 50 years old. After1998, we began negotiations with a Japanese corporation (ITOCHU – HITACHI –TOSHIBA CORPORATION) to start a rehabilitation works to the 4th energetic group,which include the setting of a new generator and steam boiler, designed and made byJapanese companies.

The rehabilitation of 4th energetic group from CET Paroseni is now the biggestinvest in energetic area, after 1989, the amount of this invest is around 191 millionEUR, and founding are around 80% from the Japanese bank credit.

2. REHABILITATION OF THE 4TH ENERGETIC GROUP

With rehabilitation of the 4th energetic group are followed the next targets: decrease of polluting emission, monitoring, evaluation and report of

polluting emission levels in accord with 2001/80/CE; increase of work length of energetic group with about 150.000 h.; increase of main equipments reliability; operating performance of energetic group will be at the same lavel like

the best groups of SEN ;The 4th energetic group (fig.3) will be equipped with reduced NOx burners with

a 400 mg/Nm3 maximum emission of nitrogen oxide, and the electro filters will beupdating to be in the European rule of 100 mg/Nm3.

Fig.3.

The rehabilitation of the 4th energetic group consists in: BABco*k HITACHI BOILER

Performances: Efficiency – 90,7%

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Increase of energetic efficiency at S.R. Paroseni plant concerning ofenvironmental European rules-94-

Availability - 91% Flow – 540 t/h Pressure – 138,2 bar Temperature – 540 °C The boiler has 4 roll mills, with capacity of 43,1 t/h each, located on +0,00height on the lateral side of the boiler. Work in good parameters is assured withthree mills. The boiler has 16 reduced NOx burners with a 400 mg/Nm3 maximum emissionof nitrogen oxide, installed on the front and back side of the boiler, burners whichpulverize the coal from the mills according with BAT techniques.

KK--116600--113300--22ÕÕPP22 TTUURRBBIINNEE Supplier: the company TURBOATOM Ucraina. The turbine is especially built for operating in co-generation (BAT technology)

with the possibility to extract maximum thermal energy, sacrificing theelectrical energy..The turbine performances are:

Electric and thermal energy produced in co-generation - 146 MW şi 150Gcal/h.

Heat specific consumption - 282 grcc/kwh Turbine availability – 96% Unit availability - 87% Flow – 540 t/h Pressure – 130 bar Temperature – 535 °C.

TTAAKKSS GGEENNEERRAATTOORR Supplier – Toshiba Company Japan The only one air cooling generator in Europe with following parameters: Voltage – 18 kV Rated power - 176,5 MVA Efficiency - 98,5%

PP332200TTGGCC EELLEECCTTRROO--HHYYDDRRAAUULLIICC CCOONNTTRROOLLLLEERR Supplier - ALSTOM France To connect at the UCTE and in order to respect the constraint, will be used a

new controller, electro-hydraulic instead of the existing one which ismechanic-hydraulic.

The special measurements (vibrations, axial movements, displacements,expansion) will be performed on-line with high quality devices.

DDIIGGIITTAALL DDIISSTTRRIIBBUUTTEEDD CCOONNTTRROOLL SSYYSSTTEEMM MMAAIINN AAUUTTOOMMAATTIIOONNSSYYSSTTEEMM ((DDCCSS))

Unit IV is endowed with a distributed control system, type TOSMAP DSprovide by Toshiba Company (fig.4).

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Visan, D., Mardare, D., Busoniu, A., Marcu, I. -95-

This system can lead by means of control loops the entire unit as follows:-boiler following- turbine following-Boiler +turbine operate independently.

The unit can work without operator interference between 50% and 100% ofload.

DCS system record the events, the operating parameters and compute on-line themain technical and economical parameters.

Fig.4.

110 kV Substation (fig.5)

5 related bays will be rehabilitated Overhead Electric Line Baru Mare II Auxiliary transformers 51 Bay for Generator 4 Transversal coupling bay and measurement group Transformer bay of 110&220 kVFor operating security the protection installation of each bay are provided with

numerical protections segregated in two main and spare groups.

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Increase of energetic efficiency at S.R. Paroseni plant concerning ofenvironmental European rules-96-

Fig.5.

REFERENCES

[1] Studiul de fezabilitate pentru reabilitarea blocului numãrul 4 de la CET Paroşeni –ISPE Bucureşti, 2000;

[2] Directiva 2001/80/CE – Limitarea emisiilor în aer a unor poluanţi din instalaţiilemari de ardere;

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) .pages 97-106

INTEGRATED STARTER-GENERATOR MACHINES FORHYBRID AUTOMOTIVE VEHICLES

DAN STOIA , MIHAI CERNAT

Abstract - The advent of higher voltages in automobiles constitutes an opportunity fornew electrical features and systems. In that regard, an integrated starter/generator (ISG) alsocalled integrated starter/alternator (ISA) would have several important benefits, most notably, itwould enable the turning off the engine at idle and provide efficient high power generation,both resulting in improved fuel economy. The objective of this paper is to provide a guideline toISG engineers and other automotive engineers as well as people who are interested in mild-hybrid electric vehicles.

Keywords: integrated starter/generator (ISG), integrated starter/alternator (ISA), mild-hybrid electric vehicles,

1. INTRODUCTION

Internal combustion engines are generally paired with two electrical rotatingmachines. One is a motor, optimised for overload operation at low speed and hightorque, functioning as starter. The other machine is optimised for continuous operationat high speed, at much lower torque, functioning as generator. Commonly availablecommercial starters are brush commutated dc machines, while typical generators areclaw pole synchronous machines (Lundell alternators) with rectified output.

Implementations of starter/generators (ISG) for automotive use are quiteattractive, and have been explored for some time. Some have reached production incurrent hybrid vehicle systems from Toyota, Honda, and others. However,starter/generator is not in wide use on conventional ICE vehicles, and hybrids onlyaccount for approximately 1% of new car sales. There are several reasons for this. Thefirst could be termed the “installed base” effect: systems become cheap and wellknown because they are in common use; the same systems are then used elsewhere be-cause they are cheap and well known. The second reason is interface: the starter isgenerally connected to the engine via gear teeth on the flywheel, while the alternator is

Professor PhD , “Transilvania” University of Brasov, Romania,

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Integrated starter-generator machines for hybrid automotive vehicles-98-

connected using a belt system. The gear ratios are generally different, and theoperational life is designed differently. Finally, the use of starter/generator introducesnew control issues.

In common use, the starter is a dc motor connected “across the line” to thebattery via a contactor, and the alternator is directly connected to the dc bus via simplerectifiers. Control of the alternator output is via control of alternator field, usuallythrough a wound field coil on the claw pole rotor. These are extremely simple, robust,and inexpensive controls. A starter/generator requires a more complex controlmechanism; one that can transition the machine between starting and generatingoperations.

A reasonable sized starter/generator would be sufficient to handle the kinds ofoverloads required in order to start the engine. While operation in overload means thatthe motor would heat rapidly, the thermal mass of a motor the size of the current startermotor is usually more than adequate to handle the start duration of an engine start. Butthe alternator is optimised for high-speed operation, and the starting loads are at lowspeeds. This means that the power electronic control system must be capable ofproviding extremely high current at low voltage for the low speed, high torqueoperation, while the same time being capable of providing normal voltage and currentfor high speed generation operation. With three-phase and brushless technologies, thismeans that the drive has to be greatly oversized in order to provide the necessarycurrent for the starting loads.

The power ratings of starters and alternators often hide a significant pitfall. Aninverter is normally rated in terms of horsepower or kilowatts. But if one looks at thedetailed ratings, both voltage and current are separately limited, and full power is onlyavailable when full voltage is combined with full current. Because of thevoltage/frequency ratio of most controlled motors, full power is only available at fullspeed. When conventional inverter is paired with a conventional motor, capable ofproviding the starting overload current at low speed and low voltage and runningcurrent, the result is a greatly oversized inverter.In automotive engineering, the development of secondary aggregates is on the verge ofa huge tap forward which reduce the overage fuel consumption by approximately 0.7-1.7 l/100 km. The extent of the reduction will depend on which partial or secondaryaggregates are “electrified” or newly added. The following electric aggregates areprimarily included: electromagnetic valve timing; electric water pump; pump forcooling; electro-mechanical brake; electric air conditioning compressor; crankshaftstarter-alternator. These aggregates of which some are innovative require a safe andbalanced energy management system made up of battery storage and electromechanicalenergy traducer (alternator) with the maximum efficiency. Whereas batteries with arein use today already have a high level of energy development, this does not necessarilyapply to the alternators, which are referred to as claw-pole generators. Its efficiency isat about 20-50% within the full-load range, which is restricted to about 2 kW poweroutput at present with no further substantial increases to be expected. The most obviousconclusion would be to use reliable and sturdy electromechanical energy converters,which are highly efficient for future electrification in automotive engineering.Otherwise a significant reduction of fuel consumption would hardly be possible.

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Stoia, D., Cernat, M. -99-

In order to reach such goals, highly-efficient alternators must be able to transmit theirrated output to a broad speed range. With reference to the crankshaft speed ofcombustion engine, its speed range would be between 100 r/min and 7000 r/min.

Therefore, contemplations on other constructive solutions were made at anearly stage and consisted of coupling the alternator and starter as an integrated systemdirectly to the crankshaft. According to this integrated solution, which consisted of oneelectric machine, only the latter was operated both as a starter motor and as analternator.

At the moment it can be noted that the following constructive alternative isappearing to be a highly integrative solution. The flywheel of the combustion engine,which is directly connected to the crankshaft, serves additionally as a rotor of thestarter-alternator and also includes clutch. Depending on the type of electrical machinethere is also an active engine vibration control, control of the driving mechanism. Thebearings are already available and are therefore not part of the starter-alternator, whichis a further advantage of this highly integrative solution. The starter is “simply builtaround the flywheel of the combustion engine” by means of which further friction lossprevented in the ISG (efficiency improvement).The electric machine with a short end-turn is valuable because a thick, short machinepackage is required in the available space. The machine rotor replaces the flywheel andtakes over its available mechanical damping function so rotor inertia is not so critical.

A histogram of vehicle propulsion energy as a percentage of drive cycle versuspower shows that most energy is consumed where the internal combustion engine isleast efficient, conversely, only a small fraction of total propulsion energy is consumedat loads points at and above the peak internal combustion engine efficiency region.

2 ISG SYSTEM CONFIGURATIONS

A conventional power-train system is composed of a gasoline/diesel engine,energy storage battery/batteries, mechanical transmission, and power-train control. Ifan ISG system is added to the power-train subsystem, a conventional power-trainbecomes a hybrid power-train system. The ISG electric drive subsystem consists of anelectric machine and a power electronic box.If a new electric machine is mounted directly on the crankshaft, the conventionalalternator and starter as well as the mass damper and flywheel, including the ring gear,can be eliminated and the new electric machine can replace their functions. This is theconcept of the crankshaft-mounted integrated starter-generator (ISG).

The electric machine with a short end-turn is valuable because a thick, shortmachine package is required in the available space. The machine rotor replaces theflywheel and takes over its mechanical damping function so rotor inertia is not socritical. The ISG machine is located at the place where the conventional alternator isremoved. It can be driven by either a separate belt or included in the existing beltsystem. The belt transfer ratio accelerates the ISG machine speed; so low rotor inertiaand high structure strength are preferred. A typical ISG system consists of an electricmachine, a power electronic inverter/rectifier, a dc-dc converter, and an optional

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Integrated starter-generator machines for hybrid automotive vehicles-100-

additional starter for initial cold cranking. A dual-voltage system can avoid reformingall vehicle 12 V loads.

3 ISG CAPABILITY REQUIREMENTS

In practice, the available 30-36 V battery voltage at motoring and the required 36-42 Vcharging voltage at generating are the main challenge during electric machine design.The requirement of a wide speed range and the high temperature of cooling mediabring several new critical issues to the electric machine in the ISG system. The ambienttemperature ranges from -40°C to 125°C, which is a typical requirement for an air-cooled ISG machine. The speed of the electric machine runs from zero to 6000 r/minfor crankshaft-mounted ISG system, which is the same as the engine speed. Themaximum operation speed of a electric machine runs as high as 13,800 -19,200 r/minwith the belt-transfer ratio 2.3-3.2.

In the 42 V dc electrical systems, the motoring performance specificationsshould be met even at a lower voltage level of 30-33 V dc and the maximum availablebattery voltage at dc input of electric machine drive is 36 V. If a 14 V dc electricalsystem is used, the motoring operations of the machine have to be fully functional at10-11 V dc voltage in spite of the battery voltage of 12 V.Under motoring operation state, for a belt-driven ISG system, the duration of acranking cycle is normally up to 1.3 s.Full engine cranking torque is required up to 250 r/min after which it is allowed todecrease to zero above engine idle speed.For quick response and frequent stop/starts, the moment of inertia of the ISG machinerotor should be as low as possible. Although cranking time can be as short as 0.08-0.35s, the cranking torque at the required higher speed is still a big challenge to machinedesigners due to low available battery voltage at low temperature, such as -30°C.The normal generating operation is required for the ISG machine from the idle speedup to the red line speed of the engine.The torque curve for sustaining generator output required to capture vehicle a shortterm, intermittent high generator output required to capture vehicle breaking energythrough regeneration into the high voltage battery. Over the interval from low engineidle (600 r/min) to approximately 2000 r/min, the ISG may also be operated as adriveline damper for torsion oscillations.All electric power required by electric loads on or off vehicle board is supplied by ISGmachine under the generating condition, so the regenerating performances of the ma-chine, including power output and efficiency, are critical specifications. Generally, theoutput power at idle engine speed shall be larger than 35-60% of the maximumcontinuous output. Within a short time, such as 1-3 min, about 1.3-1.4 per unit poweris required for a rush charge.In practice, the available 30-36 V battery voltage at motoring and the required 36-42 Vcharging voltage at generating are the main challenge during electric machine design.Besides the dilemma from voltage specifications, the requirement of a wide speedrange (from idle 600 r/min to redline 6000 r/min) and the high temperature and tempe-rature of cooling media bring several new critical issues to the electric machine in the

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Stoia, D., Cernat, M. -101-

ISG system. The ambient temperature ranges from -40ºC to 125ºC, which is a typicalrequirement for an air-cooled ISG machine.Starter operation at low temperatures (-30ºC) makes the greatest demands on thebattery, power electronics (starter currents) and electrical motor, as the torque requiredof the starter-alternator by the combustion engine is quite considerable at the given unitvolume. This torque ranges between 200 Nm and 240 Nm for medium class cars andan estimate value of 300 Nm for high class. It is to be concluded that the torquerequirement would have to be known precisely when starting the combustion engine, inparticular at low temperatures and depending on “the most inappropriate” lubricationoil. For initial cold engine cranking, the machine has to provide a breakaway torquethat is 1.5-1.8 times the nominal cranking torque to overcome the engine static torqueand rotates the engine from 0 to 10–20 r/min at -30ºC. Depending on the design of theelectrical motor/generator a starter current of 1,000 A to 1,200 A flowing over thesemiconductors would have to be expected for a 42 V on-board system. Thespeed/voltage requirement for the ISG system rules out the machine with lowweakening capability unless a costly extra dc/dc converter is added the dc bus voltage-charging and as current reducing solution for the semiconductors.

These requirements of the combustion engine and the starter alternator wouldhave to be reliably met by the electrical battery at low temperatures i.e. the battery willbe extremely strained at such low temperature with regard to high starter current andthe starting performance. Also there would have to be a sufficiently large start torque ata low temperature (motor operation). For an ideal design of the starter-alternator it isindispensable that the interval resistance of the battery is well known.As a rule it would be possible to use the decoupling capacitor in the dc link of theconverter as an additional energy source during start-up operation and consequentlyrelieving the battery. On account of the small energy storage capacity in the electricfield, very large capacities would be essential for a sufficient energy supply during thestart. The alternator is not quite as critical from the view of electronic powercomponents as the currents are approximately 100 A. During such an operation caremust be taken that the iron less as a result of the alternator frequency at high crankshaftspeed (6000 r/min) does not increase to such to large extend so that alternatorefficiency drops to value on the level of the claw-pole alternator.Starter-generator, as others automotive applications, is very constrained. These con-strains create specific behaviours (high magnetic saturation) and limitations (current,voltage, power, energy). Moreover, terminal voltage, equal to the battery voltage,varies with the state of charge and the consumed power. All these machines mustrespect very strong rules and specifications (low size, high torque, speed andefficiency). Constraint function is of various types: torque-speed characteristics;efficiency characteristics; thermal characteristics; geometric constraints; supplyconstraintsTorque-speed characteristics [5] starter mode (M1): 215 Nm from 0 to 110 r/min generator mode (G1) Pelc=1500 W at 850 r/min generator mode (G2) Pelc=2500 W at 2000 r/min generator mode (G3) Pelc=1000 W at 6000 r/min

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Integrated starter-generator machines for hybrid automotive vehicles-102-

Efficiency characteristics 80% (including power converter efficiency) for G1, G2, G3 For M1 no minimum efficiency is required. Nevertheless, the battery current

has to be limited to a maximal value.Thermal characteristics: Thermal constrains have been taken into account by thelimitation of the current density in the windings: 50 A/mm2 max for starter mode (M1) 10 A/mm2 max for generator mode (G1, G2, G3)Geometric constraints

The maximal external diameter is 255 mm2. The value of thelaminated care would be approximately 2,500 cm2.

A typical ISG system consists of an electric machine, a power electronicinverter/rectifier, a dc/dc converter, and an optimal starter for initial cold cranking. Adual-voltage system can avoid reforming all vehicle 12 V leads. On account of theconsiderable electric power increase in the vehicle, the installation of a “two-batteryon-board system” with both voltages 14 V and 42 V would appear to be most likely,also being favoured by automobile manufacturers and suppliers.The electrical machines to be taken in consideration for use in ISG system are, as arule, brushless machines: induction machines; permanent-magnet synchronous ma-chines (non salient pole or salient pole); reluctance machines.Although the number of pole pairs can be chosen relatively freely. The torque is notdetermined by the number of pole pairs at the given geometrical conditions of the com-bustion engine. In order to reduce the iron less in dynamo sheet (0,5 mm), it isimportant for the frequency, the number of pole pairs and speed, it would be best tochoose the number of pole pairs as small as possible (minimum p=1). This solution isopposed by the for overhang of the stator winding and the large height of the yoke. Thetests revealed that the unreal number of pole pairs rangers between p=3 and p=6 underconsideration of diverging influences.From the viewpoint of an electrical motor or generator constructor this new voltagelevel of 42 V for the ISG is not the best option, as the high starter currents which alsoflow at this voltage require a large number of parallel connected semiconductors in thedifficulties known. From the viewpoint of an electrical machine constructor it would beadvisable to set the second voltage as high as safety requirements permit. Therefore, abattery voltage of 100 V to 120 V would be considered which is a voltage levelcorresponding to the maximum electromotive force in low-voltage supply systems.

4. SELECTION AND COMPARISON OF ISG ELECTRICMACHINES

4.1 Machine Sizing and WindingThe D2L electromagnetic torque sealing was employed as the first step in

designing the ISG machine given the engine cranking requirement and constraints onstator OD to fit into the transmission bell housing and on rotor ID to accommodate thecoaxial clutch. Three machine technologies (induction machine, PMDC machine, andPMAC machine) can be evaluated by varying the machine stator ID (as independent

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Stoia, D., Cernat, M. -103-

variable) and calculating machine OD and torque for each machine type given a fixedstack length. The sizing equation machine is [3]:

LDABK

KKKT gxg

pie 212

(1)

where the following notations have been used:Ke - the voltage waveform factor;Ki - the current waveform factor;Kp - power factor estimate;KΦ - ratio of the rotor/stator electric loading;Dg - the machine air gap diameter, a variable;L - the machine stack length, a variable;Bg - midgap magnetic flux density;Ax stator electric loading.During this stage of machine sizing, the decision was made in function of

magnetic material of laminations. During the second phase of the design, magnitudesAx and Bg in relation (1) were coupled.The voltage of a rotating machine is determined by the winding configuration. Thevoltage across a coil in alternating magnetic field is given by the rate change of fluxcoupling this coil. The voltage of the entire machine is set by the interconnection ofthese coils. The voltage developed in coil coupling a sinusoidal ac magnetic field isdetermined by the known relation 2/ NUe , where the following notationswere been used: Ue - rms voltage; Φ - peak flux; N - number of turns; ω -angularfrequency.

Given the same motor frame, with fixed geometry and magnetic steelarrangement, different windings design result in different voltage and currentrelationships for a given mechanical output state. Motors, which may be reconnectedfor one of two different voltage stages, are in common use. For example, reconnectinga 23 V motor as a 46 V motor would double the voltage required but the currentrequired for any given torque is halved. The net result is that on the same frame, thesame electrical power input is required to produce the same mechanical power output.But voltage can be traded for current by selecting the proper winding. By selecting amotor with a high turns count, high voltage would be required at low speed, but verylittle current is required to produce high torque. A motor with a low turn count wouldmatch the output capabilities of the inverter to high speed and low torque requirementsfor alternating operation.

4.2 Induction Machines

Most induction machines in ISG applications are three-phase machines andconnected to the dc bus through a power electronic inverter/rectifier.

Most important for the design are the curves of torque versus rotor speed whenthe induction machine runs for an ISG application: the curve represents the electricpower generation from weakening, and the curve represents the electric power

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Integrated starter-generator machines for hybrid automotive vehicles-104-

generation from the idle through the maximum speed.At the beginning of engine cranking, the induction machine produces 1,5-1,6 times ofcranking torque reaching or exceeding the breakaway torque at the lowest startfrequency fmin of the stator current. At the given fmin, the stator voltage required to drivethe engine from static state can be derived from Ue/f = constant or even higher thanthis, and voltage is higher that from Uph/f = constant during conventional constanttorque/flux control because at low frequency, the stator resistance has more effect thanstart circuit reactance. The induction machine is allowed to run at slip valuescorresponding to the maximum torque with frequency variation during crankingprocedure because this is very short (0.2-0.3 s), although the slip at the maximumtorque causes a low power factor and high machine losses at low-speed range.

At each individual frequency point, the maximum torque decreases with thestator resistance while the slip corresponding to the maximum torque, sm, isproportional to the rotor resistance. This means that the low-stator resistance benefitstorque capability while low low-rotor resistance helps the thermal capability of the ISGinduction motor. This is the reason why rectangular stator windings and moreexpensive copper rotor benefit ISG machine. The maximum torque is proportional tothe square of the ratio of voltage to frequency at the high-frequency range. Therefore,the power capability of the induction machine decreases with speed increase atconstant voltage operation by flux weakening (especially for ISG electric power gene-ration), and the constant power operation can only valid within the speed variable ratioof 3-5. Fortunately, it is not necessary for the ISG machine to run at redline speedwithout compromising the power output.

4.3 Permanent Magnet Machines

The main advantage of PM machines is their high efficiency due to theabsence of field coil losses. From the efficiency and package point of view, the PMACmachine with 6-12 poles is preferable for belt-driven ISG applications while the PMmachine with concentrated no-overlap fractional slot winding is suitable crankshaft-mounted ISG.Based on the structure of PMAC machines, they can be categorized as the surface-mounted PM type or the interior-mounted PM type. The surface-mounted PM machinecombined with concentrated windings and fractional windings has been developed forvariable speed application; its speed-variable ratio has relatively low while its no-loadEMF is very high.Surface PM can be designed to achieve wide speed ranges of constant-poweroperation. The key of the new-found capability is the fractional-slot concentratedwindings.

The adoption of fractional-slot concentrated windings makes it possible tosignificantly increase the machine’s characteristic current, defined as dmch LI / ,where Ψm is the rms flux linkage and Ld is the d-axis stator inductance. Morespecifically, the conditions for optimal flux weakening operation can be achieved bydesigning the machine so that its characteristic current equal the rated current value(i.e. Ich=Ir where Ir is the rated current of the machine). The use of conventional

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Stoia, D., Cernat, M. -105-

distributed windings in such machines with integral value of slot/pole/phase makes itdifficult to meet the conditions for optimal flux weakening. More specifically, the ma-chine phase inductance of machine with distributed windings tends to be low, leadingto characteristic current values that significantly exceed the machines rated current.The low magnetic permeability of the permanent magnets in the machine’s air gap is amajor contributing factor that causes the low inductance. High values of characteristiccurrent lead to rapid drops in the machine’s torque and power production capabilitieswhen the machine spins at speed above its rated speed.In contrast, the introduction of fractional-slot concentrated windings makes it possibleto significantly increase the machines phase inductance. With proper design, the valueof the characteristic current can be lowered and tuned to match the machine’s ratedcurrent achieving the conditions for optimal flux weakening. By introducingappropriate control for the flux-weakening regime, such a machine can achieve verywide speed ranges of constant power operation.

The current limitation circle in the sinusoidal-IPM machine is similar to that inthe surface-mounted PM machine. The stator current phasor must be inside the currentlimit circle to prevent damaging the inverter and overheating the machine, whicheverhas limitations, i.e. is<Imax. Unlike the surface mounted PM machine, the reluctancetorque in the IPM machine adds one more limitation to the operation area in d-q plane.The current id has to meet the torque limitation of [ 0)( qddf LLI ] if motoringoperation with iq>0 or a generating operation with iq<0. The torque limit area can befurther expressed by half-plane equation )(/ qdfd LLi .That is, if adjusting iq>0 for motoring and iq<0 for generating, the equation displays theright-half plane at the critical torque line of )(/ qdfd LLi The voltage limitationellipse in IPM machines have the centre located on the d-axis, and its distance from d-qplan origin is approximately equal to three-phase short-circuit current (Isc = -Ψf / Ld).The machine with p pole pairs can run for constant power by flux weakening ifΨf / Ld<Imax. The risk for this design consideration is a possible demagnetisation of thePM when the d-component of the stator current is higher than short-circuit current Iscbut is still within the current limit circle at the deep-flux weakening operation. The PMmaterials, such as NdFeB or SmCo, with a property curve extending to the thirdquadrant in B-H plane become necessary.In general, the operation during flux weakening must be limited within the intersectionof the current limit circle and the voltage-limitation ellipse as well as the torque-limitplane for each given speed.The no-load EMF of the IPM machine at its highest speed and the lowest temperatureshould be controlled within a reasonable range to keep the power electronics inverter inthe ISG system from being damaged.

The rectangular PMDC (dc brushless) machines with surface-mounted PMdoes not meet the voltage requirements at generating and the wide-flux weakeningspecifications at motoring of the ISG machine, unless a dc/dc converter is addedbetween the electronic inverter bridge and the battery. The speed-variable ratio is stillrelatively low while its no-load EME is very high.

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Integrated starter-generator machines for hybrid automotive vehicles-106-

5. CONCLUSIONS

Integrated starter/generator (ISG) is a solution for mild hybrid vehicles. High efficien-cies, low cost and easy implementation are required. Various types of electric machineshave to be considered and lead comparisons between behaviour of different machinesstructure: induction machine and PM machine, in ISG system configuration and spe-cifications. A qualitative analysis of the practical characteristics for these machines isgiven in Table 1.

By preliminary tests resulted advantages for the induction machine due to itsbeing sturdy and reliable which provided good experimental results with the use ofmodern electronics. Of course, special attention must be paid to construction (air gap).The PM machine has the disadvantage that the good magnetic characteristics are “un-determined” on purpose in order to control the voltage and that the thermo-stability ofthe permanent magnets is not very high. In case of an intern short circuit the PMalternators would brake the car unexpectedly (important question off security).

Table 1: A qualitative analysis of practical characteristics of ISG machinesElectric Machine Type PMDC PMAC IMEfficiency and compactness X X XLow torque ripple and noise X XEasy closed-loop control XFewer control sensors XWide speed range X XHigh power applications X X X

With ISG applications, the technology and experience will benefit to not onlythe ISG developers and customers, but also the entire generation of hybrid electricvehicles, especially the full-hybrid vehicle.

REFERENCES

[1] W. Cai, “Starting Engines and Powering Electric Loads with One Machine,”in IEEE Industry Applications Magazine, Nov./Dec. 2006, pp. 29-38.

[2] S. Chen, R.R. Henry, and Y. Xue, “Design and testing of a belt-driveninduction starter-generator,” IEEE Trans. Ind. Applications, vol.38, no 6, Nov./Dec. 2002, pp.1525-1533.

[3] D.D. Stoia, “Induction motor and dc brushless in integrated inverter-electrical machine design,” “Transilvania” University Publisher, Brasov, 2006 (in Romanian).

[4] T.M. Jahns, “Flux weakening regime operation of interior PM synchronousmotor drive,” IEEE Trans. Ind. Applications, vol.23, no 4, July/Aug. 2000, pp. 681-689.

[5] G. Friedrich, L. Chédat, “Need of an optimal design and control approach,”EMD’05, Madison, WI, 2005, pp. 1529-1534

[6] I.A.Viorel “Special electrical machines for ISA systems” Revista de politicastiintei, raport, Cluj-Napoca, 2005 (in Romanian).

[7] V. Hajek, M. Travnicek, B. Kysely, “Integrated Starter-Generator,” ACEMP2004, Istanbul, Turkey, 26-28 May 2004.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 107-111

MODERN SYSTEM FOR MONITORING AND DIAGNOSISOF THE MECHANICAL AND ELECTRICAL DEFECTS

FOR HIGH CAPACITY INDUCTION MOTORS

SORIN DEACONU , GABRIEL NICOLAE POPA , IOSIF POPA ,IOAN RODEAN

Abstract: This paper presents a modern system for monitoring and recording thevibrations of the high capacity induction electric motors, for the purpose of predictive diagnosisof electrical or mechanical defects. Thus, technical and logistic actions can be taken in due timeto minimize the costs incurred by a failure occurrence.

Keywords: monitoring, recording, diagnosis, vibrations of high capacity inductionelectric motors, minimum costs per defect.

1. INTRODUCTION

The high power asynchronous machines are vital elements of the productionlines or even of a factory. Their accidental, unpredicted failure can lead to productionoutages which could last as long as several weeks or even months (if the respectivemachine is not available on stock at the manufacturer factory, or if it is a singularproduct), causing lost which could be tens times higher than in case of using anintegrated defects monitoring and diagnosis system.

These systems become indispensable for all major equipment, and especially forthe electric motors larger that 200 kW.

Assistant Professor Ph D. Eng, , University Timisoara Lecturer Ph D. Eng., University Timisoara Eng., Kronosphan S.A. Sebes, Romania

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Modern system for monitoring and diagnosis of the mechanical andelectrical defects for high capacity induction motors-108-

2. THE METHOD CONCEPT

Vibrations monitoring for the bearings of an induction motor – workingmachine train is a component of the modern predictive maintenance systems, which isbased on sensors, controllers and state of the art analysis techniques.

The sensors are speed transducers or acceleration transducers type. The speedtransducers provide a high measurement accuracy of the absolute vibrations in thenarrow frequency range (0 2500 Hz), with the advantage of easy installation andconnecting. The acceleration transducers enable recording within a wider frequencyrange (0 20 kHz). Thus all the relevant vibration frequencies can be preciselymeasured, and based on these measurements, the defect type can be correctlydiagnosed.

Figure 1 shows the block diagram for a monitoring, alarm, recording anddiagnosis system for the vibrations caused by the occurrence of a mechanical orelectrical defect in a system with electric motor.

Fig.1 The block diagram for a monitoring, alarm

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Deaconu, S., Popa, G., N., Popa, I., Rodean, I. -109-

Legend:- ML - driven equipment;- MEA - electric motor;- 1, 2, 3, 4 – vibrations transmitters installed on bearings area;- S.M.A.T – monitoring, alarm and data communication system;- A.U.D. – programmable automation for defects monitoring and recording;- PC - process computer.

At the AUD block level the decisions are taken in terms of alarming, andrecording the vibrations which overpass the allowable limits, which are sent to theprocess computer for further data processing. Based on the recorded vibration spectrumand on the vibrations amplitude, the defect type can be diagnosed with a precision ofover 95 %, either on motor or on driven equipment area.

3. EXPERIMENTAL RESULTSIn this chapter we will present the case of an induction motor from wood pulp

grinding equipment operating in the plastic-faced agglomerated wooden board factoryS.C. Kronosphan S.A. Sebes. The motor rated technical data are:

- Rated voltage 6000 V;- Rated power 7000

kW;- Rated frequency 50 Hz;

- Rated speed 1492 rpm;- Rated efficiency N = 0.95- Rated power factor cos = 0.92;

- Type: AMB 630 L4L BAM;- Producer: ABB Industria, Italia.The speed transducers installed on motor bearings read the overpassing of the

allowable vibration level and recorded the vibrations trend during idle run as well as inload operation.

The Figure 2 below presents the recorded vibration spectrum with theircorresponding amplitudes.

Figure 3 presents the diagram of the vibration speed versus motor speed in idlerun mode and in normal load mode, based on the data listed in Table 1.

Table 1 Data listed

n[rpm]

750 850 950 1050 1150 1250 1350 1490Idlerun v

[mm/s]0.28 0.29 0.3 0.37 0.43 0.95 0.78 0.9

n[rpm]

760 845 962 1075 1132 1286 1345 1472

Ope

ratio

n m

ode

Ratedload v

[mm/s] 0.3 0.31 0.33 0.4 0.45 1.1 0.9 1.07

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Modern system for monitoring and diagnosis of the mechanical andelectrical defects for high capacity induction motors-110-

Fig.2 The recorded vibration spectrum with their corresponding amplitudes

Fig.3 The diagram of the vibration speed versus motor speed

Based on the diagrams in Figure 2 we have reached the conclusion that thevibration level is generated by the interruption of few stator bars. A decision was made

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Deaconu, S., Popa, G., N., Popa, I., Rodean, I. -111-

to replace the motor with a spare motor, and this work was prepared in 10 days. Theworks for replacing the motor took 30 hours. Considering the factory production levelon a daily basis, identifying the defect in advance enabled a reduction of losses by1200000 EUR, which means the cost of purchasing six new motors.

4. CONCLUSIONS

The predictive maintenance concept is gaining a crucial importance in theframe of reliable operation of a modern enterprise. This concept aims to minimize thelosses caused by the occurrence of a defect.

REFERENCES

[1]. J.A. Antonino, P.Jover, ş.a., Wavelet analysis for the detection of inter – turnshortcircuits and broken rotor bars in induction machines, ICEM 2006, Chania, September 2 ÷5, Crete Island, Grecee, PMM 4 – 3.

[2]. K., Dabala, Modified method to determine rotor bar-iron rezistance in three-Phase copper squirrelcage induction motor, ICEM 2006, Chania, September 2 ÷ 5, CreteIsland, Grecee, PMM 4 – 6.

[3]. Gerling, D., Hildebrand, H., ş.a., Test – bench for high – speed high – powerelectrical drives, ICEM 2006, Chania, September 2 ÷ 5, Crete Island, Grecee, PMM 4 – 8.

[4]. Fiser, R., Bugeza, M., ş.a., Detection of broken rotor bars in induction motordrives using run-up test, ICEM 2006, Chania, September 2 ÷ 5, Crete Island, Grecee, PMM 4 –17.

[5]. Liese, M., Vibration sparking, an unrecognized damage mechanism of highvoltage windings, ICEM 2006, Chania, September 2 ÷ 5, Crete Island, Grecee, PMM 4 – 12.

[6]. Balan, H., Tîrnovan, R., Karaissas, P., Vibroacoustic methods in the diagnosis ofelectric machines, ICEM 2006, Chania, September 2 ÷ 5, Crete Island, Grecee, PMM 4 – 28.

[7]. Deaconu, S., Popa, G.N., ş.a., Diagram for artificial charge loading ofasynchronous machine and the study of the influence of the frequency change on the chargeloading, EPE 2002, Tom XLVIII (LII), fascicola 5, Iaşi, 2002.

[8]. Deaconu, S., Tutelea, L., Experimental identification of the ideal regime at theinduction machine, Annals of the Faculty of Engineering Hunedoara, Tom III, fascicola 2, ISSN1454 – 6531, pag. 173 ÷ 178, 2005.

[9]. Deaconu, S., Popa, G.N., Popa, I., Wind power station with induction generatorand static frequency converter, UNIVERSITARIA SIMPRO 2006, ISSN 1842 – 4449, pag. 31÷ 33, Petroşani, 2006.

[10]. Popa, G.N., Popa, I., Deaconu, S., Automate programabile în aplicaţii, EdituraMirton, Timişoara, 2006.

[11]. Deaconu, S., Maşini electrice. Culegere de probleme, Editura Politehnica,Timişoara, 2005.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 112-119

NEW APPROACH IN MEASUREMENT-BASED POWERNETWORK MODELING BY USING SMART SENSORS

MIRCEA RISTEIU, ADRIAN TULBURE, MOISE ACHIM,COSMIN COVACIU

Abstract: The paper is part of an energetic dispatching system project and is focusedon interfacing the local parametric measuring system to the remote processing step. Formeasuring procedure in high power networks the data safety is the main issue. We haveimplemented a Zigbee- based smart sensor system which consists of full- function (FFD) andreduced-function devices (RFD). The FFD system is programmed for measuring and routingfunctions. Selections of transmission parameters are based on side information that is obtainedfrom the demodulation and decoding processes within the receiving radio for EMCcompatibility. Such a change in transmission parameters also reduces the interference that thetransmission causes to unintended receivers. For this strong demand we have modified sensorhardbit header by integrating a Zigbee ping-pong data packet for the transmission rateevaluation. In this stage, we have tested the sensors for temperature, light and voltage inputdata.

Keywords: Zigbeee, smart sensor, measurements-based modeling, stack development,802.15, TCP/IP, adaptive-transmission protocol, wireless network protocols, mobilecommunications

1. INTRODUCTION ON SEMICONDUCTOR DEVICES FOR LOWPOWER WIRELESS NETWORKS

Comprehensive monitoring and control of industrial processes and equipmentis crucial to achieving efficient production, minimizing cost, and ensuring safety ofstaff and public. However, providing enough wired sensors – perhaps thousands -

Associate prof., PhD. at University of Alba Iulia Senior lect., PhD. at University of Petrosani Professor, PhD. at University of Alba Iulia Eng. at CARPSIT SRL Alba Iulia

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Risteiu, M., Tulbure, A., Achim, M., Covaciu, C. -113-

tomonitor and control an average industrial process is costly and complex business.Applications range from meter reading, through pipeline flow measurement, tomachine control. Apart from being cheaper and more flexible, wireless sensors can alsobe used in hazardous environments inaccessible to normal wired systems.

In this paper, we deal withthe problem of mutualunderstanding thedifferences between IEEE802.11 WLANs (WirelessLocal Area Networks) andshort-range radio systemsbased on the Zigbeetechnology, or equivalently,IEEE 802.15 WPANs(Wireless Personal AreaNetworks). These systemswill operate in the ISM(Industrial, Medical and

Scientific) frequency bands,i.e., the unlicensed spectrum

at 2.4 GHz. IEEE 802.15 uses a FHSS (Frequency Hopping Spread Spectrum) scheme,while IEEE In this paper, we present a coexistence mechanism based on a simpletraffic shaping technique. The proposed mechanism is to be performed at the WLANstations in presence of a 802.15 voice link. It does not require a centralized trafficscheduler and can be implemented in non-collaborative mode, thus allowing forinterference mitigation between co-located and non co-located 802.11 and 802.15devices. Performance, as well as advantages and disadvantages, of the presentedalgorithm are compared with those of the so called MEHTA scheme, which is acollaborative algorithm proposed within the IEEE 802.15 Working Group.

IEEE 802.11 and IEEE 802.15.3 target at designing PHY and MACspecifications for wireless local area network (WLAN) and wireless personal areanetwork (WPAN), respectively. They adopt different philosophies for MAC design,namely CSMA/CA in 802.11 and TDMA in 802.15.3. An interesting problem is theperformance of each MAC working on the same physical layer, e.g., ultra wideband(UWB). The results show that the newly added mechanisms of 802.11e, such astransmission opportunity (TXOP) and Block Ack, improve its throughput greatly,making it comparable to that of 802.15.3. In addition, 802.15.3 MAC has easier powermanagement by utilizing its TDMA access method. ZigBee fills yet another nitch. It isa PAN technology based on the IEEE 802.15.4 standard. Unlike Bluetooth or wirelessUSB devices, ZigBee devices have the ability to form a mesh network between nodes.Meshing is a type of daisy chaining from one device to another. This technique allowsthe short range of an individual node to be expanded and multiplied, covering a muchlarger area.

Fig.1 Typical measurement implementation

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New approach in measurement-based power network modeling byusing smart sensors

-114-

The chipset and the stack are incomplete without a profile, which defines themodule application. As mentioned previously, there are public profiles and privateprofiles. For public profiles, ZigBee Logo Certification is available; private profiles arenot intended to interoperate and therefore cannot be certified. Implementing profiles,either public or private, is no small undertaking. In addition to the need to licensedevelopment tools from the stack providers and attending a training class, we have tobe prepared to spend a fair amount of time studying the various firmware componentsthat constitute the ZigBee stack. Also we have to make sure that the firmwareengineers are familiar with the microcontroller used in the platform. While none ofthese items is insurmountable, they do add to development costs and time to market.

2. ZIGBEE TECHNOLOGY IMPLEMENTATION FOR IN-SITUUMEASUREMENTS

In our approach we used smart sensor system and it is based on 8-bit single-chip microcontroller 78K0/KF1+ (µPD78F0148HGK) 128KB Flash, 512KB serial

Flash, 8KB RAM, A/Dconverter, with 2420 radiotransceiver. For our purposewe built up a clientapplication packet for usingObject Oriented approacharound a Xmesh server.Before running real time

measurements we havebuilt up a virtual sender

(local emulator) (figure 4) where we have programmed fixed packets, for comparisonand errors checking.

Fig.2 Sensors position in situ

Figure 3 Configuration interface of the real-time measurementapplication

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Risteiu, M., Tulbure, A., Achim, M., Covaciu, C. -115-

On the other hand we have executed device control center for realmeasurements. This OEM application is designed to be an interface (“client tier”)between a user and a deployed network of wireless sensors. It provides users the toolsto simplify deployment and monitoring (figure 5). It also makes it easy to connect to adatabase, to analyze, and to graph sensor readings. The associated server protocol is amultihop mesh networking protocol that has various options including low-powerlistening, time synchronization, sleep modes, any-to-base and base-to-any routing. Allof our sensor and data acquisition boards are supported with these enabledapplications. The installation of database environment (PostgreSQL) will automaticallyinstall and configure a local PostgreSQL 8.0 database on the machine when that optionis checked. The installation requires administrative privileges on the system, includingthe ability to create a new user called postgres. The Data tab on the applicationinterface displays the latest sensor readings received for each node in the network. Anycolumn of data can be sorted by left clicking the top. This allows you to sort by nodeID, parent, temperature, voltage, last result time, or any other sensor reading. Forconfiguring the communication protocol between gateway (FFD) and measurementstation some extra facilities have been developed.

Gateways, together with their related system software, are a key component ofWSNs. Their duties include protocol conversion; acting as proxy servers (thuseliminating the need to poll every node from an application or management tool); andperforming sensor management functions such as network definition, monitoring,deployment, and configuration. Additional duties may include alert and alarmprocessing; sensor logging and database management; application programminginterfaces (APIs); security key management; traffic analysis and optimization;application integration; and routing management. Gateway TCP/IP applicationprogramming interfaces enable developers to leverage WSN technology using familiarInternet programming paradigms. Protocol conversion will break down barriersbetween WSNs and other types of networks. Gateway standards such as Univeral Plugand Plan (UPnP) and OPC support integration of diverse devices, including computers,electronics, security and automation components, and other networked devicesspanning wireless and wired networks.

2. WIRELESS MEASUREMENT- BASED SETUP

By implementing this setup, we have started measurement analysis. The datapackets are framed (at the start and end) by 0x7e (126) (SYNC_BYTE) bytes. Eachpacket has the form: <packet type><data bytes 1…n><16-bit CRC>.

Each packet is framed on either end by a SYNC_BYTE. The value of theSYNC_BYTE is 0x7E. The type field indicates the type of packet sent. There are fivepacket frame types:

P_PACKET_NO_ACK = 0x42(66): A user-packet with no acknowledgementrequired.

P_PACKET_ACK = 0x41: A user-packet that requires acknowledgement.

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New approach in measurement-based power network modeling byusing smart sensors

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P_ACK = 0x40: Required response for P_PACKET_ACK packet. P_UNKNOWN: Unknown packet type received. Requires response of type

P_UNKNOWNData is the packet payload. If the packet payload contains the special

SYNC_BYTE, it is escaped out. The escaping algorithm is described below.The 2-byte CRC is a redundancy check on the packet type and the data bytes.

It is used by the receiving application to verify the packet is not been corrupted duringtransport. The CRC calculation includes the type byte through the end of the datapayload. If the SYNC_BYTE is sent in data portion of the application it would confusethe receiving application by making prematurely end the packet. To avoid this, if aSYNC_BYTE is in the data portion of the packet, the byte is escaped out. Escape bytesare proceeded with 0x7d (ESC_BYTE), then the byte value X0R (exclusive or) with0x20. For example, 0x7e is converted to 0x7d5e; 0x7d and 0x7e bytes must beescaped; 0x00 to 0x1f and 0x80 to 0x9f can be optionally escaped. By followingXServe User’s Manual (XServe_Users_Manual_7430-0111-01_B.pdf , pag 188) wehave access to the programming environment of TinyOS as:

Bin 126,66,125,94,0,17,125,93,22,0,0,0,0,0,0,0,0,0,0,125,94,0,180,1,0,194,100,110,0,0,82,109,66,143,126

Hex 7E 42 7D 5E 00 11 7D 5D 16 00 00 00 00 00 00 00 00 00 00 7D 5E 00 B4 0100 C2 64 6E 00 00 52 6D 42 8F 7E

After processing:

Bin 126,66,125,94,0,17,125,93,22,0,0,0,0,0,0,0,0,0,0,125,94,0,180,1,0,194,100,110,0,0,82,109,66,143,126

Hex 7E 00 11 7D 16 00 00 00 00 00 00 00 00 00 00 7E 00 B4 01 00 C2 64 6E 00 0052 6D

Because the header of TinyOS is:7E 00 11 7D 16 00 00 00 00 00 00 00 00 00 00 7E 00 B4 01 00 C2 64 6E 00 0052 6D

With the associated commands:- dest_address - Single hop destination address: 7E 00 (126, 0) => byteoffset="0"length="2" type=”uint16”- am_type - Active message type: 11 (17) => byteoffset="2" length="1" type="uint8"- group - Active message group ID: 7D (125)=> byteoffset="3" length="1" type="uint8"- length - Length of entire message: 16(22) => byteoffset="4" length="1" type="uint8"

And the associated chain header:00 00 00 00 00 00 00 00 00 00 7E 00 B4 01 00 C2 64 6E 00 00 52 6D.

The XMesh header is:00 00 00 00 00 00 00 00 00 00 7E 00 B4 01 00 C2 64 6E 00 00 52 6D

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Risteiu, M., Tulbure, A., Achim, M., Covaciu, C. -117-

With the main associated commands:- sourceaddr - Single hop sender address: 00 00 (0,0)=> byteoffset="5" length="2"type="uint16"- originaddr - Node ID of originator of message: 00 00 (0,0)=> byteoffset="7"length="2" type="uint16"- seqno - Sequence number for link estimation: 00 00 (0,0)=> byteoffset="9"length="2" type="int16"- Socket - Application ID: 00 (0)=> byteoffset="11" length="1" type="uint8"

And, the associated chain header is: 00 00 00 7E 00 B4 01 00 C2 64 6E 00 0052 6D

The associated combined commands are:- XSensor Header: 00 00 00 7E 00 B4 01 00 C2 64 6E 00 00 52 6D- board_id - Sensor Board ID: 00 (0)=> byteoffset="12" length="1" type="uint8"- packet_id - Sensor Packet ID; 00 (0)=> byteoffset="13" length="1" type="uint8"- Parent – Sensor Parent: 00 7E (0,126)=> byteoffset="14" length="2" type="uint16"

The main conclusion related to sensor analysis is that each sensor has ownpacket structure. The packet ends with a CRC that is calculated on the entire packetexcluding the packet header and the CRC field itself. A CRC is calculated by XORingthe current byte with a shifted CRC accumulator. The CRC Is always 2 bytes.(XServe_Users_Manual_7430-0111-01_B.pdf , pag 68 ).So, by extracting the specofoccode from 7E 00 11 7D 16 00 00 00 00 00 00 00 00 00 00 7E 00 06 00 00 BE C0 7A60 79 8E 74, result: 00 7E – parent; 00 06 – epoch; C0 – Light; 7A – Thermistor; 60 –magX; 79 – magY; 8E – accelX; 74 – accelY. Measured data (case study) exportedinto datasheet is shown in next figure:

Fig.4 Measured data, exported into datasheet

4. SELF- HEALTHING NETWORK. MULTI-HOPE PROTOCOL

In order to fit this requirement, the main components of the setup are:- End Devices, also called Nodes, Edge Nodes, Devices, or Reduced FunctionDevices (RFDs), are battery-powered devices that wake up periodically and send datato a host..

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New approach in measurement-based power network modeling byusing smart sensors

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- Routers, also called Mesh Nodes, Coordinators, or Full Function Devices(FFDs), form a wireless backbone that ferries messages in a multi-hop fashion acrossthe network. Routers allow messages to flow in various directions on demand andbuffer messages for nearby End Devices that are currently sleeping.- Gateways, also called Bridges, Controllers, Internet Interfaces, or PANCoordinators, are usually envisioned as Internet appliances that provide an interfacebetween the WSN and the Internet. Gateways control and monitor the WSN,consolidate data from various nodes, execute business logic, and provide a TCP/IPinterface to the outside world.

5. CONCLUSION. ENSURING MULTI-HOPE PROTOCOL

It is a goal at some point to add mesh routing support to this stack. The figure 6shows the diagram form multi-hope and self-healthing situation.

In this approach, wireless sensor networks offer numerous benefits overprevious networking solutions for many applications, including lowered costs, the

Fig.6 Multi-hope and self-healthing configuration for a studycase

Fig.5 Integrating smart sensors into TCP/IP configuration

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Risteiu, M., Tulbure, A., Achim, M., Covaciu, C. -119-

ability to leverage infrastructure for multiple applications, and the capacity torestructure the network quickly and easily, as well as security, scalability, and ease ofadministration.

The catch-all phrase for low power, low data rate sensor networks targeted atcondition monitoring, lighting and climate control as well as safety and security. Thegoal is to provide a standard, yet extensible, protocol stack for use with 802.15.4 radioswith enough flexibility for use in limited power environments for low latency, singlehop networks as well as longer distance, multi-hope mesh network configurations.There are also noteworthy proprietary options for similar technology. So, the main prosare: standards based sensor networking allows multi-sourcing, interoperability; multi-path mesh architecture can overcome difficult RF environments.

REFERENCES

[1] Xin Wang, Yong Ren, Jun Zhao, Zihua Guo, Yao, R. Comparison of IEEE802.11e and IEEE 802.15.3 MAC, Emerging Technologies: Frontiers of Mobile and WirelessCommunication, 2004. Proceedings of the IEEE 6th Circuits and Systems Symposium onVolume 2, Issue , 31 May-2 June 2004 Page(s): 675 - 680 Vol.2

[2] xxx A Zigbee-subset/IEEE 802.15.4, Multi-platform Protocol Stack, IEEE802.xx, 2006

[3] xxx IEEE Std. 802.15.4, Part 15.4: Wireless Medium Access Control (MAC) andPhysical Layer (PHY) Specifications for Low-Rate Wireless Personal Area Networks (LR-WPANs), pp. 679.

[4] xxx Zigbee Alliance, Zigbee SPecification Version 1.0, pp. 376. Available online atwww.zigbee.org

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 120-125

POSSIBILITIES TO PROTECT AGAINST EXPLOSION THELOW CURRENT CIRCUITS MADE OF MICRO-DRIVINGS

SORIN BURIAN, JEANA IONESCU , MARIUS DARIE

Abstract: The low current circuits represent an ever-growing trend in the industrialapplications, which involve the occurrence of explosive atmospheres. This paper intends tounderline the conditions and the limits required for using micro-drivings on low currentscircuits protected by intrinsic safety.

Key words: intrinsic safety, micro-drivings

1. INTRODUCTION

It is widely recognized the fact that the intrinsic safety type of protection issuitable and recommended for the protection of low currents apparatus/electric systemswhich operate in areas with hazards of explosive atmospheres. But the use of theintrinsic safety type of protection on low current circuits which enclose mini/micro-drivings is a domain which has been less approached. This paper intends to identifyand present the parameters specific for the intrinsic safety type of protection applicableto low currents apparatus / systems.

2. SPECIFIC PARAMETERS – GENERAL PRESENTATION

The technical solution selected for the protection of equipment with theintrinsic safety type of protection involves a limitation of the conveyed energy and ofthe one stored in the protected circuits to non-hazardous values, with the considerationof the predictable failures with cumulative effects.

Consequently, it is natural that the specific standard for this type of protectionregulates the maximum admitted values for the parameters: maximum admitted values

Ph D.Eng. at the INSEMEX PETROŞANI

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Burian, S., Ionescu, J., Darie, M. -121-

for the parameters: maximum voltage (U0), maximum current (I0), maximum power ofthe source (P0), maximum equivalent capacity allowed for connection to the intrinsicsafety output of the source (C0), maximum equivalent inductance allowed forconnection to the intrinsic safety output of the source (L0).

For the purpose of this paper the “source” shall be any circuit which maygenerate/transfer energy to that part of the apparatus/system located in the hazardousarea.

Since the specific standard defines a safety factor of 1.5 and 1, depending onthe number of failures and on the protection level (ia or ib), the following lines shallfocus on the stricter values (with the safety factor of 1.5).

3. LIMITATION FOR INDUCTIVE MICRO / MINI-DRIVINGS

There follows a presentation of tables with values and of charts for themaximum admitted inductance in relation to the maximum voltage of the source (U0),gas / vapours subgroup and to the source type (linear / non-linear).

1

10

100

1000

10000

0 10 20 30 40 50

U0 [V]

L 0 [

H] IIC

IIBIIA

Fig. 1 – Value of the maximum admitted inductance which can be connected to the output of anon-linear source in relation to the idle voltage of the source

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Possibilities to protect against explosion the low current circuits made ofmicro-drivings-122-

1

10

100

1000

0 10 20 30 40 50

U0 [V]

L 0 [

H] IIC

IIBIIA

Fig. 2 – Value of the maximum admitted inductance which can be connected to the output of alinear source in relation to the idle voltage of the source

Table 1 Value of the maximum admitted inductance, which can be connected to the outputof a source in relation to the idle voltage of the source

L0 [H]Non-linear source Linear sourceU0 [V]

IIC IIB IIA IIC IIB IIA3 6 25 32 11 44 566 4 17 21 8 31 40

10 1 5 7 1 22 2811 1 3 4 5 19 2512 1 1 1 3 16 2215 1 1 1 1 1 120 3 2 2 5 3 125 20 9 3 19 6 730 57 26 13 25 37 940 770 170 15 270 95 3150 130 1300 220 130 210 310

4. LIMITATIONS FOR CAPACITIVE MICRO/MINI-DRIVINGS

There follows a presentation of tables with values and of charts for themaximum admitted capacitance in relation to the maximum voltage of the source (U0),gas / vapours subgroup and to the source type.

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Burian, S., Ionescu, J., Darie, M. -123-

0,01

0,1

1

10

100

1000

0 10 20 30 40 50

U0 [V]

C0 [

F] IICIIBIIA

Fig. 3 – Value of the maximum admitted capacitance which can be connected to the output of asource in relation to the idle voltage of the source

Table 2 - Value of the maximum admitted capacitance which can be connected to theoutput of a source in relation to the idle voltage of the source

C0 [F]U0 [V]IIC IIB IIA

3 100 1000 10006 40 1000 1000

10 3 20 10011 1,97 13,8 6012 1,41 9 3615 0,58 3,55 1420 0,22 1,4 5,525 0,11 0,84 2,9730 0,066 0,56 1,8240 0,033 0,26 0,8850 0,02 0,15 0,49

5. LIMITATIONS OF POWER FOR SOURCES THAT SUPPLYMICRO/MINI-DRIVINGS

There follows a presentation of tables and of charts for the maximum admittedcapacitances in relation to the maximum voltage of the source (U0), gas / vapourssubgroup and the source type.

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Possibilities to protect against explosion the low current circuits made ofmicro-drivings-124-

0,10

1,00

10,00

100,00

0 10 20 30 40 50

U0 [V]

P 0 [W

] IICIIBIIA

Fig. 4 – Value of the maximum admitted power that can be delivered by a non-linear source tothe apparatus located in hazardous area

0,10

1,00

10,00

100,00

0 10 20 30 40 50

U0 [V]

P 0 [W

] IICIIBIIA

Fig. 5 – Value of the maximum admitted power that can be delivered by a linear source to theapparatus located in hazardous area

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Burian, S., Ionescu, J., Darie, M. -125-

Table 3 – Values of the maximum admitted power that can be delivered by a source to theapparatus located in a hazardous area

P0 [W]Non-linear source Linear sourceU0 [V]

IIC IIB IIA IIC IIB IIA3 15,00 15,00 15,00 7,50 7,50 7,506 30,00 30,00 30,00 15,00 15,00 15,00

10 50,00 50,00 50,00 25,00 25,00 25,0011 26,40 55,00 55,00 27,50 27,50 27,5012 7,42 26,05 42,18 30,00 30,00 30,0015 1,77 4,97 7,43 8,47 23,27 35,3520 0,90 2,24 3,34 2,86 6,97 10,4925 0,70 1,63 2,43 1,81 4,19 6,2930 0,63 1,38 2,04 1,41 3,14 4,7340 0,60 1,20 1,76 1,06 2,30 3,4650 0,65 1,15 1,65 0,93 1,95 2,90

6. CONCLUSIONS

Since the specific standards contain the maximum admitted values forinductances and capacitances valid for linear sources only, we have used an expertsoftware for simulating such types of circuits within the range 0-5A, 0-50V.

As a result of this study, we have noticed that approximately above 12V, theadmitted inductance that can be connected to the output of a source shall rise a lot andthe admitted capacitance that can be connected to the output of a source and themaximum admitted power delivered by a source shall diminish to a great extend whenthe value of the idle voltage increases.

Under 12V for the idle voltage of the source, the variation of the parametersL0, C0 and P0 is being smoothed mainly because of the range limitation for currents (0-5A) required by the software.

The analysis in this paper makes reference only to strict capacitive and strictinductive apparatus.

REFERENCES

[1] SR EN 50020:2003, Electrical apparatus for potentially explosive atmospheres.Intrinsic safety “i”

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 126-132

POWER SUPPLY AND DESIGN PROBLEMS OFLONGWALL INSTALLATIONS OF RATED VOLTAGE

ABOVE 1 kV IN UNDERGROUND COAL MINES

PIOTR GAWOR, SERGIUSZ BORON,

Abstract: The power requirements of modern longwall systems in underground coalmines have increased to over 2,5 MW of total demanded power. The article presents selectedproblems of supplying such installations from existing power networks in coal mines. Problemsof assuring the required quality of energy and safety of operation as well as some problemsrelated to the starting of face conveyors have been presented.

Keywords: underground mining, electrical safety, power systems, longwall electricalinstallations.

1. INTRODUCTION

The tendency to increase the effectiveness of coal extraction process in Polishcoal mines and the evolution of electrical equipment resulted (in recent years) insignificant increase of power demand in longwalls. The rated power of particularmotors reached 500 kW while total power of electrical equipment in longwall (coalshearer, face conveyor, stage loader, crusher, pumps etc.) can exceed 2,5 MW.Supplying such a network with 1000 V (voltage usually used in conventionallongwalls) is impractical or even impossible, mainly because of excessive voltagedrops, requirements for short circuit protection and limited conductor size of cables.The main method of improving supply quality is to increase supply voltage.

Ph. D., D.Sc. Department of Electrical Engineering and Process Control in MiningFaculty of Mining and Geology, Silesian University of Technology, Gliwice, Poland Ph. D., Department of Electrical Engineering and Process Control in MiningFaculty of Mining and Geology, Silesian University of Technology, Gliwice, Poland

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Gawor, P., Boron. S. -127-

2. CHARACTERISTICS OF MIDDLE VOLTAGE LONGWALLNETWORK

Utilization of middle voltage (in Poland usually 3,3 kV) to supply longwallequipment gives following advantages: lower currents at start-up and during normal operation of motors, lower voltage

drops and lower energy losses in longwall installation, possibility of decreasing cable sizes, possibility of increasing the distance between the power station (supplying

transformer) and the coal face even to 3000 m, what eliminates the necessity ofmoving the transformer station during exploitation of longwall and eliminatesthe heat emanated by the transformer from the air ventilating the face.

However, the decision to use higher voltage, must be preceded by the analysis oftechnical and economical aspects, taking into account, among others, the followingfactors: high cost of electrical equipment, motors and cables rated 3,3 kV, justified only

in high-capacity longwalls, suitable parameters of mining power system, especially short circuit power, increase of electrical hazards.

As far as the safety is concerned, Polish mining regulations introduce somespecific (in comparison to low voltage networks) requirements for MV longwallinstallations: increased to 2,0 sensitivity coefficient of short circuit protection devices

(additionally, the short circuit protection in the transformer station should workas a backup for protection in the starter with sensitivity coefficient 1,5), limited to 2,5 F phase-to-earth capacitance of cables in the network, necessity to use special double-screened flexible cables.

One of the tasks of the designer of longwall installation is to determine themaximum rated power of motors that can be supplied from given MV network and tocalculate the longest possible distance between the power station and the coal face. Themost important factors limiting these quantities are: the voltage drop under normal condition; the supply voltage of motor shouldn’t

be lower than 0,95Un, the problem is that the actual value of this voltagedepends not only on voltage drops in designed installation, but also on thevoltage at the bus-system of the switchgear supplying the longwall, whichsometimes is difficult to estimate, requirements for the sensitivity coefficient (defined as a ratio of minimum short

circuit current to the setting of short circuit protection); to fulfill this requirementthe minimum short circuit current has to be at least 2,4 times greater than themaximum operating current (during the start-up of the motor), voltage drop at the motor start-up; the mechanical torque produced by the motor

is approximately proportional to the square of the voltage and for some oflongwall drives, which require relatively high torque at the start-up (especiallyface conveyor), it may be difficult or even impossible to start a loaded motor.

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Power supply and design problems of longwall installations of ratedvoltage above 1 kV in underground coal mines-128-

3. PROBLEMS OF FACE CONVEYORS SUPPLY

The biggest problem in longwall installations design is to provide satisfactorysupply conditions for face conveyors. The extremely high friction forces associatedwith conveying system require big torque that has to produced by electrical motors. Atypical drive consist of 2÷3 induction squirrel-cage motors of total rated power oftenexceeding 1 MW. With the exception of systems with fluid coupling (describedbelow), these motors are simultaneously started what results in very big voltage drop.

The situation is complicated by the fact, that the nominal in-rush current ofsome types of motors exceeds 7In. In the traditional drive system all the motors of faceconveyor are started by the contactor starter. The main disadvantage of this system isthat, due to excessive voltage drops, it’s sometimes impossible to provide requiredstarting torque and low voltage level at the starter may be a reason of contactordropout. Furthermore, the in-rush current of 2 or 3 motors supplied from onetransformer outlet can be too high to provide required sensitivity of short circuitprotection in the power station.

The maximum power rating of a single motor that can be supplied in thelongwall depends (apart from rated voltage of the motor) mainly on the parameters ofsupplying network (short circuit power), the cables length and size and the nominalparameters of the motor (in-rush current and starting torque). The simplified scheme ofone motor supply is shown on fig. 1.

Fig. 1. Simplified scheme of motor supply

The most important elements of the scheme are: power system Q characterizedby the short circuit power SkR’’, switchgear R, power station T, starter SM, motor M andcables K1 to the power station, K2 to the starter and K3 to the motor.

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Gawor, P., Boron. S. -129-

One can derive the equation that helps to predict the dependence between theshort circuit power of the distribution network and the maximum rated power of amotor [1]:

3

min

min2

22

2''

101

1,1

nM

MSMns

nRkR

PUcUUUk

US (1)

Where:Un – rated voltage of the motor, kVUnR – rated voltage of the distribution network, kVUSM – operating voltage at the starter before start-up of the motor, kVUMmin – minimum required voltage on the motor at the start-up, kVPn – maximum rated power of the motor in the longwall, kWks = RQ/XQ – ratio of supplementary resistance to reactance of the distribution

network , - ratio of primary to secondary rated voltage of the transformer,c, - coefficients characterizing the properties of motor during the start-up and

properties of supply network:

nnn

nr

IIkc

cos rrsk sincos

In – nominal current,Ir – in-rush current,kr=Ir/In,cos n, cos r – power coefficients of the motor: nominal and at the start-up,n – nominal efficiency factor of the motor, - coefficient depending on the parameters of the network:

rKKTKrKKTK XXXXRRRR sincos 32'

132'

1

For the typical parameters of the distribution network and longwall installationthe exemplary dependence of Pn max on the Sz for different required voltage levelsduring the start-up of the motor is shown in the fig. 2 [1].

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Power supply and design problems of longwall installations of ratedvoltage above 1 kV in underground coal mines-130-

200

400

600

800

1000

1200

1400

20 40 60 80 100Short circuit pow er, MVA

Mot

or ra

ted

pow

er, k

W

0,8Un 0,7Un 0,6Un

Fig. 2. Maximum power rating of the 3,3 kV motor as a function of short circuit powerof MV distribution network

Typical values of short circuit power in the underground distribution networksof coal mines vary between 40÷100 MVA, so, as can be seen in the fig. 2, it may bedifficult or impossible to start a motor rated 400 kW or more (one should rememberthat the face conveyor drive consists of more than one motor). To avoid problems withthe low voltage level, in recent years another elements of face conveyor drive systemare introduced: two-speed motors, thyristor starters (so called soft-start devices) andfluid coupling.

3.1. Two-speed motors

Two-speed motors used in face conveyor drives are built for a constant torquewith RPM ratio 1:3 or 1:2. The full analysis of starting conditions, especially ofphenomena during switching the speeds is difficult, because it requires the knowledgeof actual motor load, switching time etc. The main advantages of two-speed motordrives are: lower in-rush current on the slow speed (practically two times lower than of

single-speed motor) which helps to keep the voltage drop within acceptablelimits and makes possible to fulfill the requirement of protection sensitivitycoefficient, high starting torque on the slow speed which makes possible to start and unload

even overloaded conveyor.To take the full advantage of two-speed motors the controller has to be able to

switch from slow speed to fast in very short time.

3.2. Thyristor starters

Utilizing thyristor starters makes possible to increase the voltage and thetorque gradually during the start of the motor. Controller can keep the current at the

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Gawor, P., Boron. S. -131-

previously set level (so called current start) or just increase the voltage from the initialvalue (voltage start). The main advantage of thyristor starters is limiting mechanicalstresses to shafts, clutches, chains of face conveyor etc. However, the designer of thenetwork has to consider the most disadvantageous conditions, so, when calculatingvoltage drop or sensitivity of protection, one must assume that the load torque of themotor is maximum. The voltage level, at which the motor starts to rotate, depends onthe mechanical load of driven machine, which means that, if the conveyor isoverloaded, the starter won’t limit the current (the motor will start only when thevoltage is at its maximum). In fact, from the designer of electrical installation point ofview, there could be no difference in the results of the calculations between contactorand thyristor starter.

In some applications thyristor starter works with two-speed motor, usuallywith the slow speed started by the contactor and fast speed by the thyristor starter. Themost important benefits of this system is the possibility of unloading overloaded faceconveyor (high torque on slow speed) and after that soft start of fast speed with limitedstresses to the mechanical elements and limited in-rush current.

3.3. Drives with fluid coupling

In this system the torque is transferred from the motor to the reduction gearboxof a drive through a fluid coupling. The amount of transferred torque can be changedby adjusting fluid level in the coupling. The advantage of this system comes from thefact, that the motor starts practically unloaded, so there is no problem with the voltagelevel at the motor. During the start of the face conveyor even the critical moment of themotor can be utilized. Motors designed to work with fluid coupling have low startingtorque (e.g. 1,2∙Mn) and high critical torque (e.g. 3,2∙Mn). The nominal in-rush currentof these motors is usually relatively high (e.g. 7,8 ∙In), what can cause too low voltagelevel at the starter, but on the other hand, motors don’t need to be startedsimultaneously, which limits the voltage drops and problems with sensitivity of shortcircuit protection.

4. CONCLUSIONS

1. The possibility of supplying high power electrical equipment from existing powersystem in underground coal mine is conditioned mainly by: short circuit power of distribution network, method of starting the motors.

2. Proper start of face conveyor supplied from power system with short circuit powernot greater than 60 MVA may require using two-speed motors or fluid couplings.

3. The maximum distance between the transformer station and the coal face can belimited by: excessive voltage drops during normal operation, too low starting torque of the motor due to low voltage level caused by high in-

rush currents,

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Power supply and design problems of longwall installations of ratedvoltage above 1 kV in underground coal mines-132-

required sensitivity coefficient of short circuit protections in the transformerstation or in the starter, too low voltage at the contactor of the starter during start-up of the motors.

REFERENCES

[1]. Gawor P.: Prognosis of possibilities of feeding the high-efficiency wall complexesin the existing distribution network of coal-mine. International Conference “BalancedDevelopment in Mining”, Gliwice, Poland 2005 r.

[2]. Boron S.: Designing of medium voltage mining networks in longwall faces –selected problems. International Conference “Balanced Development in Mining”, Gliwice,Poland 2005 r.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 133-138

PROBLEM VIEWING THE DRIVE OF LARGE POWERMACHINES FROM COAL EXTRACTION INDUSTRY

ORBAN MARIA, POPESCU CRISTINEL, CURELEANU SORIN,BLANARU LIVIU

Abstract: In the exploitation process, the technological lines contain bucket wheelexcavators (BWE), belt conveyers (BC and dumping machines (MH) for having a largeproductivity and the other machines which are driving using asynchronous motors (630 kW,6kV, 71A, 980 ro/min, k=0,92). It is recommanded to reduce the electrical energy consumptionthrough choosing a transmission raport in dependence with the structure of the electrical systemdrive.

Key words: energetically ground, technological flux, lignite, electrical energyconsumption

1. INTRODUCTION

Taking into account the competition on the energetically market, energeticallygrounds as Rovinari, Turceni, Isalnita, etc. was developed from 2004. The basic sourceis the lignite which is extracted in the lignite open pits from Oltenia coal basin.

The price of solid fuel, gases and oil increases from day tot day due to theecological restrictions which are against of mining activities. The achievement costsare bigger and bigger as the lignite open pits from energetically grounds become`center of cost` and gives the price of RON/tone utile or Ron/kWh.

It is necessary that each of economic agent has to take technological andtechnical measurements of restructure, to reduce the electrical energy consumption.

The Energetical Grounds (CE) Rovinari and Turceni, Isalnita-Craiovarepresents the reorganiztion and restructure result of electrical energy activity. Thelignite open pits are integrated as the cost parts of energy production in the energetical

PhD Associate Professor University of Petrosani PhD Lecturer University of Petrosani PhD Student Eng.University of Petrosani

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Problem viewing the drive of large power machines from coalextraction industry-134-

grounds. The lignite production is not subsidized in Romania. The lignite consumptionwill be about 30 mil.tone/year in 2005 as well as in 2010.

The asynchronous motors in schortcut or induction motors are frequently usedin electrical drives for open pits machines. The motor `s power are from 100 to 630 kWand the open pits costumers are supplied from transformer stations about 2x4MVA,20/6 kV using different electrical cables.

The lignite open pits from Oltenia are equiped with technologies in continousflux characterized by: the lignite deposits are excavated by bucket wheel excavators(BWE) with the following capacities 470 l, 1300 l, 1400 l, 2000 l and productivityabout 1680 m 3 /h - 6500 m 3 /h; the belt conveyer has the productivity about 1400 -12500 m 3 /h ; the laying down machines have capacity about 2500 -12500 m 3 /h.

2. THOROUGHGOING STUDY OF PROBLEM

For avoiding the construction of some asynchronous motors with reduced speedfor to drive mechanisms of mining tools it is necessary to accustom oneself the powerof motor to the gauge of tools. To fulfill this reason, the transmission of power frommotor to work mechanism is made through the transmission mechanism as shown inthe picture no. one. In the dynamic stage the drive motor develops un torque necessaryto accelerate the own masses and to win the total torque (static and dynamic) reportedto the motor shaft.

Fig.1 The drive structure

Fig.2 Triangle diagram

J M i J L

M

M M LM T

sMLL

t

L

M S

L

T L

L

t t3

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Orban, M., Popescu, C., Cureleanu, S., Blanaru, L. -135-

The transitory stage duration it is as so short as the energetically transfer ofshaft is large. This transfer is depending by the transmission rapport of the mechanismand it is maximum when the transmission rapport is optimal, the rapport leads to aminimum time of starting, of stopping and change the sense from some mining tools asBWEs, BCs and MHs resulting from obtaining the biggest accelerations on the motor’sshaft.

The moving equation is:

dtdJMM s

(1.1)

The transmission mechanism as transformer of moving (M – motor; MT –transmission mechanism; ML – work mechanism) is characterized by the transmissionrapport:

i =LL

(1.2)

In case of driving with transmission mechanism and trapezium diagram (this isthe most useful case used in site) it is necessary that the starting (acceleration till thestage speed) and breaking (reduction from the stage speed to zero) to be made in theshortest time and have an energy consumption as small as is possible. Forsimplification it is takes into account that the acceleration is made using a trianglediagram (fig.2) described by the speed and moving integral:

L = dtL , dtLL (1.3)

The global displace made by the mechanism on the entire cycle of diagram is:

Lt

Lt

LL ttdtdt 2100 2

121

(1.4)

If the transmission mechanism has an unitar efficiency (as BWE, BC, etc) andrapporting all the parameters to the mechanism shaft and taking into account theconservation power and cinetical energy rule, results:

MM Lred , MiMML

red

, 2

21

lredJ = 22

21

21

LLM JJ ,

Or LMred JiJJ 2 (1.5)From the equation no.1-1 and for starting and breaking periods of mechanism

shaft we can obtain the acceleration express for these period:

LM

spLp JJi

MiMdt

d

2

: ,LM

sfLf

JJi

MiMdt

d

2

: (1.6)

The above expressis show the acceleration and decceleration evolution independence with the driving system strucure and by the optimal transmission rapport.

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Problem viewing the drive of large power machines from coalextraction industry-136-

If we take into acount the inertial moments LM JJ , =constant and the torquesM, sM = constant, integrating rel (1.6) we determ the acceleration time t1 anddecceleration time t 3 and total time t L which depend by transmission rapport and it ispossible to be esteem the optimization criteria for transmission mechanism:

t

sfspLMLL MiMMiM

JJi 112 2 (1.7)

3. DETERMING THE OPTIMAL RAPPORT OF TRANSMISSION

We have to determ that transmission rapport which assure maximum values foracceleration and decceleration (rel.1.6), or to assure the maximum change of energy tothe work mechanism shaft, or to minimize the work time (1.7) for a given value ofwork mechanism displace (rel.1.4).

In this case the minimum necessary condition of work results through make thederivate, of criteria function in dependence with transmission rapport, to be zero:

pMM

s

p , fMM

s

f , jL

M mJJ (1.8)

If the drive function is supposing to be without load M s =0, fp , ,the above condition becomes:

M

L

joptj J

Jm

imi 1012 (1.9)

The acceleration in tha strating time is limited by the restrictions of thedeveloped torque of motor while the deceleration of breaking can be increase throughthe static breaking couple and/or working with a suplimentary break, but the maximumacceleration (miniminal time) problem appears for the starting period.

Canceling the derivate from (1.6) we can obtain the maximimum accelerationcondition (1.10) and the optimal transmission rapport(1.11):

022 M

L

p

soptopt J

JMM

ii

(1.10)

M

L

p

s

p

s

jopt J

JMM

MM

mp

pi

22

111

(1.11)The maximum value of acceleration results through replace the transmission

rapport with its optimal rapport in (1.6):

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Orban, M., Popescu, C., Cureleanu, S., Blanaru, L. -137-

M

Lopt

p

sopt

M

pp

JJi

MMi

JM

2

max

(1.12)If we consider (1.11) adn replace in (1.12) we obtain:

M

L

s

P

M

L

s

p

M

L

s

p

M

pl

JJ

MM

JJ

MM

JJ

MM

JM

2

2

2

maxmax

)(

(1.13)Making an rapport with (1.6) to its maximum value (1.13) result:

LM

sp

p

Mopt

L

Lr

JJi

MiMJJi 2max

2

2(

M

L

p

s

M

L

p

s

p

s

JJi

MMi

JJ

MM

MM

2

2

) (1.14)

a) for p

s

MM

0,5 b) for p

sMM

2

Fig.3 The relative acceleration in dependence with transmission rapport

0 1 2 3i

1 2 3 i

r

2

1

1,4

1

0,6

0,2

M

LJJ

0,2

1 5

1010 5 1

0,2

M

LJJ

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Problem viewing the drive of large power machines from coalextraction industry-138-

4. CONCLUSIONS

From picture no.3 we can draw some conclusions:- the optimal values of transmission rapport increase in the same time with

increasing ofp

s

M

L

MM

JJ

, so at the driving of work mechanisms with large static and

inertial torques (as belt conveyers) is necessary to use a reduction while driving ofwork mechanisms with small static and inertial torques the direct coupling is enough.

- at the starting the acceleration increase to maximum value and then it decreasein short spets with the increasing of transmission rapport so in the site the transmissionrapport is equal with the optimal rapport.

- the maximum values of acceleration are as bigger as the rapportsp

s

M

L

MM

JJ

, are

smaller.-the obtained results are avaible as for trapesium diagram as the triangle diagram

and for changing sense too, both of them has a acceleration period and a deccelerationperiod.

It is requiring to put a corelation between the driving motor, the transmissionmechanism and work mechanism to assure the maximum power transfer (an optimaltransmission rapport of reductor) when the component elements of driving system arechoosing.

REFERENCES

[1.] Ghita Constantin Elemente fundamentale de masini electrice, E. Printech,Bucuresti 2002

[2.] Orban M. Daniela Modernizarea actionarilor electrice la excavatoarele dincarierele de lignit in vederea cresterii eficientei lor, teza de doctorat , Petrosani, 1999

[3.] Manolea Ghe., s.a. Actionari electromecanice, Reprografia Univ. din Craiova,Craiova 2000

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 139-147

REFLECTIONS ON THE QUALIFICATION OF THEGENERATION UNITS FOR PROVIDING THE SERVICE

CONSISTING IN REACTIVE POWER WITHIN THEVOLTAGE SECONDARY CONTROL RANGE

VICTOR VAIDA

Abstract: Qualifying the generation units for providing the reactive power within thesecondary control range is an approach in increasing the efficiency and operation reliability ofthe power plants as well as of the power system. The synchronous generator P/Q diagramplotting by testing is needed in order to have the generation unit qualified for the secondarycontrol. At Deva-Mintia Power Plant, P/Q diagrams have been plotted for 5 generation units,which will be declared fully qualified.

Keywords: system services, voltage secondary control range, P/Q diagram

1. INTRODUCTION

The qualification of the power generation units for providing the systemservice consisting in reactive power within the voltage secondary control range isachieved in accordance with the provisions of the operation procedure for qualifyingthe internal producers as system services providers, elaborated by Transelectrica (TEL- 07 VOS – DN/154).

Qualification criteria in this case are:The excitation control system should ensure the variation of the reactive power

supplied/absorbed by the Transmission Network or by the distribution network, inview of a quick and stable offset of the

- voltage variations that occur during normal operation;- The Automatic Voltage Regulator should act continuously, free of any

instability, on the entire operation range of the generator;- The Generator should be able to repeatedly sweep the reactive power range,

within the limits of the P/Q diagram for which it was designed;

Prof. Dr. Eng. S.C.Electrocentrale Deva S.A.

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Reflections on the qualification of the generation units for providing theservice consisting in reactive power within the voltage

secondary control range-140-

- The generator should be able to provide the rated active power at anyoperation point between cosφ = 0.85 inductive and cosφ = 0.95 capacitive;

- The value of the reactive power delivered in stable operation should be fullyavailable for voltage variations of ±5% in the 400 kV network and of ±10% inthe 220 and 10 kV networks;

- There should exist means of measurement and control of the reactive energygenerated/absorbed within the voltage secondary control ranges;

- The generator P/Q diagram should be plotted.The ANRE procedure, code 35.1.432.1.01, defines the terms and conditions of

payment for the voltage control service by generating/absorbing reactive energy, inaccordance with the operation P/Q diagram of the unit.

The above mentioned procedure has defined the voltage secondary controlranges on the P/Q diagram: Q1 – inductive area and Q2 – capacitive area, situatedbetween the maximum operation limit and a limit jointly agreed by the grid operatorand the system service provider.

To practically implement the ANRE regulations regarding the voltagesecondary control, the real operation P/Q diagrams of the synchronous generator needto be accurately determined by tests and measurements.

The operation in inductive mode is conditioned by the limit of the excitationcurrent and by the stator current limit, both determined without exceeding theallowable temperatures.

The operation in capacitive mode is conditioned by the warming up at thefront end of the generator stator, i.e. at the stator front teeth (the last laminated platebundle with recesses).

2. THE P/Q DIAGRAM OF SYNCHRONOUS GENERATORS

The P/Q diagrams of the synchronous generators are needed also for makingplanning, operation and operation analysis more effective

The P/Q diagrams allow the dispatcher of the National Power System to loadand unload the synchronous generator reactive power according to the system’s needsand the reactive power resulting from the balancing market.

The theoretical P/Q diagrams and those plotted by testing are used forcalculating static and transient stability, operational planning and implementation ofthe normal operation configurations of the National Power System.

In accordance with the Transmission Grid Code (TGC), the power plants shallsubmit the Transmission System Operator (TSO) the theoretical P/Q diagrams for thenew and rehabilitated units when they obtain the permit to connect to the grid, whilefor the units already in operation they shall submit actual P/Q diagrams plotted bytesting.

In accordance with the TGC, the TSO may request the electricity producers toperform some tests to prove that the respective generators are able to generate reactivepower according to the submitted data. Thus the TSO dispatcher may order theloading/unloading of the tested unit to Pmin stable and Pmax stable and shall create all the grid

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Vaida, V. -141-

conditions necessary for such loading/unloading with the needed maximum/minimumreactive power.

3. DETERMINING THE P/Q DIAGRAM OF THE SYNCHRONOUSGENERATORS OF DEVA-MINTIA POWER PLANT BY TESTING

P/Q diagram plotting by testing was performed at Deva-Mintia Power Plant,together with ICEMENERG, for 5 synchronous generators (no. 2, 3, 4, 5 and 6). Wewill present here the plotting method and the results thus obtained for the rehabilitatedunit no. 3.

The synchronous generator no. 3

The Generator no. 3 is provided with stator winding direct cooling by distilledwater, whilst the rotor windings and the active stator core are cooled by hydrogen inclosed circuit inside the generator. The distilled water is circulated through the statorwindings by means of pumps (water inlet pressure is 2.8 bar and the nominaltemperature is 40 °C) and is cooled by means of heat exchangers installed inside thegenerator. The cooling hydrogen is circulated inside the generator by means of fans (of3 bar rated pressure), installed on the rotor shaft and is cooled in gas coolers installedinside the generator body (hydrogen nominal temperature is 32°C).

The stator windings are three-phased, short-pitched, in two layers, made ofcopper bars with elementary conductors through which distilled water is circulated forcooling.

The stator cooling water pressure at the winding inlet should be lower (byapproximately 0.2 bar) than the hydrogen pressure inside the generator to avoidhydrogen entering the distilled water system.

Before rehabilitation and upgrading, the rotor winding was provided withradial cooling using the hydrogen inside the generator and a system of coolingchannels. When the rotor was upgraded, it was equipped with a more effective coolingsystem, with increased heat dissipation in the winding area, and new insulationmaterials of class F were provided, allowing the increase in the generator power, betteroperation in transient modes and a more effective cooling of the winding due to thesubslot cooling system.

The generator has the following allowed operation modes:a) Normal operation at rated voltage, of 15.75 kV. When voltage variations arewithin 5% of the rated voltage, the generator provides the rated output with thenominal power factor (cosφ=0.95), while the stator current varies by 5% from the ratedcurrent.b) The operation at asymmetric loads creates a rotating magnetic field of negativesequence, counter to the rotor magnetic field, therefore crossing the rotor field atdouble sequence. The effect of the asymmetric operation is the dangerous heating ofthe rotor, even if the current does not exceed the allowable values. The allowablenegative sequence current should not exceed 8% of the stator rated current. The loadand phases instability is obviously different for a period of time.

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Reflections on the qualification of the generation units for providing theservice consisting in reactive power within the voltage

secondary control range-142-

In case of an unbalanced short circuit, the duration of the short circuit shouldbe so that the result of multiplying the inverse current square root by its duration (inseconds) does not exceed the number 8 [4].c) If frequency varies within a range of 2% of the nominal value, the generator

output does not change. However if the frequency variation is between 2% and 5% ofthe nominal value, the generator voltage and current do not change. The generator isnot allowed to operate with a frequency exceeding the nominal value by more than 5%.d) The generator output cannot be increased, if the water temperature at the gas

cooler inlet decreases below 24°C. If the gas temperature increases over 33°C or thewater temperature increases over 40°C, the generator output should be reduced (by7.5% at an increase by 5°C, by 17.5% at an increase by 10°C, and bz 52.5% at anincrease by 15°C). Water maximum temperature at stator winding outlet is 75°C. If thecooled gas temperature exceeds 45°C, the generator output needs to be reduced, and ifthat is not enough then the generator should be disconnected from the grid.e) From the process point of view, the following issues need to be followed:- If stator winding temperature exceeds 75°C, the generator should must be

decreased;- If cooling water flow decreases to 18 m3/h (the rated flow is 30 m3/h), an alarm is

generated, and the generator trips when the flow is 13 m3/h, with a 2-minute delay.- The cooling water conductivity must not exceed 13 μS/cm (the normal value is 2.5

μS/cm).- The generator is not allowed to operate if there are water leakages in the stator

windings.- The generator is not allowed to operate with a hydrogen pressure that is 10% less

than the 3 bar nominal pressure or with purity less than 95%.f) The operation of the generator with underexcitation is limited by the heating of

the generator front ends and by the stability limit. The loading in capacitive mode canbe determined on the P/Q diagram of the generator.g) When operating in asynchronous mode, the loading of the generator must not

exceed 40% of the nominal load during more than 5 minutes.During the first 30 seconds of asynchronous operation, the generator load should

be decreased to 60%, and during the following 90 seconds, down to 40% of thenominal load. During the asynchronous operation, the stator current must not exceed,on any phase, 110% of the nominal current.

However, according to the PE 130 regulations, it is forbidden to operate thegenerator in the asynchronous mode.

4. DETERMINING THE P/Q DIAGRAM OF THE UNIT 3GENERATOR AT DEVA-MINTIA POWER PLANT

The methodology for determining the operation limits of a generator consistsof determining the maximum heating in the generator’s active parts: stator copper,stator core, rotor winding and generator stator front laminated plate bundles.

The following allowable temperature values are provided for our Unit 3generator:- Stator winding: TCu max=105°C;

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Vaida, V. -143-

- Rotor winding: TCu ex=115°C;- Active core: TFe=105°C;- Hot distillate at stator winding outlet: TDC=85°C;- Hot H2 in the generator: THc=75°C;- H2 nominal temperature: THn=32°C;- Cold distilled water nominal temperature: TDn=40°C ± 5°C;

Maximum allowable heating of the generator active parts, relative to the coolingmedium at the inlet are:

DTcu max = TCu max - TDn = 60°C DTFe max = TFe max - THn = 73°C DTex max = Tex max - THn = 83°C

In view of plotting the P/Q diagram, the temperatures of these active parts of thegenerator are measured, as follows:- For the stator winding bars, by means of RTD’s installed between bars in the sameslot;- For the stator core, by RTD’s installed between the bar at the bottom of the slot andthe bottom of the slot;- For the front teeth, by means of RTD’s installed in the first stator radial groove andtowards the outside of the first stator plate bundle;- For the cold distillate temperature, local readings are used.

For the long-term inductive operation, the generator operation limits aredetermined by defining the maximum heating that can occur in the stator windingcopper bars, in the stator magnetic core and the excitation rotor winding.

For the long-term capacitive operation, some thermal and electromagneticphenomena occur, that affect only the front end of the stator, without having anyimpact on the central part of the stator, by greatly heating the stator teeth at the end ofthe generator stator. Therefore, the operation limits of a generator for long-timecapacitive operation (underexcited) are related to the determination of the maximumheating occurring in the teeth area of the front laminated plate bundle, which, ifexceeding the allowable values, may damage the insulation between stator plates andmay cause local melting spots and ageing of the stator winding insulation.

During generator no. 3 testing, the following issues were observed:- Verifying the generator nominal operation point in inductive mode at the maximumpossible active power, P=Pn; Q=Qn;- Determining the maximum capacitive operation at the maximum active powerP=Pn; Q=Qcap max;- Verifying the minimum active power operation point in inductive mode whenoperating with two boilers, P=Pmin, Q=Qind max;- Verifying the minimum active power operation point in capacitive mode whenoperating with two boilers, P=Pmin, Q=Qcap max;

Based on the performed tests and measurements, the actual P/Q diagrams wereplotted, having sections determined by the maximum stator current, by the minimumrotor current and by other thermal aspects.

The static stability curves determine the generator capacitive operation.Some tests were performed with the unit in operation with one or two boilers.

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Reflections on the qualification of the generation units for providing theservice consisting in reactive power within the voltage

secondary control range-144-

CET Mintia -TG 3 Incalzirea elementelor active in functie deQla P=226 MW - extrapolare

10

15

20

25

30

35

40

45

50

55

60

0 10 20 30 40 50 60 70 80

Q [MVAr]

DT

[*C

]

Dtcust

Dtfe

DTd

DTex

Fig.1 The heating of activeelements at P = 225 MW

CET Mintia -TG 3 Incalzirea elementelor active in functie de Q la P=80 MW - extrapolare

10

15

20

25

30

35

40

45

50

55

60

-60 -40 -20 0 20 40 60 80 100 120 140 160 180 200

Q[MVAr]

DT

[*C

]

Dtcust

Dtfe

DTd

DTex

Fig. 2 The heating of activeelements at P = 80 MW

Further to the tests and the P/Q diagram plotting the following conclusionswere reached:

The temperatures of the stator copper, stator core, stator front teeth and of therotor excitation windings did not reach the maximum allowable values in any of thetesting operation modes (Fig.1, 2, 3, 4, 5, 6).

The curves extrapolated over the entire inductive operation range of theturbogenerator in accordance with the theoretical P-Q diagram, which represents themaximum operation range, do not generate limit values for the heating of the generatoractive parts (stator copper and core, and rotor copper) and they do not restrict the P/Qcapacity diagram.

The capacitive operation is limited only by the static stability curve.The charts in Figures 1 and 2 below present the heating of the active parts of

the generator as a function of the reactive power Q, at P=226 MW and P=80 MW,corresponding to the operation of the unit with one or two boilers.

The charts in Figures 3 and 4 present the temperature of the front teeth, on theinner and outer side, at P=225 MW.

Mintia - TA 3 Temperatura dintilor frontali (fata interioara) in diverseregimuri la P=225 MW

30

35

40

45

50

55

60

65

0 20 40 60 80 100 120 140 160 180 200

L [mm]

Td

[*C

] #REF!

226+j0

225+j70

Fig. 3 Temperature of the front teeth(inner side) at P = 225 MW

Mintia - TA 3 Temperatura dintilor frontali (fata exterioara) indiverse regimuri la P=225 MW

20

25

30

35

40

45

50

0 20 40 60 80 100 120 140 160 180 200

L [mm]

Td

[*C

] #REF!

226+j0

225+j70

Fig. 4 Temperature of the front teeth(outer side) at P = 225 MW

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Vaida, V. -145-

The charts in Figures 5 and 6 present the temperature of the front teeth, on theinner and outer side, at P=80MW.

5 – practical static stability curve (10% reserve) and the capacitive operation limit;For therehabilitated generator no. 3, having the rated capacity of 234.8 MW (210 MW beforerehabilitation), the nominal power factor of 0.95 (0.85 before rehabilitation), the nominalexcitation current of 2164 A (Iexn=2600A before rehabilitation), ALSTOM company hadsubmitted a theoretical P/Q diagram.

By trials and testing the actual P/Q diagram was plotted, which confirmed thetheoretical diagram (Fig.7).

Fig. 7 Theoretical and actual P/Q at U=Un, for Unit 3 generator

1 – turbine power limit;2 – stator current limit;3 – nominal rotor current limit;4 – minimum rotor current limit;6 – natural static stability curve.

The P-Q diagrams were plotted also for the operation with the generator terminalvoltages of 0.95 Un, 0.9 Un, 1.05 Un, 1.1 Un.

The operation range of the generator within the P/Q diagram is given by theminimum area delimited by the curves of the diagram (Fig.8).

1 – turbine power limit; 2 – stator current limit;

Mintia - TA 3 Temperatura dintilor frontali (fata interioara) in diverseregimuri la P=80 MW

30

35

40

45

50

55

60

0 20 40 60 80 100 120 140 160 180 200

L [mm]

Td

[*C

] 80-j35

80+j0

80+j140

Fig. 5 Temperature of the front teeth(inner side) at P = 80 MW

Mintia - TA 3 Temperatura dintilor frontali (fata exterioara) indiverse regimuri la P=80 MW

20

25

30

35

40

45

0 20 40 60 80 100 120 140 160 180 200

L [mm]

Td

[*C

] 80-j35

80+j0

80+j140

Fig. 6 Temperature of the frontteeth (outer side) at P = 80 MW

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Reflections on the qualification of the generation units for providing theservice consisting in reactive power within the voltage

secondary control range-146-

3 – maximum rotor current limit; 4 – minimum rotor current limit; 5 – practical static stability curve (10% reserve) and the capacitive operation limit; 6 – natural static stability curve.

Fig. 8 Practical operation areas of the Unit 3 generator at U=Un

The minimum excitation current of 658 A, was determined by calculation sothat the generator should be able to operate with Pmin=70MW and Q=-56 MVAr at Un.

When operating with two boilers, there are areas on the P/Q diagram wherethe generator cannot operate as the maximum and minimum power is defined fromthermal point of view, Pmax=234.8 MW, Pmin=140 MW, and when operating with oneboiler, Pmax=90 MW; Pmin=70 MW. The Unit cannot operate over the shadowed areasin Figure 8.

5. THE VOLTAGE SECONDARY CONTROL RANGES

The ANRE methodology for determining the prices for the power systemservices defines the procedure for calculating the qualified suppliers’ rate for providingthe reactive power needed for voltage control.

The voltage secondary control range is defined by those areas on the P/Qdiagram of the synchronous generator where the generation/absorption of the reactiveenergy is costly and stressful for the generator and where the generated reactive poweris paid for.

The primary voltage control range is defined by that area on the P/Q diagramof the synchronous generator where the reactive energy generated/absorbed is not paidfor. The secondary voltage control ranges for the qualified generators are jointly agreedby the interested parties, the TSO and operators. The issue of the reactive powermarket emerged in Europe in 1996, and is not hom*ogeneously regulated, each countryhaving its own regulations in that respect. Using the same methodology as for the othergenerators of Deva-Mintia Power Plant, the diagram presented in Figure 7 is used forthe Unit 3 generator, and the primary and secondary control ranges have been definedon this diagram. (Fig.9), when U=Un and the cooling media at the nominaltemperatures.

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Vaida, V. -147-

Fig. 9 Determinarea benzilor de reglaj al tensiunii pe diagrama P/Q.

For the inductive operation mode, the control ranges are defined by a straightline, Q =53 MVAr, and for the capacitive operation mode by a straight line Q = -10MVAr. (at the point where the nominal power line crosses the practical static stabilitycurve). The secondary voltage control ranges are noted Q1 and Q2.

From the presented facts it can be concluded that Unit no. 3, like the Units 2,4, 5 and 6 for which the P/Q actual diagrams were plotted, is able to provide the systemservice consisting in the secondary voltage control, being capable of generating-absorbing reactive power.

6. CONCLUSIONS

1. The qualification of the generation units to provide system services is afeasible solution for improving the operation reliability and efficiency of the generationunits as well as the power system as a whole.

2. The power units of Deva-Mintia Power Plant are capable of providing thesystem service that is the secondary voltage control, as they are able to generate/absorbreactive energy and can therefore be qualified finally and fully for providing thissystem service.

REFERENCES

[1]. SC Transelectrica. Operational Procedure for qualifying the internal producersas system services providers – Tel – 07VUS – DN/154.

[2]. ANRE. The ANRE procedure, Code 35.1.432.1.01./1999, regarding termsand conditions of payment for the services of voltage control by generating/absorbing

reactive electricity.[3]. SC Transelectrica. Operational Procedure – The operation modes of the power

generators within the National Power System. Code Tel. 07 III RS – DN/196.[4]. ICEMENERG – SC Electrocentrale Deva. The determination by testing of the

thermal limitations of the P/Q diagram in view of qualifying the Unit 3 Turbogenerator ofDeva-Mintia Power Plant for providing the voltage control system service in accordance withthe ANRE regulations – 2006.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 148-153

RESEARCHES ON THE RISK FACTORS WHEN USINGELECTRO-INSULATING MATERIALS IN

CONSTRUCTION OF TECHNICAL EQUIPMENTINTENDED FOR USE IN AREAS WITH EXPLOSION

HAZARDS

NICULINA VĂTAVU*, ADRIAN JURCA**, FLORINA MUNTEANBERZAN***

Abstract: The use of electro-insulating materials in construction of technicalequipment intended for use in areas with explosion hazards give rise to many problems becauseof the microclimate which contributes to insulation impairing (ageing), thus leading to anincreased risk of technical equipment malfunction and generating faults and/or explosions.

In order to prevention the faults (the risk factors) in technical equipment used in areaswith explosion hazard, a basic measure is considered to be the requirement of improving theirconstruction, having in view the use of electro-insulating materials with superior characteristicsrelated to their behavior to surface currents leakage in wet conditions, to electric arc, toinflammability and to high temperatures.

The proof and the comparative tracking indices represent an important parameter toassess the performances of electro-insulating materials used in construction of technicalequipment intended for use in potentially explosive atmospheres. The testing method simulatesthe specific requirements for the electric arc or creepage or clearance through the electro-insulating materials, and the results are being used for a proper adequate selection of thematerials.

Keywords: explosion hazard, explosion risk, explosion protection, explosiveatmosphere, comparative tracking indices

*D:Eng, senior scientific researcher III at INSEMEX Petroşani** D:Eng, scientific researcher at INSEMEX Petroşani*** D:Eng, research assisstant at INSEMEX Petroşani

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Vătavu, N., Jurca, A., Berzan, F. M. -149-

1. INTRODUCTION

Using of electro-insulating materials in construction of apparatus designed tobe used in potentially explosive atmospheres raises important issues due to themicroclimate conditions that have a decisive influence on their quality, regardinginsulation degradation (ageing), so leading to an increased fault hazard in electricapparatus and, also, possible damages and/or explosions.

It has been ascertained that the main cause of insulation ageing is representedby the physical-chemical irreversible alterations within the electro-insulating material,due to exploitation stresses and mainly due to thermal stresses. Related to this, it hasbeen found that the thermal breakdown voltage, respectively the dielectric rigidity ofmaterial may be increased by choosing materials with high thermal conductivity andlower electric conductivity and thermal coefficients; by decreasing the workenvironment temperatures (especially in the case of thick insulations, where innerlayers show a slower cooling process); by diminishing the stress periods.

It is of a great importance that selection of electro-insulating materials to bemade on a full knowledge of the electric, mechanic and thermal functions which mustbe fulfilled in operation conditions.

2. TECHNICAL CONDITIONS AND SAFETY REQUIREMENTS FORTHE ELECTRO-INSULATING MATERIALS

The electro-insulating materials used in construction of electrical equipmentfor potentially explosive atmospheres shall conform the safety requirements in theproduct standards, in the technical equipment general standards (with the specific typesof protection) SR EN 60947/1-2001; SR EN 60079-0; SR EN 50018-2003; SR EN50019-2003 and in the general standard of the electro-insulating materials used inconstruction of electrical equipment STAS 6790-1989 and also in the specificstandards prescribing the test methods.

According to STAS 6790-1989, the electro-insulating materials, in form of testsamples (specific to each test) shall have the following mechanical, electrical andthermal properties, and the test and check methods shall conform to the productstandards, with the following completions:- Resistance to static bending checked according to SR ISO 178 (bend stress atmaximum load): minimum 50 MPa;- Resistance to Charpy shock determined on samples without notch checked accordingto SR EN ISO 179-1, 2: minimum 2 kJ/m2;- Resistance to compression checked according to SR EN ISO 604 (STAS 587 clause3; 4; 6) : minimum 10 MPa ;- Volume resistivity: - minimum 108 cm for equipment having Un 127 V;

- minimum 1010 cm for equipment having Un > 127 V;- Surface resistivity: - minimum 108 for equipment having Un 127 V;

- minimum 1010 for equipment having Un > 127 V;The surface and volume resistivity is verified according to the DECISION no.

27/2004 tat replaced partially STAS 6107 clauses 3; 4; 5; 6; 7; 8 ; 10, after

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Researches on the risk factors when using electro-insulating materials inconstruction of technical equipment intended for use in areas

with explosion hazards-150-

conditioning of 120 h at a temperature of (40 ± 2)°C and a relative humidity of(50±2)%, respectively SR HD 429 S1 and SR HD 568 S1.- The proof and comparative tracking indices in humidity conditions CTI and PTI:minimum 175 V at 50 drops. The proof and comparative tracking indices are checkedaccording to SR EN 60112-2004 (which replaced STAS 6205-1986). If anencapsulation or a part of an encapsulation serves directly to support uninsulated liveparts, the resistance to leaking currents and the clearance distances on the inner wallssurfaces of the encapsulation shall correspond to the comparative and proof trackingindices minimum 250 V at 50 drops;

In the flameproof capsulations of Group I, the electro-insulating materialssubject to electric stresses that may produce electric arc in air as result of nominalcurrents higher than 16 A (in commutation apparatus as switches, contactors,separators) shall have an comparative tracking index to surface leaking currents equalor greater than IRC 400M, according to SR EN 60112.

When the electro-insulating materials above mentioned do not correspond tothis verification, they may be used though, if their volume is limited to 1% of the totalempty enclosure, or if an adequate detection device allows power disconnection of theenclosure on the inlet side before the electro-insulating material possibledecomposition may lead to dangerous situations. The testing station shall verify thepresence and efficiency of those devices.

The lengths prescribed for the clearance distances depend upon the workingvoltage, the resistance to leaking currents on the electro-insulating materials surfaceand also upon the configuration of the electro-insulating parts of the equipment.

The inorganic insulating materials, e.g. glass and ceramics are not subjected tothe above verification, they are conventionally classified into Group I.

This classification applies to electro-insulating materials without ribs ornotches. If the electro-insulating parts do have notches or ribs, then the minimum valueof the clearance distance for the working voltage over 1100 V shall be taken as the onein the next superior group.

According to comparative tracking indices to surface leaking currents, theelectro-insulating materials (without ribs or notches) are divided into 3 groups:

- group I of materials: IRC 600;- group II of materials: 400 IRC < 600;- group III of materials: 175 IRC < 400.

- The dielectric rigidity: determined according to SR EN 60243/1,2,3 and it representsthe ratio between the breakdown voltage and the distance between the electrodes onwhich the voltage is applied. The test voltage can be applied in 3 ways:- control test - voltage is raised at the prescribed value and maintained constant for 1

min. or 5 min;- short time test - voltage is raised from 0 with an even increasing rate, so as the

breakdown will occur after 10...20 s (quick apply)- the test in steps of 20 s - it begins from the value of 40% of the probable breakdown

voltage. The step value is chosen among a row of successive pre-established values(in kV).

- The resistance to electric arc checked according to STAS 6415/1, 2:

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Vătavu, N., Jurca, A., Berzan, F. M. -151-

- as a minimum, the steps 2 and 3 for materials intended for manufacture ofitems that shall withstand to low voltage electric arcs;

- the resistance step prescribed in the product standard, for materials intendedfor manufacture of items that shall withstand to high voltage and low currentselectric arcs.

The condition of resistance to electric arc is not mandatory when:- the items are manufactured of plastic materials immersed in an encapsulation

mass (e.g. epoxy resins);- the electro-insulating materials are used in electric equipment having Un

maximum of 60 V, regardless the power;- the electro-insulating materials are used in electric equipment having a

maximum power of 50 VA, regardless the voltage;- the electro-insulating materials are used in electric equipment having a

maximum voltage of 127 V and a maximum power of 250 VA and wherethere is no danger or sparks and electric arcs occurrence.

- The resistance to glowing checked according to STAS 6174 clauses 3; 4; 5, it shallbe: minimum burn class 2- The thermal stability Martens checked according to STAS 6174 clauses 3; 4; 5, itshall be minimum 100°C- The temperature indices "IT" corresponding to the point of 20.000 h of the thermalendurance graph, without losing more than 50% of the resistance to bending(determined according to SR EN 60216/1, 2): at least 20 K higher than the hottest pointon encapsulation or part of encapsulation taking into account the maximum servicetemperature but a minimum of 80°C for electro-insulating materials and 120°Cceramics.- The resistance to flammability checked according to SR ISO 1210 clauses 6; 7; 8; 9,combustion time shall be less than 15 sec. and degradation shall not reach the 75 mmmarking.

3. ELECTRO-INSULATING MATERIALS BEHAVIOUR INOPERATION

In operation conditions, insulation of electric apparatus, especially of those ofhigh voltage, is subjected to various stresses by separate or combined actions ofmagnetic, electric, thermal, electro-dynamic or mechanic fields. These stresses actdirectly or indirectly towards insulation degradation (ageing) or even damaging byinsulation breakdown or creepage.

The physic phenomenon of impairing the electric apparatus insulation differsto a certain extent if it takes place outside (breakdown or creepage of outer insulation)or inside (breakdown or creepage of inner insulation), if it takes place inside thelongitudinal or transverse (main) insulation, between the apparatus phases.

The disruptive discharge phenomenon is based on ionization processesdevelopment and on their diffusion in form of avalanche of electrons.

Breakdown is accompanied by luminescent and acoustic phenomena,especially under operation conditions, where, due to the high short-circuit power of the

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Researches on the risk factors when using electro-insulating materials inconstruction of technical equipment intended for use in areas

with explosion hazards-152-

source, the initial discharge transforms in electric arc, with all its unwantedconsequences.

In some reactions, the grater molecules decompose into smaller molecules,where new ions are generated and they diminish the dielectric rigidity and decrease theinsulation resistance of the electro-insulating material.

Generally, those chemical reactions have an action of ageing on the insulation,with different speeds related to regime temperatures (permanently or intermittently)and related to the insulation particularities. For example, the inorganic insulationpractically does not age at the operation temperature of the high voltage electricapparatus.

When choosing the electro-insulating materials, a great importance have theirbehavior when an electric arc may occur in an encapsulation as a result of toovervoltages produced in the commutation moment, of surpassing the rupturingcapacity or different mechanical damages in the commutation apparatus.

The value of explosion pressure produced in the case of an short-circuit witheffect of electric arc depends upon the electric current intensity and upon the durationof electric arc. When an electric arc occurs in an enclosure, in the presence of electro-insulating materials, especially organic materials on basis of phenolic resins withorganic materials filling, due to high temperatures, these become current conductivefact which leads to their decomposition.

In case where the quantity of hot decomposition gases is greater than the onethat may be evacuated outside, a pressure rise within the enclosure will occur leadingto its deterioration. If the quantity of gas is lesser or equal to the one evacuated on theoutside, then there will be no inner pressure rise but flame jets on outside may occur.

From this point of view, the electro-insulating materials are divided into threegroups. In the first group are included the electro-insulating materials on whichdecomposition continues even after the quenching of the electric arc. This groupincludes plastic materials on basis of phenolic resins with organic filling materials. Inthe second group are included the electro-insulating materials for which decompositioncontinues as long as the electric arc persists. This group comprises electro-insulatinginorganic materials on basis of polyester resins filling. In the third group are includedthe electro-insulating materials that do not decompose under an electric arc influence,as the ceramic materials.

As a result, the short-circuits with electric arc within the encapsulations aredangerous, they may provoke damage to the enclosures either as a result of highpressures, or as a result of electric arc creepage to the enclosure walls and then itsbreakthrough.

As a remark, the regulations in force both in our country and abroad do notinclude provisions to ensure the required measures to reduce or diminish these hazards.Thus, no norm regulates the minimum thickness of enclosure walls made of differentmaterials, according to the pressure that may occur, in order to prevent a short-circuitwith electric arc, or according to the ways of breakthrough the enclosure walls in thecase of creepage of these short-circuits.

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Vătavu, N., Jurca, A., Berzan, F. M. -153-

4. CONCLUSIONS

In order to prevent the damages to electric equipment intended for use inenvironments endangered by explosive atmospheres, it is considered as necessary toimprove their construction by using in encapsulations of electro-insulating materialshaving superior characteristics regarding resistance to electric arc, leaking currents onsurface in humidity conditions, flammability and temperature. Having this in view, it isconsidered necessary to remove from utilization the electro-insulating materials onbasis of bakelite, textolite, pertinax etc., and to replace them with materials that areresistant to electric arc and surface leakage currents.

The laboratory tests that reproduce the most the stresses specific to electric arcand creepage in operation (that alter and show the ageing phenomenon in materials) arethe ones of flammability and comparative tracking and proofing indices on surface onhumidity conditions. This is the reason of imposing for the electro-insulating materials(in the case of group I flameproof enclosures) which are subject to electric stresses thatmay lead to electric arc at a current higher than 16 A (in the commutation apparatus asswitches, separators, contactors) an surface proof and comparative tracking indices thatis equal or above 400 V at 50 drops (determined according to SR EN 60112) and acombustion maximum time of 15 seconds (determined according SR ISO 1210).

REFERENCES

[1] Ifrim A., Materiale electrotehnice, Editura Didactică şi Pedagogică, 1979[2] Lică, V., Materiale electroizolante, vol. 1+2, Editura tehnică 1992[3] STAS 6790-86, Materiale electroizolante utilizate în echipamentele electrice

pentru atmosfere potenţial explozive[4] SR EN 60079-0:2005, Aparatură electrică pentru atmosfere potenţial explozive.

Cerinţe generale[5] SR EN 60079-1:2005, Aparatură electrică pentru atmosfere potenţial explozive.

Capsulare antideflagrantă ‘d’[6] SR EN 60079-7:2004, Aparatură electrică pentru atmosfere potenţial explozive.

Securitate mărită ‘e’[7] SR EN 60112:2004, Metodă de determinare a indicilor de rezistenţă şi de ţinere la

formarea de căi conductoare a materialelor electroizolante solide

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 154-159

SIMULATION SOFTWARE FOR STATIC SWITCHCONTROLLERS

MARIUS MARCU, ILIE UTU, FLORIN POPESCU, PANA LEON

Abstract: This paper present a simulation software for d.c. and ac static switchcontroller function, made like a Windows independent application helping with Visual Basic’ssoftware packages. The simulation windows is dynamically modifying in accord with staticconverter working regime.

Keywords: a.c. switch controller, d.c. switch controller, static converter, simulationsoftware.

1. INTRODUCTION

The development of industrial automation led by default also to theimprovement of electrical actuating systems, a fortiori such kind of the systemsrepresent the most spread conversion format to electrical energy in mechanical energy.

The static converter (CS) had become an important element in alimentationsystems with electrical energy to every kind of consumers. The most frequently, thestatic converters are used in adjusting systems to the static action, in this case theassignment being an electrical engine. Hereby, by an adequate command given by acontroller in to a close circuit, the static converters adjust the output electrical energyparameters, to the necessity demand by electrical engine.

The simulation software for static converter function it is realized like aWindows independent application helping with Visual Basic’s software package. Onceone of the simulation software is launched one window is opened, allowing choosingthe simulation type to be run, using radio buttons. The window also contains twobuttons, one for continuing the simulation (Continua), the other for exit the application(Iesire).

Associate professor, dr. eng., University of Petrosani Assistant, eng., University of Petrosani Lecturer, dr.eng., University of Petrosani

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Marcu, M., Utu, I., Popescu, F., Pana L. -155-

Following the simulation start-up, the simulation window is opened,containing three main parts:

A part which contains simulation scheme. Simulation scheme isdynamically modifying its margin colors which are in conduction at acertain moment.

Another part it is dedicated to information zone. This zone presenting thetext type information as regards to function mode to the converter analyzed(semiconductor elements which are in conduction, semiconductor elementsdirectly polarized, etc.). Inside of this zone it is also find buttons forcommand angle modification, for choosing the function dial, etc.

The third part it is the zone where is dynamically getting up the waveforms characteristic to the static converter analyzed.

Beside this zones, one of simulation windows also containing a pull-downmenu type, for modification of some parameters or for choosing of different type ofassignment. Moreover the window have two command buttons, one for starting upthe simulation (Simulare), who then it is transforming in button for hold up thesimulation (Stop) and a button for the exit of the window (Iesire).

2. STATIC SWITCH CONTROLLER SIMULATION

The static switch controllers are converters were the exit size have the sameform with the entry size, after modifying the command angle of thyristors obtainingthe converter out put of voltage variation.

Figure 1 shows the application of main window of static switch controllerssimulation software application, it allows selection for a. c. switch controllers, single-phase or three-phase, respectively the simulation for d.c. switch controllers.

Fig.1. The application of main window of static variators simulation software application

2.1. A.c. switch controllers

Figure 2 shows the simulation window for a single-phase switch controllerwith resistive charge. It can be seen the main menu to choose the type of switchcontroller (with two thyristors, with one thyristor or with a thyristor across a diodebypass), and also the charging type. The charge may be resistive, inductive or resistive-inductive type.

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Simulation software for static switch controllers-156-

Fig.2. The simulation window for a single/phase switch controller with resistive charge

Along the simulation, it has been modified the command angle of the switchcontroller, in order to evidence also the way of voltage modification, respectively ofthe current through charge. The command angle may be modified using up/downarrows, being shown their values.

Figure 3 shows the simulation windows for single-phase switch controller withresistive-inductive charge. In case of resistive-inductive charge the software request byan additional window the input of power factor value.

Fig. 3. The simulation windows for single/phase switch controller with resistive-inductive charge.

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Marcu, M., Utu, I., Popescu, F., Pana L. -157-

For the three-phase a.c. switch controller, the simulation window it is showedin figure 4 for a resistive charge. The simulation has been performed by modifyingcommand angle.

Fig.4. The simulation windows for three-phase switch controller with resistive charge.

2.2. D.c. switch controller

The d.c. switch controller, the chopper, it is the static converter who transformthe entry continue voltage into a orthogonal voltage impulses. The exit voltage mediumvalue its may be modified between 0 and entry value of voltage, in function with therapport between the period when the chopper is controlling and the period when this isblocked.

Figure 5 shows simulation window for function simulation of one of staticvariator by a quadrant realized with thyristor, being represented the wave formscharacteristic to the charge, the main thyristor and the switch off circuit.

Entering command in the main thyristor conductivity is to be done by pushingthe related command button and to switch off the main thyristor, its related push buttonis pressed.

Figure 6 shows the simulation window related with the d.c. switch controller,in four quadrants from the same window, it is possible to be modified the operationquadrant (using the four radio buttons) and also the period for the switch controller orconductivity period.

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Simulation software for static switch controllers-158-

Fig. 5. Simulation window for function simulation of d.c. switch controller by aquadrant realized with thyristors.

Fig.6. The simulation window related with the d.c. switch controller,in four quadrants

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Marcu, M., Utu, I., Popescu, F., Pana L. -159-

3. CONCLUSIONS

This documentation describes a Windows application, useful for understandingthe functioning of the static variators, converters, typing to cover all the neededaspects. This application has an teaching purpose, being useful for the studentsstudying static converters.

REFERENCES

[1]. Marcu, M., Borca,.D. Convertoare statice în acţionări electrice. EdituraTOPOEXIM, Bucureşti, 1999

[2]. Tunsoiu,Ghe., Acţionări electrice. Editura Tehnică, Bucureşti,1981.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 160-163

SOME RESULTS IN SOLVING FIELD ENGINEERINGPROBLEMS USING FINITE ELEMENT METHOD

NICOLAE DAN, VISALON DAN

Abstract Finite Element Method (FEM) is one of the most reliable numerical methods insolving complex engineering problems in real–life applications. This method is extensively used inthe field of structural mechanics, civil engineering and fluid mechanics; however the method isapplied with the same success in other areas of engineering such as electrical and magnetic. Thesimilarities are discussed on practical examples to better illustrate the analogy.

Keywords: finite element method (FEM), numerical examples, heat transfer, magneticand electrostatic fields, incompressible fluid flow.

1. INTRODUCTON

The finite element package ABAQUS is used next to solve the field problemsmentioned above. ABAQUS is an advanced FEM package dedicated for solving non-linear stress analysis, mechanical contact, and heat transfer problems. To better illustratethe analogies between the engineering fields, it will be shown that using the heatconduction capability in ABAQUS all four classes of problems mentioned in literature [1]can be solved. In fact if a finite element algorithm is available for any of the areaspresented in literature [1], the same finite element algorithm can be easily adapted tosolve the other classes of problems.

2. NUMERICAL EXAMPLES

a) Heat TransferFirst the heat transfer field in an electrical machine will be investigated. Due to

problem’s symmetry, only a part of the cross-section is considered in the analysis. The

PhD, ABAQUS Inc., USA Assoc. Prof. PhD, University of Petrosani, Romania

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Dan, N., Dan, V. -161-

heat sources in Eq. 1.1 (literature [ 1]) are the Joule losses in the rotor’s armature slot andthe core losses in the ferromagnetic material. Equivalent thermal conductivities wereconsidered for the air-gap and for the slot region [3]. On the sides the boundaryconditions are natural (Neumann), and Dirichlet boundary conditions on the bottom edge.Convective boundary conditions are specified on the upper (external) surface.

0)(

eyx TThyTk

xTk (1)

Where:h = heat transfer coefficient

eT = surrounding air temperatureThe thermal results are presented in Figure 2; NT11 in the legend indicates the nodaltemperatures.

Fig. 7. Electrical machine cross-section Fig.2. The mesh and the isothermal lines

b) Magnetic Field Problem

The magnetic field example is performed on the same configuration shown inFigure 1. The heat transfer capability is used again to solve the magnetic vector potentialproblem (Eq.1.2, literature [1]). The thermal conductivity is replaced by the magneticreluctivity, and the temperature is the two-dimensional magnetic vector potential. Theboundary conditions are hom*ogeneous on all edges. The magnetic flux distribution(constant vector potential) is shown in Figure 3.

To obtain the magnetic flux density (in the air-gap for example), from the heattransfer variables, we relay on the analogy with elemental heat flux.The heat flux components and the heat flux magnitude for the isotropic material (at theelement integration points) are given by:

)(;; 22yxyx y

TkxTk

(2)

The magnetic flux density components, and the magnitude, are given by:

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Some results in solving field engineering problems usingfinite element method-162-

)(;; 22yx

zy

zx BBB

xAB

yAB

(3)

Magnetic flux density

00.10.20.30.40.50.60.70.8

1 2 3 4 5 6 7 8 9

airgap elementsB[

T]

Fig.3. Magnetic flux distribution. Fig.4. Magnetic flux density in the air-gap.

Therefore the magnetic flux density magnitude can be easily obtained from theheat flux magnitude by dividing by the thermal conductivity. Similar calculations are alsovalid for orthotropic materials. The magnetic flux density in the air-gap, calculated usingthe above observations, is presented in Figure 4.

c) Electric Field Problem

The study domain represents an electrical capacitor (Figure 5). Following thesame analogy, the temperature in this case is replaced by the electric scalar potential(Eq.1.3, literature [1]).

Fig.5. Electrical capacitor. Fig.6. Equipotential line distribution.

The thermal conductivity becomes the electric permittivity for this case. Theboundary conditions are hom*ogeneous on the external edges; non-zero Dirichletconditions (opposite sign) are prescribed on the capacitor’s armatures. The FEM mesh isintentionally more refined in the area of high electric potential.

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Dan, N., Dan, V. -163-

The contours of the constant electric potential are presented in Figure 6. Againthe electric filed intensity VE

can be calculated similar as in Eq. (2-3, literature

[1]).

d) Incompressible Fluid Flow Problem

The study domain is a water pool in which the fluid is pushed diagonally by asolid structure, Figure 7. The problem is solved in terms of velocity potential function

presented in Eq. 1.4 (literature [1]). The boundaryconditions are Dirichlet on the top surface and on theimpinging structure, and hom*ogeneous Neumann onthe sides. The velocity field was computed based onthe analogy used presented in the previousapplications (Eq. 2-3, literature [1])

Fig.7. The fluid domain and the velocity field.

3. CONCLUSIONS

The similarities between the engineering field problems were presented onpractical examples. The heat transfer capability in ABAQUS FEM dedicated package wasused to solve four other classes of engineering problems.

Note: the “License Student” package was presented by ABAQUS to the Facultyof Electromecanics on the occasion of celebrating 50 years since this branch of theUniversity of Petrosani was founded. The package offers us the possibility ofimplementing numerous finite element algorithms in the process of solving other classesof engineering problems.

REFERENCES

[1] Dan, V., Dan N., “Theoretical Aspects in Solving Field Engineering ProblemsUsing Finite Element Method” , Annals of the University of Petrosani, 2007.

[2] ABAQUS User’s Manual, Version 6.5, 2005.[3] Dan, N, Ledezma, G.A., Craiu, O., “An improved Algorithm for Coupled Thermal

and Magnetic Problems in Electromagnetic Devices”, HTD-Vol. 348, Volume 10, ASME 1997.[4] Sivester, P.P., Ferrari, R.L, 1996, “Finite Elements for Electrical Engineers,

Cambridge University Press

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 164-167

STANDARDISATION TEST METHODS USED ATASSESSMENT OF PRODUCT CONFORMITY WITH THE

REQUIREMENTS OF PREVENTING THE EXPLOSIVEATMOSPHERE IGNITION BY ELECTROSTATIC

DISCHARGES

FLORIN ADRIAN PĂUN, LEONARD LUPU, FLORINA MUNTEANBERZAN***

Abstract: It is very important to take adequate protection measures to prevent theelectrostatic discharges from persons or their clothing for ensure a suitable level of securityagainst explosions in dangerous Ex areas. Preventing the electrostatic charging of men, ofclothes or on the surrounding objects suppose an ensemble of complex means and measures,hardly to supervise even in the present conditions of scientific knowledge.

Having in view this matter, it resorts to using of some standardized testing methodswhich allow further risk assessment of explosive atmospheres by the electrostatic dischargesfrom clothing. Also a standardized testing method is to determination the dissipation capacity ofcharges. The principle of this test method supposes the charging by induction of the specimentest and then the determination the dissipation capacity of charges accumulated on this.

Taking into account the assessment criteria for materials/products from the ignitionrisk point of view of the explosive atmosphere by electrostatic discharges, the main criteria isthe electric conductivity (see SR EN 13463 -1, (SR EN 50014:2004) substitute with SR EN60079-0, SR EN ISO 20344, STAS 11 004-88, SR EN 61340-4-1, SR EN 1149-1:2002, SR EN1149-2:2003). The newest assessment criteria are based on the charge determination (SR EN61340-4-1) and the electrostatic discharge time determination (SR EN 1149-3:2004).

Key words: electrostatics, explosive atmosphere, explosion protection, electrostaticdischarges, corona discharges.

Scientific researcher,Ph D.Eng. at the INSEMEX-Petroşani Assistant researcher, Ph D.Eng. at the INSEMEX-Petroşani

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Păun, F., A.,Lupu, L., Berzan, F. M. -165-

1. INTRODUCTION

It is well known that the ignition risk of the explosive atmosphere occurs whentwo conditions are simultaneously fulfilled:

- an explosive atmosphere which could be a mixture of the gases, vapors,dusts, powders, lints and air with concentration within the upper and lower explosivelimits and an ignition source of adequate energy to initiate the atmosphere are present.

If one of these conditions but preferably both of them are avoided, the ignitionrisk of the explosive atmosphere is diminished and even eliminated.

2. STATIC ELECTRICITY - POTENTIAL IGNITION SOURCE FORAN EXPLOSIVE ATMOSPHERE

The static electricity is a phenomenon that frequently occurs in industrialsactivities. Sometimes it represents a part of technological process as painting in theelectrostatic field, substances separation, deducting a.s.o., but many times it occursaccidentally and could represent a risk source, causing technological damages, firesand explosions.

The essential risk is that of fires and explosions due to discharges ofelectrostatic nature in explosion hazard areas respectively with explosive atmosphereor explosive substances. Also through the electrostatic discharges from all surroundingobjects or from the operating personnel, the sensitive operation and control apparatuscould be unexpectedly switched on. In some activities which imply manual work, thestatic electricity has an undesirable action on the human body having a negativeinfluence over his mental. Also, electrostatic discharges from persons represent a shockrisk which may lead to accidents at personnel implied in the different activities such as:work in a processing machine, or carrying out operations at a certain height, as a resultof miss handling caused by scared personnel.

Considering the risks presented by static electricity, it is necessary to takeprotection measures against them. Prevention of electrostatic charge formation,accumulation and discharge from metallic elements is carried out by bounding to earth.

Frequent use, on a larger and larger scale, in the industrial activities, of non-metallic materials susceptible to major electric charging, produces problems regardingmethods and means of protection against static electricity. Because their electric chargedegree is influenced by many factors that are difficult to control in practice, in thesome situations the risk of the static electricity formation cannot be preventedentirely, being necessary to take an assembly of measures for the purpose of theirlimitation within non-dangerous values according to endangered system influence.

Another technical solution for diminishing the dangers generated by staticelectricity could be employment of conductive and dissipative materials instead of non-conductive materials. Many materials were once entirely non-conductive, such asrubbers or plastic materials, now available in the dissipative category.

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Standardization test methods used at assessment of product conformity withthe requirements of preventing the explosive atmosphere

ignition by electrostatic discharges-166-

3. METHODS AND TECHNIQUES FOR ASSESSMENT OF PRODUCTCONFORMITY WITH THE SAFETY REQUIREMENTS FOR PREVENTIONOF IGNITION SOURCES BY ELECTROSTATIC DISCHARGES

Taking into account the assessment criteria for materials/products from theignition risk point of view of the explosive atmosphere by electrostatic discharges, themain criteria is the electric conductivity (see SR EN 13463 -1, (SR EN 50014:2004)substitute with SR EN 60079-0, SR EN ISO 20344, STAS 11 004-88, SR EN 61340-4-1, SR EN 1149-1:2002, SR EN 1149-2:2003). The newest assessment criteria are basedon the charge determination (SR EN 61340-4-1) and the electrostatic discharge timedetermination (SR EN 1149-3:2004).

3.1 Test method for measurement of charge decay

The principle of the methods supposed charging by induction of a testspecimen. In the few seconds under test specimen, which is placed on horizontal line isplaced an electrode field without to have contact with the test specimen. Then on theelectrode field is applied a high voltage. If the specimen test is conductive or heldconductive elements a charge with opposite polarity at the electrode field is induced bythe test specimen.

The field from the field electrode which is struck on the conductive elements,it’s not cross by the test specimen and the effective field reduced in the same mannerso that is characteristic to the material supposed at test method. This effect is measured

and recorded in the specimenpast with a suitable electricalsounder field measuring.In the time what inducingcharges sum in the testspecimen increase the effectivefield recorded by measuringelectrical sounder decrease.This decrease of the field isused to determination of thehalf time decay charge and ashield factor. The test method ismade to twelve specimens withdimensions (50 ± 2) mm x (300± 2) mm, which is cutting up

from a fabric sample or clothes; is cutting up six specimens test in the warp sense andsix specimens test in the filing sense or in width. Three test specimens cutting up in thewarp sense respectively three test specimens cutting up in the filing sense will be usedwith stems (rods) type HDPE and three test specimens cutting up in the warp senserespectively three test specimens cutting up in the filing sense will be used with stems(rods) of aluminum. The samples shall not comprise seams. Handling of the testspecimens will be done only on their edges to avoid their contamination.

Fig. 1 Arrangement of equipment for induction chargingtest method

Key: 1 charge amplifier; 2 recording device; ; 3 fieldmeasuring probe; 4 guard ring; 5 specimen clamping

ring; 6 test specimen; 7 support ring; 8 field electrode; 9voltage generator

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Păun, F., A.,Lupu, L., Berzan, F. M. -167-

The test apparatus is composed by following:- a field electrode (a rustless steel plate with diameter 70 ± 1 mm fixed on

insulating support);- guard ring;- specimen clamping ring;- voltage generator capable to produced a voltage of (1200 ± 50) V;- electrical sounder field measuring;- recording device.

REFERENCES

[1]. SR EN 1127-1 : 2003 Atmosfere explozive - prevenirea exploziilor şi protecţiacontra exploziilor. Partea 1. Concepte de bază şi metodologie

[2]. SR EN 13463 - 1:2003 Ehipamente neelectrice pentru atmosfere potenţialexplozive Partea 1: Metode şi cerinţe de bază

[3]. SR EN 50014:2004 Aparatură electrică pentru atmosfere potenţial explozive.Cerinţe generale înlocuit cu SR EN 60079-0:2005 Aparatură electrică pentru atmosfereexplozive gazoase. Partea 0: Condiţii generale

[4]. SR EN ISO 20344:2004 Echipament individual de protecţie. Metode de încercarepentru încălţăminte.

[5]. STAS 11 004-88 Pardoseli pentru încăperi cu pericol de explozie; Determinarearezistenţei de descărcare şi a rezistenţei de scurgere a sarcinilor electrostatice

[6]. SR EN 61340-4-1 Electrostatică Partea 4-1: Metode de încercare standardizatepentru aplicaţii specifice. Rezistenţa electrică a pardoselilor şi a straturior de acoperire

[7]. SR EN 1149-1:2006 Îmbrăcăminte de protecţie. Proprietăţi electrostatice. Partea1 . Metodă de încercare pentru măsurarea rezistivităţii de supafaţă.

[8]. SR EN 1149-2:2003 Îmbrăcăminte de protecţie. Proprietăţi electrostatice. Partea2. Metodă de încercare pentru măsurarea rezistenţei electrice la traversarea materialelor(rezistenţă verticală)

[9]. SR EN 1149-3:2004 Îmbrăcăminte de protecţie. Proprietăţi electrostatice. Partea3 . Metodă de încercare pentru măsurarea capacităţii de disipare a sarcinilor.

[10]. BS 5958: Part 1:1991 Cod of practice for Control of undesirabile staticelectricity. General considerations

[11]. Ulrich von Pidoll Determining the incendivity of electrostatic discharges withoutexplosive gas mixtures, PTB Germany

[12]. CLC/TR 50404 June 2003 Electrostatics - Code of practice for the avoidance ofhazards due to static electricity

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 168-175

STOCHASTIC MODELS FOR RELIABILITY ANALYSIS OFPROTECTION SYSTEMS

LEON PĂNĂ, ION FOTĂU, HORIA ŞERBAN

Abstract: A small part of power system, including one or more protection systems, ismodeled by using mathematical techniques: Markov theory, renewal theory, Petri nets andMonte Carlo simulation. In this paper the Markov models from protection systems are discussedand analyzed.

Keywords: reliability, protection system, failure to operate, mal-trip

1. INTRODUCTION

An industrial supply network system consists of a combination of lines orcables, power transformers and incoming power sources including co generators. Thepower cables, overhead lines and transformer form the main supply network, whichprovides a reliable power transmission from sources to loads.

A protection system protects the power system from the harmful effect orfaults. a fault is an abnormal system condition, which is in most cases a short circuitand occurs as a random event . In general, protection systems do not prevent damage tothe power system, they operate after some detectable damage has already occurred.

In this section an overview of protection models used in reliability analysis andthe stochastic models of the protection systems used in other area will be presented.The models are not discussed in full detail, only the main characteristics are presented.For more information, references are included.

Of the qualities required of the protection systems [1, 2, 4, 5] the two of maininterest to us here are:Selectivity or discrimination The protection system is effectiveness in isolating

only the faulty part of the system.Stability The property of remaining in operation with faults

occurring outside the protected zone.

PhD. Lecturer Eng. at the University of Petrosani PhD. Student at the University of Petrosani

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Pană, L., Şerban, H. -169-

In other words, the power system protection should isolate the fault and refrainfrom action for the rest. These two aspects of the protection lead to two aspects of thereliability of the protection as defined by the IEC [1].Reliability of protection The probability that a protection can perform a

required function under given conditions for a giventime interval.

Dependability The probability for a protection of not heaving afailure to operate under given conditions for a giventime interval.

Security The probability for a protection of not having anunwanted operation under given conditions for a giventime interval.

Reliability is generally defined as a measure of certainly that a piece ofequipment or system will perform as installed.

Start

Assign the fault location

Calculate the fault currentdistribution

Calculate all relay operationtimes

Find all the fastest operationof relay

Find out the fastest operationof relay store the operation

time to t fi

Set i=1

Figure 1 The flow chart for the reliability algorithm to clear onesimulated faults

i=i+1 StopIs completelyclear the fault

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Stochastic models for reliability analysis of protection systems-170-

In figure 1 is illustrated the flow chart for the reliability algorithm to clear onesimulated faults.

Here the two principal failure modes of the protection appear, namely, failureto operate and unwanted operation. These two terms will reappear further on, but thereis more to failure of the protection than this. For example, the unwanted operation canbe spontaneous, or due to an event in the power system (often a fault outside the zoneto be protected, i.e. an external fault). The failure can be due to a relay failure, a circuitbreaker failure, a current transformer failure or even due to an error in the calculationof the setting. The first aspect of the protection to be modeled in a stochastic way wasthe fault clearance time [1, 2]. Once the probability density function of the faultclearance time is known, of the fault clearance time is known, the required time-grading can be calculated for any given value of the acceptable chance of unwantedoperation. A similar concept is used for stochastic assessment of transient stability [2,3, 4, 5].

2. SYSTEM PROTECTION MODEL AND RELIABILITYALGORITHM

At the occurrence of fault on a power system, the current is almost always greater thenthe pre-fault load current in the components in the vicinity of the fault. The operational time ofan overcurrent relay depends on its operating characteristics. Figure 2 shows the operationaltime of an overcurrent relay with definite-time characteristic. Such a relay does not operate(operating time is infinite) as long as the current magnitude is less than Ip. If the currentmagnitude exceeds Ip the relay operate after Ts seconds.

t

IIp

ts

Figure 2 Overcurrent relay with definite-time characteristic

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Pană, L., Şerban, H. -171-

In order to design a protection system, one must be able to represent andevaluate the performance of protection systems. Thus, methods of representing theperformance of relays alone and in relation to other relays of the protection system arerequired. In this section, the relay-unit that has the simplest operating characteristic isintroduced. The operating characteristic of any relay can be represented by a set ofrelay-units. Moreover, this section presents a method for representing the performanceof a protection system.

A relay-unit (denote by r) is the relay that has a simplest operatingcharacteristic, as shown in figure 3. Such a relay operates after a pre-set delay times ts,in case of any fault for which operating quantity q is above the pick-up value qp. Ingeneral, the operating quantity of a relay-unit can be any function of the currents andvoltages of the component being protected.

As overcurrent relay with a definite time characteristic is an example of arelay-unit with the component current at the operating quantity. Such a relay operatesfor all currents above the pick-up setting of the relay. It is possible to set up a relay-unitthat operates for values smaller than the pick-up value and take no action for valuesabove the pickup. Under-voltage and one step impedance or distance relays areexamples of such a relay.

t

qq p

ts

Figure 3 Unit-relay is operating characteristic

r

t t

I I

R1 R1

r1,1 r1,2

r1,1

r1,2

Figure 4 Complex characteristics by combining relay-units

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Stochastic models for reliability analysis of protection systems-172-

Due to simplicity of the operating characteristics of relay-units, every relay-operating characteristic can be represented by a combination of a set of relay-units.

In figure 4 two steps and an inverse characteristic are represented by acombination of two relay-units. In this paragraph, a small letter “r” denotes each relay-unit (e.g. r1, r2) and each protective relay that consist of one or more relay-units isdenoted by a capital “R”.

The dynamic equation for the OC relay operation time calculation is definedby IEEE standard C37.112-1996 as shown in equation (1):

1)I(t

10T

(1)

where:)I(t Is the relay disc traveling time from 0 to operating distance at fault

current IFor the three consecutive fault currents, I1, I2, I3 the tactual is calculated as

follows:

2

11

2

11 i

fi3fiactual

2f1factual32

2f

1

1f

t

tt 3

tt

t 2

t

0 1

tt

1ttt

1tttt1

tt

tt

1dtt1dt

t1dt

t1 actual

2f1f

2f1f

1f

1f

(2)

where:321 t,t,t are the relay operating times at fault current 321 I,I,I

respectively.The inverse definite minimum time lag (IDMTL) over current relay (OC)

operating time for “n” steps of fault currents with n consecutive fault currents is shownin following equation:

1n

1i

1n

1i i

finfiactual t

t1ttt (3)

The protection is here considered to consist of four parts:

Main protection Backup protection Breaker failure protection

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Pană, L., Şerban, H. -173-

Circuit breakerA protection system has two alternative ways in which it can be unreliable it

may fail to operate when it is expected to (referred to as fail-to-trip), or it may operatewhen it is not expected to (referred to as mal-trip). This leads to a two-prongeddefinition of the reliability of protection systems.

3. ASSUMPTION AND SITUATION DESCRIPTION

The following assumptions are used in modeling the system: After a failure to operate, which is followed by a repair, and after maintenance the

relay is working properly. The times to failure of a relay (TTF) are independent and exponentially distributed

with parameter p. This means that if a relay is last seen healthy at time ht , than thechance the relay is dormant at time t is equal to:

h)tt(p tfor te1)tT(P h (4)

Here T is the moment at which the relay becomes dormant.

Times between short circuits (TBSC) are independent and exponentiallydistributed with parameter . Since short circuits are cleared immediately in themodel, the chance that a short circuit will happen in the next interval of time t isequal to:

tsh e1)tT(P (5)

Here shT denote the time to the next short circuit. The time between two successive maintenance (TBM) is independent and in a

protection system with “n” relay, the TBM is exponentially distributed withparameter μ/n. All “n” relays are maintained at the same time. The average numberof relays maintained in one unit of time then equals.

Due to characteristics of matrix T, the changes in )t(Pi will diminish int . With this, the set of differential equations reduces to set of linear equations

having the form:

OPT (6)

where

P a column vector whose ith term is steady-state probability of residing in state i

Since the elements in each columns of matrix A add up to zero, the determinant of T inzero and, therefore, the equations in (9) are not linearly independent.

Each equation is linear combinations of others. To provide an additional equation, thesimple fact is recognized that the state probabilities must add up to 1 at time t, and therefore:

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Stochastic models for reliability analysis of protection systems-174-

1Pn

1kk

(7)

For this reason, the steady-state probabilities can be obtained by solving the followingmatrix equation:

CPT ' (8)

where:

'T a matrix obtained from matrix A by replacing the elements of an arbitrarilyselected row p by ones

P a column vector whose ith term is the probability of residing in state I

C a column vector with the pth element equal to one and other elements set tozero

In figure 5 the standard graphical representation of the Markov model isshown. The model contains two relays. Short circuit lead to the fail-to-trip if bothrelays are dormant at the time of occurrence at the short circuit. Maintenance isperformed simultaneously at both relays. The times between maintenance are

exponentially distributed with parameter2 .

The three states of this model are defined as follows:State 1: In this state both relays are healthy. The short circuit and the

maintenance do not cause a transition when the system is in this state.Both relays can fail with rate p. this cause a total transition rate out ofstate one, equal to 2p.

State 2: In this state one of the relays is dormant. In this case short circuits donot have any influence on the state of the model because the relay that

is healthy will work properly. Maintenance with rate2 will cause a

R1 UPR2 UP

1R1 DNR2 UP

2

Figure 5 State-space diagram for a system comprising two protectiverelays

pR1 DNR2 DN

3

2

2

2p

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Pană, L., Şerban, H. -175-

transition to state 1 while the failure of the healthy relay with rate p,will cause a transition to state 3.

State 3: In this state both relays are dormant. Maintenance with rate2 will

cause a transition to state 1. Short circuits with rate , while the systemis in a state 3 will cause a failure to operate and the repair of bothrelays that is represented by a transition to state 1.

The matrix T is:

2p0

0p2

p222

p2

TTT

TTT

TTT

T

332313

322212

312111

(9)

The matrices T’ and C is:

1

C,

111

0p2

p222

p2

T ' (10)

Solving equation (8) results in:

2

22

3

2

1

1'

p8

2p4

p22

p62p8p121

P

P

P

CTP (11)

REFERENCES

[1]. International Electrotechnical Vocabular. Chapter 448: Power System Protection.IEC 50(448): 1987. Geneve: IEC, 1987

[2]. Anderson P.M., Reliability modeling of protective systems, IEEE Transactions onPower Apparatus and Systems, vol.103 (1984), p.2207-2214

[3]. Anderson P.M. and Agarwal S.K., An improved model for protective systemsreliability, IEEE Transactions on Reliability, vol. 41 (1992), p. 422-426

[4]. Anders G..J., Probabilistic concepts in electric power systems, New York: JohnWiley & Sons, 1990

[5]. Billinton R. and Allan R.N., Reliability evaluation of power systems, London:Pitman, 1984

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 176-182

STUDY DYNAMIC OF A SYNCHRONOUS GENERATORWITH ELECTRONIC LOAD

JENICA ILEANA CORCĂU

Abstract: In this paper is present study dynamic and analysis of a system consisting ofa variable-speed synchronous generator that supplies an active load (inverter) through a three-phase diode rectifier. A particularity of the described system is strong non-ideal operation of thediode rectifier, a consequence of the large value of generator’s synchronous impedance. Thispaper presents a new average model of the system. The average model accounts, in a detailedmanner, for dynamics of generator and load, and for effects of the non-ideal operation of dioderectifier. In particular, the systems control-loop, responsible for stability and proper impedancematching between generator and load, an difficult to design without an accurate small-signalmodel.

Keywords: variable-speed synchronous generator, electronic load, control-loop,stability, small-signal model.

1. INTRODUCTION

This paper presents study dynamics of the system whose block diagram isshown in figure 1. It is a 150kW generator with inverter output, in which a naturalgas engine drives a synchronous generator. Field voltage is provided to maingenerator by means of a separate, smaller synchronous machine, an exciter.

In order to make engine operation as efficient as possible, speed is variedfrom 1800 rpm to 4000rpm according to a load-versus-speed relationship consideredoptimal for the engine. Such variable speed operation affects generator design inseveral ways, of which the most important for study is the effect it has on the valueof main generator’s synchronous inductance [1].

Lecteuer Ph D., University of Craiova, Faculty of Electrotechnics, Division Avionics,[emailprotected]

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Corcău, J., I. -177-

Fig.1. Block diagram of the studied system

The system shown in figure 1 cannot work in open loop: dc link voltage dcv ,needs to be regulated at a constant value 800V for the inverter to operate properly[1]. Since diode rectification provides no means of regulation, constant dc-linkvoltage can be achieved only by adjusting the exciter’s field voltage .fdv That can bedone by closing the dc-link voltage feedback control-loop, as shown in figure 2.

Fig.2. Block diagram of studied system in closed loop

2. AVERAGE MODEL EQUATIONS

In figure 3 is presents implement the average generator/rectifier model [2].

Fig.3. Block diagram of the average model

The dc source can be either a voltage or a current source; the d and q axisload can be given by either’s current or voltage sources.

The equations of average model are [2]),cossin( qdvdc vvkv (1)

),sin( i

dcd k

ii

(2)

),cos( i

dcq k

ii

(3)

.q

dvvarctg

(4)

)],cos()sin([ qdidc iiki

(5)

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Study dynamic of a synchronous generator with electronic load-178-

,sinv

dcd k

vv (6)

,cosv

dcq k

vv (7)

.q

dvvarctg

(8)

It can be seen that the average model’s equations establish a “transformer-like” relationship between the generator’s output in the dq reference frame and therectifier’s dc output.

2.1. Linearized average modelThe average model’s equations, presented in relationships 1 to 8 are non-

linear because they contain products of variables, as well as trigonometric functions.For some purposes such as control-loop design, it is necessary to study the linearizedsystem. In many causes, software used for simulation of the average model is capableof linearizing system equations, after it determines the steady-state operating point.An example using software Matlab/Simulink, is procedure “linmod” obtainedliniarized system equations. However, it is useful to find analytically the linearizedversion of average model equations. That makes it possible to easily simulate casesthat would cause numerical problems in determining the steady-state operating point,as well as to find the liniarized state space representation of the system. In this modelthe steady-state value of an average variable x will be denote X , while x~ representssmall perturbation of same variable. The scope is to find a linear state spacerepresentation of the system consisting of the exciter, main generator and dc load.This is obtained by combining the machine’s equations with the liniarizedgenerator/rectifier average model’s equations, and equations describing the dc load[3]. This is algebraically tedious process that does not introduce any new concepts. Ifthe generator’s speed is constant and treated as a parameter of the system; are lineardifferential equations, and they can be rewritten for small perturbation by simplyadding a tilde to all currents and voltages. Since both the exciter’s and maingenerator’s equations will be treated in this paper, index “e” will be added to allparameters and variables relative to the exciter; and index “a” to those entire relativeto the main generators.

3. STATE-SPACE REPRESENTATION OF THE SYSTEM

State-space representation of the system is,BuAxx (9)

Where

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Corcău, J., I. -179-

adc

akq

akd

aq

ad

efd

eq

ed

viiiiiii

x

~

~~~~~~~

(10)

Is the vector of state variables, and

sarcina

efd

iv

u ~~

(11)

Is the vector of system’s inputs.In order to find matrices A and B from (9), the system’s equations will be

written in the formGuFxxE (12)

After that, matrices A and B can be calculated as

,1FEA (13)

.1GEB (14)

The matrices E and F are [3]

88

88

99

000000000000000)(00

0)(000000)(0

0000000000)(000)(

eLLL

LLLfLfLbLLLbLLLfLfL

LLLlalalLLllalaLllLL

E

amqalkqamq

mdalkdamdaeqamdaedamd

aqdcamqamqals

addcamdamdalsaeqamdaedamd

emdelfdemd

aeaeeqqemqelseqd

aeaeemdedqeddemdels

(15))( 2188 aqdcaddc bbbbe ,

888584

54

45

21

12

0000000000000000000

000000

000000000000000000

fffR

RfLrRffLfLfLfrR

RLrRf

frR

F

akq

akd

aqdcamdaaqqasaeqamdaaedamda

addcamqaaddas

efd

emdeeqqes

eddes

(16)

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Study dynamic of a synchronous generator with electronic load-180-

),(21 emdelseeqd LLrf ),(12 emqelseedq LLrf ),(45 amqalsaadq LLrf

),(54 amdalsaaqd LLrf ,2184 aqdadd rbrbf ,2185 aqqadq rbrbf

.12188 aqdcaddc fbfbf

,

00000

00

010000

82

g

rr

Gaql

adl (17)

.2182 aqladl rbrbg

If a resistive load were connected to the dc-link, equations which allow us todetermine matrices E, F and G can easily be modified by substituting

,~~

l

adcsarcina R

vi (18)

Where lR is the load resistance. In that case, the only input to the system isrepresented by exciter’s field voltage ( efdv~ ). If the dc-link voltage is considered to besystem’s output, the output equation can be written in the form

,~ DuCxvadc (19)

,10000000C (20)

].0[D (21)

4. TRANSFER FUNCTIONS

A liniarized representation of the system allows finding system’s transferfunctions. For dc-link voltage controller design, it is necessary to have Bode plots offunction transfer control-to-output. This transfer function can be found fromlinearized state space representation as

.)(~~

1 DBAsICvv

efd

adc (22)

In table 1 are listed the transfer function’s poles and zeros numerically for theoperating point characterized by: 3340rot/min, 105kW current source load and fieldvoltage 33V. In table 2 consists the transfer function’s poles and zeros numerically forthe operating point characterized by: 3340rot/min, 105kW resistive load and fieldvoltage 33V and table 3 are listed the transfer function’s poles and zeros numerically

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Corcău, J., I. -181-

for the operating point characterized by: 2240rot/min, 15kW resistive load and fieldvoltage 26V.

Table 1Zeros(rad/s) Poles (rad/s) Gain1074,4 -1721,6+3008,2j 1832,4338,6+745,2j -1721,6-3008,2j338,6-745,2j -2111,6-731,7 11,8+62j-615,9 11,8-62j11,7 15,3

-27,6Poles (rad/s)

Table 2Zeros(rad/s)

Poles (rad/s) Gain

1074,4 -1662,7+2524,3j 1832,4338,6+745,2j -1662,7-2524,3j338,6-745,2j -2111,6

-731,7 89,3+119,5j-615,9 89,3-119,5j11,7 15,1

-27,3-43,7

Table 3Zeros(rad/s)

Poles(rad/s)

Gain

5372,1 -13879 1832,44642,3 -1489+7301j

649 -1498-7301j-815,9 4012-731,7 -40

-4,5 20Zeros(rad/s)

-8

2

In figure 4 is presented the block scheme of simulation for two constants input.

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Study dynamic of a synchronous generator with electronic load-182-

1Vadc

33

Vefd

Vadc

To Workspace

x' = Ax+Bu y = Cx+Du

State-Space

Scope

131.25

Isarcina

Fig.4 The block scheme in SimulinkFig.5. The variation in time of the output

voltage

In figure 5 is presented the variation in time of the output voltage .adcVIt can seen of that current source load, as opposed to resistive load, makes the

system more difficult to stabilize in closed loop.

5. CONCLUSIONSIn this paper is presented a study dynamic of synchronous generator with

electronic load. It present a new average model of system studied. This modelaccounts in a detailed manner, for dynamics of generator and load, and for effects ofthe non-ideal operation of diode rectifier. A liniarized representation of the systemallows finding system’s transfer functions. For dc-link voltage controller design it isnecessary to have plots of functions transfer control-to-output, which represents thesystems control-to-output transfer function. Dependence of this transfer functions onthe operating point and nature of dc load was discussed from the point of view of dc-link voltage control-loop design.

REFERENCES

[1]. Jadric I., Borojevic D., Jadric, M. Modeling and control of a synchronousgenerator with an active dc load. IEEE Trans., Power Electronics, vol. 15, no.2, march 2000.

[2]. Corcau, J. Three-phase synchronous generator modeling as subsystem of a PDS(Power Distribution System). 7th International Conference of Applied and TheoreticalElectricity ICATE 2004, 14-15 octomber, Baile Herculane, pp. 543-546.

[3]. Corcau J. Sisteme evoluate de comanda si control al proceselor din instalatiileelectrice ale avioanelor. Teza de doctorat, Universitatea “ Politehnica”, Bucuresti, aprilie,2006.

[4]. Louganski K. P. Modeling and analysis of a DC power distribution system forin 21st century airlifters. Doctoral dissertation, Virginia, 1990.

[5]. Elbuluk, M. E., Kankam, M.D. Potential starter/generator Technologies forFuture Aerospace applications. IEEE AES Magazine, vol.11, no.10, 1996, pp. 1724.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 183-187

TENSIONS INVERTORS WITH COMMUTATION ONTHREE LEVELS. MATHEMATICAL MODELING;

STRUCTURAL DIAGRAM

CONSTANTIN BRÎNDUŞA

, MIHAI PĂSCULESCU, DRAGOŞPĂSCULESCU

Abstract: The tension inverter with commutation on three levels is applied in electricaction systems specific to electric urban traction. Based on commutation functions the tensioninvertors with commutation on three levels it can mathematical modeled. Beginning from themathematical model it can be made a structural diagram of the tension inverter withcommutation on three levels.

Keywords: tension inverter, three levels, urban frame, mathematical model, structuraldiagram.

1. INTRODUCTION

The working hypothesis for the modelling of the semi-conductor powerdevices considered are: commutation as working regime, with the neglect of thecommutation times and the voltage failures for the conduction in direct sense, fromhere resulting the fat that the converter is consider without losses.

Every converter type has construction and functioning particularities thatimpose certain restrictions when passing to the mathematical modelling process. Themathematical modelling of the voltage invertors, thus of the static power converterswithout the intermediary circuit, can be done in many ways, and they are:

- throughout the state equations that most of the analysis packages of theelectronic power circuits are based on;

- through the use of the Laplace transformant;

PhD Student. Eng. University of Petrosani Professor PhD .eng. University of Petrosani Assistant PhD Student Eng. University of Petrosani

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Tensions invertors with commutation on three levels. mathematicalmodeling; structural diagram-184-

- through the analysis of the spatial phasor;- on the basis of the discrete samples, method which can be applied to the

semi-conductor power devices which work in commutation regime, etc..The chosen modelling method is based upon the commutation functions, taking

into account also the MATLAB utilitarian.

2. MATHEMATICAL MODELING; STRUCTURAL DIAGRAM

On the basis of the electronic scheme of principle assembly inverter of voltagewith commutation on 3 levels and asynchronous engine, (figure 1), we will obtain themathematic level and the structural scheme.

Fig. 1 The electronic scheme on principle assembly inverter of voltage withcommutation on 3 levels and asynchronous engine

For shaping the inverter of voltage with commutation on 3 levels (to see fig.1),is been considered the ideal case in which the two groups RC divide in equal way theUd tension. For shaping the inverter of voltage with commutation on 3 levels i tis usedthe function with commutation on three levels Cf3 , (Tab.1):

Table 1Nr.crt.

Tip inverterof voltage

Commutationfunction

Valuesfunction

Variable:tiristor sext.

Variable:tiristor jext.

Variable:tiristor mint.

1 1;3;5 1a;3a;5a 0 1a;3a;5a;

4a;6a;2a

1 Inverter withcommutationon 3 levels

Cf3

-1 4;6;2 4a;6a;2a

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Brînduşa, C., Păsculescu, M., Păsculescu, D. -185-

By utilizating the Cf3 function result”s table 2:

Table 2Type circuitforce

Voltage fase R Voltage fase S Voltage fase T

Inverter ofvoltage CR

dR f

uu 30 2

CSd

S fu

u 30 2 CT

dT f

uu 30 2

Motor asinc. uRN= uR0- uN0 uSN= uS0- uN0 uTN= uT0- uN0

In case we have a connection Y asynchronous engine, we have the relation:uN0 = (uR0 + uS0 + uT0)/3 (1)

Taking into account the relations previously presented it results the structuralscheme three phase inverter of voltage with commutation on 3 levels, (fig.2).

Fig 2 The structural scheme and the mask block, three phases voltage inverter withcommutation on 3 levels

Afte rit was expected the models and the structural scheme corresponding withthe two invertors of voltage are similar, indifferent of the commutation functions whichstand at the base of modelation.

This thing allows the introduction of a mathematical drives λ, and obtaining aunitary structural scheme and the corresponding mask block., (fig.3).

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Tensions invertors with commutation on three levels. mathematicalmodeling; structural diagram-186-

Fig 3 The structural scheme and the mask block, three phases voltage inverter withcommutation on λ levels

The λ driver is defined in N multitude and has the value according to table 3.

Table 3 The value for λ driverNr. Type circuit force Type comut. Values op.λ Commut. function Cf1 Inverter of voltage 2 levels 2

Cf22 Inverter of voltage 3 levels 3

Cf3

Fig 4 The structural scheme and the mask block, three phases voltage inverter withcommutation on 2 levels

It can be observed that through allocating value 2 to λ driver we have the caseof the inverter of voltage with commutation on two levels and the Cf2 commutationfunction, (fig.4).

So the structural scheme and the generalized mask block, (fig.3), it transformin structural scheme and mask block inverter of voltage witf commutation on two

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Brînduşa, C., Păsculescu, M., Păsculescu, D. -187-

levels.By allocating value 3 to λ driver we have the case of inverter of voltage with

commutation on 3 levels and the Cf3 commutation function. So the structural schemeand the generalized mask block (fig.3), it transform in structural scheme and maskblock inverter of voltage with commutation on three levels, (fig.2).

The two models have included in their structure the model of the asynchronengine of traction MAT, the bundle with this is been made through tension and thestator current. The commutation function generated by the control system of tractionallow the control of the ensemble tension inverter – asynchron engine.

3. CONCLUSIONS

Se pot trage urmatoarele concluzii:- The mathematic modelling of the voltage inverter with commutation on 2

levels, on the basis of the electronic scheme of the principle assembly voltage inverterwith commutation on 3 levels - asynchronous engine can be made through the use ofthe commutation function with 3 levels;

- The structural scheme and the mask block assembly voltage inverter withcommutation on 3 levels - asynchronous engine is obtained on the basis of themathematical model;

- Is been established a structural, unitary scheme, no matter the voltage invertertype, (commutation on 2 or 3 levels);

- The necessity of establishing an unitary voltage inverter model, indifferentlyof the number of inverter commutation levels

REFERENCES

[1]. Brînduşa,C.,ş.a., Sisteme electrice de transport neconvenţionale (A23); Rama demetrou acţionată cu motoare asincrone; Execuţie şi experimentare modele (Faza 23.1),Contract cercetare 606C- Anexa A, Institutul naţional de cercetare şi proiectare pentru maşinielectrice, echipament electric şi tracţiune, Craiova, 1992.

[2]. Brînduşa,C.,Păsculescu,M., Popescu,L., Drive systems behavior analysis inurban electric traction with Matlab software extensions, Simpozion InternaţionalMultidisciplinar „UNIVERSITARIA SIMPRO” ,2006, Petroşani, Editura UniversitasPetrosani, 2006.

[3]. Nicola,D.A.,Cismaru,D.C., Mathematical models for control simulation oftraction induction motors, ICATE’98, Craiova, 1998.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 188-191

TENSIONS INVERTORS WITH COMMUTATION ON TWOLEVELS. MATHEMATICAL MODELING; STRUCTURAL

DIAGRAM

CONSTANTIN BRÎNDUŞA, MIHAI PĂSCULESCU

DRAGOŞ PĂSCULESCU

Abstract: The tension inverter with commutation on two levels is applied in electricaction systems specific to electric urban traction. Based on commutation functions the tensioninvertors with commutation on two levels it can mathematical modelade. Beginning from themathematical model it can be made a structural diagram of the tension inverter withcommutation on two levels.

Keywords: tension inverter, two levels, urban frame, mathematical model, structuraldiagram.

1. INTRODUCTION

Every converter type has construction and functioning particularities thatimpose certain restrictions when passing to the mathematical modelling process. Themathematical modelling of the voltage invertors, thus of the static power converterswithout the intermediary circuit, can be done in many ways, and they are:

- throughout the state equations that most of the analysis packages of theelectronic power circuits are based on;

- through the use of the Laplace transformant;- through the analysis of the spatial phasor;- on the basis of the discrete samples, method which can be applied to the

semi-conductor power devices which work in commutation regime, etc..The chosen modelling method is based upon the commutation functions, taking

into account also the MATLAB utilitarian.

PhD Student.Eng., University of Petrosani Professor PhD Eng. University of Petrosani Assistant PhD Student University of Petrosani

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Brînduşa, C., Păsculescu, M., Păsculescu, D. -189-

Taking into account the voltage inverters type used in the electric action withstatic converters and asynchronous traction engines namely voltage converters withcommutation on 2, in their modelling we will define through tables the commutationfunction, (table 1).

Table 1Nr.crt.

Tip inverter of voltage Commutationfunction

Valuesfunction

Fase inverter

1 R;S;T1 Inverter with commutationon 2 levels Cf2 0 R;S;T

1 R;S;T 0 R;S;T

3 Inverter with commutationon 3 levels Cf3

-1 R;S;T

The working hypothesis for the modelling of the semi-conductor powerdevices considered are: commutation as working regime, with the neglect of thecommutation times and the voltage failures for the conduction in direct sense, fromhere resulting the fat that the converter is consider without losses.

2. MATHEMATICAL MODELING; STRUCTURAL DIAGRAM

On the basis of the electronic scheme of principle assembly inverter of voltagewith commutation on 2 levels and asynchronous engine, (figure 1), we will obtain themathematic level and the structural scheme.

For the modelling of the voltage inverter with commutation on 2 levels is usedthe commutation function in 2 levels, Cf2 , (Tab.2):

Table 2Nr.crt.

Tip inverter ofvoltage

Commutationfunction

Valuesfunction

VariableTiristor s

VariableTiristor j

1 1; 3; 51 Inverter withcommutation on 2levels

Cf2 0 4; 6; 2

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Tensions invertors with commutation on two levels. mathematicalmodeling; structural diagram-190-

Fig 1 The electronic scheme on principle assembly inverter of voltage with commutation on 2levels and asynchronous engine

Fig 2 The structural scheme and the mask block, three phases voltage inverter withcommutation on 2 levels

By utilizating the Cf2 function it results table 3:

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Brînduşa, C., Păsculescu, M., Păsculescu, D. -191-

Table 3Type circuitforce

Voltage fase R Voltage fase S Voltage fase T

Inverter ofvoltage

uR0= Ud CRf2 uS0= Ud CSf2 uT0= Ud CTf2Motor asinc. uRN= uR0- uN0 uSN= uS0- uN0 uTN= uT0- uN0

In case we have a connection Y asynchronous engine, we have the relation:uN0 = (uR0 + uS0 + uT0)/3 (1)

Taking into account the relations previously presented it results the structuralscheme three phase inverter of voltage with commutation on 2 levels, (fig.2).

3. CONCLUSIONS

We can draw the following conclusions:- The mathematic modelling of the voltage inverter with commutation on 2

levels, on the basis of the electronic scheme of the principle assembly voltage inverterwith commutation on 2 levels - asynchronous engine can be made through the use ofthe commutation function with 2 levels;

- The structural scheme and the mask block assembly voltage inverter withcommutation on 2 levels - asynchronous engine is obtained on the basis of themathematical model;

- The necessity of establishing a structural, unitary scheme, no matter thevoltage inverter type, (commutation on 2 or 3 levels);

- The necessity of establishing an unitary voltage inverter model, indifferentlyof the number of inverter commutation levels.

REFERENCES

[1]. Brînduşa,C.,ş.a., Sisteme electrice de transport neconvenţionale (A23); Rama demetrou acţionată cu motoare asincrone; Execuţie şi experimentare modele (Faza 23.1),Contract cercetare 606C- Anexa A, Institutul naţional de cercetare şi proiectare pentru maşinielectrice, echipament electric şi tracţiune, Craiova, 1992.

[2]. Brînduşa,C.,Păsculescu,M., Popescu,L., Drive systems behavior analysis inurban electric traction with Matlab software extensions, Simpozion InternaţionalMultidisciplinar „UNIVERSITARIA SIMPRO” ,2006, Petroşani, Editura UniversitasPetrosani, 2006.

[3]. Nicola,D.A.,Cismaru,D.C., Mathematical models for control simulation oftraction induction motors, ICATE’98, Craiova, 1998.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 192-195

THE ANALYSIS OF THE LC-TYPE PASSIVE FILTERS’INFLUENCE UPON THE POWER SUPPLY NETWORK OF

A REZISTIVE CONSUMER USING THE LABVIEWPROGRAM

IOAN BACIU, CORINA CUNŢAN

ABSTRACT. This work is analysing the influence of the passive filters upon theparameters of the single-phase power supply line of a rezistive consumer using the LabVIEWprogram. The filter’s model is represented by the mathematical function related to eachharmonic in part, expression which is introduced based on a previously established law. It’saiming the possibility to modify the filter’s expression depending on the power supply line’sparameters.

Key words: LC filters, power, current, voltage

1. WORK’S PRESENTATION

In order to compensate the harmonics of the currents absorbed from thedistribution networks by different consumers of which supply is made by commutationelements are used passive and/or active power filters of high performance.

In the usual case, the passive filters are influenced by the modification of theown resonance frequency of the power supply network. This present survey isanalyzing the situation when the own filter’s frequency is modifying by a sinusoidallaw and the network’s frequency remains unmodified. The operation is emphasized byshowing on the same graphic the input voltage, the current and signal’s power on theload resistance, as well as by showing the related frequency spectrum, determined withthe Fourier Transformation of the current from the circuit by connecting the LCfilter.It’s used a signal generator which allows to obtain two dephased output signals,with a phase displacement imposed depending on the capacitor’s and coil’s values,which is the one introduced by the two elements in the circuit. The two

Dipl. Eng University from Timişoara, Faculty of Engineering from Hunedoara Ph. D. Eng University from Timişoara, Faculty of Engineering from Hunedoara

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Baciu, I., Cunţan, C. -193-

elements are modeled by a mathematical law and which takes into account thesinusoidal shape we want to have the filter’s impedance module.

xNL

LX sin

xn

CCXsin

10

1

where: L and C are values to be imposed for the coil, respectively capacitor.N is a weighting factor of inductance’s valuen is a weighting factor of capacitor’s valuexsin signal generated by a sinusoidal signal generator

Considering the two ideal elements, without loss resistance, is obtainingthe LC circuit’s impedance:

xC

n

NLx

C

nx

NLZ sin)10(sin10sin

Having the impedance value, will be obtained the current through the LCcircuit:

1sinsin2sin2 tt

xZUt

ZU

FI ;1t

where: represents the phase displacement introduced by LC for the signalgenerator’s function from the input circuit on the load circuit sR , and is thegenerator’s pulsation.

SRCXLX

arctg

Is obained: - the energy stored in the LC filter by the relation:

)sin

10sin(2212)(

212sin

212

212

21

xC

nx

NLICXICxILCULInE

- input signal inUtUinU sin2

- signal’s power on the filtration circuit

tUttZUP sin21sin2

- current through the filtration circuit

1sinsin2sin2 tt

xZUt

ZUI

Is applied the Fourier Transformation upon the current and is obtained thespectrum’s module for a sampling sequence of 250Hz.

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The new european concept of explosion protection for the non–electricalequipment intended for use in explosive atmospheres-194-

The circuit’s operation diagram (fig. 1) drawned in LabView allows thevisualization of the connexions between the elements which intervene, as well as themodality to implement the mathematical relations.

Thus are obtained the wave shapes of the voltage, current and power (fig. 2), thefrequency spectrum (fig. 3) and the energy stored in the LC filter (fig. 4).

Fig.2

Fig.1

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Baciu, I., Cunţan, C. -195-

2. CONCLUSIONS

The harmonics spectrum emphasizes the existence of the harmonics in theform of the curtent through the filter, harmonics which have a large spectrum andrelatively small values against the fundamental. For the signal power on the filter isfound its double variation frequency, as well as a shape distorsion at maximum values.Also, one can observe the phase displacement imposed between voltage and current.

Interesting is how it’s presenting the shape of the energy stored in the LCfilter, being obtained more simultaneous values, which leads to more sinusoides ofdifferent amplitudes and identical frequency.

REFERENCES

[1] Pop E., Naforniţă I., Tiponuţ V., Toma L., Mihăescu A., - Metode înprelucrarea numerică a semnalelor, Editura Facla, Timişoara 1986;

[2] Cottet F., Ciobanu O., - Bazele programării în LabVIEW , Editura Matrix Rom ,Bucureşti 1998

1

Fig.4 Magnetic energy

Fig.3 Frequency spectrum

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 196-198

THE LIGNITE ROLE AS THE PRIMARY SOURCE IN THEELECTRICAL ENERGY SUPPLY IN ROMANIA

CURELEANU SORIN, BLANARU LIVIU, STOICHITOIU ANGHEL

Abstract. This study is analyzing the odds of coal production industry after theintegration of our country into the European Community

Key words: lignite, energy, power

1. INTRODUCTION

The investments concerning the National Energetic System (S.E.N.) havepermitted our country to become energetically since 2004 a full-rights member in theEuropean Union.

2. THE ROLE OF THE LIGNITE IN POWER GENERATION

Recently the reorganization of the coal-based power generation wasaccomplished by founding the Energetic Complex in Rovinari, Turceni and Craiova. Inthis system, the open pit coal mines are integrated like cost-centre of the powerproducer. In the following table is illustrated the Romanian energy productionprognosis in the interval 2005 – 2010:

Table 1 [GWh]Total production 2005-

760002010-88000

2015-102000

2020-112000

Coal-based power plants 31000 33000 35000 35000Hydro-centrals 13700 14200 14600 15000Fuel-oil and nuclear power plants 29800 39100 50400 60000

PhD Student. University of Petrosani Professor PhD .Eng. University of Petrosani

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Cureleanu S., Blanaru L., Stoichitoiu, A. -197-

The considerations about the internal energetic resources in the biggestRomanian burning power plants are as follows: the existing coal (lignite and browncoal) is used by the big thermo-electrical power plants (CTE) of the national energeticsystem endowed with high performance energy generation installations and natural gas(imported and indigene) are imposing the expansion and the development of thetransport and distribution network. Heavy fuel oil importing is an important issue on anon-predictable market.

Based on the analyses of the Romanian extracting industry recovery trend, thesignificant aspects are as follows: the natural resource (coal) is ensuring a large amount of the primary resources

for the energetic sector, presenting on the internal market a large absorptioncapacity;

there is an important capacitive potential partially worn-out physically andmorally, only partly used, with a structure not enough adapted to the newcompetitively standards from the European Union and other developedcountries;

the equipment and technology’s performances can be substantially improvedby an accelerated and selective modernizing effort of the production capacitieswith viability real chances;

it is still available qualified personnel with technical capacity comparable withthe one from the developed countries, etc.For a large time interval the coal is the base energetic resource for Romania.

The situation of the energetic fuel consumption is as follows: (fig. 1)

Fig. 1 Romanian fuel consumption situation:

1. heavy oil – 3%;2. other conventional resources – 4%;3. nuclear – 11%;4. natural gas – 16%5. regenerative – 28%;6. coal – 38%;In the present tight competition situation in the energetic market, when the

ecological restrictions are derogatory for the Energetic Complex Structures, where thebasic fuel is the lignite and the price of the solid fuel, oil and natural gas is increasingas well, the marketing compartments are looking for improved organization methodsby technical and technological restructuring. The target of these measures is to reducethe specific energy cost price especially by reducing the extracting cost of the lignite.

165432

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The lignite role as the primary source in the electrical energy supply inRomania-198-

Our lignite has an average lower caloric capacity compared with other Europeanzones, having higher ash content, and the outturn of the lignite power plants (CTE) isless than the ones using the brown coal or hydrocarbons.

Lignite-based power generation has the following benefits: production costs closer than oil; ensuring the use of the internal resources and diminishing of the hydrocarbons

fuel import; the primary investments are lower than nuclear power plants and hydro

centrals with the same installed power; ensuring a higher zonal number of employment, thus resolving an important

social aspect; thermal energy is produced in co-generation with electric power; environmental problems are solved by the present technologies.

The adapting process of the open pit mining to the free market conditions, whenthere are still some technical endowment pending problems, can be accomplished byadopting a complex reorganization system aiming managing components, as well asmining and environmental components.

3. EUROPEAN DIRECTIONS FOR MINING INDUSTRY

The principal instruments for implementing the European legislation consist ofthe European directions with a large impact over the Romanian mining industry. Weare mentioning the 94/22/EC direction regarding the licensing and the license use forhydrocarbons exploit, 92/91/EC direction regarding the minimal requirements for themining extraction personnel safety and the proposed instruction for waste materialsdisposal management in the extraction industry.

4. CONCLUSIONS

In the future, the coal will take an important share in power generation as well asin the economical development of the society.

An energy saving active policy will be applied in parallel with the energyproduction cost savings. The available internal lignite reserves is about 55 years ofabout 35 millions tons per year in the open pit mines and for the brown coal is about3.5 million tones.

REFERENCES

[1] European AQUIS Requests;[2]CESCO Consulting Committee Declaration about the role of coal in the XXI

century Europe (July 1999);[3] EUROCOAL Report – PATROMIN Magazine;[4]LEGEA 3 / 2001 – Kyoto Protocol ratification on the United Nation Convention

about Environment and Climate Altering.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 199-204

THE NEW EUROPEAN CONCEPT OF EXPLOSIONPROTECTION FOR THE NON–ELECTRICAL EQUIPMENT

INTENDED FOR USE IN EXPLOSIVE ATMOSPHERES

ADRIAN MARIUS JURCA, MIHAELA PĂRĂIAN, EMILIANGHICIOI, NICULINA VĂTAVU***

Abstract: Non-electrical equipment has been used for over one hundred years inindustry branches with environments having potentially explosive atmospheres generated bygas, vapor, mist and/or combustible dust. Thus, a great deal of experience has been gained inthe application of protective measures to reduce the risk of ignition to an acceptably safe level.With the introduction of the ATEX Directive 94/9/EC and the inclusion of non-electricalequipment in its scope, it became necessary to produce standards which have to include:ignition protection concepts, protective measures clearly defined and, nevertheless, the benefitof the extensive experience gained over the years. In the case of non-electrical equipment, thereference standard is SR EN 13463-1:2003, Non-electrical equipment for potentially explosiveatmospheres Part 1: Basic method and requirements, that specifies the basic method andrequirements for design, construction, testing and marking of the non-electrical equipmentintended for use in potentially explosive atmospheres in air of gas, vapor, mist and/orcombustible dusts. This standard must be applied together with the European standardsregarding the specific types of ignition protection, part of those in courses of harmonization.

Keywords: non-electrical equipment, explosion prevention, explosion protection,ignition sources, explosive atmosphere

1. GENERALITIES

Explosion protection is of particular importance to safety; since explosionsendanger the lives and health of workers as a result of the uncontrolled effects of flameand pressure, the presence of noxious reaction products, and consumption of theoxygen in the ambient air, which workers breathe.

PhD.Eng, scientific researcher at INSEMEX Petroşani Ph.D:Eng, senior scientific researcher I at INSEMEX Petroşani Ph.D:Eng, senior scientific researcher II at INSEMEX Petroşani

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The new european concept of explosion protection for the non–electricalequipment intended for use in explosive atmospheres-200-

For this reason, the establishment of a coherent strategy for the prevention ofexplosions requires that tehnical and organisational measures be taken at theworkplace, that shall be decided individually for each case.

Technical measures for explosion protection means all measures that: prevent the formation of hazardous explosive atmospheres, avoid the ignition of hazardous explosive atmospheres or mitigate the effects of explosions so as to ensure the health and safety of

workers.As general rule: preventing the formation of hazardous explosive atmospheres

must always be given priority.If is not possible to prevent the formation of a hazardous explosive

atmosphere, its ignition must be avoided. This can be achieved by protective measureswhich avoid or reduce the probability of ignition sources. To lay down effectiveprecautions, one must know the various types of ignition source and the ways in whichthey operate. The probability that a hazardous explosive atmosphere and a source ofignition will be present at the same time and place is estimated and the extent of themeasures required is determined accordingly. This is done on the basis of the zonesystem described below, from which the necessary precautions are derived.

In many cases, it is not possible to avoid explosive atmospheres and sources ofignition with a sufficient degree of certainty. Measures must then be taken to limit theeffects of an explosion to an acceptable extent. Such measures are

explosion-resistant design; explosion relief; explosion suppression; prevention of flame and explosion propagation.Requirements for work equipmentThe employer must ensure that work equipment and all installation materials

are suitable for use in hazardous places. In doing so, he must take account of thepossible ambient conditions at the workplace in question. The work equipment must beso assembled, installed and operated that it cannot cause an explosion.

In order to facilitate the selection of appropriate apparatus and the design ofsuitable installations, hazardous areas are divided into zones 0, 1 and 2 according to SREN 60079-10, and equipment is divided onto categories, according to EuropeanDirective 94/9/CE.

In most practical situations where flammable materials are used, it is difficultto ensure that an explosive gas atmosphere will never occur. It may also be difficult toensure that apparatus will never give rise to a source of ignition. Therefore, insituations where an explosive gas atmosphere has a high likelihood of occurring,reliance is placed on using apparatus which has a low likelihood of creating a source ofignition. Conversely, where the likelihood of an explosive gas atmosphere occurring isreduced, apparatus constructed to a less rigorous standard may be used.

Extent of protective measuresLevels of protection required for group IIG equipment

Zone Presence of explosive atmospheres(explosion hazard)

Avoidance of effectiveignition sources(ignition hazard)

Level ofprotectionrequired

Group IIcategory

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Jurca, A., M., Părăian, M., Ghicioi, E., Vătavu, N. -201-

2 Infrequently and for a short period only During normal operation Normal 31 Likely to occur Also during foreseeable

malfunctions (single fault)High 2

0 Continuously, for long periods orfrequently

Also during raremalfunctions (twoindependent faults)

Very high 1

Levels of protection for Group I equipment(mining)Group I comprises equipment intended for use in the underground parts of

mines, and to those parts of surface installations of such mines, likely to becomeendangered by firedamp and/or combustible dust.

Group I category M1 (very high protection level): Products of this categoryare required to remain functional for safety reasons when an explosive atmosphere ispresent and is characterised by integrated explosion protection measures (two means ofprotection or safe against two faults).

Group I category M2 (high protection level): These products are intended tobe de-energised in the event of an explosive atmosphere (safe in normal operation andfor severe operating conditions).

Essential requirementsThe essential requirements include all those requirements necessary in order to

attain the objective of a directive. Essential requirements are of mandatoryapplication. Only products complying with the relevant essential requirements can beplaced on the market. Essential requirements must be applied depending on the hazardsinherent to a given product. But the directives do not contain information on how theessential requirements could or should be met. Thus, manufacturers need to carry outhazard analysis to determine whether a product complies with the essentialrequirements. This analysis should be documented and included in the technicaldocumentation of the product.

2. HARMONISED STANDARDS

There are different ways of demonstrating conformity either directly toessential requirements or to harmonised standards. Harmonised standards providedetailed specifications in terms of objectives with regard to the practical fulfilment ofessential requirements. Harmonised standards are of voluntary application.

One standard does not necessarily cover all essential requirements of onedirective. It might be that only one, or selected, essential requirements are addressed bythe harmonised standards.

The application of harmonised standards may drastically simplify and speed upthe procedure for conformity assessment.

A number of harmonised standards is available in the field of explosionprotection. For electrical equipment, these standards are published by CENELEC. Fornon-electrical equipment explosion protected equipment and protective systems thesestandards are prepared by CEN/TC 305.

The main standards prepared for non-electric equipment intended for use inpotentially explosive atmospheres are: the main standard that establishes the basic

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The new european concept of explosion protection for the non–electricalequipment intended for use in explosive atmospheres-202-

method and requirements for design, manufacture, test and marking for non-electricequipment intended for use in potentially explosive atmospheres of gas, vapor, mistsand dusts (SR EN 13463-1) and then the specific standards comprising the types ofexplosion protection:

“fr” : Protection by flow restricting enclosure (SR EN 13463-2)“d” : Protection by flameproof enclosure (SR EN 13463-3)“g” : Protection by inherent safety (pr EN 13463-4)“c” : Protection by constructional safety (SR EN 16463-5)“b” : Protection by control of ignition source (SR EN 16463-6)“p” : Protection by pressurisation (pr EN 16463-7)“k” : Protection by liquid immersion (SR EN 16463-8)

Up to the present there were harmonized as SR, the general standard and thestandards with the types of protection: flow restricting enclosure “fr”, flameproofenclosure "d", constructional safety "c", control of ignition source „b” and liquidimmersion „k”.

3. ASSESSMENT OF IGNITION HAZARDS

All equipment and all parts of it shall be subjected to a formal documentedhazard analysis and lists all of the potential sources of ignition by the equipement andthe measures to be applied to prevent them becoming effective. Examples of suchsources include hot surfaces, naked flames, hot gases/liquides, mechanically generatedsparks, adiabatic compression, shock waves, exothermic chemical reaction, thermitereactions, self ignition of dust, electrical arcing and static electricity discharge.

Protective measures /types of protection shall be considered and/or applied inthe following order: ensure that ignition sources cannot arise; ensure that ignition sources cannot become effective ; prevent explosive atmosphere reaching the ignition source; contain the explosion and prevent flame propagation.

Protective measures/types of protection provided in the non-electric equipmentstandards are the following:

Protective measure Type of protection“c” : Protection by constructional safetyensure that ignition sources cannot arise“g” : Protection by inherent safety

ensure that ignition sources cannot becomeeffective

“b” : Protection by control of ignition source

“fr” : Protection by flow restricting enclosure“p” : Protection by pressurisation

prevent explosive atmosphere reaching theignition source

“k” : Protection by liquid immersioncontain the explosion and prevent flamepropagation

“d” : Protection by flameproof enclosure

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Jurca, A., M., Părăian, M., Ghicioi, E., Vătavu, N. -203-

4. ASSESSMENT FOR THE GROUP II EQUIPMENT

In the case of category 1 equipment, the list shall include all potential ignitionsources that are effective or may become effective during expected malfunction andrare malfunction. It shall also indicate the measures to prevent the ignition usedaccording to this standard and the igntion protection standards listed in the scope ofthis standard which have been applied. Category 1 equipment shall not have andignition source that is effective or may become effective in normal operation.

In the case of category 2 equipment, the list shall include all potential ignitionsources that are effective or may become effective during normal operation andexpected malfunction. It shall also indicate the measures to prevent the ignition usedaccording to this standard and to the ignition protection standards listed in the scope ofthis standard which have been applied.

In the case of category 3 equipment, the list shall include all potential ignitionsources that are effective or may become effective during normal operation. It shallalso indicate the measures to prevent the ignition used accordingto this standard and tothe ignition protection standards listed in the scope of this standard which have beenapplied.

5. CONFORMITY ASSESSMENT/ PROCEDURES

Before being placed on the market, products that are covered by the NewApproach directives must be submitted to a conformity assessment procedure. Theappropriate conformity assessment procedure in accordance with the levels of possiblehazards and with the necessary levels of protection and confidence required is definedin the Directive 94/9/CE.

6. MARKING

Marking example for non-electrical equipment

Marking according to Directive 94/9/EC: name and address of the manufacturer, designation of series or type, serial number, if any,

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The new european concept of explosion protection for the non–electricalequipment intended for use in explosive atmospheres-204-

year of construction CE marking ( first line; but not on components), identification number of the Notified Body involved in the production

surveillance, the (well-known) Epsilon-X in a hexagon, the symbol of the equipment-group and category, for equipment group II, the type of hazard, gas (G) or dust (D) additional marking required by standards or due to certification

BIBLIOGRAPHY

[1] Directive 1999/92/EC of the European Parliament and of the Council of 16December 1999 on minimum requirements for improving the safety and health protection ofworkers potentially at risk from explosive atmospheres. Official Journal No. L 023, 2000-01-28,57-64,

[2] Directive 94/9/EC of the European Parliament and the Council of 23 March1994 on the approximation of the laws of the Member States concerning equipment andprotective systems intended for use in potentially explosive atmospheres. Official Journal No. L100, 1994-04-19,

[3] Non-binding Guide of Good Practice for implementing of the EuropeanParliament and Council Directive 1999/92/EC on minimum requirements for improvingthe safety and health protection of workers potentially at risk from explosive atmospheres,European Commission, DG Employment and Social Affairs, Brussels, April 2003

[4] ATEX-Guidelines: Guidelines on the Application of Council Directive 94/9/ECof 23 March 1994 on the approximation of the laws of the Member States concerningequipment and protective systems intended for use in potentially explosive atmospheres.European Commission, Second edition, July 2005

[5] Heino Bothe ATEx 94/9/EC - Identification and treatment of non-electrical ignitionhazard in standards

[6] Beyer Michael European New Approach Directive Structure and ATEx Directive94/9/EC

[7] SR EN 13463-1 Non-electrical equipment for potentially explosive atmospheres.Part 1 : Basic method and requirements

[8] SR EN 13463-2 Non-electrical equipment for use in potentially explosiveatmospheres. Part 2: Protection by flow restricting enclosure “fr”

[9] SR EN 13463-3 Non-electrical equipment for use in potentially explosiveatmospheres. Part 3: Protection by flameproof enclosure “d”

[10] prEN 13463-4 Non-electrical equipment for use in potentially explosiveatmospheres. Part 4: Protection by inherent safety “g”

[11] SR EN 13463-5 Non-electrical equipment for use in potentially explosiveatmospheres. Part 5: Protection by constructional safety “c”

[12] SR EN 13463-6 Non-electrical equipment for use in potentially explosiveatmospheres. Part 6: Protection by control of ignition source “b”

[13] prEN 16463-7 Non-electrical equipment for use in potentially explosiveatmospheres. Part 7: Protection by pressurisation “p”

[14] SR EN 13463-8 Non-electrical equipment for use in potentially explosiveatmospheres. Part 8: Protection by liquid immersion “k”

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 205-210

THE OPTIMAL OPERATING RANGES OF THE STEAMGENERATORS WITH NATURAL CIRCULATION

WORKING ON POWDWRED COAL IN THE ROMANIANPOWER PLANTS

IOAN VASIU

Abstract: The work presents some conclusions of the author's research carried outwith the aim of increasing the energetic efficiency of the steam generators with naturalcirculation, running on coal in pulverized state in the Romanian thermal power plants.

The exergetic analysis of the thermodynamic processes, which take place in thesethermal installations, made possible the identification of an optimal operating range,characterised by an increased overall efficiency and lower fuel consumption.

An optimal range of the air-powdered coal mixture temperature, flue gas outlettemperature and consumed fuel flow was established, while maximum values of exergeticefficiency are registered.

Keywords:: powdered coal combustion, high exergetic efficiency, low consumed fuel.

1. INTRODUCTION

The fossil fuels are now in a dominant position in the structure of the primaryenergy resources used in order to produce heat and electric energy in the thermal powerplants. An important part of the energetic processes in the thermal cycle of the powerplants are achieved inside the equipments of the steam generators, when there occurs aconversion of the chemical energy of the fuels in thermal energy contained in the livesteam produced by the installation.

At present, the energetic steam generators working with coal pulverizationhave a low overall efficiency due to the important thermal losses which are registeredin the actual stage of development of this installations, [2].

Taking into account the actual Romanian energy conditions, the steamgenerators with pulverized coal burning will be utilized in thermal power plants in thefuture. Therefore, the increase of the overall performances of this type of installations

Lecturer, Ph.D. at the University of Oradea, Faculty of Energy Engineering

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The optimal operating ranges of the steam generators with natural circulation working on powdwred coal in the romanian power plants-206-

during operation became a requirement in order to diminish the fuel consumption, toreduce the electricity and heat cost, to protect de primary sources of energy of thecountry.

The qualitative analysis of the thermodynamic processes developed in theenergetic steam boilers with natural circulation running on pulverized coal, through anexergetic efficiency, made it possible to identify the optimal ranges of the someoperating parameters inside which the global efficiency reaches maximum values, [2].

The exergy represents the maximum useable fraction of an energy form, whichcould be obtained by a reversible transformation in another energy form, taking intoconsideration the state of the ambient.

2. EXPERIMENTAL RESEARCH

The experimental research has been achieved in the installation of a steamgenerator with natural circulation delivering 400 ton/hour (111.1 kg/s). The furnace isfully screened with membrane walls consisting of tubes of low diameters having 60x5mm.

The main technical characteristics of the experimental steam generator atnominal load are: steam flow 1.111nD skg / ; thermal capacity 340tnP tMW ;superheated steam temperature 823nT K ; steam pressure 7.13np MPa ; feedwater temperature 503aaT K ; combustion air temperature 513acT K ; flue gasestemperature after heater 413gevT K , [2].

The processes of preparing and burning coal powder achieved in the thermalpower plants are indicated in figure 1.The coal grinding equipment is composed of 6mills having 30 ton/hour, of which 4 – 5 mills were maintained in operating state inorder to assure the thermal load of the steam generator, required inside the power plant

Hot flue gases for coal predrying

Air preheater Fluegases

PowderedoutletRaw coal coal-air Flue supply mixture gasesM4 M1 M2 Secondary M3Primary air air

M5 Slag

Atmospheric Preheated combustion air discharge

air intake

Fig. 1. Powdered coal preparation and combustion systemused in the thermal power plants

Predryingand

grindingsystem

Powderedcoal

burningsystem

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Vasiu, I. -207-

at a certain point. The powdered coal fineness was in range of 604009.0 R % , inaccordance with the fan mills grinding elements wear cycle. Coal pre-drying isachieved using hot flue gases, extracted from the final part of the furnace at atemperature of 950ºC. The air for the process of combustion was preheated at 190 –220ºC in a regenerative equipment using the recovered heat of the outlet flue gases. Forthe burning of powdered coal a technology of preparation with coal dust concentratorand direct blowing sketch in furnace of the flow mixture of air – coal has been used,[2].

The values of the sizes for the fuel supply, the combustion air, the flue gases,the slag and ash discharge circuits used in the exergetic analysis have been measured inthe following points, indicated in figure 1: M1-flow and characteristics of theconsumed coal; M2- primary air-coal dust mixture parameters; M3-preheated aircombustion temperature; M4-flue gases outlet temperature; M5-incompletely burnt

content from slag andash.

The chemical andenergetic properties ofthe coal are variable ina wide range during theoperation of the steamgenerator. For thisreason it was necessaryto define a fuel havingmiddle properties. Theaverage properties ofthe equivalent burntfuel, which is a mixturebetween coal and oil,are indicated in table 1,[2].

The main fuelused for the steamgenerator running was

low-grade coal, characterised by high humidity and ash content, having a reducedheating power. The flame support of the powdered coal burner was assured by usingoil with low sulphur content.

3. MATHEMATICAL EQUATIONS OF THE EXERGETIC ANALYSIS

The exergetic efficiency of the steam generator e can be expressed in thefollowing form [1], [2] :

1001100

te

tu

e EEE

[%] (1)

Table 1-Average characteristics of the equivalent fuelChemical elementary

analysis al initial state

Symbol Unit Averagevalues

Carbon iemC ,

% 74.23

Hydrogen iemH ,

% 86.1

Sulphur(combustible)

iecmS ,

% 16.1

Nitrogen iemN ,

% 61.0

Oxygen iemO ,

% 22.9

Total humidity ietmW ,

% 24.34

Ash iemA ,

% 17.29

Low heating valueat initial state

8 140

High heating valueat combustion state

23 421

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The optimal operating ranges of the steam generators with natural circulation working on powdwred coal in the romanian power plants-208-

where : uE [kW] - useful exergy output flow produced by steam generator,tE [kW] - total exergy input flow of the analysed thermal system,

e [kW] - sum of the exergy flows lost from installation.Total exergy input flow results from the balanced equation :

euaafafcecht EEEEEE , [kW] (2)

in which : chE [kW] - chemical exergy input flow of the equivalent fuel,

fceE , faE , aaE [kW] - physical exergy of the equivalent fuel, combustionair and feed water input flows.

The components of the total exergetic input flow tE , are defined as follows,[2], [3]:

neech eBE , [kW] (3)

ppppp

ocpcc

c

ofce tcB

TT

tcBTT

E

11 , [kW] (4)

acioaefe

acio

fa iVBTT

E

1 , [kW] (5)

aaiaaiaaio

aa iDTT

E

1 , [kW] (6)

The useful exergy output flow uE is defined by equation :

aci

acio

aceaceoo

aefeaaiaaiababu iTT

iTT

VBeDeDE 11 , [kW](7)

The sizes mentioned in the relations (3) – (7) represent: ]/[,, skgBBB pce -equivalent fuel flow, coal, fuel oil flow; ]/[ kgkJene -specific exergy of the equivalentfuel; pppc cc , - medium value of specific heat at constant pressure of the coal, fuel

oil; f -air ratio in the furnace; ]/[ 3 kgmV Noae -theoretical air volume for the equivalent

fuel burning; ][, Ctt pc - coal, fuel oil temperature; ]/[, kgkJii aceaci -specificenthalpie of combustion air before and after preheater; ][, KTT aceaci - temperature ofcombustion air before and after preheater; ]/[, skgDD abaai -feed water input flow,delivered steam flow; ]/[],[ kgkJiKT aaiaai -feed water input temperature and specificenthalpie; ]/[, skgee abaai -feed water input and delivered steam specific exergy.

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Vasiu, I. -209-

4. RESULTS AND CONCLUSIONS

The behaviour of the steam generator working with coal in pulverised statewas analysed in 6 operating regimes characterised by delivered steam flow inside therange of 66.1 kg steam/s – 108.6 kg steam/s (238 ton steam/hour – 391 tonsteam/hour).

Based on experimentalmeasures, the calculations achievedaccording to the relations (1) – (7)indicated in chapter 3, havepermitted to establish the totalexergy input flow tE , the usefulexergy output flow uE and, finally,the values of the exergetic efficiency

e of the analysed steam generator.The graphic correlation

established by experimentalresearch, based on exergeticanalysis, between the operatingparameters measured in coalpreparation and flue gases circuits,

on the one hand, and the exergetic output, on the other hand, takes into evidenceoptimal ranges of the steam generator running on coal pulverisation, characterised by

maximum efficiency and lower fuelconsumption.

The admission of air-powdered coal mixture in theburning space at optimaltemperatures, which results from theproper increase of the preheatedcombustion air temperature, led tothe improved ignition and burningconditions of coal particles, due tothe higher level of the combustiontemperature achieved inside thefurnace. The high intensity of theabstracted heat in the combustionspace was obtained through a good

carbon oxidation. At the same time, the process of heat transfer to the screened wallsplaced in the radiation zone becomes stronger due to the uniform thermal load of thefurnace.

All these thermal processes have a remarkable contribution to the decrease ofthe main exergy losses which left the steam generator furnace, consist in the exergylost flows by ireversibility of the burning and heat transfer processes, as parts of thetotal exergy losses e .

Fig. 2. The dependence between theprimary mixture tenperature and the

exergetic effiency

172,3

156,4152,3

147,2

161157,2

202122232425262728

145 149 153 157 161 165 169 173 177 Primary mixture temperature at the

burners inlet tc [0C]

Exer

getic

eff

ienc

y [%

]

Fig.3. The influence of the flue gas outlettemperature about the exergetic effiency

of the steam generator

174

180

182,5

183,5

186

185

202122232425262728

172 174 176 178 180 182 184 186 188

Flue gases temperature t gev [ 0

C]

Exer

getic

eff

icie

ncy

[%]

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The optimal operating ranges of the steam generators with natural circulation working on powdwred coal in the romanian power plants-210-

The influence of the air-powdered coal temperature, measured at the outletfrom mills separators, about the exergetic efficiency is shown in the figure 2. A range

of the primary mixturetemperature at the burners inlet

Ctc 158154 can beobserved, while the exergeticoveral output reaching thehighest values, [2].

By increasing the heatflow delivered to thecombustion air in the preheater,the temperature of the fluegases was reduced after thisthermal equipment and, in thisway, an important diminishingof the exergy losses by the fluegasses exhausted from the

steam generator, was achieved.A zone of the flue gasses temperature's at the outlet of the steam generator,

Ctgev 182181 , was established in a graphical way, in which the maximum valueof the exergetic output can be registered, (figure 3), [2].

The increase of the efficiency of the steam generators, by operating in anoptimal range of the technological parameters, had an important effect on the reducingof the consumed fuel flow. The correlation between the equivalent fuel flowconsumption and the exergetic output of the steam generator is shown in figure 4. In arange of the burnt fuel, maximum values of the exergetic efficiency can be observed. Inthe case of the analysed steam generator, between 2827 eB kg coal/s, the highestvalues of the exergetic output 5.25e % are obtained, [2].

This experimental research has a practical importance for the specialists in thefield of thermoenergetics working in the power plants equipped with steam generatorswith natural circulation burning pulverised coal, in order to define the fuelconsumption required for running with high performances.

REFERENCES

[1]. Mădărăşan, T., Bazele termotehnicii, Editura Sincron, Cluj-Napoca, 1998.[2]. Vasiu, I., Performanţele generatoarelor de abur energetice pe cărbune pulverizat,

Editura Universităţii din Oradea, 2003.[3]. Bejan, A., Thermal design and optimization, Ed. Wiley, Interscience, New-

York, 1996.

Fig. 4. Maximum exergy efficiency of thesteam generator defined by an optimal fuel

consumption

21,47

23,65

26,47

28,34

28,77 32,05

10

14

18

22

26

30

20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35Equivalent consumed fuel flow B e [kg/s]

Exer

getic

effic

iency

[%]

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 211-214

THEORETICAL ASPECTS IN SOLVING FIELDENGINEERING PROBLEMS USING FINITE ELEMENT

METHOD

VISALON DAN, NICOLAE DAN

Abstract: In this paper we present a more unified view on FEM applied to fieldproblems. A short introduction to the equations governing heat transfer, magnetic, electric, andirrotational fluid flow problems is presented first. The finite element algorithm is shortly outlined.Although the similarities between different engineering fields are mentioned in the literature [1],[2], there is still a strong tendency to separate the formulation of FEM from area to another.

Keywords: finite element method (FEM), heat transfer, magnetic and electrostaticfields, algorithm, numerical examples.

1. INTRODUCTIONLet’s consider first the governing equations for some common two-dimensional

boundary-values problems.a) Heat transfer problem.

The heat transfer differential equation for the steady state two-dimensionalconduction problem and orthotropic materials is:

0)()(

q

yTk

yxTk

x yx (1.1)

where:

yx kk , = thermal conductivity in x and y directionsT = temperature, andq = heat source rate per unit volume

b) Magnetic field problem.

Assoc. Prof. PhD, University of Petrosani, Romania PhD, ABAQUS Inc., USA

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Theoretical aspects in solving field engineering problems usingfinite element method ---212-

The two-dimensional magnetic field problem in terms of magnetic vector potential:

zz

yz

x Jy

Ayx

Ax

)()( (1.2)

where:

yx , = magnetic reluctivity in x and y directions

zA = magnetic vector potential, and

zJ = current densityThe domain was assumed infinitely long in the axial direction and therefore the magneticvector potential has only one component (e.g. it becomes a scalar quantity).

c) Electrostatic field problem.

The Maxwell’s equation that governs electrostatics written in terms of electricscalar potential is:

)( V (1.3)with: = electric permittivityV = electric scalar potential, and = charge density

d) Incompressible inviscid flow.

The Navier-Stokes equations under irrotational and incompressible two-dimensional flow condition:

02

2

2

2

yx(1.4)

Where denotes the velocity potential. The flow velocities are given by:

xv

xu

; (1.5)

It is sometimes convenient to describe this type of flow in terms of stream functionequation

02

2

2

2

yx(1.6)

Where denotes the stream function. The flow velocities can be calculated in this caseas:

xv

yu

; (1.7)

The equations (1) to (7) are similar partial differential equation in terms of a fieldvariable. Other similar physical problems may include seepage flow, torsion of shafts,fluid film lubrication. This class of engineering problems is usually called field problems.

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Dan, V., Dan, N. -213-

As a result, having implemented the FEM equations for one of these problems all otherproblems could be solved by re-interpreting the field variable, the derived variables, andthe field constants.

2. ALGORITHM OF THE FINITE ELEMENT METHOD

The basic idea in the finite element method is to find the solution of a complexproblem by replacing it by simpler ones. The solution region is considered as build ofmany smaller interconnected subdivisions, called finite elements. In each subregion, orfinite element, an approximate solution is assumed. These elements are interconnectedat specified points called nodes. The actual variation of the field variables (such astemperature, potential function) inside elements is assumed to be defined by the valuesof the field variable at the nodes. The approximating function is called interpolationfunction or shape function.

There are two classes of variational methods, which are used to obtain thespecific finite element equations: pure variational methods and energy functionalmethods. The energy functional methods assume that there is an energy functionalassociated with field distribution, while the pure variational method is more general.Although both of these methods can be used for solving the field problems presented inchapter 1, we present here the Galerkin variational method (also called the method ofweighted residuals).

By multiplying any of the field equations by a set of weighting functions w , andintegrating over the study domain we have:

D yx qyTk

yxTk

xw 0))()(( (2.1)

where we considered the field problem as being the heat conduction equation. Integratingby parts, the following equation can be easily obtained:

dSnTwdDqwdD

ywk

yT

xwk

xT

SDyD x

)( (2.2)

where S represents the part of the domain’s surface where the derivative is known.Equation 2.2 is called the weak form of the finite element problem. The application ofthe above Galerkin variation approach to the finite element method can be described inthe following steps:

1. Divide the study domain D in N finite elements (quadrilateral elements forthe application considered here)

2. Assume the variation of the field variable (temperature in this particularcase), in each element as bi-linear:

4

1),(),(

a

eaa

e TyxNyxT (2.3)

where: eT represents the temperature variation inside each element, ),( yxN a

are the interpolation (or shape) functions, and eaT are the nodal temperature values. Note

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Theoretical aspects in solving field engineering problems usingfinite element method ---214-

that in the Galerkin approach the shape functions aN have the same form as theweighting functions w .

3. Assemble the elemental equations to obtain the overall system ofequations. Therefore the equation (2.2) in finite element form becomes:

})({1

e

S

ee

D

eeeee

ey

e

D

eex

eM

edS

nTwdDqwdD

ywk

yT

xwk

xT

eee

(2.4)

where M represents the total number of finite elements covering the domain D . 4. Solve the resulting general system of equations.

The elemental temperature variation inside one element (Eq. 2.3) can be written:xyyxyxT e

4321),( (2.5)where the coefficients in the above can be determined by enforcing the temperatures atthe four nodes of the element:

444434214

334333213

224232212

114131211

yxyxTyxyxTyxyxT

yxyxT

(2.6)

The evaluation of the coefficients in the above (Eq. 2.6) is usually greatlysimplified by using the natural (local) coordinates of the element, which will both varybetween (-1, +1). The relationship between the natural and actual Cartesian coordinates isobtained by well-known coordinate transformations, which can be found in any finiteelement literature.

3. FINAL NOTES

The similarities could be extended to the three dimensional analyses. For thiscase the magnetic vector potential reduces to three scalar equations, however thedivergence of the magnetic potential needs also to be determined to completely define themagnetic field (gauge condition)

REFERENCES

[1] Rao, S.S., 1982, “The Finite Element Method in Engineering”, Pergamon Press , NY.[2] Bathe, K.J, 1982, “Finite Element Procedures in Engineering Analysis, Prentince

Hall, NJ.[3] Dan, N, Ledezma, G.A., Craiu, O., “An improved Algorithm for Coupled Thermal

and Magnetic Problems in Electromagnetic Devices”, HTD-Vol. 348, Volume 10, ASME 1997.[4] Sivester, P.P., Ferrari, R.L, 1996, “Finite Elements for Electrical Engineers,

Cambridge University Press

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 215-217

THERMOENERGETIC BLOCK ON COAL POLLUTIONVECTOR: WATER HYDROCONVEYER FOR ASHES

ANDREEA BRÎNDUŞA, IOSIF KOVACS, ADRIANA BOCIAT

Abstract: In the energetic industry the evacuation of the ashes specific to the burningprocess in the thermo energetic blocks is made hydraulic based on the pollution vectors water hydroconveyer in the ashes and slag warehouses. The main problem concerning the returning of water inthe hydro conveyer circuit consists in making a suitable decantation so that the load withsuspensions is diminished.

Keywords: water hydro conveyer, coal, thermo energetic block, pollution vector

1. INTRODUCTION

The energetic blocks, with installed powers of great values from our country,have as basis turbo- generators of an apparent power of 388 MVA, an active power of330MW, the THA330-2 type and the steam turbine of the FIC 330 MW type.

The steam turbine of the FIC 330 MW type has the following technicalcharacteristics:

- the maximum cont. power:330MW - the power of overcharge: 345MW- the revolution: 3000rpm - the pressure in. IP: 186atm- the temperature in. IP:535C - the debit in. IP: 1035t/h- the pressure ot.IP: 49,8atm - the temperature ot. IP:344C- the debit ot. IP: 1023t/hThis are to be found at the level of the Energetic Complexes Oltenia (CE

Turceni, CE Rovinari, Ce Craiova).The evacuation of the ashes specific to the burning process in the thermoenergetic

blocks is made hydraulic based on the pollution vectors water

PhD Student. Ec. University of Petrosani PhD Professor.eng. University of Petrosani

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Thermoenergetic block on coal pollution vector: water hydroconveyer for ashes-216-

hydroconveyer in the ashes and slag warehouses.The main problem concerning the returning of water in the hydroconveyer circuit

consists in making a suitable decantation so that the load with suspensions is diminshed.As a rule industrial water that supply the thermoenergetic blocks are surface

water which temperature varies depending on the season and geographical areas in the0- 300C interval.

In the case of the thermoenergetic blocks from the Craiova Energetic ComplexTurceni and Rovinari we have a common characteristic that they bot huse the samesource of industial water, river Jiu. The collected and evacuated water in and from riverJiu is made throu the collecting and evacuating points and the Evacuation andCollection Channels. The volumerical debit industrial water, collected from Jiu, isprovided through some big capacity pumps and through modifying the level of theupstrem dam point.

2. WATER HYDROCONVEYER FOR ASHES TO THE ENERGETICBLOCKS

The energetic blocks with great values impose in their function big volumes ofcollected and evacuated industrial water. Some of that collected water is used toevacuate the ashes obtained through burning solid fuel, in this case with lignit a type ofcoal.

Hydro conveyer water is recalculated in proportion of 70-80%.The main problem concerning the returning of water in the hydroconveyer circuit,

consists in making a suitable decantation so that the load with suspensions is diminshed.A flooaded moist waste dump can contain up to 30% moisture between the

ashes particle.This paper presented the washing tests in cascade on ashes type Craiova

Energetic Complex– SE Isalnita. In table 1 is presented the granulometrical analysis onashes of the Craiova Energetic Complex– SE Isalnita, and in table 2 is presented theashes chemical composition base don oxide

Table 1Nr. crt. Grain Diameter [mm] Sample [%]1 > 0,5 02 > 0,25 103 > 0,09 504 > 0,045 94

Table 2Nr. crt. Components Composition [%]1 Fe2O3 10,582 Al2O3 20,383 CaO 8,834 MgO 7,455 SiO2 47,11

The washing agent was demineralizated water, and the used proportion was 1part ashes at 10 parts water.

The mixture water-ashes have been agitated for 24h, and the washing water has

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Brînduşa, A., Kovacs, I., Bociat, A. -217-

been analyzed and stained. It has been done PH and conductibility measurements andhave been determined the SO4

2 , Na+, Ca2+ ions concentration.The determination results are presented in table 3.

Table 3The analysed

parameterUM Sample

I II IIIpH 10,42 7,82 8,53

Conductivitate µS/cm 1984 1161 918Ca2+ mg/l 400 252 192Na+ mg/l 22 27 23,2SO4

2 mg/l 764,5 592 438

3. CONCLUSIONS

The evaluation of the environment performance of the industrial branch-Energetic industry- is absolutely necessary in an open and interconnected societyspecific to the XXI century, where the globalization phenomenon is present all over.

The biggest consumption of industrial water from the surface area leads to:- the necessity of introducing solutions and technical methods which can stop

the growth slope of the consumption of industrial water- the necessity of permanent monitorisation of the physical-chemical

parameters, water collected and evacuated from the industrial giants, EnergeticComplex.

Base don the type of the tests presented we can make the conclusions:-we have a important mobilization of ions SO4

2 , cca. 31%;- we have a mobilization of ions Ca2+, cca. 7%.- the Ph value covers the 7,5-10 interval;-the conductibility evolution presented a growth of washing saline water

REFERENCES

[1]. Brînduşa, A.,Kovacs, I., Physical-chemical parameters water collected andevacuated at the energetic blocks, Simpozion internaţional multidisciplinar “UNIVERSITARIASIMPRO 2006”, Universitatea din Petroşani, Petroşani, 13-14 octombrie 2006.

[2]. Brînduşa, A.,Bulucea, A., Considerations upon industrial wastewater purifyngequipments, Simpozion naţional “ Ingineria mecanică şi mediul ”, Universitatea din Craiova,Craiova, 6-7 octombrie 2006.

[3]. Brînduşa, A., The factors of degradation of the environment and df the touristpotential specific to the autochthon relief, Simpozion internaţional multidisciplinar“UNIVERSITARIA SIMPRO 2006”, Universitatea din Petroşani, Petroşani, 13-14 octombrie2006.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 218-221

THERMOENERGETIC BLOCK ON COAL POLLUTIONVECTOR: BURNING GAS

ANDREEA BRÎNDUŞA, IOSIF KOVACS

Abstract: Burning gas is one of the pollution vectors specific to the thermoenergeticblocks and they are the result of the procces of burning the coal. The main problem concerning thereturn of burned gas in the environment is making a suitable filtration so that the load withsuspensions is diminshead and disseminated on big areas.

Keywords: burned gas, coal, thermoenergetic block, pollution vector

1. INTRODUCTION

At the level of the Energetic Complex from Oltenia (CE Turceni, CE Rovinari,CE Craiova) we have thermo energetic blocks with installed power of great valueswhich have as base turbo generators of 388 MVA apparent power, 330 MW activepower, of THA 330-2 type and the steam turbine of FIC 330 MW type.

The steam production is made in steam boilers in which takes place theburning of the solid fuel of lignite type. It has developed varied technologies whichcombines the diversity of the firebox with the way of putting the radiant pipes ofspecial steel, through which circulates the production water, the heated steam and is away of evacuating the slag made from burning the coal.

In the firebox takes place the process of reaction between the burning air andthe combustible with the forming of burning gas at high temperature. The evacuationof burning gas in the atmosphere is made through the evacuation pipes (gas channels,gas fan, evacuation chimney).

The pollution source for air is the emission of the effluent from burning gasresulted from burning combustible in fireboxes of burning boiler as: NOx, SO2, CO2,CO, dust, (table1).

PhD. Ec. University of Petrosani Professor PhD .eng. University of Petrosani

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Brînduşa, A., Kovacs, I., -219-

Table1Nr. crt. Poluant Valoare1 NOx [mg/Nm3] 200-5002 SO2 [mg/Nm3] 2000-45003 Pulberi [mg/Nm3] 40-504 CO2 [%] 8-105 CO [mg/Nm3] 40-120

The main problem concerning the returning of burned gas in the environmentconsists in making a suitable filtration so that the load with suspensions is diminishedon big areas of land.

2. BURNED GAS, ENERGETIC GROUPS. EFFLUENTS EMITTED

If some fireboxes make together an exploitation unit, the thermic power of theexploitation assemble (total thermical power) is determined for the limitation of theemissions of every firebox. The application of this foresight ( Ord. 462/1993 mod.)makes obligatory the reduction of the emissions at all boilers, indifferent of thethermical power, if the power station, has a thermical power bigger than 150 MW.There are no derogations from the norms bound to the age of the boilers, and the periodof life.

A calculation of emissions is presented in table 2 and it refers to this case: TheEnergetic Complex Craiova-SA Craiova II, the chimney of evacuated burned gas nr.1.

Table 2boiler/ cos 2Inalt. cos[m] 160Diam. virf [m] 9

month Ian Feb Mar Apr Mai Iun IulDebit g.a.[miiNm3/luna]

10,1*108 14,2*108 15,5*108 9*108 5,9*108 6*108 9,6*108

Debit g.a.[miim3/luna]

16,1*108 22,5*108 24,3*108 18,5*108 9,3*108 9*108 16*108

Cons.coal[t/luna]

217811 299427 318940 185387 116700 105 2*105

Cons. pacura[t/luna]

3160 4074 5095 2908 1915 1366 2303

Emission SO2[t/luna]

3685 5055 5415 3145 1983 2175 3455

Emission NOx[t/ month]

411 566 619 354 207 247 397

Emissiondust[t/month]

71 97 104 60 38 42 66

Conc. SO2 [mg/Nm3]-6%O2

4445 4473 4478 4479 4521 4538 4486

Conc. NOx[mg 495 501 512 503 472 516 515

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Thermoenergetic block on coal pollution vector: burning gas-220-

/Nm3]-6%O2Conc. Pub [mg/Nm3]-6%O2

85 86 86 86 87 87 86

Month Aug Sep Oct Nov Dec TotalDebit g.a. [miiNm3/ month]

6,9*108 6,6*108 12,2*108 12,9*108 12,6*108 121*108

Debit g.a. [miim3/ month]

11,2*108 10,7*108 19,5*108 20,7*108 19,8*108 194*108

Cons. coal[t/month]

153357 142892 254589 275676 261150 2,6*106

Cons. pacura[t/ month]

1480 1888 3083 3047 3931 34250

Emisie SO2[t/luna]

2564 2410 4282 4625 4424 43217

Emisie NOx [t/month]

294 274 481 602 490 4941

Emisie dust[t/month]

49 46 82 88 85 826

Conc. SO2 [mg/Nm3]-6%O2

4473 4463 4497 4492 4481 53826

Conc. NOx[mg/Nm3]-6%O2

512 508 506 585 496 6122

Conc. Pulb[mg/Nm3]-6%O2

85 85 86 86 86 1031

3. CONCLUSIONS

The evaluation of the environment performance of the industrial branch-Energetic industry- is absolutely necessary in an open and interconnected societyspecific to the XXI century, where the globalization phenomenon is present all over.

The biggest consumption of industrial water from the surface area lead to:- the necessity of introducing solutions and technical methods which can

stop the growth slope of effluents in the atmosphere;- the necessity of permanent monitorisation of the physical-chemical

parameters, pollution vectors : burned gas from the industrial giants, EnergeticComplex.

Thouse Energetic Complex have in common four big characteristics:- big power installed: of order *1000MW;- they are situated in the same hydrographic basin, the river Jiu basin, which is

situated in the neighborhood of the river;- there are Energetic Complex which use as prime substance inferior coal of

lignite type from the Oltenia miner basin;- it polluted a commune region definite so ,such from the commune

geographical elements and the specific elements of activity ( technological processes ofproduction and socio-economical services) very close.

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Brînduşa, A., Kovacs, I., -221-

REFERENCES

[1]. Brînduşa, A.,Kovacs, I., Physical-chemical parameters water collected andevacuated at the energetic blocks, Simpozion internaţional multidisciplinar “UNIVERSITARIASIMPRO 2006”, Universitatea din Petroşani, Petroşani, 13-14 octombrie 2006.

[2]. Brînduşa, A.,Bulucea, A., Considerations upon industrial wastewater purifyngequipments, Simpozion naţional “ Ingineria mecanică şi mediul ”, Universitatea din Craiova,Craiova, 6-7 octombrie 2006.

[3]. Brînduşa, A., The factors of degradation of the environment and df the touristpotential specific to the autochthon relief, Simpozion internaţional multidisciplinar“UNIVERSITARIA SIMPRO 2006”, Universitatea din Petroşani, Petroşani, 13-14 octombrie2006.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 222-225

URBAN FRAME WITH STATIC CONVERTER ANDASYNCHRONOUS MOTORS. DIRECT FIELD

OREINTATION

CONSTANTIN BRÎNDUŞA, MIHAI PĂSCULESCU, MARIUSPOPESCU

Abstract: Direct Field Oreintation DFO is perfectly possible to be implemented in thecase of electric urban frames. This can be made with the help of the electrical control framecomputer system. The structural diagram in the case of Direct Field Oreintation DFO is basedon mathematical models of asynchronous motors and static converter.

Keywords: vector control, urban frame, asynchronous motor, static converter.

1. INTRODUCTION

In defining a computerized control system for the urban train having in thecomputers electrical frames with modern action (CTF+MA), we start from an electricalscheme of traction of the vehicle. Thus considering the fact that we are dealing with anelectrical frame with the VM+VM composition the computerized control system isdistributed and will operate in real time, similar to the one used in the case of theautomated production lines.

The important characteristic of such a computerized control system is theintegrated network of data buses which, in order to reduce to minimum the cablesvolume, it is necessary to be made with optical fibres. This assures the synchronizedfunctioning of the electrical frames which compose the urban train, includes adiagnosis system and a services system of information and advertisem*nt forpassengers.

PhD Student. University of Petrosani Professor PhD .eng. University of Petrosani Associat Professor PhD .eng. University of Craiova

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Brînduşa, C., Păsculescu, M., Popescu, M. -223-

Fig 1 Structure urban train (VMA1+ VMB1+ VMA2+ VMB2+ VMA3+ VMB3)

Fig 2 The system structure computerizated urban electrtical train control

The control system is earmarked on 4 levels:- the urban electrical frames train operation system;- the urban electrical frames train control level;- engine wagons, electrical frame control level;- equipments control level.

2. URBAN FRAME; DIRECT FIELD OREINTATION

The regulation of the asynchronous engine’s speed can be done at the sameperformances with the regulation from the continuum power engine, through theseparate control of the flux. However in this case, the one of the asynchronous engine,we are facing a series of problems connected to the identification of the position of therotor flux’s phasor ψr

’ in the referential (α,β), the making of all the operationsespecially in the coordinates transformations, obtaining the values of the currents

1CA

M

R1MTVA1

R1SLVB1

R2SLVA2

R2SLVB2

R3SLVA3

R3SLVB3

1CB

2CA

2CB

3CA

3CB

Tren

urbanNivel

Operare

tren

NivelControl

tren

ControlREU-VM

ControlEchipa-mente

Magistrala opticatren

Contaut tren(ATC)

Cab cd.V. set

Mt 1-VA

Cont aut.tract/frin

Conttren

Control REU-VMA

E.c. VAtrac

E.c. VAfrin

E.c.VAserv

IntE / O

Cab cd.V. set

Sl 1-VB

Control REU-VMb

E.c. VBtrac

E.c. VBfrin

E.c.VBserv

ItE / O

RAMA 1 Vagon MasterVMA

RAMA 1 Vagon SlaveVMB

(PDF) ANNALS OF THE UNIVERSITY OF PETROŞANI 2007.pdf· Annals of the University of Petroşani, Electrical Engineering, 9 (2007)-3-CONTENTS Dašić Predrag, Nedeff Valentin, Curčić Srećko, - DOKUMEN.TIPS (224)

Urban frame with static converter and asynchronous motors. Direct fieldorientation-224-

resulted from the control scheme through the adequate command of the voltageinverter which fuels the asynchronous traction engine and which has a restrictivecommutation frequency.

In the case of the work speeds, of relatively medium values, the rotor flux canbe determined, through calculation, on the basis of the voltages and the tractionasynchronous engine measured in real time. We are dealing with the control methodcalled direct (Direct Field Orientation- DFO), the developed method, in the beginning,by Blaschke and which is encountered in a series of applications, in the electricalactions with static converters and asynchronous traction engines.

The structural scheme is presented in fig.3.As in the case of every PI regulator we find input parameters the prescribed

value and the reaction one. Thus we have:- for Reg ψr

’: entering size ψr’*, ψr

’; exit size isx*;

- for Reg isx: entering size isx*, isx ; exit size usx;

- for Reg isy: entering size isy*, isy; exit size usy.

Fig 3 Structural scheme direct vectorial control (DFO)

The curent isy* is obtained from the prescribed values M couple and rotor flux

ψr’* base on the relation:

'*

**

23

r

sy

p

Mi

(1)

In their turn the two components usα and usβ, of the stator voltage us’s phasor inthe referential (α,jβ) that the asynchronous traction engine must be fuelled with, areobtained on the basis of voltages usx and usy after the coordinates transformationthrough the ejε factor. The asynchronous engine is fuelled by a modulation in duration

p23

IT

Reg

MID

Ψr’*

M*

isR,isT

ejε

ejε

e-jε

FLUX

AF

MLMAT

Reg

Reg

Ψr’ isx

isy*

isx*

usx

isy

usy

usα

usβ

isβ

isα

Ψrα’

Ψrβ’

εΨr

usR,usT

ud

id

isx

isy

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Brînduşa, C., Păsculescu, M., Popescu, M. -225-

voltage inverter MID (PWM), the modulation being achieved on the basis of the twocomponents usα and usβ.

The structure of the FLUX block allows the calculation of the components ofthe stator current isα and isβ and those of the rotor flux ψrα

’ and ψrβ’, in the referential

(α,jβ).The AF block’s structure allows the calculation of the ψr

’phasor’s module, onthe basis of the e-jε factor, which allows the coordinates transformation from the (α,jβ)referential into the (x,jy) referential.

3. CONCLUSIONS

We can draw the following conclusions:- In the earmarking of the urban electrical frames train control system on 4

levels we take into account the electrical traction scheme of the vehicle, evenlydistributed on the entire urban train, including the traction function, braking;

- Direct vectorial control (DFO), at electrical frames with modern acting (CTF+ MA), it allows the regulation of the asynchronous engine’s speed at the sameperformances as in the case of the continuum current engine, through the separatecontrol of the flux.

- It has been established the structural scheme direct vectorial control (DFO).

REFERENCES

[1]. Brînduşa,C.,ş.a., Sisteme electrice de transport neconvenţionale (A23); Rama demetrou acţionată cu motoare asincrone; Execuţie şi experimentare modele (Faza 23.1),Contract cercetare 606C- Anexa A, Institutul naţional de cercetare şi proiectare pentru maşinielectrice, echipament electric şi tracţiune, Craiova, 1992.

[2]. Brînduşa,C.,Păsculescu,M., Popescu,L., Drive systems behavior analysis inurban electric traction with Matlab software extensions, Simpozion InternaţionalMultidisciplinar „UNIVERSITARIA SIMPRO” ,2006, Petroşani, Editura UniversitasPetrosani, 2006.

[3]. Nicola,D.A.,Cismaru,D.C., Mathematical models for control simulation oftraction induction motors, ICATE’98, Craiova, 1998.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 226-231

USING GRAPHICAL PROGRAMMING VEE Pro 6SOFTWARE FOR FUNCTION SIMMULATION OF THEGRINDING AGGREGATES TO MAINTAIN OPTIMUUM

SPECIFIC ENERGY CONSUMPTION

VISALON DAN , CAROL ZOLLER

Abstract: Between the absorbed power and the ore fill of the aggregate there is proovedan extremal connection, [1]. So, we propose to use the information from the filling transducer tocommand the input flow, obtaining a PC working system within which productivity is at its best.A specific graphical software, for simulation of the optimuum command of the ore gridingaggregates, interfaced with the PC by a data acquisition board for input-output proces controlwas developed. With some adjustments, the software can be implemented for real time driving tooptimum of the ore griding aggregates.

Key words: griding aggregates, productivity, VEE Pro 6 software.

1. INTRODUCTION

The specific consumption of energy in copper ore grinding and separationprocess, using high capacity autogenous aggregates, in primary phase and ball mills inthe second stage, (figure 1), is about 35 kWh/t. That specific consumption can bedecreases with 5 to 10% by introducing a control system. As the aggregates drive isaccomplished with 4 MW synchronous motors, to decrease the specific consumption is adesiderate of high actuality.

Associate professor, PhD University of Petrosani, Professor, PhD University of Petrosani

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Dan, V., C. Zoller -227-

It’s impossible to decrease the consumption maintaining constant ore feed flowrate and water - ore ratio, because of the continuous variation of the physical andmechanical properties (which can be expressed by grinding ability).It is usual to command the feed flow rate depending on the absorbed power (figure 2)together with electrical energy measured, but aggregates can be overloaded orunderloaded because of the non-linear character of the dependence between power andfilling.

2. FEED FLOW CONTROL

Knowing that this dependence has an extremal character, we propose a feedflow rate control system that uses, besides the information concerning the powerabsorbed by the driving motor, the information about the load (filling) with ore. Theload information is given by a transducer of oil pressure in the bearing or a weighttransducer.

This solution is based on the following considerations:

The grinding aggregates productivity is mainly determined bythe quantity of material in the aggregate (by its filling degree).Between the productivity and the material reserve (fillingdegree) there is an extremal dependence (figure 3), which isexpressed by:

2max x*)k(xyy

where:ymax – maximum productivity;x* - ore reserve for which the productivity is maximum;k – constant, aggregate characteristic.

8500x3800

5200x8000

Ø2000

A

Fig.1. Block diagrame of the gridding process

ΔWAE

WC3u6

WX3u11

WT3u2

WE3u1

WI3u4

WR3u5

JQ3u10

WQ3u3

JC3u7

JX3u12

JT3u10

C – DACI CLICA

JT3u9

Fig. 2. Feed flow the absorbed power

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Using graphical programming vee pro 6 software for function simulation of the grinding aggregates to maintain optimuum

specific energy consumption-228-

It is unanimously recognized that, between the driving power and the productivity,there is the following dependence: the maximum productivity is obtained at themaximum consumed power.

It is justified to use process control methods based on power control as long as it isdifficult to appreciate the grinding capacity and power information is moreaccessible.

If y1 is the driving power and m the grinding ability (a high m meaning easygrinding), we assume that:

- y1 increases monotonously with y2 and m (figure 4.a);- y1 decreases monotonously with the increment of the ore density ;- y2 (the pressure in the bearing) is linearly dependent on the reserve (x) and

density () (figure 4.b).The system we have conceived aims to maintain the aggregate load at the value x*,

corresponding to the nominal power. As practically x* is not known because of thestochastic variation of the ore characteristics, in order to determine x* (for dy1/dx=0),the procedure is the following:

- for a certain x=x1, y1(x1) is read and memorized;- x1+x is read and x1+2x is commanded;- if y1(x1+x)> y1(x1), x1+2x is commanded;- if y1(x1+x)< y1(x1), x1-x is commanded;- y1(x1-x) is read and memorized, and so on.So, if x belongs to the domain for which y1< y1max, we command the increment of

the load x by increasing the feed rate u. As the point y1max moves continuously, it isnecessary that the system follows permanently the algorithm above. In order to be surethat the variation of the power (y1) is caused by the load (x), the system needs to useanother information (y2), which is the pressure in the bearing, depending linearly on x(figure 4.b).It is necessary to use two transducers: one of active power and another oneof weight on the bearing, in order to provide information from the technological process.Using just some information (absorbed active power, filling degree and re-circuitedflow), we achieved the control by discrete steps of the feed flow rate in a view to obtainmaximum processing capacity.

y1

u

x

y1

y2

y

M

y1maxy1(x1+x)

y1(x1)

x1 x1+x x*

a) b)Figure 3

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Dan, V., C. Zoller -229-

3. CONTROL ALGORITHM

The control algorithm, developed initially for a microprocessor control, is goingthrough the following stages:

a) It checks whether the starting conditions are fulfilled; if they are, the conveyerfor feeding the aggregate with ore is started; if not, the restrictions are signaledoptically and acoustically;

b) It operates, on different stages, SUBi:transfers the active power value to M1 and the pressure in the bearings value to M3;resets the active power integrator;transfers the content of the M1 memory to M2, with a delay of seconds; transfers

the content of the M3 memory to M4; transfers the value of the active power toM1; transfers the value of the pressure in the bearings to M3.

c) It evaluates the variation of the power value that is measured at the beginning andat the end of the period . If P>0, it commands a new step of ore feed increment and ifP<0, it commands the decrement of the feed flow by a step.

c1) If P>0, after incrementing the feed flow by +Qal, SUB.1 is run again and ifPand P1 is logicall determined. If P and P1>0, Qret (return flow) is checked. IfPandP1<0, the decrement -Qal is commanded and the program returns to ET.2.Depending on the correlation of the return flow Qret, it will take the decision: if Qret< Qret

max, it is commanded again +Qal; otherwise, it jumps to ET.4 checks whether theabsorbed power is between its limits: Pmin P Pmax. If this condition is accomplished,the algorithm goes on with the pressure (P1) check in the bearing. If P1min P1max, theprogram jumps to ET.2 and the process is restarted following the algorithm. If one of theconditions is not fulfilled, this situation is signalized optically and acoustically and, aftera period of (4 – 5)T when the technological process gets stabilized, the control isrestarted beginning with ET.1.

c2) If P<0, it results the necessity of decrementing the feed flow and, starting withET.5, it is checked whether the conditions P>0 and P1<0 are fulfilled simultaneously

y1

x

y2

x

1>2>3

32

1

m1>m2

3.m1

2.m1

1.m11

.m2

a) b)

Figure 4

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Using graphical programming vee pro 6 software for function simulation of the grinding aggregates to maintain optimuum

specific energy consumption-230-

with the condition Qret<Qret min. After checking whether P and P1 are included within theadmissible interval, the algorithm continues cyclically until the process stabilizes itselfwithout needing to reduce Qal.

This procedure lasts until the maximum of the function P=f(Qal) is reached. Fromthis moment on, the aggregate works on the stable characteristic as long as P<0 andP1<0. Afterwards, +Qal is commanded and, after running SUB.2, the program ET.5 isrestarted.

If the curve maximum is moving to the right, that is P<0 and P1>0, -Qal iscommanded if Qret> Qret max. The cycle continues with SUB.2 and it restarts with ET.5. Ifthese conditions are not true, it restarts with ET.1.

The above described algorythm was developed using a graphical programmingsoftware, HP VEE Pro6, for simmulation of the described proces, in the first stage,(figure 5) and for future optimuum control of the ore gridding aggregates, using PC anddata acquisition interfaces, in the second stages.

In figure 6 is presented the pannel interface of the simmulator, that presentingthe graphical instruments to be set up by operator as: measured parameters, ( pressure, absorbed active power, etc.,) prescriptions for limiting parameters evolutions, between minimuum and

maximuum; delay between data acquisitions times, etc.

Time evolution of the controlled parameters and regulated parameters arepresented also in to graphical pannel as data recorder charts and bargraphs.

Fig. 5 Graphical programming software

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Dan, V., C. Zoller -231-

Fig 7 Tthe pannel interface of the simmulator4. CONCLUSIONS

For huge girding aggregates the working regime at nominal power and maximumgrinding capacity means, energetically speaking, to reduce the specific electric energyconsumption.

Between the absorbed active power and the ore fill of the aggregate there is anextremely connection, we propose to use the information from the filling transducer tocommand the input flow, obtaining a PC working system within which productivity is atit* best.A specific program for simulation of the optimum command of the ore girdingaggregates, using HP VEE Pro 6 software was developed in the paper.

REFERENCES

[1] Dan Visalon, Carol Zoller - Metodă pentru reglarea automată optimală a puteriiagregatelor de măcinare autogenă a minereurilor complexe. Brevet de invenţie nr RO 121061,2006, OSIM Bucureşti ;

[2] *** Agilent Technologies: VEE Pro user‘s guide. Agilent Technologies, Inc, E2110-90062. USA, 2000.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 232-236

VOLTAGE ELECTRONIC REGULATOR FOR AIRCRAFT

JENICA ILEANA CORCĂU

Abstract: In this paper is presenting a study about one electronic regulator of voltageafferent of one starter/generator who equipped the IAR-99 aircraft; it is regulating the voltagesupplied by the generator D.C. of 9kW who discharges in bus of IAR 99 aircraft 28,5 Vdcvoltage, simultaneous with the loads equaling in case of connecting of two groups of generatesin parallel. Also, the voltage regulator protected the generator at overvoltage. The principle ofworking if this regulator consists in modulating in time of one impulse group with frequencyf=400Hz 50Hz applied winding to exciting of generator. It is presenting the block scheme ofthis regulator and electronic scheme, the waveform of generators voltage, making the amplitudeand frequency of ripple.

Keywords: electronic regulator of voltage, starter/generator, ripple, modulating in time ofimpulse.

1. INTRODUCTION

The voltage regulator for starter/generator is designated for: 1) the governingvoltage supplied by generator D.C. who has ensuring at the way out a voltage equalwith 28,5Vdc value at 300A, simultaneous with the equaling of loads, in case ofconnecting in parallel of two groups of generators; 2) the protection of 9kW generatorat overvoltage simultaneous with the discrimination of defect sewer with a view toconnect in parallel two groups of generators, the blocked of this would been ensuredthrough the agency of excitation relay.

The principal of working of regulator is based on modulating in time ofcontinuos group of impulses with the 400 50 Hz frequency applicated coilinggenerator excitation. Mean value of power through excitation coiling so, will dependson value of filling factor of waveform, from behind this would be approximate 50%for voltage value of way-out +28,5 Vdc generator.

Lecteuer Ph D., University of Craiova, Faculty of Electrotechnics, Division Avionics,Romania, [emailprotected]

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Corcău, J., I. -233-

The filling factor modification, respectively the modification of equated valueof the power through excitation coiling has compensated through the feedback isprovided for this purpose the voltage variations at the way out of generator.

Thus, the growth tendency of voltage value of way out is quiding at asubtraction on value of filling factor of waveform, respectively of mean value of powerthrough excitation coiling, and each-other, the growth tendency of voltage value ofway out is quinding at one growth of value of filling factor of waveform, respectivelyof mean value of power through excitation coiling.

Eliminated the parts of protection of voltage regulator block scheme of oneelectronic voltage regulator destinated to work completely with the board generatorD.C. with powers until 9KW is presenting in figure1.

In figure 2 are presenting the diagrams of variation of factor for 3 cases;Ug=Uref ; Ug>Uref ; Ug<Uref . The principle scheme of electronic regulator voltage whoworked completely with board generators D.C. of power until at 9KW is presenting infigure 3 [4].

Fig.1. Block scheme of voltage electronic regulator

The voltage of the terminal generator tacked from agency of voltage factor istotaling with a slow variable supplied by the tooth-saw voltage generator. Voltageresulting is comparing from comparator-amplifier with reference voltage.

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Voltage electronic regulator for aircraft-234-

Fig.2. Command impulse modulation diagram

When the voltage from the summator is signal-bigger then reference voltage,comparator is opening, and when this is signal-smaller comparator has blocked. Atway-out of comparator will have rectangular impulses between 0 and 1, after have thegenerator tendency is bigger or smaller than the reference voltage.

The voltage regulator for starter generator noticed the way-out voltagegenerator has applied a part of this voltage for first time non-invertor on 3 terminal, ofCI1 (LM101AH) operational amplifier of other way-out inversor (2 terminal) has beenapplied a reference voltage tacked from a Zener diode.

Over the reaction voltage applied of CI1 operational amplifier is near a signalwith waveform tooth saw with 40050Hz frequency, so that the CI1 operationalamplifier is working like a switching comparator, his way-out has been a rectangularsignal with the same frequency, but is variable filling factor.

Filling factor [3]

,Tt i (1)

where Tt i , it - impulse duration e, T - period.This filling factor is a different function between feedback voltage applied

non-inverter for entry of operational amplifier and reference stabilized voltage appliedfor entry non-inverter of the same operational amplifier (the 2 terminal).

The way-out of operational amplifier is amplifying with stage of amplifierpower realized by T7 transistor; the signal obtained like had been used then fortransistors command that is working in switching regime T1 and T2 that feeded theexcitation coil of generator assured in this way the regulating of voltage at way-out ofgenerator.

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Corcău, J., I. -235-

2. THE IMPULSE MODULATING IN TIME

The impulses modulations in time consist in transferring characteristic of )(txbase signal over the caring un presented by a series of rectangular impulses [3].

).()( tt p (2)

).()( tkxt (3)

,cos))](1(sin[2

2)(1

)(1

tnntxkntxk

txn

DDMID

(4)

where p - duration carrier ,T2

, T - period .

It is remarking that this signal contains the base signal and a double infinity ofcomponentd with armoning carring modulated in stage. After the filtration type lowpass filter obtain base signal. The blocks through block scheme that has realized themodulation in time are: block reference voltage, block divizor voltage, blockcomparator and block amplifier.

3. THE LINEARIZATION WAVEFORM VOLTAGE

In figure 4 are presenting the waveforms voltage of terminals generator [1],where dt - the time that transistor is opening (conduction) and it - the time thattransistor is closing (blocked).

.idc ttt (5)

The relative during time of opening and closing are

c

dd t

t ,

c

cc t

t , .1 cd (6)

dtUtg

2

1 ,itUtg

2

2 , ,d

dd

d2 ii

dd

tt

Utt

UU

(7)

whereid t

Ut

U

dd,

dd

the equated velocity of various of voltage in two stare of

transistor.

The repeater frequency of one cicle is

.1

i

i

d

d

dcd

d

cc ttttt

tt

f

(8)

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Voltage electronic regulator for aircraft-236-

.2

dd

2d

d

2d

d

c

ii

c

dd

dd

ft

U

ft

Utt

U

U

(9)

Of equation (9) results

.2

dd

2d

d

Ut

U

Ut

U

fi

id

d

(10)

The ripple frequency of voltage depends even not by ripple amplitude, buteven by growing and lawering velocity of excitation current respectively of voltage atterminals, so this velocity depends of circuit excitation [1].

For adjustable systems voltage who used the generator in impulses, thecommutation frequency constituted a constant size, it has just modificated the relativeopening d , who can have two limit values 0 and 1 of what the voltage ripple stoppedand therefore U is annulling.

4. CONCLUSIONSIn this work is presenting the block scheme and principle of electronic

regulator voltage destinated for regulating the voltage generator with 9KW power, ofcourse are presenting the waveform of generator voltage and switching those, havedetermined the amplitude and ripple frequency.

REFERENCES

[1]. Aron, I., Paun, V. Echipamentul electric al aeronavelor. Editura didactica siPedagogica, Bucuresti 1980.

[2]. Barna, A. Amplificatoare operationale 222 exemple si probleme. EdituraTehnica Bucuresti 1971.

[3]. Mateescu, Adelaida. Semnale, circuite si sisteme. Editura Didactica siPedagogica, Bucuresti, 1984.

[4]. *** Regulator electronic de tensiune pentru aeronava IAR-99. Documentatietehnica.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 237-241

WEAR VALUATION OF BRAKING ACTIV MATERIAL ATURBAN ELECTRIC FRAMES BRAKE REGIME

DRAGOS PASCULESCU , CONSTANTIN BRINDUSA,

Abstract: In the case of subway electric frames operation it is necessary to estimate theenvironmental impact of the mechanical brake unrecovered energy. The amount of the materialdeveloped in the mechanical brake process (particularly, the clogs wear) it is depending on themechanical brake unrecovered energy. Because this mechanical braking energy can be consideredequal (like value) to the electrical energy (the active component) of the starting process, in thepaper had been simulated a transient start regime, using MATLAB software and SIMULINK-SimPower Systems Extensions. Consequently, it had evaluated the active braking material wear (thesabots wear) in the subway frames mechanical brake process, which has important environmentaleffects.

Keywords: transient start regime, MATLAB software and SIMULINK-Sim PowerSystems Extensions

1. THEORETICAL CONSID0ERATIONS

The modern subway urban electric frames are based on the driving systems withvoltage and frequency static converters and traction asynchronous motors. These electricaldriving systems allow to realize the vehicle electric brake, even with the energy recovery.

But, the vehicle brake regime can be also realized in a mechanical way, on thebasis of the mechanical contact between the clog and the motor wheel rim. In this case,the environmental impact is important and it must be taken into account, because thesubway frame it is operating into a closed (underground) space and the material amountdeveloped into the mechanical brake process (particularly, the clogs wear) it isconsiderable, depending on the unrecovered energy which it is resulting in the mechanicalbrake regime.

For the quantitative evaluation of the unrecovered energy in the brake regime itcan estimate that this energy is equal to the electrical energy absorbed by the driving

Assistant PhD.Eng. at University of Petrosani, Romania PhD. Student Eng. at University of Petrosani, Romania

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Wear valuation of braking activ material at urban electric frames brake regime-238-

system in the transient starting regime of the vehicle. That is true in the mostdisadvantageous hypotheses of the drive system, meaning:

- only the mechanical brake it is taken into account; the electrical brake it is notapplied in this case;

- the mechanical losses caused by the aerodynamic friction are insignificantly;- the mechanical losses in the system of the mechanical movement transmission

are not important, having been neglected;- the electric losses in the driving system (electrical cables, power electronics

elements etc.) are insignificantly.Consequently, the mechanical braking energy will be considered equal (like

amount) to the electric energy (the active component) received in the starting process.Therefore, in the paper will be simulated the transient starting regime of an electricsubway urban frame, which is equipped with traction asynchronous motors,type MAB T1.

2. SIMULATION MODEL AND MATLAB SOFTWARE

There is considered a traction asynchronous motor MAB T1, which is an electricmotor in a special construction, designed to operate in extremely heavy conditions. Thesemotors are made to ensure the development of the traction torques, respectively, thetraction forces at the electrical drive vehicles.

Discrete,Ts = 2e-006 s.

v+-

Vab

Te

To Workspace4

wm

To Workspace3

is_abc

To Workspace2

Vab

To Workspace1

t

To Workspace

Scope

m

is_abc

wm

Te

MachinesMeasurement

Demux

Tm

m

A

B

C

Induction MotorMAB T1

-K-

Gain

Constanttorque

Clock

AC Voltage Source2

AC Voltage Source1

AC Voltage Source

<Rotor speed (wm)>

Vab (V)

<Electromagnetic torque Te (N*m)><Electromagnetic torque Te (N*m)>

Fig.1. Simulation scheme for the vehicle behavior study in starting transient regime bydirect network connection

For the simulation model from the Fig.1, there had been used the MATLABsoftware and the SIMULINK-Sim Power Systems Extensions. This model is based on theblocks specific to the electric drives, such as "Asynchronous Machine". "Machines

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Pasculescu, D., Brindusa, C. -239-

Measurement Demux", as well as on the blocks with general applications from Simulinklibrary. In the technical literature there are presented technical data upon these, this paperemphasizing the potential of a such approach in the study of the traction electric motors.There are graphical drawn the time variation waves of the speed, the stator current and theelectromagnetic torque developed by the motor in the transient starting regime of thesubway electric frame. The traction motor MAB T1, with the technical characteristicspresented in Table 1, it is made by S.C. ELECTROPUTERE CRAIOVA S.A., for theurban electric frames, type subway, from the METROREX Bucuresti network.

Table 1 The traction motor MAB T1, with the technical characteristics

Nr. Tip Simbol MAB T1(Y)

1 Rated power ( kW ) Pn 702 Rated voltage ( V ) Un 5603 Rated current ( A ) In 964 Starting current ( A ) Ip 7205 Rated frequency ( Hz ) fn 606 Variation range of supply voltage

frequency (%)D 2

7 Rated power factor cosφn 0,868 Poles pairs number p 39 Rated speed ( rpm) nn 113510 Rated efficiency (%) ηn 0,8711 Rated torque ( Nm ) Mn 58912 Starting torque ( Nm ) Mp 647,913 Stator resistance ( Ω ) R1 0,069

Starting from the data presented in Table 1, there had beendetermined/estimated the quantities values presented in Table 2.

Table 21 Zp 0,4522Ω 4 X1 0,2177Ω2 R2

’ 0,0531Ω 5 X2’ 0,2177Ω

3 X1+X2’ 0,4354Ω 6 Xμ 4,5405Ω

where:- Zp represents the starting impedance;- R'2 represents the rotor resistance related to the stator;- X1 = X'2 represent the leakage reactances;- Xμ represents the magnetizing reactance.

On the basis of the values presented in Table 1 and Table 2, there had resultedthe characteristics from Fig.2, which are representing, in the MATLAB space, the waveforms for the main quantities which are characterizing the vehicle starting transientregime.

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Wear valuation of braking activ material at urban electric frames brake regime-240-

Fig.2. Electromechanical quantities definite for vehicle starting transient regime

Consequently, it can be determined the energy (the active component) absorbedby the system in the transient starting regime:

)(10cos3 3 kWstIUE llaabs (1)

Therefore, it will result:

kWsEaabs 9,1471025,086,02

10005603 3

Estimated, it can be considered that the amount of the material developed in themechanical brake process (particularly, the clogs wear) it is proportional to the mechanicalbraking unrecovered energy. Taking into account the previous hypothesis, of the equality(like value) between the mechanical braking unrecovered energy and the electrical startingenergy (the active component), on the basis of the relation (1) it can be determined the

(PDF) ANNALS OF THE UNIVERSITY OF PETROŞANI 2007.pdf· Annals of the University of Petroşani, Electrical Engineering, 9 (2007)-3-CONTENTS Dašić Predrag, Nedeff Valentin, Curčić Srećko, - DOKUMEN.TIPS (241)

Pasculescu, D., Brindusa, C. -241-

wear rate of the braking active part, as below:aabsFe Eakkr *lg21 (2)

where the coefficients a, k1 and k2 are experimentally determined and they are varying infunction of some disturbing factors, like the material type, the contact pressure, the contactsurface, the environment temperature and humidity and the local cooling.

Further on, considering a traffic with the frequency N3, on a subway line(thoroughfare) of approximately 20 km, with an average of N4 stations (equivalent to atunnel with a complete aerating), it will result (as percentage) the active material wearamount, determined by the following relation:

(%)10 43213

FerNNNNR (3)where:N1 = number of days / year

N2 = number of hours / day N3 = number of trains / hour N4 = number of stations / thoroughfare

Table 3 The resulted dataQFe 80*

10-380*10-3

80*10-3

80*10-3

80*10-3

80*10-3

80*10-3

80*10-3

80*10-3

80*10-3

80*10-3

80*10-3

N1 240 240 240 288 288 288 365 365 365 220 220 220N2 20 20 24 20 20 24 20 20 24 20 20 24N3 12 10 12 12 10 12 12 10 12 12 10 12N4 20 20 20 20 20 20 20 20 20 20 20 20

R(%) 92 76 110 110 92 132 139 116 168 84 70 101

On the basis of the data of the table as before, it results that, in the hypothesis ofan electrical brake absence, it would appear a wear of the mechanical braking equipmentup to 100% during the entire year, leading, therefore, to its replacement.

3. CONCLUSIONS

The presented method represents a new approach in the study of theunderground environmental impact of the travelling transport on the basis of the transportsystem realized with urban subway electric frames. The material amount released in theair and laid down into an underground (closed) space constitutes an important problemboth for the environment and for the travelling transport safety, because the metals oxidescan lead to serious perturbations in the centralized control system of the electric framestraffic.

REFERENCES

[1] Krause P.C., Wasynczuk O.,Sudhoff S.D., Analysis of Electric Machinnery,IEEE, 1995.

[2] Brînduşa,C.,ş.a., Sisteme electrice de transport neconvenţionale (A23); Rama demetrou acţionată cu motoare asincrone; Execuţie şi experimentare modele (Faza 23.1), Contractcercetare 606C- Anexa A, Institutul naţional de cercetare şi proiectare pentru maşini electrice,echipament electric şi tracţiune, ICMET, Craiova, 1992

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 242-245

PC TO CY8C29466 MICROCONTROLLER SERIALCOMMUNICATION METHOD

DOBRA REMUS

Abstract: This project shows how to connect the PSoC (Programmable System onChip) mixed-signal array to a PC via an RS-232 serial interface. The scheme described in thispaper consumes minimum current and works with applications that require low voltage. Theaim of this project is to illustrate a data transfer between PC and PSoC and write the data bytes,which come from the PC (software) via RS232, to the PSoC device ROM (Flash) memory.

Keywords: CY8C29466 microcontroller, RS-232 serial interface

1. INTRODUCTION

To connect a PC to a CY8C29466 microcontroller via serial port, dedicatedlevel translators, such as MAX232, are used. This paper demonstrates how to develop asimple, low supply current and low-cost level translator, which in many situations canreplace a more expensive, dedicated level translator.

RxD

TxD

MAX

232 TxD

RxD CY8C29466 ProcessAnalog In

Analog Out

Fig.1 Block diagram for serial communication PC - MicrocontrollerA level converter chip is required to connect a PC to a PSoC device with an

RS-232 serial interface. Process

Assistant PhD student, University of Petrosani

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Dobra R. -243-

But there is a simpler solution that works well with the PSoC device. Thissolution is efficient with all PCs and has the standard UART interface for bothstationary and portable devices.

The project provides efficient data exchange by using a supply voltage of 2.8to 5 volts and it consumes very minimal current and supports data exchanges at a rateof at least 9600 bps.

Figure 2 illustrates communication protocol implementation.

Fig.2 Communication algorithm

This algorithm has been written to get the information coming from the PC(software) via RS232 to the PSoC device and then write to the memory unit of ROMinside the device. The RX8 User Module checks the port continuously to interpret anydata byte that has been sent from the PC. Then it waits for the receiving to complete.When data has completely been received, the RX8 checks for errors.

(PDF) ANNALS OF THE UNIVERSITY OF PETROŞANI 2007.pdf· Annals of the University of Petroşani, Electrical Engineering, 9 (2007)-3-CONTENTS Dašić Predrag, Nedeff Valentin, Curčić Srećko, - DOKUMEN.TIPS (244)

PC to CY8C29466 microcontroller serial communication method-244-

Fig.3 Graphical interface of the serial connection

3. MAIN PROGRAM

#include <m8c.h>#include"PSoCAPI.h"#define RESOLUTION 12#define SCALE_BG (( 1 <<RESOLUTION)/55)int iResult;void main(){ BYTE bgPos;

UART_1_Start(UART_PARITY_NONE); UART_1_CPutString("ExampleADC_UART_LCD"); UART_1_PutCRLF();

PGA_1_Start(PGA_1_MEDPOWER);

ADCINC12_1_Start(ADCINC12_1_MEDPOWER); ADCINC12_1_GetSamples(0); LCD_1_Start(); LCD_1_InitBG(LCD_1_SOLID_BG);

LCD_1_Position(0,0); LCD_1_PrCString("PSoC LCD"); M8C_EnableGInt; while (1)// Main loop { if (ADCINC12_1_fIsDataAvailable()!= 0) { iResult = ADCINC12_1_iGetData()+ 2048; and clear flag ADCINC12_1_ClearFlag(); LCD_1_Position(1,0); //display result on LCD in hex and as a bargraph LCD_1_PrDecInt(iResult); bgPos =(BYTE)(iResult/SCALE_BG); LCD_1_DrawBG(1, 5, 11, bgPos); } }}

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Dobra R. -245-

1234567891011121314 15

16171819202122232425262728

LCD1

16

LCDRS LCDRW

LCDE

LCDD4

LCDD5 LCDD6

LCDD7

LM29

31

C1

C2

P1

12345678 9

10111213141516

MAX

232

RxD

TxD

Rx

Tx

CY8C29466

5V

+Vcc

C3C4

C5C6

C7

Fig.3. The connection between PC an CY8C29466

In the figure 3 is shown the low cost possibility to connect PC to a cypressmicrocontroller. This is possible with Max232 device, and if is necessary to realize realtime measurement with an autonomic apparatus the microcontroller will be suppliedtrough a stabilizer device.

2. CONCLUSIONS

The design discussed in this paper is a model for several other data acquisitionand control systems using PSoC Designer, which provides analog and digital migrationrequired for any laboratory or industrial automation. This compact design can bemounted on the system under automation and interfaced with the PC through serialcommunication.

REFERENCES

[1] *** Cypress 3210 MiniProg tehnical documentation

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 246-253

ANALYSIS OF THE LUEMBERGER EXTENDEDESTIMATOR USED WITHIN A VECTORIAL-TYPE

ELECTRICAL DRIVING SYSTEM WITH ANINDUCTION MOTOR

CORNELIU MÂNDRESCU, OLIMPIU STOICUŢA

Abstract: In this paper we present the analysis through simulation of the extendedLuemberger estimator using the Matlab – Simulink platform. Within this analysis we emphasizethe errors between real rotor flux and the estimated one as well as the error between real rotorspeed and estimated one.

Keywords: Luemberger estimator, values rotation method, values moving method

1. IMPLEMENTATION OF THE INDUCTION MOTOR

In order to implement the induction motor in Matlab – Simulink we will use theS_Function blocks within Simulink. The structure of the simulation scheme of theinduction motor is presented in Figure 1.

Fig. 1. Structure of the induction motor’s scheme

Assoc.Prof.Eng.Ph.D., University of Petroşani Assist.Eng., University of Petroşani

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Mândrescu, C., Stoicuţa, O. -247-

From this figure one may notice that the fourth entry variable is considered to berotor resistance.

This is justified in the analysis phase of the extended Luemberger estimator, inorder to emphasize the sensitivity of the extended Luemberger estimator when rotorresistance of the induction motor is changed.

In order to emphasize the source code, written in Matlab language, of theinduction motor we will consider that the motor has the following electrical andmechanical parameters:

]W[500PN ; ]V[127U N ; ]A[9.2IN ; min]/rot[1400n N ;2zp ; ]Nm[41.3M N ; ][495.4R s ; ][365.5R r ;

]mH[165Ls ; ]mH[162L r ; ]mH[149Lm ; ]Kgm[00095.0J 2 .Under these circ*mstances the source code in Matlab that is given to the

S_Function block corresponding to the induction motor is:

function [sys,x0,str,ts] = motor_inductie(t,x,u,flag)switch flag, case 0, [sys,x0,str,ts]=mdlInitializeSizes; case 2, sys = mdlUpdate(t,x,u);

case 3, sys = mdlOutputs(t,x,u); case 9, sys = []; otherwise error(['unhandled flag = ',num2str(flag)]);endfunction [sys,x0,str,ts]=mdlInitializeSizessizes = simsizes;sizes.NumContStates = 0;sizes.NumDiscStates = 5;sizes.NumOutputs = 5;sizes.NumInputs = 3;sizes.DirFeedthrough = 1;sizes.NumSampleTimes = 1;sys = simsizes(sizes);x0 = [0;0;0;0;0];str = [];ts = [2000/(150e+6/2) 0];function sys = mdlUpdate(t,x,u)Rr=5.365;Rs=4.495;Ls=165e-3;Lr=162e-3;Lm=149e-3;J=0.95e-3;zp=2;s=1-(Lm^2/(Ls*Lr));

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Analysis of the luemberger extended estimator used within a vectorial-typeelectrical driving system with an induction motor-248-

Ts=Ls/Rs;Tr=Lr/Rr;T=2000/(150e+6/2);B=[1/(s*Ls) 0 0; 0 1/(s*Ls) 0; 0 0 0; 0 0 0; 0 0 (zp*sign(x(5)))/J];A=[-((1/(Ts*s))+((1-s)/(Tr*s))) 0 Lm/(Ls*Lr*Tr*s) (Lm/(Ls*Lr*s))*x(5) 0; 0 -((1/(Ts*s))+((1-s)/(Tr*s))) -(Lm/(Ls*Lr*s))*x(5) Lm/(Ls*Lr*Tr*s) 0; Lm/Tr 0 -(1/Tr) -x(5) 0; 0 Lm/Tr x(5) -(1/Tr) 0;

-((3*zp^2*Lm)/(2*J*Lr))*x(4) ((3*zp^2*Lm)/(2*J*Lr))*x(3) 0 0 0];F=eye(5)+A*T+(A^2)*(T^2/2);H=B*T+A*B*(T^2/2);sys=F*x+H*u;function sys = mdlOutputs(t,x,u)sys = x;

2. IMPLEMENTATION OF THE LUEMBERGER ESTIMATOR

The schematics of the Luemberger estimator used to estimate rotor fluxes andstator currents is presented in Figure 2.

Fig. 2. Luemberger estimator schematics

Under these circ*mstances the Matlab source code given to the S_Functionblock corresponding to the Luemberger estimator is:

A. In case of projecting the estimator based on proportional self valuesmethod:

function [sys,x0,str,ts] =Luenberg1(t,x,u,flag)switch flag, case 0, [sys,x0,str,ts]=mdlInitializeSizes; case 2, sys = mdlUpdate(t,x,u);

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Mândrescu, C., Stoicuţa, O. -249-

case 3, sys = mdlOutputs(t,x,u); case 9, sys = []; otherwise error(['unhandled flag = ',num2str(flag)]);endfunction [sys,x0,str,ts]=mdlInitializeSizes;sizes = simsizes;sizes.NumContStates = 0;sizes.NumDiscStates = 4;sizes.NumOutputs = 4;sizes.NumInputs = 5;sizes.DirFeedthrough = 1;sizes.NumSampleTimes = 1;sys = simsizes(sizes);x0 = [0;0;0;0];str = [];ts = [2000/(150e+6/2) 0];function sys = mdlUpdate(t,x,u)Rr=5.365;Rs=4.495;Ls=165e-3;Lr=162e-3;Lm=149e-3;J=0.95e-3;zp=2;s=1-(Lm^2/(Ls*Lr));Ts=Ls/Rs;Tr=Lr/Rr;T=2000/(150e+6/2);A=[-((1/(Ts*s))+((1-s)/(Tr*s))) 0 Lm/(Ls*Lr*Tr*s) (Lm/(Ls*Lr*s))*u(5); 0 -((1/(Ts*s))+((1-s)/(Tr*s))) -(Lm/(Ls*Lr*s))*u(5) Lm/(Ls*Lr*Tr*s); Lm/Tr 0 -(1/Tr) -u(5); 0 Lm/Tr u(5) -(1/Tr)];B=[1/(s*Ls) 0; 0 1/(s*Ls); 0 0; 0 0];C=[1 0 0 0; 0 1 0 0];F=eye(4)+A*T+(A^2)*(T^2/2);H=B*T+A*B*(T^2/2);a1=-((1/(Ts*s))+((1-s)/(Tr*s)));a2=-1/Tr;a3=Lm/Tr;c=Lm/(s*Ls*Lr);k=1.3;k11=(a1+a2)*(1-k);k12=u(5)*(1-k);

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Analysis of the luemberger extended estimator used within a vectorial-typeelectrical driving system with an induction motor-250-

k22=-k12/c;k21=(a3+a1/c)*(1-k^2)-k11/c;L=[k11 -k12; k12 k11; k21 -k22; k22 k21];Ld=L*T+A*L*(T^2/2);U=[u(1);u(2)];Y=[u(3);u(4)];x=F*x+H*U+Ld*(Y-C*x);sys=x;function sys = mdlOutputs(t,x,u)sys=x;

B. In case of projecting the estimator based on self values rotation:

The program for this case is resembling the previous one, except that the lines inbold are to be replaced with the following ones:

c1=Lm/(s*Ls*Lr);c=1/c1;k=1.4;teta_min=15*pi/180;w_max=6000*pi/30;ka1=teta_min/w_max;teta=ka1*u(5);kr=k*cos(teta);ki=k*sin(teta);k11=(1-kr)*(a1+a2)+ki*u(5);k12=(1-kr)*u(5)-ki*(a1+a2);k22=(1-kr^2+ki^2)*(a3+c*a1)-c*k11;k21=-2*kr*ki*(a3+c*a1)-c*k12;L=[k11 -k12; k12 k11; k21 -k22; k22 k21];Ld=L*T+A*L*(T^2/2);

C. In case of projecting the estimator based on self values rotation:

The program for this case is resembling the first one, except that the lines in boldare to be replaced with the following ones:

c1=Lm/(s*Ls*Lr);c=1/c1;delta=-1;k11=-2*delta;k12=0;

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Mândrescu, C., Stoicuţa, O. -251-

k21=c*(a1+2*delta)-c*delta*((a2^2+u(5)^2)^-1)*(a1*a2^2+a2*(a1+a2)*delta+a2*delta^2+(u(5))*(delta+a1));k22=c*delta*u(5)*(a1+delta)*((a2^2+u(5)^2)^-1);L=[k11 -k12; k12 k11; k21 -k22; k22 k21];Ld=L*T+A*L*(T^2/2);function sys = mdlOutputs(t,x,u)sys=x;

3. IMPLEMENTATION OF THE EXTENDED LUEMBERGERESTIMATOR

Based on the things previously presented we can realize the simulation schemeof the extended Luemberger estimator. This will contain, as known, the speed adjustingmechanism or speed estimator. The simulation scheme realized in Simulink ispresented in Figure 3.

Internal structure of the adjusting mechanism is in Figure 4.As one may notice in Figure 4 we also emphasized the PI regulator used to

estimate speed, implemented using trapeze digitization method (Tustin method).

Fig. 3. Extended Luemberger estimator block schematics

Fig. 4 Internal structure of the adjusting mechanism

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Analysis of the luemberger extended estimator used within a vectorial-typeelectrical driving system with an induction motor-252-

4. ANALYSIS OF THE EXTENDED LUEMBERGER ESTIMATOR

In order to analyze the extended Luemberger estimator we considered the casein which the Luemberger estimator is projected based on self values proportionalitymethod. Under these circ*mstances using a sampling time of 2000/(150e+6/2) and a nilresistant torque during the first 0.5 seconds and then a resistant torque. Equal to thenominal one, following the simulation we obtain the variations with time of the rotorflux in the dq coordinates as well as the variation of speed. Following the simulationwe can realize a comparison between the real rotor flux and the estimated one as wellas the real speed and the estimated one. These results are obtained after we power themotor with an amplitude tension of 2U N . The graphs mentioned above arepresented in Figure 5.

Fig. 5 Real and estimated speed with estimated and real speeds errors

One may notice that between the real and estimated speed big differences do notappear. In order to observe the small differences between the two speeds in thefollowing we present the graph of errors for the two speeds.

In a resembling manner we will present the variation in time of the rotor flux,emphasizing both the variation with time and the error between them. In the graphsbelow we present the variations with time of the estimated flux on the d axis comparedto the real flux on the d axis and the variation with time of the estimated flux on the qaxis compared to the real flux on the q axis. The graphs mentioned are presented inFigure 6. One may notice, in this case also, that between the real and estimated rotorflux big differences do not appear. In order to observe the small differences betweenthe two fluxes corresponding to the d axis we will present the graph of the errorbetween the two fluxes.

Fig. 6 Real and estimated rotor flux corresponding to the d axis with error

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Mândrescu, C., Stoicuţa, O. -253-

In a resembling manner the real rotor flux and the estimated one correspondingto the q axis is presented in Figure 7.

One may notice, in this case as in the preceding case that between real rotor fluxand the estimated one big difference do not appear. In order to observe the smalldifferences between the two fluxes corresponding to the q axis we will present thegraph of error of the two fluxes.

Fig. 7 Real and estimated rotor flux corresponding to the q axis with error

5. CONCLUSIONS

Based on the presented algorithms one can realize a real time simulation withhardware in the loop that will allow to obtain the self values of the estimator, motorand the regulating system in various working regimes of the motor, meaning a realtime analysis of the motor- estimator ensemble stability.

The results presented above can constitute a refference point in projecting asensorless vector regulating system.

Following the simulation one can conclude that the extended Luembergerestimator has a very good dynamics for low, medium or high speeds so that it isrecommended to be used in sensorless vector regulating schemes.

REFERENCES

[1] C.Ilas, V.Bostan, Tehnici adaptive de control a motorului asincron: comandavectoriala fara masurarea vitezei , Litografia U.P.B. (2001)

[2] M. Hilairet, C. Darengosse, F. Auger, P. Chevrel, Synthesis and analysis ofrobust flux observers for induction machines, IFAC Symp. on Robust Control Design, Prague.(2000)

[3] O. Stoicuta, H. Campian, T. Pana, The Comparative Study of the Stability of theVector Control Systems that Contain in the Loop Luenberger and Kalman Type Estimators,IEEE-ITTC International Conference on Automation, Quality & Testing, Robotics AQTR 2006(THETA 15), Cluj-Napoca, (2006)

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 254-259

APPROACH ON DISTRIBUTIONS FOR CONTROLSYSTEMS WITH RELAY TYPE NONLINEARITIES

MONICA LEBA, EMIL POP, PETRE VAMVU

Abstract: In this paper are presented distributions, their properties and applications innonlinear system control. Using the definition of distributions, the mathematical formulas forrelay type nonlinearity elements are determined. Based on distribution properties there can beeasily designed flexible and reliable nonlinear systems with relay type nonlinearities. Using thistheory there were designed, modeled and simulated the complex distributions that have manypractical applications in nonlinear system control.

Keywords: distributions, relay, nonlinear systems

1. NONLINEAR SYSTEMS WITH SEVERE NONLINEARITIESOVERVIEW

One of the most developed theory, witch dominate the last century was LinearDynamical System Control Theory. But linear systems represent only an approach ofreal systems and some time unacceptable approximation for others. In the real world,all the systems are nonlinear because the process and phenomena are always nonlinear.The nonlinear systems use nonlinear operators to describe their mathematical models.This approach is very exhaustive and is impossible to find general equations andmethods for entire nonlinear systems class. There are only some methods to analyzeseveral classes of nonlinear systems. The type of nonlinearities from the systemsdefines its classis. The nonlinearities can be classified in light and severe, according tothe possibility of linearization. The light nonlinearities have good linear approximation,while for the severe nonlinearities the linear approximation has unacceptable errors.

The light nonlinearities are continuous and differentiable and the severe ones haddiscontinuities and are not differentiable.

PhD. Lecturer at the University of Petrosani PhD. Professor at the University of Petrosani Assistant Eng. at the University of Petrosani

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Leba, M., Pop, E., Vamvu, P. -255-

The second category includes a wide range of switches like digital, relay and logicelements. A most used class of nonlinear systems is called relay type systems. In fig.1are examples for these categories of nonlinearities: light and severe (relay types). Fornonlinear systems with relay types nonlinearities elements is difficult to write amathematical model, because there are equations with polymorph form, discontinuitiesand many non derivable points. This is a difficult barrier to avoid.

Fig.1. Nonlinear elements: a) Block diagram; b) Light; c) Severe (relay types)

If this element contains one light nonlinearity like in fig.1.b the equation can bewritten quite simple as follow:

0);1)exp

0));1exp1)(

udtdauabsB

udtdauabsB

uy (1)

If this element contain severe nonlinearity like in fig.1.c the equation is moredifficult to be written. The nonlinearity is discontinuous. The equations are as follows:

;;0

0;

0;

;;0

0;

0;

)(

dtdu

buBaub

uaBuaB

uB

dtdu

buBbua

auBuaB

uB

uf (2)

These model equations are difficult to use and many times become unacceptablefor simulation. For this reason there are used generalized functions or distributions toavoid these difficulties.

2. MATHEMATICAL SUPPORT FOR APPLICATION OFDISTRIBUTIONS IN RELAY TYPE NONLINEAR SYSTEMS

Sever nonlinearities, like above, cannot be represented as closed mathematicalformula because they present a lot of discontinuities, non-derivations, discretetransitions etc. In the classical theory this regions are avoided, eliminating the

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Approach on distributions for control systems with relay type nonlinearities-256-

discontinuities and never using the derivation operator in critical points. This approachhas two disadvantages: first, the representation is complicated and unusual and second,just the discontinuities are eliminated where the systems work.

These difficulties can be eliminated by distribution theory extending thefundamental concepts, like derivability, to the whole domain, and can be easy to writethe mathematical models and evaluate its qualitative properties, by simulation.

Now, in the next part the mathematical support for distributions will beconsidered. The distributions can be defined as the functional transformations betweentwo linear spaces. We consider the n-dimensional Euclidian real space Rn, organized asa vectors space. The elements of this space are n-coordinates vectors: n21 x,...,x,xx , n21 y,...,y,yy . On this space will be considered the

applications RR:f n .From this applications will be selected x which are continuous, derivable and

the derivates are continuous with zero value out of their domain. The domain of thesefunctions is compact. The space of x functions continuous and derivable is Kn andhas the properties: n

21nm

21 Kxx:R,,Kx,x ;

0xlim:Kx kk

mk

.

This is a fundamental space. In this space will define the functional applications: RxfRKf m :: .

Distributions are real, linear and continuous functional defined on fundamentalspace. The most important distributions in nonlinear systems are: pulse, step and rampdistributions.

The pulse distribution or Dirac pulse is defined as follows: 0:: xRK m ; mKx (3)

1dxx;0x;0x;0

xR

, (fig.2.a)

Fig.2. Distribution x and its properties

Proposition 1The Dirac distribution has the following properties:

1. 000 xxxaxxxa , (fig.2.b)

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Leba, M., Pop, E., Vamvu, P. -257-

2.

x1x ; xx

3.

p

iixx

xifxf

1'

1 ; xi are simple solutions: 0xf , (fig.2.c)

4.

p

1iii

' xxsxfdx

xfd; 0xf0xfs iii

The step distribution or Heaviside distribution is defined bellow (fig.3.a):

0;00;1

;:xx

xRK m

Proposition 2The Heaviside distribution has the following properties:

1. xx 1 (fig.3.b); xsignxx (fig.3.c)

2. axaxax 122 ; xfxfxf )( ; x

dxxd

Fig.3. Heaviside distribution and its properties

The ramp distribution is defined as follows (fig.4.a):

0x;00x;x

xr;RK:r m

Fig.4. Ramp distribution and its properties

Proposition 3The ramp distribution has the following properties:

1. xxxxr (positive ramp); xxx (negative ramp) (fig.4.a,b)2. xxxsignxx ; axaxaxaxaxr 22 (fig.4.c,d)

3. xx ' ; xx ' ; xxx ; xxx21;xxx

21

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Approach on distributions for control systems with relay type nonlinearities-258-

Theorem of concatenationConsider the fi(u), i є N a set of real functions defined on closed interval, θ(u) step

distribution, μi characteristic function of Ii and f(u) the distribution obtained by fi(u)concatenation. There are relations:

iii

iiii

iiii

iiiiiiii

dtduufuf

aIifaubIifbu

baIifbaubau

)]()([)(

),[];[],();(1

],[];)([ 2

The demonstration of this theorem result as a consequence of the last threepropositions presented above. Based on the elementary distributions properties andusing the theorem of concatenation, there can be obtained complex and polymorphdistributions, like the examples shown in fig.5.

Mathematically these distributions have the following formula, respectively: auauBuy (4)

0;

0;

dtduaubuBdtdubuauB

uy

(5)

0;

0;

dtduausignBdtduausignB

uy(6)

)16(]42

[)127()4()65()2()2(

)2()2()2()65()2()127()4()(

22

222

222

uuuuuuuuuu

uuuuuuuuuuuf (7)

Fig.5. Complex and polymorph distributions: a) Tri-state; b) Tri-state with window; c) Two-state with window; d) Concatenation

3. MODELING AND SIMULATION OF DISTRIBUTIONS

In this section the elementary distributions and some properties will be simulated.In fig.6 the model of tandtsign,tr,t,t were simulated.

In fig.7 there are presented the simulation model and results for several relaytype complex distributions, like tri-state, window tri- and two- stare and concatenation.

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Leba, M., Pop, E., Vamvu, P. -259-

Fig.6. Simulation of elementary distributions

Fig.7. Simulation of complex distributions: a), b) Simulink models; c) Tri-state;d) Window Tri-state; e) Window Two-state; f) Concatenation

4. CONCLUSIONS

1. The distributions are very useful for nonlinear system elements approach.2. For nonlinear systems with relay nonlinearity it is easy to write a distributions

mathematical model. Using the concatenation theorem, it is possible torepresent the mathematical model of complex polymorph distributions.

3. The modeling and simulation of relay type nonlinear systems using thedistributions theory and properties is very easy to implement.

BIBLIOGRAPHY

[1] KECS W.W.: Teoria distributiilor si aplicatii. Ed.Academiei, Bucuresti, 2003.[2] SCHWARTZ L.: Theorie des distributions. Paris, Hermann, 1951.[3] POP E., LEBA M.: Contribution to sine delta pulse width modulation control of

three-phase inverter. Galati, Proceedings of 11th National Conference on Electric Drives, 2002.[4] POP E.: Nonlinear systems. Introduction and applications in electrical drive

control. Jahresbericht des IEE nr.13, Clausthal, Germany, 2002.[5] LEBA M.: A new PWM controller based on distributions properties. microCAD

2006, Miskolc, Hungary, 2006

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 260-265

AUTOMATIC WIG WELDING CONTROLUSING FEEDFORWARD NEURAL NETWORK

GABRIELA BUCUR, LIVIU BUCUR

Abstract: The paper presents the WIG arc welding industrial system control blockdiagram based on the correction of the trajectory welding torch through the welding seam.Welding trajectory is corrected using an automated control system in witch the control functionis realized with a feedforward neural network based on backpropagation algorithm. Thereaction signal for the neural controller is obtained from the acquisition system of the voltagevalues of the arc-welding process.

Key words: neural network, backpropagation, welding process, robots.

1. INTRODUCTION

The final purpose of a welding operation is to achieve a welding seam thatsatisfies many imposed conditions. These conditions results from technological generalsystem analysis, system witch is composed by power source – welding source – arcwelding system, welding seam, manipulation system and control system. Theimprovement of the welding quality is achieved by the trajectory correction, based onfollowing the welding joint, processing the acquired signals in the command systemand modifying, if necessary, the welding parameters. The paper present the way toprocess the welding-arc voltage with neural network [1]. That result can be applied inautomated robotic welding based on the corection of the trajectory welding torchthrough the welding seam.

*Lecturer, Ph.D. at the “Petroleum-Gas” University of Ploieşti, Department ofControl Engineering and Computers, Romania Mathematician, Ph.D. Student, “Florin Comisel” School of Ploiesti, Romania

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Bucur, G., Bucur, L. -261-

2. WIG WELDING MATHEMATICAL MODEL WITH NEURALNETWORK

The paper presents the arc welding – power source model for the WIG weldingprocess [4]. For this model, an input is the electrical arc external length lae, created bywelding source. In 11 element, lae is added to the arc electrical arc internal length lai,created by penetration p and to the external perturbatin of arc length la

*.

Fig. 1. WIG arc welding – power source model with neural network [4]

The output of 11 element is the welding arc total length la, which istransformed from XXVI transfer element in arc welding voltage ual. In the same time,the XXVII transfer element has the arc welding power like input and the electrical arcvoltage uai like output.

In 12 element, uai is added to the ual and to the perturbation ua*. The result is

the electrical arc voltage ua which is transmit to power source. Figure 1 present the arcwelding – power source model with a neural network.

The inputs of neural network are the signal ua, means arc voltage, obtainedfrom a real welding process and an arc voltage reference signal, ua

ref[2], analyticallycomputed. The output of neural network is used to command a robot engine forcorection of trajectory welding torch through the welding seam.

3. NEURAL NETWORK STRUCTURE

The neural network structure is presented in figure 2. The input vector contain310 neurons, the hidden layer contain 50 neurons and use the tan-sigmoid transfer

XXVI XXVIII XXVIII

XXXI

XXVIII

XXVII

WELDING SEAM

Power source

Electrical arc

RNA

Urefla

*

la

e

la

ua

e

ua*

ua

i

uaiau

iar

ia

ia*

ur*

ua

ia

ia

ua

la

i

11

12

13

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Automatic wig welding control using feedforward neural network-262-

function and the output layer contain only one neuron and use the purelin transferfunction.

Fig. 2. Neural network designed structure

The reference signal Uref [V] = f(time) is analytically obtained using the modelof WIG welding process [3]:

62.3)2cos(07.0)sin(13.0 ttUref

arc [V]. (1)

4. NEURAL NETWORK SIMULATION

Neural network simulation was realized with the MATLAB program:

time=0:0.1:30.9; time vector 31 seconds discretised by 100msx= - 0.13*sin(pi*time)-0.07*cos(2*pi*time)+3.62; reference signal (Figure 3)plot(time,x,'b');

Fig. 3. Reference signal

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Bucur, G., Bucur, L. -263-

xlabel('Timpul [s]');ylabel( 'Semnalul de referinţă: U_r_e_f [V]' );p=dlmread('date_p.txt','\n'); process signal (Figure 4)length(p);plot(time,p,'m');xlabel('Timpul [s]');ylabel('Semnalul din proces: p [V]');

Fig. 4. Process signalp=p' ;net = newff (minmax(p), [310 50 1], { 'tansig' 'tansig' 'purelin' } , 'trainrp' , 'learngd','msereg' ) ; on create a backpropagation feedforward networknet = init(net);net.trainParam.show = 10;net.trainParam.epochs = 300;net.trainParam.goal = 1e-2; [net,tr]=train(net,p,x);pause;plotperf (tr)a = sim(net,x); the output of the network (Figure 5)

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Automatic wig welding control using feedforward neural network-264-

Fig. 5. Output signal

plot(time,a,'r');xlabel('Timpul [s]');ylabel('Ieşirea reţelei antrenate: a [V]');pause;e=x-a; error signal (Figure 6)net.performParam.ratio=20/(20+1);perf=msereg(e,net); network performanceplot(e,'g') ;xlabel('Timpul [s]');ylabel('Semnalul erorii: e [V]');

Fig. 6. Error signal

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Bucur, G., Bucur, L. -265-

It was used the trainrp training algorithm for the neural network because theoutput and error signal is most appropriates for our purpose.

5. CONCLUSIONS

Theoretical and experimental background from this paper, means weldingprocess control using analyze an arc welding parameter (electrical arc voltage) is avery good start point for another research in welding area. A substantial amount ofresearch is being conducted with the goal of developing an intelligent, fully automaticwelding system. These intelligent methods have been applied to control the behavioralcharacteristics of the welding process in order to improve quality and productivity inall industrial areas.

BIBLIOGRAPHY

[1]. Bucur, G. , Automated control system for robotic electrical arc welding, Ph.D.Thesys, Ploiesti, 2002.

[2]. Bucur, G., Dumitrescu, St., Micloşi, V., Neural network control in roboticwelding processes. Journal of Symposium “35 de ani de activitate a Universităţii Petrol-Gaze laPloieşti”. Vol.LIV, 38-43, 2003.

[3]. Deheleanu, D., Welding Technology., Editura Sudura, Cluj-Napoca, 1999.[4]. Micloşi, V., Welding Equipments, Editura Didactica si Pedagogica, Bucureşti,

1984.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 266-271

ELECTRONIC GOVERNMENT–REFLECTIONS OVER THEDESIGN OF A REGIONAL DEVELOPMENT STRATEGY

IRIMIA ROXANA-ADINA *, VLĂSCEANU ALINA NICOLETA **

Abstract: EGov refers certainly to more use of IT, but more importantly to attempts toachieve more strategic use of IT in the public sector. It is about changes in the internalgovernment operations that come about as IT is used for automation, cooperation, integrationamong government agencies and as tools assisting in decision processes. E-Government refersto government’s use of information and communication technology (ICT) to exchangeinformation and services with citizens, businesses, etc. E-Government may be applied bylegislature, judiciary, or administration, in order to improve internal efficiency, the delivery ofpublic services, or processes of democratic governance.

Keywords: E-government, digital economy, regional development strategy,Information Communications Technology, E-regional portals

1. INTRODUCTION-DIGITAL ECONOMY

Information Communications Technology (ICT) has been identified as a keyenabler in the achievement of regional and rural success, particularly in terms ofeconomic and business development. The potential for achieving equity of servicethrough improved communications infrastructure and enhanced access to government,health, education and other services has been identified. ICT has also been linked to theaspiration of community empowerment where dimensions include revitalizing a senseof community, building regional capacity, enhancing democracy and increasing socialcapital.

With the proliferation of information and Web sites, it becomes increasinglydifficult to find relevant information via the Internet. Web portals have developed to

* university assistant Ph.D. candidate, The Christian University “Dimitrie Cantemir”-Bucharest- [emailprotected]** university assistant Ph.D. candidate, The Christian University “Dimitrie Cantemir”-Bucharest- [emailprotected]

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Irimia R.,A., Vlăsceanu A., N. -267-

facilitate the location of online information. Examples include: community portals,geographical or interest-based; business portals, internally or externally focused; andgovernment portals, for particular groups such as businesses, young people, women orregional communities. In most cases, the objectives include providing efficient accessto information, resources and services, reaching a larger audience, and providing"anytime, anywhere" service, 24 hours a day, seven days a week.

2. PERSPECTIVES ON ELECTRONIC GOVERNMENT

E-Government, also known as e-gov, digital government or online governmentrefers to government’s use of information and communication technology (ICT) toexchange information and services with citizens, businesses, and other arms ofgovernment. E-Government may be applied by legislature, judiciary, or administration,in order to improve internal efficiency, the delivery of public services, or processes ofdemocratic governance. The primary delivery models are Government-to-Citizen orGovernment-to-Customer (G2C), Government-to-Business (G2B) and Government-to-Government (G2G). The most important anticipated benefits of e-government includeimproved efficiency, convenience, and better accessibility of public services. While e-government is often thought of as "online government" or "Internet-basedgovernment"—many non-Internet based "electronic government" technologies can beused in this context, including telephone, fax, PDA, SMS text messaging, MMS, and3G, GPRS, WiFi, WiMAX and Bluetooth. There are many considerations and potentialimplications of implementing and designing e-government, including disintermediationof the government and its citizens, impacts on economic, social, and political factors,and disturbances to the status quo in these areas. In countries such as the UnitedKingdom, there is interest in using electronic government to re-engage citizens withthe political process. In particular, this has taken the form of experiments withelectronic voting, aiming to increase voter turnout by making voting easy. Economicand revenue-related concerns include e-government's effect on taxation, debt, GrossDomestic Product (GDP), commerce and trade, corporate governance, and its effect onnon-e-government business practices, industry and trade, especially Internet ServiceProviders and Internet infrastructure.

The concept of electronic government (eGov) is about to emerge from apractitioners’ concept to one that also attracts research. Conferences abound, andresearch scales up from individual researchers and projects to institutes, both thosegoverned by industry, such as IBM’s Institute for Electronic Government and thosegoverned by universities, such as the Center for Technology in Government at AlbanyUniversity. Research and development programs such as the EU Information SocietyTechnologies and Government Online are focusing on developing strategic andtransferable IT uses in government. Research institutes with the focus on policies anddevelopment focus increasingly on IT use, such as the Institute for Development Policyand Management at the University of Manchester. It is hard to estimate the amount ofeffort to implement eGov currently going on around the world. Many things relevant tothe field come under different names.

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Electronic government–reflections over the design of a regionaldevelopment strategy-268-

Fig. 2: Intermediaries in e-government processes

Fig.1 Basic elements and relations in a democratic government system.

3. BASIC ELEMENTS AND RELATIONSHIPS INTO AN E-GOVERNMENT SYSTEM

E-government communications procedures frequently require clear andunambiguous identification of the citizen and the public entity involved before thecommencement of relations, otherwise the operation cannot be carried out. Without therelevant data, therefore, relations are restricted to the simple presentation ofinformation to the citizen by public institutions.

To integrate the research from different disciplines and on different topicsrelevant to eGov, there is a need for defining a context in terms of the public sectormodel. In simple terms, and at a general level where national differences do not matter,a democratic government is organized as shown in figure 1:

In practicethe system isof coursemuch morecomplex, the

politicalimpact

administrations can exertby havingthe expertisenecessary to

preparedecisions in complicated matters isoften acknowledged. The citizenact in many other ways than bycasting votes, for example theyorganize in many ways, and theylobby. There are a number ofrelations, and that each node in thesystem influences both the othersby a number of relationships– allnodes are interrelated in a complexpattern. The details of theserelations are always underdiscussion and borders keepchanging slightly.

Currently, however, they are in a process of profound change in many countries,for several reasons including globalization, economic constraints, changingdemographics and the availability of IT. This change can simplistically but effectivelyis described by two perspectives: Omnipresent IT Organizational change

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Irimia R.,A., Vlăsceanu A., N. -269-

In figure 2, is represented in a more complex manner the e-government process and theintermediaries involved in the process. They have appeared because the Internet incombination with government outsourcing policies has given rise to new businessopportunities. They are currently working in a field where new relations are emerging,not just because of the emergence of e-business, but also because governments acrossthe world are currently in a process of change for several other reasons. New actorswill have a potentially important role because they bring to the field the importantknowledge about how to use the Internet as a social medium, not just the technicalitiesof it. They will form the social practices that will guide the policies of electronicgovernment.

The weaknesses of Internet use for e-government purposes comprise bothproblems inherent in the nature of the Net and the difficulties resulting from privateownership of telecommunications networks, as well as the initial adaptation of theinfrastructure to the needs of e-commerce. This last limits the field for e-government,which is affected by a wider range of considerations than the optimization of profit.In particular, this relates to: assignation of names and addresses, security of communications, respect for privacy and other legal principles, provision of access to the Internet and other communications networks, as well

as telecommunications security services.

4. E-REGION DEVELOPMENT – VIRTUAL REGIONALPLATFORMS

Studying the actual approach at the European level in the e-government area, itcan be identified the preponderant existence of the traditional e-government servicesand the lack of the virtual design of the development strategy at the regional level. Thenew web technologies offer support for the efficient communication among mainactors in the contemporary society, reduces the costs and increase the effectiveparticipation rate of the main regional entities and individuals (citizens and experts) inthe democratic process of the regional development strategy design. It offers also thepossibility of an iterative process for the refinement of the regional objectives andpriorities. A realistic solution in this context is the design and development of virtualplatforms, which ensures the possibility of a wider debate on a scientific and realisticbase, offered by a set of detailed and relevant indicators and various analysis andscenarios, as embedded knowledge. The interactive regional platform facilitates themanagement of the regional intelligence capital and best practices, in the benefit of theregion. It creates also the premises for a better supervision regarding theimplementation of the regional strategies, and support the process of finding the bestsolutions for fulfilling the established goals. The main processes and interactionsinvolved in the design of the regional development strategy are presented in the fig. 3.

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Electronic government–reflections over the design of a regionaldevelopment strategy-270-

5. THE INFORMATION SOCIETY AND THE REGIONAL POLICIES

For Europe's regions and regional policy, the new technologies are both anopportunity and a challenge. An opportunity because these technologies create newprospects for development, especially in the more isolated regions, and a challengebecause of the digital divides between rich and poor regions, urban and rural regions,and even within regions. Today, however, a region's competitiveness lies in itspotential for innovation and the new technologies can be an instrument for socialintegration or a source of exclusion if not available to all. Regional developmentpolicies for 2000-2006 have consequently been steered towards the informationsociety. Today, the information society is an integral part of the development programsbeing implemented under the Structural Funds and it’s contribute to the developmentof the Europe of knowledge and know-how.

Two principles underpin interventions in support of the information society:- the reorientation, allowing for exceptions of course, of structural assistance to thenew technologies (human resources, innovation, etc.) rather than infrastructure, to helpcreate the "digital reflex" that is sometimes lacking in Europe;- the consistent and structured integration of the information society into the priorityobjectives of regional policy.

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Irimia R.,A., Vlăsceanu A., N. -271-

6. CONCLUSIONS

The mutations that appeared in the modern world in all the areas demonstratethat the implementation of new technologies does not represent only the assimilation ofsome concepts and techniques, but also it states the transition to a new economy, thatof the informational society, along with a knowledge revolution. Although, in somespecialists’ opinions, the new technologies do not restructure the whole context of thesocio-economic life, guarding its magic in Silicon Valley, it cannot be denied that theinformational society made a spectacular debut, having a major impact over humansociety.

BIBLIOGRAPHY

[1]. Ake Gronlund, Electronic Government: Design, Applications and Management,Idea Group Publishing, 2002.

[2]. Muresan, M., European dimension of information society , Tribuna EconomicaMagazine No. 2/2006, Bucharest, 11 jan 2006, pag 85-88, 2006

[3].Guiding Principles for Sustainable Development of the European Continent,CEMAT, Council of Europe, 2000

[4]. The Structural Funds and their co-ordination with the Cohesion Fund (Guidelinesfor 2000 – 2006), European Commission, Brussels, 1999

[5]. European Commission Regional Policy[6]. Centre for Urban and Regional Development Studies[7]. Tratatul de aderare a României la UE din aprilie 2005

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 272-277

EMBEDDED-SYSTEM ZUR STEUERUNGLEISTUNGSELEKTRONISCHER MODULE

ADRIAN TULBURE, MIRCEA RISTEIU

Abstract: Die Tendenz für Schaltungszwecke in der Leistungselektronik istheutzutage eine Kombination aus den Eigenschaften des MOSFET’s und des Bipolartranzistorsimmer mehr einzusetzen. Diese IGBT-Bauelemente sind in der Lage hohe Schaltleistungen beiguten Wandlungsgüten mit reduzierten Steuerleistungen zu realisieren. In wieweit sich dieleistungelektronischen Wandler optimieren lassen, hängt auch vom eingesetztenSteuerungssystem ab. Für die Steuerungszwecke eignen sich aufgrund des Aufbaukonzeptesund schneller Leistungskern mit eingebauten Schnittstellen, die Microcontroller-Systeme. Indiesem Zusammenhang wird in diesem Beitrag das am Lehrstuhl für Automa-tisierungstechnikder Universität Petrosani vorhandene Embedded-System vorgestellt. Das System besteht auseinem Microcontroller, Peripherie und leistungselektronischen Modulen und wurde fürSteuerungszwecke entwickelt und im Labor getestet.

Keywords: Embedded-System, 16Bit-Mikrocontroller, Software-tools,Steuerleistung, Schaltleitung, PWM.

1. ANLEITUNG. DER 16-BIT MICROCONTROLLER.

Durch die Verfügbarkeit fortgeschrittener leistungselektronischerKomponenten: Power-IGBT, Hyper-MOSFET, Si-Cd-As Schottky Dioden ist esmöglich heutzutage leistungsfähige elektronische Wandler aufzubauen, welche sogarunter Sonderbedingungen zuverlässig funktionieren können.

Für die zugehörigen Mess-, Steuer- und Regelungsaufgaben eignet sich dieFamilie von C166-Mikrokontrollern am besten. Die Einsatzfelder vonMikrokontrollern sind heutzutage: low-cost Anwendungen (Druker, Scanner,Laufwerke), Standard-Anwendungen (Automotive, Motorsteuerungen, Messgeräte)und High-End-Anwendungen (A/D Wandler, PWM-Einheiten, CAN-Bus).

Lecturer at the University of Petrosani Ass.-Prof. at the “1 Dec.1918”-Univ. of Alba-Iulia

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Tulbure, A., Risteiu, M. -273-

1

2

3

4

5

6

7

Der Microcontroller C167 besteht aus folgenden Funktionseinheiten [1], [2]: 16-BitCPU-Kern, interner Oszillator, interner Daten- bzw. Programmspeicher (bis 128 kBFlash ROM), peripheral Event bzw. Interrupt Controller, 9 Ports, 2 Timer Einheiten, 2serielle Schnittstelle, A/D Wandler mit 16 Kanälen und 10 bit Auflösung, 4 PWM-Einheiten, 2 CAPCOM Einheiten mit mit 16 Kanälen und 4 Timer und den Watchdog-Modul.

Der 16-Bit Rechenkern besteht aus: Execution Unit mit Pipeline, 16 bit AL-Unit und folgende Systemregister: Processor Status Word (PSW), System Config(SYSCON), Adressenregister (IP, CSP u.a.) und Stack Register.

Eine Partikularität von Mikrokontroller ist bitadressierbare Speicherbereichezuzulassen und zwar:

im ESF-Register (0F100h bis zum 0F1FFh) im SF-Register (0FF00h bis zum 0FFFFh) im internen RAM /(0FD00h bis zum 0FDFFh).

2. DAS EMBEDDED-SYSTEM

Das Minimalsystem besteht aus einem C167 CR zusammen mit einerTaktquelle und Stromversorgung. Ein erweitertes System beinhaltet je nach Bedarfsowohl ein externen Speicher als auch externe I/O Peripherie. Der Adressbereich kannbis zum maximal 16Mbyte für Daten, Programme und I/O-Konfiguration, gemäß vonNeumann Arhitektur, erweitert werden.

Während des Programmablaufs holt der Prozessor die Instruktionen aus demROM und die Operanden/Daten aus dem RAM. Das Segmentation-Bit vom SYSCONsoll festlegen, wie die Adresierungsart stattfinden: segmentiert oder unsegmentiert.

Abb.1 Ansicht der Entwicklungsboard

Das Entwicklungsboard (Abb.1) ist eine Platine (160mm x 100mm) gefertigt inMulti-Layer Technik. Folgende Hardwaregruppen ergänzen die Ausstattung:

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Embedded-system zur steuerung leistungselektronischer module-274-

Spannungs-versorgungskreis (Abb.1,/1/), Schalter zum Bootstrap-Modus (Abb.1,/4/),Steckerleisten zur externen Signale (Abb.1,/7/), serielle RS232 Konverter (Abb.1,/3/),Oszillator und Reset-Kreis (Abb.1,/2/), externe Speicher (RAM oder EPROM (Abb.1,/6/)) und Jumper zur Einstellung verschiedener Modus und Funktionen (Abb.1,/5/).

Die Embedded Systemen bestehen aus dem Hardwareteil, welche schonbeschrieben wurde und aus dem Softwareteil. Für die optimale Arbeit soll dasSoftware-Packet die Entwicklungsumgebung und die dazugehörigenHilfstools/Werkzeuge beinhalten. Bei dem untersuchten System erfolgt dieMikrocontroller-Programmierung mit Hilfe folgender Soft-Werkzeuge (Abb.2) : CodeWriter – einfacher Texteditor (Textbearbeitungsprogramm) cp166 / c166 – Ansi Compiler der den Zugriff auf alle µC-Ressourcen hat. m166 – Macropreprozessor-Software, der eine QuellCode in Asembler liefert a166 – Cross-Assembler, geeignet für die untersuchte Mikrocontroller-Familie l166 – Lokator und Linker, der Objekt-Dateien von c166 oder a166 oder aus

Bibliotheken zu einem fertigen Programm bindet.

Abb.2 Kompilierung-Struktur

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Tulbure, A., Risteiu, M. -275-

srec166/iee166/ihex166 – Code-Converter, der aus einem *.out Datei einehardwarespezifische Datei zur Portierung auf einen PROM erstellt.

Die Entwicklungssoftware enthält noch ein Cross View Debugger (xfw166), der dasDebuggen von den in C, C++ oder Asemmbler geschrieben Quell-Dateien ermöglicht.Um die Peripherie nachzubilden sind unterschiedliche typsabhängige Treibervorhanden. Um die Effizienz der Programmierungsarbeit zu erhöhen, sollen alle dieseSoft-Werkzeuge zusammengefasst und per Maus-Click aufrufbar sein. So eineUmgebung mit freundlicher Bedienoberfläche steht dem Anwender unter der NamenIDE (Integrated Development Environment) zur Verfügung.

3. DER STEUERTEIL

Der Mikrokontroller besitzt vier PWM (Puls-Weiten-Modulation)-Einheiten,welche unabhängig von einander gesteuert werden können. Alle vier Einheiten werdenvia Oszillator (OSC/Abb.3) mit dem Systemtakt versorgt. Der Takt kann mittels desBits (PTIx) zusätzlich mit 64 geteilt werden.

Durch Setzeneines entsprechendenControl-Bits wird derTakt weiter an einenZähler mit zweiKomparatoren (Width undPeriod) geschaltet. Für dieAusgabe des Steuersignalsauf einem I/O-Pin(POUTi) ist das Bit PENxzuständig. Jeder Pinzwischen Pin7.0 bis zumPin7.3. hat eineentsprechendes Ausgabe-Latch. In Abhängigkeit

von seinem Zustand (Eins / Null) wird das reale PWM-Signal oder das invertierteSignal am Ausgang generiert.

Die Einheit ist mit einem Interrupt Control Register (PWMIC) ausgestattet, dervier IRQ-Bits beinhaltet, um identifizieren zu können, welche Kanal welche Interruptausgelöst hat.Über das Bit PB01 vom Register PWMCON1 (Abb.3, unten) lassen sich dieSteuersignale vom Kanal 0 bzw. 1 verknüpfen.Über das PWM Channel-Mode-Control-Bit (PMx) wird die Betriebsart festgelegt: Standart PWM (Edge Aligned PWM); Symmetrische PWM (Center Aligned PWM) Burst Mode Single Shot Mode

Abb.3 Aufbau der PWM-Einheit [3]

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Embedded-system zur steuerung leistungselektronischer module-276-

4. DER LEISTUNGSTEIL

Die Auswahl des Treibers erfolgt nach dem Ansatz, dass der Treiber in der Lagesein muss, die notwendige Steuerleistung und den maximalen Gatestrom abzugeben.In dem Zusammenhang ist es üblich die Ansteuerschaltung abhängig vom erwünschtenSchaltverhalten, Bauteilspezifikationen und Umgebungsbedingungen zu entwerfenbzw. dimensionieren. Dazu hat sich in letzter Zeit folgendes Vorgehen bewährt:

1. Messtechnische Bestimmung der Gateladung, Qg (Abb.6)2. Berechnung der Gatekapazität, Cg3. Ermittlung der Ansteuerleistung, Pg4. Berechnung des Gatestromes Ig / Gatewiderstandes Rg.

Das Applikations-Spektrum jeweiliges leistungselektronischen Bauteils lässt sich ausder unterstehenden Tabelle entnehmmen.

Tab.1 Eigenschaften der leistungselektronischen Bauteile.Eigenschaft

Komponent

Umax [kV]Imax [kA]

Strom-dichte

[A/cm3]

Steuer-param.

Steuer-block

Steuer-leistung

Schalt-geschwindigkeit

GTO 4,54

100-200 iG komplex s.gross langsam

BT 1,40,6

30-50 iB komplex gross mittel

IGBT 3,31,2

~50 uG einfach s.klein schnell

P-MOSFET 1-0,10,1-0,3

10-20 uG einfach s.klein s.schnell

Abb.4 Aufbau des Prüfstandes für die Leistungshalbleiter

Die Hauptkomponenten des Leistungskreises sind: die externe Leistungsquelle(nicht im Bild), der IGBT-Schalter (7), auf dem Kühlkoerper und die ohmische Last

8

1

2

3

4

567

9

10

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Tulbure, A., Risteiu, M. -277-

(5). Der Steuerkreis besteht aus folgenden Komponenten: 16-Bit Mikrokontroller (1)und die Treiber-Platine (2), welche über die Gleichstrom-Spannungsquelle (3) versorgtwird. Die messtechnische Untersuchung wurde mit Hilfe von Stromzangen (6),Voltmeter (9) und Trennverstärker (8). Alle Messungen wurden mit dem Tektronix-Oszilloskop (10) aufgezeichet und gespeichert.

5. MESSERGEBNISSE

Die erhaltenenMessergebnisse an derSchnittstelle zwischen denSteuer- und Leistung-steil (amAusgang des µC Abb.1 /7)sind in der Abb. 5 vorgestellt.

Die Abbildung 6 stelltden Einschaltvorgang mit

unterschiedlichenGateströmen dar. ZumSchalten muss eine bestimmte

Gate-Ladung Qg vorhandensein, welche vonsprungartigen (A) oderglätteren (B) Strömenaufgebracht werden kann.Die Einflussfaktoren für dieSchaltzeiten des IGBTs sinddie inneren Kapazitäten, dieparasitären Induktivitätenund der Gatestrom.

LITERATUR

[1] von Berg B., Groppe P.: Das grosse C167-Mikrocontroller Praxisbuch, pp.134-146, Editura Franzis. Poing 2001.

[2] Tulbure, A: Netzgespeiste ASM mit elektronischer Käfigumschaltung zur aktivenSchwin-gungsdämpfung, pp. 54-64, Editura Papierflieger. Clausthal 2003

[3] Klaus, Rolf.: Der Mikrokontroller C167, Hochschul Verlag der ETZ. Zürich2000.

Abb.5 Oszilogramm des Steuersignals an derAusgangsleiste

Abb.6 Zusammenhang zwischen dem Gate-Strom und Gate-Ladung ).Messergebnisse beim Ein-Ausschalten des Halbleiters [2]

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 278-286

EQUIPMENT USED IN PRIMING OF THE BLASTINGCARTRIDGE WITH CYPRESS MICROCONTROLLER

ARON POANTA, DAN DOJCSAR, BOGDAN SOCHIRCA

Abstract : In this paper is described a device used in the priming of the electricalblasting cartridge who supply the whole electrical priming energy. This device offers a muchbetter security compare to the present similar devices because it eliminates the human factorerrors. Also this device verifies and monitors the blasting line states and has the ability ofblocking the blasting in improper functioning conditions. The system has the possibility ofblasting line diagnosis with the state displaying. The device was conceived and tested, andsatisfies the expectations in varied working conditions like underground with explosive gases orin quarries.

Keywords : blasting cartridge, programmable logic device, explosive areas,CYPRESS-PSoC microcontroller.

1. INTRODUCTION

The devices used for the priming of the electrical blasting cartridge must to supply,in the blasting network, the whole electrical priming energy. The device’s powersupply can be the electrical network, an electrical generator or a battery. The necessaryenergy for the blasting network is supplied from capacitors. The capacitors takes thenecessary energy from a single power supply and delivers in a very short time(milliseconds) in the blasting network. Taking into consideration the consequences,with catastrophic effects, witch can appear in the improper working context for thisdevices, by standards are established the exactingness for the equipments. Thisexactingness refers, in function of the environment nature (on the ground,underground, dry or humid environment, explosive gases etc), to the level oh thedelivered electrical impulse, the charged voltage, the current impulse duration for the

PhD. Professor at the University of Petrosani PhD. Lecturer at the University of Petrosani Assistant Eng. at the University of Petrosani

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Poanta, A., Dojcsar, D., Sochirca, B. -279-

priming of all the cartridges form the network, an other standards referring to theenvironment conditions an priming control, the undesirable blasting avoidance etc.

The extant equipments achieves this standards by a series of mechanical blocksby keys or buttons witch involves a commands succession made by human operator.Besides the involve of the human factor the extant equipments not achieves an integritycontrol of blasting lives and not ensures a charged voltage according to the blastingcircuit resistance. The charged voltage is pre established in function of the acceptedmaximum value for the blasting circuit resistance and can’t be charged in function ofthe real resistance.

All this constituted the premises for this device synthesis witch removes the mentionedaspect and increases the safety level for the priming of the electrical blasting cartridge.

2. THE SELECTING OF THE PRIMING CIRCUIT PARAMETERS

The necessary energy for priming the electrical blasting cartridge is suppliedfrom a capacitor, witch must to be charged with a voltage witch ensures a safe impulselevel for priming. The estimate of the energy amount witch is delivered to thecartridges was made starting from the equivalent diagram (figure 1) witch contains thecapacitor C charged an a voltage U (from a proper circuit) witch, at the startingblasting command, delivers the accumulated energy to the blasting network simulatedby a equivalent resistance R.

Fig. 1. The equivalent diagram of the priming circuit

The equivalent resistance R is given by the cartridge resistance RC, the numberof the connected cartridge NC and coupling cable resistance RCABLE in the followingexpression :

CABLECC RR*nR (1)The charged energy in the capacitor (E) depends on the capacity C and the

charged voltage U :

2CUE

2

(2)

The delivered current over the blasting network is obtained from the nextexpression, obtained from the II Kirchhoff on the equivalent circuit.

0idtC1i*R (3)

RCt

e*RUi

(4)

C R

iK

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Equipment used in priming of the blasting cartridge with cypress microcontroller-280-

The delivered energy from the capacitor at the resistance unit ( the specificenergy WS) in the blasting circuit at a complete capacitor’s discharge will be:

ΩWs

RE

2RCUdte*

RUdtiW

2RC2t

2

2

2S (5)

This equation indicates that the blasting circuit resistance can’t exceed acertain limit value given by the necessary energy for a single priming.

The capacitor, with equivalent capacity C=33 μF/1200V, is achieved byconnecting in series three capacitor with value 100μF/400V. To not overloading thecapacitors, the maximum charging voltage was limited to 1100V.

For the medium intensity cartridges the capacitor discharging time is limited toduration t1=4ms, after this the line must to be setting in short-circuit.

The current delivered in circuit in this interval can not decrease under theadmitted value:

1,9AI*1,25I SA (6)where IS=1,5A is the current value for a certain priming.

The maximum value of the circuit resistance is founded from the expression(4) on condition that for t=t1=4ms, the current in the circuit is equal to current IA:

max

1 21,121

AI RRt

eRUe

RU

C

(7)

In this way was obtained the expression for calculation the maximumresistance

21,121R*ln*RR*6,31 maxmaxmax (8)It was obtained the calculated value of Rmax ≈423Ω

By limiting the maximum resistance to the value R=400Ω, the current I0, at themoment t=0, will be :

2,75ARUI0 (9)

But the resistance R depends on the number of the cartridges connected incircuit and, in function of this, must to computing the charging voltage. Thisdependence will be determined from the necessary energy at the resistance unit witchmust to be, for the medium intensity cartridges at value WS=16mWs/r, and for a certainpriming at value:

Sc W*1,4W (10)This value was achieved from expression (5) for t=t1=4ms. The capacitors

energy is in the fallowing form:

Re33 10*8210*4

2c 1

2RCUdtiW (11)

The charging voltage depending on the resistance is show in the followingexpression :

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Poanta, A., Dojcsar, D., Sochirca, B. -281-

)eC(1

W*R*2U

R10*8

C3

(12)

The diagram of the function U=f(R) traced in MATLAB is in the shape represented infigure 2:

200

400

600

800

1000

1200

1 26 51 76 101 126 151 176 201 226 251 276 301 326 351 376

Fig. 2. The dependence U = F(R)

From the diagram can be noticed that the curve U=f(R) is not linear forR<30Ω, but, for R>30Ω, the curve is almost linear and can be approximated by astraight line described by the equation:

400)2,4(R1100U (13)If the voltage is computed with this equation (13) then the values are almost

equal comparatively with the values computed with the exponential equation (12). Thedeviations are greater for R<30Ω, but the values are higher, even for this domain, thenthe exponential equation values, and this involves limit values lower than the specificenergy. The linear equation approximation made possible the values computing by amicrocontroller.

3. THE HARDWARE STRUCTURE.

For the synthesis of the device bloc diagram was identified the technicalfunctional specifications. Besides the specifications stipulated by standards was takeninto consideration, further functions like: diagnosis, safety running, displaying someinteresting parameters and charging its bordering in the established limits. For theinterface between device and user must be inserted a user control block, which ensuresthe device control by the user.

The start/stop key ensures : the connecting of the charging power supply, thepower supply of the electronic control block and the block for the constant currentinjection in the charging network for measuring the blasting circuit resistance.

The dialogue key allows the starting of the diagnosis menu and finding theuser command. The blasting key validates the blasting command, allows thetransmission of the blasting command to the initiating explosion block and then

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Equipment used in priming of the blasting cartridge with cypress microcontroller-282-

activates the line’s short-circuit block (after 4 ms, time computed by the electronicblock).

The device must ensure the measuring of the blasting line resistance, thechecking of the limits bordering (maximum 400 Ω), the power supply checking (notmore than 12 V), the computing of the charging voltage in function of the circuitresistance and displaying this values and/or some important messages (on analphanumeric display). Beside this, the device must ensures the control of the constantcurrent generator, the capacitors charging control, the initiating control and after 4 msthe line’s short-circuit control.

On the ground of this specifications was synthesized the device’s block diagram (fig.

3).

Fig. 3. The device’s block diagram

The user’s control block (BCU) ensures the interface between user and device.This block allows the user’s equipment control by the start/stop button (P/O), thediagnosis button (BD) and the button for the blasting priming (BAD). The powersupply (SA) lie in a 12 V storage battery and a circuit which allows to charge it fromthe electrical network. The electronic control block (BCE) administrates the wholedevice working and monitories it’s proper running. This block lies on the CYPRESSCY8C29466 microcontroller and the auxiliary circuits.

The displaying of the measured parameters and the afferent messages isachieved by a displaying block (BA). The displaying block lie in the integrated circuitAC162B which contains in its structure the control circuit (KS0066), a driver and theLCD display with two symbol’s lines and 16 symbols on the line. The measurement ofthe line resistance is achieved by injecting in the line a constant current, obtained fromthe generator circuit of constant current (CGCC). The capacitors charging with theproper voltage for cartridge priming is achieved by a capacitors charging circuit (CIC)controlled by a microcontroller using a control block for the charging circuit (BCCI).

LINIEP/O

BD

BADBCU

SA SS

BCE

ABCCI/CSL ASS

MTACD/FAD

AACGS

MR

BA

D RS E R/W

CICADCCSL

CSL

CGCC

MTI

BCCI BADCIC

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Poanta, A., Dojcsar, D., Sochirca, B. -283-

The CIC back contains, in addition, a voltage divisor witch samples the capacitorscharging voltage, applied on the analog input RAO/RNO of the microcontroller. Thecartridge blasting is achieved by the priming blasting circuit (CAD), controlled by amicrocontroller, but only in the case of the parameters bordering in the establisheddomain and of the proper positioning of the blasting priming key (BAD). The line’sshort-circuit after 4 ms since the blasting command, is achieved by the line’s short-circuit circuit (CSL). The two circuits have a similarly structure and contains the powercircuit achieved with thyristors and the control circuit. On the ground of the blockdiagram was achieved the main electric diagram and then in ORCAD, the printedcircuit board (PCB).

4. THE DEVICE’S SOFTWARE

For the software conceive afferent to this device was taken into considerationthe technical and functional specifications and the device architecture. The workingalgorithm, based on the specification, is concise described by the logic diagrampresented in figure 4.

The starting command is given from the P/O button witch through BCUgenerates the signals ASS (continuous power supply) and ABCCI/CSL (power supplyof the BCCI/CSI block).Through the BD key can be selected either the diagnosis or themain running made witch transmitters to the microcontroller the CD/F signal(diagnosis/ main running command). In the diagnosing made appears on the display theafferent welcome message, following the displaying of the blasting commands number.Here is achieved the battery voltage measuring (MTA signal) and the measuring of theblasting line resistance (MR signal) using the A/D converter inputs from themicrocontroller (RA2/AN2 input and RA1/AN1 input respectively). The measuredvalues are displayed if they are in the pre-established domains or is displayed the errormessages like: “DESCHARGED BATTERY”; “BLASTING LINE BREAK”; “TOBIG RESISTENCE”, etc. In the main warming mode is verified if the parameters arein the proper domain, is given the command for charging the capacitors (CI), iscalculated the charging voltage and is verified the computed charging voltage, and,after this voltage attains the desired value, is displaying the message “WAIT FORINITIATING” to inform the user that the priming command is ready. The primingcommand is given by the BAD block from the BCU block witch generates the ADsignal (blasting initiating) witch evolves for the microcontroller to generate thecommand signal for blasting initiating CAD. This signal commands the BAD block todeliver in the line the capacitor’s voltage. After 4 ms, the μc generates the CCSLcommand to the CSL circuit for the line short-circuit.

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Equipment used in priming of the blasting cartridge with cypress microcontroller-284-

Fig. 4. The diagram of the working algorithm

Fig. 5

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Poanta, A., Dojcsar, D., Sochirca, B. -285-

For the undesirable blasting commands avoidance, the CAD command isinactive if the BAD key is not in the proper position. It was conceived the runningalgorithm and the programs written in the microcontroller’s assembly language for theMPLAB software. In the next part of the paper is presented the main program andsome relevant procedure used in the running algorithm. The MAIN program respectsthe algorithm presented in figure 4.

Of course, was conceived the others routines like : displaying the all messages,testing the BD key position, bordering in the limits testing, ASS, ABCCI/CSL,ACGCS signals generation, BCU testing, short-circuiting the line, blasting countincrementing etc. The equipment (device) was achieved and tested in the labconditions.

5. CONCLUSIONS

The device avoids the improper blasting commands produced by the humanoperator. The capacitor’s charging voltage hat not a pre-established value it iscomputed in function of the blasting circuit resistance. The blasting initiatingcommand can not be started if the parameters of the blasting line, the voltage of thepower supply, the charging voltage, etc, are not in the pre-established limits.

There are displayed continuously: messages witch informs about theequipment state, the values of the interesting parameters, etc. The device was achievedand tested in the lab condition and the results confirms the validity of the theoreticalgrounds. The achieved functions and the high safety level justifies the device’susefulness in the afferent industries.

BIBLIOGRAPHY

[1] Milonir B. - Bazele teoretice şi practice ale sensibilităţii electrice a detonatoarelorcomerciale şi conceperea unor surse optime pentru detonare.

[2] Pop E, Leba M. - Microcontrolere şi PLC, Ed Didactica si Pedagogica, Bucuresti,2003

[3] Poanta A, Pătrăşcoiu N.- Circuite şi echipamente electronice în industriaminieră, Editura Didactica si Pedagogica, Bucuresti, 1997

[4] Tat S. Matei I. Fissgus K. Îndreptar de tehnica securităţii în minerit.[5] Thum W. Procedee moderne de împuşcare în cariere şi probleme de securitate a

muncii în diferite ţări.[6] xxx CYPRESS CY8C27xxx, CY8C29xxx Data sheets.[7] xxx Blaster hand book Cleveland,Ohio,ISEE USA 2000[8] xxx Die electrische Zungung prosp Dynamit Nobel

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 286-291

EXPERIMENTAL MODEL FOR PREDICTIVE CONTROLOF THE PUMPING AGGREGATES USED FOR WATER

DRAIN IN ROŞIA MINING PIT

POPESCU LUMINIŢA, GROFU FLORIN, POPESCU MARIAN**

Abstract: The preventive and predictive maintenance allows immediate trackingdown, locating and identifying the fault or the broken piece. In this way, it is possible to planthe stop and minimally reduce the time needed for repairs. The costs for preventive andpredictive maintenance recorded in the same time interval will be smaller.

Key word: preventive, predictive, vibration analysis, acquisition system

1. Introduction

The preventive and predictive maintenance allows immediate tracking down,locating and identifying the fault or the broken piece, also the calculus of the time ofwork in safety conditions of the machine. In this way, it is possible to plan the stop, toprepare the intervention team, to command necessary machine parts and to minimallyreduce the time needed for repairs. The costs for preventive and predictivemaintenance recorded in the same time interval will be smaller.

The mail causes of the vibrations in the industrial equipments are:- bearing damage;- dynamic lack of balance of the wheels;- wheels leave their center;- damaged gearings;- resonance because of the: non corresponding rigidity; not respected work technology; wrong design;

- closing of the electric circuits through bearings;

PhD professor at the University Constantin Brancusi Tg-Jiu lecturer at the University Constantin Brancusi Tg-Jiu

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Popescu L., Grofu F., Popescu M. -287-

- transmitted vibrations;- damaged couplings;- increased temperature in bearings because of inefficient cooling systems;- liquid flow through pipes.

In figure 1 arethe faults which appearmost frequently to theindustry dynamicequipments.

2. EXPERIMENTAL MODEL

Predictive detection of the faults in the pumping aggregates from the Roşia deJiu Mining Pit has been made through vibration analysis in the bearings of theentrapment engine and also in the pump’s bearings. To build such a system, first anexperimental model was built from an entrapment engine and an axel with two ballbearings, a new one and one with obvious damages. The vibrations are observed withpiezo electric sensors whose output signal is applied to a signal conditioning circuit tobe then transformed in digital signal using an acquisition system. The digital signal istransmitted after that to a calculus system to be processed in order to obtaininformation regarding the state of work of the observed system. The structure of theexperimental model is the one presented below.

where:1- computer orcalculus system;2- acquisition system;3- conditioning system;4- vibration sensor;5- ball bearing which istested;6- entrapment engine;7- module for enginecommand.

2.1

1

2

345

6

5 4

7

Fig 2. Structure of the experimental model

Damaged ballbearings

Lack ofbalance

Couplingsoff centre

Hightemperatures

Damagedreducers

Fig.1 Fauts met at equipments

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Experimental model for predictive control of the pumping aggregatesused for water drain in roşia mining pit-288-

Requirements for the system:

- In order to be able to analyze a high range of frequencies, first of all thevibration sensor must have a high range of working frequencies, which is found atpiezoelectric sensors. Because the conditioning circuit is simple, this type of sensor isideal for the system. When a wave is received, it is important to know that most of thetimes, high frequency information is more important. When an acceleration signal isintegrated to obtain information about movement, the response in frequency decreasesa lot as level, and lot of small variations of the signal cannot be analyzed. The study ofthe movement is difficult at high frequencies, because in most cases, that is the rangewhere signals for damaged ball bearings appear.

That is why the acceleration is measured to determine different parameters.-the signal conditioning circuit must be a simple circuit, but which allows

initial processing, like adjustment, amplifying – which are necessary to the sensor’sconnection to the acquisition system, upon the signal received from the sensors.

-the acquisition system is the most pretentious part of the monitoring system.Because of the rough environmental conditions, and also the big distance between thesensors and calculus system (hundreds of meters) it is necessary that the acquisitionsystem to be placed as close to the sensors as possible. And it also must be robustbecause it is an industrial environment.

It is necessary that a high frequency spectrum cam be analyzed (of maximum ahundred kHz). To be able to do the Fourier analysis, a very high speed of acquisition isrequired (hundreds of thousands samples/second), and also a great number of samples.

For the experimental model two ball bearings were used on a single 6308C3row, mounted at the heads of an axel activated through a belt by an alternative currentengine, with the revolution of 1400 rotations/minute (figure 2). The vibration sensorsare of MAQ36 type, one for each ball bearing.

For the experimental model, the signal conditioning circuit was mounted closeto the mechanical part, and because of that, we took care that ground loops can’tappear. The acceleration sensors can, for that reason, be mounted in direct contact withthe exterior clothing of the bearing, without adding isolating materials which wouldhave decreased the natural mounting frequency. To reduce the tribo-electric effect, thechosen signal cable was shielded and fixed so in doesn’t vibrate due to the mechanicalparts. After calculating the frequencies which may appear as a effect to damagedcomponents of the bearings, the accelerometers and way of mounting them waschosen, taking into account the real working conditions of the system which will beused in Roşia Mining Pit. Because in case of the real system the distance between theaccelerometers and conditioning circuit is high, we used a charge amplifier for thesignal received from the sensors. After planning this circuir, its simulation in Pspice,we effectively buit it.

For an exact analisys of the acquisitioned signals, a high acquisition speed wasrequired, which implied high communication speed with the process computer. As thedistance between the acquisition system and the process computer was over a hundredmeters, a very complicated communication interface had to be planned and realized.

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Popescu L., Grofu F., Popescu M. -289-

Because the analysis of the vibrations in the bearings of the pumpingaggregates is neither continuous, nor in real time, we adopted the solution of a highconversion speed and the possibility of local saving of an important number ofsamples. The results of the conversions are then transmitted at demand to the processcomputer through the serial interface RS485, with a 38400 bits/second transfer rate.

After the studies regarding the analogical-digital converter types and of theavailable high speed microcontrollers, the acquisition system was completed. It isbased on the high speed microcontroller, DS89C420, produced by Dallas, and also theanalogical-digital converter MAX120, with a conversion speed of up to 500.000samples/second.

In order to reach acquisition speeds of over 400.000 samples/second, we gaveup generating the clock impulses needed for the converter, which was connected to aclock signal with a 6MHz frequency, from an external quartz oscillator. In this way,the conversions are continuously executed, the result of the previous conversion beingavailable during current conversion. The microcontroller only saves the results of theconversions. For reception and visualization of the data, a graphical interface was madein LabView (figures 3 and 4):

Fig. 3 The signal corresponding to a good ball bearing with the detail of a zone

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Experimental model for predictive control of the pumping aggregatesused for water drain in roşia mining pit-290-

After the acquisition, a number of over 500.000 samples resulted for eachchannel. To reduce the time for transmission in case of errors, the resulted sampleswere divided in 8 data packages, each package being separately transmitted andverified to be correct. After correct receiving of all data packages and creating a signaldata package on the computer, the numerical analysis is performed upon the data.

Fig. 4. The signal corresponding to a damaged ball bearing with the detail of a zone

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Popescu L., Grofu F., Popescu M. -291-

3. CONCLUSIONS

After the numerical processing of the data through filtering and fast Fouriertransform, the specters for power in figures 3 and 4 were obtained, corresponding to agood ball bearing and to a damaged one.

From the analysis of the two power specters, it results that we have acomponent given by the rotation frequency of the axel (f0=28 Hz), which hasapproximately the same value for the two ball bearings. We observe that for the goodbearing there are other spectral components, but smaller, and for the damaged bearingthere are spectral components even higher than the fundamental component, f0. Thesespectral components appear at lower than f0 frequencies and at higher ones.

Taking into account the information presented above about the causes ofvibration appearance, after the calculus is made, we could say that in case of damagesin ball bearings, there may appear spectral components at frequencies of 10 Hz(damaged cage), 26 Hz (axel rotation), 80 Hz (damaged ball), and also on otherharmonics of the fundamental. Also, lower frequencies than f0 appear in mechanicalclearance in the gearing.

Analyzing figure 4, for the damaged ball bearing we observe the existence inthe power spectrum of the components with very close frequencies to the onescalculated theoretically, but also of other spectral components. Only on the basis of thetheoretical analysis of the observed data, the following conclusion can be drawn aboutthe damaged ball bearing: has its cage very deteriorated (visible with the naked eye),has the exterior trajectory and one of the balls with faults and a powerful off centeringand mechanical clearances in the gearing.

An exact diagnosis can be made through the practical study of a big number ofball bearings with only one fault, study of the resultant spectral components andcreating a data base corresponding to that type of gearing and ball bearing.

BIBLIOGRAPHY

[1]. The automation and dispatching of the water evacuation process from the lignitemining pit EM Roşia. Research Contract no. 276/C/2002, National Lignite Company of Oltenia.

[2]. Grofu Florin. Acquisition systems and numerical processing of the signals for thecontrol of the industrial processes. PhD thesis 2007.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 292-297

EXPERIMENTAL MODEL FOR MONITORING APUMPING AGGREGATE USED FOR WATER DRAIN IN

ROŞIA MINING PIT

POPESCU LUMINIŢA, OLARU ONISIFOR*, GROFU FLORIN

Abstract: In mining pits coal basin appear different problems because water resultedfrom infiltrations and rain. To drain water there are used pumping aggregates. In order to reducethe electrical energy waste, we first need a correlation between the energetic parameters and thetechnological parameters. The functional correlation of the parameters can be realized through acomplex informatics system, which assumes data acquisition, process control and elaboration ofcommands.

Keywords: electrical energy, informatics system, data acquisition, process control .

1. INTRODUCTION

In lignite mining pits from Oltenia’s coal basin appear different problemsbecause of the high amount of water resulted from infiltrations and rain.

To drain these amount ofwater there are used pumpingaggregates whose number dependson the area of the pit and of theestimated quantity of water from thatpit. In figure 1 there is a view of ajomp (water collector basin).

In order to reduce theelectrical energy waste, we first needa correlation between the energeticparameters (absorbed currents,power factor - cos φ etc) which

PhD professor at the University Constantin Brancusi Tg-Jiu lecturer at the University Constantin Brancusi Tg-Jiu

Jompcolector

Pumpingaggregates

Local acquisition system,communication module

Fig. 1. Jomp collector (collector basin)

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Popescu L., Olaru O., Grofu F. -293-

characterize the electrical engines which operate the evacuation (drain) pumps and thetechnological parameters (water level in the collector basin, warning level of the waterin the basin, clogging level, depressurization from the breathe in column of the pumps,pressure from the breathe out column etc.).

The functionalcorrelation of the parametersabove (and others) can berealized through a complexinformatics system, whichassumes data acquisition,process control andelaboration of commands. Infigure 2 and 3 there are

presented the quantities which must be taken over by the acquisition system.With the data presented, this experimental

model proposes the following objectives:1. performance of the pumps in

automated regime considering thequantity of water to be evacuated;

2. monitoring the energetic regime offunctioning for the electrical engineswhich operate the pumps;

3. control of the technical state of thepumping aggregates.

1.1. Performance of the pumps in automated regime

At this point it has been followed the performance of the pumps with the waterlevel in the collector basin. For this, we measured:

1. water level in the basin – h1[m], clogging level in the basin – h2[m];2. warning level (defined as minimal level of the water in the basin at the breathe

in of each pump) h3 [m]3. depressurization in the breathe in column of the pump 1 p11[bar];4. depressurization in the breathe in column of the pump 2 p12[bar];5. pressure in the breathe out column of pump 1 p21 [bar];6. pressure in the breathe out column of pump 2 p21 [bar];7. evacuated volume measured on the breathe out column of pump 1 Q1[mc/h];8. evacuated volume measured on the breathe out column of pump 2 Q2[mc/h].

To realize these objectives we need a data acquisition system at the level of thepumping aggregates (electric box) and another acquisition system at the level of theelectrical house, which takes over and processes the data and transmits them to thedecisional units.

h1h3h2

clogger

referencelevel

Fig. 3. Simplifiedrepresentation of a jomp

Fig. 2. Simplified representation of pumping aggregates

Electricengine 1

Pump 2Pump 1 P11

P21

P12

P22

I1, U1, cos φ1,ΔξM1

I2, U2, cos φ2,ΔξM2ΔξP1

ΔfP1

ΔξP2

ΔfP2

Electricengine 2

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Experimental model for predictive control of the pumping aggregatesused for water drain in roşia mining pit-294-

1.2. Monitoring the functioning regime

At this point we try to obtain a maximum energetic effective power at thepumping aggregates. For this, we measured:

1. absorbed current of the engines which operate the pumps, i1 [A], i2 [A].2. supply voltage of the operating engines U [V].3. phase difference between current and tension, cos φ.These parameters are measured, administrated and transmitted to the process

computer by the acquisition and protection module SEPAM 1000. Also, we identifiedthe state of the switching equipments: switches, separators, fuses, contractors:

- separators: general separator , interrupt separator, motive separators- station general interrupt ,motor fuses: (at both operating engines)- void contactor: Cm1, Cm2 (at both operating engines).- contact – tension presence, with logical „1” for presence and logical „0”

for absence, state of protections. Also there are monitored the environmental conditions with the following sensors:

1. temperature sensors inside electric box2. temperature sensor for exterior temperature-initializes the anti freezing regime3. sensor level for precipitations.

2. DATA ACQUISITION SYSTEM

The general presentation of the data acquisition system and the module inwhich the informatics application is structured is presented in figure 5.

The system for acquisition and control is based upon three levels:

Level 1 – Local panel (the cofret near the pumps)

At this level there are the field equipments responsible with the acquisition ofthe main analogical signals. So Real-Time Fieldpoint (RT FP2015) will take over theanalogical signals (4..20mA) for flow, pressure, depressurization, level, signals whichwill be numerically converted on 12 bits and transmitted to the process computer fromthe electric house. Also, it has 16 digital output channels and 16 digital input channelsused for different operations at the level of the pumping group. The digital inputs readthe state of the off, on and other buttons, which will be used after in the data base tosee the working profile of that pump.

In this panel is also positioned the vibration board, which takes over 4 signalsof vibrations (2 pumps and 2 engines) in a buffer, with a frequency till 50kHz. Thesesignals are memorized in the board memory and after that are transmitted at the processcomputer’s (which is in the electric house) demand for processing. It was decided thatthe board to be placed close to the vibration sensors, because the vibration signal canbe easily be perturbed through its analogical transmission at distance.

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Popescu L., Olaru O., Grofu F. -295-

Level 2 – Electrical house

At this level, the process computer is positioned. It will communicate with thecomputer at the dispatcher through radio communication system, using the TCP/IPprotocol.

The process computer from the electrical house is configured as master, whichmeans that it must function continuously for process administration. In the situationthat the computer does not work from various reasons, the process functions arerealized manually. At this computer there are connected through a 5 channel switch thefollowing equipments: the SEPAM, the radio antenna and the Fieldpoint (FP 2015which is placed in the electric box near the pumps). At this computer is also connectedthrough a RS485 port the 4 channel acquisition board of the vibrations which is placedin the electric box near the pumps. The process computer in the electrical house (NIPXI RT8187) is a product of the National Instruments, built especially for real timeapplications and so, besides the hardware configuration for the industrial environmentit disposed of an operating systems with powerful real time facilities. It is notscheduled to operate with monitor within the application, but it has a video board and amonitor can be attached for testing.

At this computer there is another acquisition and control board, made withmicrocontroller, placed in the electrical house, and connected through a RS485 portwhich takes over the digital signals from the states of the fuses, states of the contactors,and also it controls the on and off states of the two engines of the pumps.

With the help of the screen, the good function of the whole assembly is testedand also, the sensors are calibrated through software, after the technological(electronic) calibration. All the data processing is made at this level with the purpose ofhaving a smaller number of octets which must be sent to the dispatcher, and so thecommunication time to be reduced. In this way, the gained time is used for morecomplex processes at the level of the process computer and in the same time, thereliability of the communication with the dispatcher is increased.

Level 3- Dispatcher

This level is represented by the computer in the dispatcher room, the computerwhich is connected through radio communication system with the equipments in theelectrical house of the pumps (level 2). At this computer are also connected directlythrough the RS232 serial port the acquisition board built as a core with microcontrollerwhich takes over the signals from the precipitation transducer and the environmenttemperature transducer. These transducers have been placed at the dispatcher level tohave valid global information in the whole pit. At the present moment, at thedispatcher, there are presented as a monitoring application, all the quantities measuredat the level of the whole application.

The computer at the dispatcher is organized as client for the computer at level2, which is the process computer in the electrical house. In this way, we give a higherimportance to the process, and the dispatcher can connect asynchronously to theprocess computer to obtain data, but the controlled process is prior.

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Experimental model for predictive control of the pumping aggregatesused for water drain in roşia mining pit-296-

Fig. 4 The structure of the acquisition and control system

3. CONCLUSIONS

1. The main interaction of the operators with the automated process is throughthe computer from the dispatcher. There is a graphical interface organized under a veryintuitive synoptic scheme. With the help of the interface is presented the wholeinformation received from the sensors.

2. Through monitoring the value for the water flow for a pump by thedispatcher, conclusions may emerge about the increase of the pump’s usage, or thatpump 2 on the same column was started. Also, the decrease of water flow can becaused by the clogging in the pump.

Electrical house>>Pumping group-level 2

Communicationantenna Switch 5

channelsETHERNET

Instrumentationcomputer

NI PXI RT8187

SEPAM Acquisition boardwith microcontroller

for engine control

RS 485

Dispatcher-level 3

Switch 5 channelsETHERNET

Communicationantenna

Acquisition boardwith

microcontroller

Precipitation andtemperature

sensor

RS 485UTP

Local panel>>Pumping group-level 1

FP 2015 FP-AI-100 FP-AI-100 FP-DI-301 FP-DO-401

RS 485Acquisition boardfor vibrations

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Popescu L., Olaru O., Grofu F. -297-

3. In case that the pump is stopped and we have breathe out pressure, it meansthat the pump can be started only by the opening of the upstream vent. Otherwise, itmust be started through manually input of water.

4. The level information is used by the operator to periodically calibrate. Thisthing is used because of the fact that the position of the level transducer isn’t fixed (thearchitecture of the jomp is modified, the height of the sorb is modified, the pumpingsystem is moved into another jomp) and the initial calibration is invalid. In this way,the dispatcher can periodically introduce a zero reference (reference valid only at thattime) and after that to follow the increases and decreases of level comparing to thatreference.

5. Using the information from the precipitation transducer, more pumps can bestarted with anticipation so that the increase of the level isn’t waited and after that thepumps to start.

6. Using the information given by the temperature sensor from the cofret, theheating installation is started to maintain the temperature in the cofret at low values, forthe components to function.

7. Using the information given by the environment temperature sensor from thedispatcher, the anti freezing regime for work can be started and it assumes starting thepumps at some time intervals, function of the temperature of the environment to avoidtheir freezing.

BIBLIOGRAPHY

[1].Popescu L., Olaru O., Vulpe I., Grofu F. The automation of the water evacuationprocess from the lignite mining pit. 5th European Conference of Young Research and ScienceWorkers in Transport and Telecommunications, 23 – 25 June 2003, Zilina, Slovak Republic.

[2].Popescu L., Olaru O., Popescu M., Grofu F., Gidei G., Pumps function andelectrical motors monitoring with vibrations transducer. Proceedings of 5th InternationalCarpathian Control Conference ICCC’ 2004, Zakopane Poland May, 25-28, 2004, pag.641-646.

[3].The automation and dispatching of the water evacuation process from the lignitemining pit EM Rosia. Research Contract no. 276/C/2002 , National Lignite Company ofOltenia.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 298-305

FCC MODEL PREDICTIVE CONTROL

CRISTINA POPA, CRISTIAN PATRASCIOIU

Abstract: The fluid catalytic cracking Unit (FCCU) has a major effect on profitabilityof on oil refinery. The FCCU is difficult to model well due significant nonlinearities andinteractions. The purpose of this study is to develop a controller based on model predictivecontrol algorithm. The paper is structured in four parts: the structure of the process, themathematical model, the algorithm MPC for FCC and results.

In the first part of this paper is analyzed the catalytic cracking process where areidentified the subsystems of process associated and the interaction between this subsystems.The model is essential element of an MPC Controller. The second part of this paper containsdynamic and steady state elements of modeling for each subsystem that was emphases withinanalysis process structure. The model predictive control was developed in Matlab using theMPC block from Predictive Control Toolbox. In last part of this paper the authors presents theresults of the simulation. The simulation results reveal a superior behavior when the modelpredictive control is used on the FCC.

Keywords: kinetic, cracking, modeling, FCC, simulation.

1.INTRODUCTION

The fluid catalytic cracking (FCC) unit is one of the most important andcomplicated process in the petroleum refining industry. The complexity of the processfrom the point of view of modeling and control is determined by: i) strong interactionsbetween the reactor and regenerator; ii) large degree of uncertainty in the kinetics ofthe cracking reactions and catalyst deactivation by co*ke deposed in the riser reactor;iii) uncertainty co*ke burning process in the regenerator.

Process structure of the catalytic cracking includes next subsystems: reactor,regenerator, preheating furnace (V. Marinoiu, 1992).

Assit.Eng. at the Petroleum – Gas University of Ploiesti Prof., Ph.D. at the Petroleum – Gas University of Ploiesti

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Popa, C., Patrascioiu, C -299-

The reactor represents the principal element of the catalytic cracking plant.Because the modeling of the reactor is very difficult, the authors propose thedecomposition in three subsystems (C. Popa, 2004).

This are:i) The interfusion nod subsystem, located at the de base of the riser, here the

fresh gas oil is brought into contact with the hot regenerated catalyst, whichleads to the vaporization of the gas oil. It assumed that the vaporization ofthe feed is instantaneous.

ii) The riser subsystem is a vertical standpipe 25-40 m in length. All crackingreactions take place in riser over a short time 2.5 s. These reactions areprimarily endothermic.

iii) The reactor-stripper subsystem, located at the top of the reactor, asubsystem that realizes the catalyst separation from the feed stock vaporsand the reaction products.

The regenerator is a large cylindrical vessel, where the co*ke deposited on thecatalyst surface as result of the cracking reactions is burned off using air. Air enters theregenerator through an air distributor located at the bottom of the regenerator.

2. MATHEMATICAL MODEL OF THE FCC UNIT

In order to obtain the mathematical model of the reaction block, eachsubsystem was treated in a separate way (Pătrăşcioiu C, Popa C., 2004).

The interfusion nod

The model of the interfusion node is represented by a heat balance in thesteady state regime (Ali 1997). The temperature of the interfusion node Tin is calculatedwith the relation:

pmpmppcatcat

in CQCQT 1 mpvapmppmpmpregpcatcat QHTCQTCQ . (1)

The riser subsystem

The mathematical model of the riser subsystem is structured in the nextcomponents: kinetic model, material and heat balance.

Kinetic model. The elaboration of mathematical model of riser requiredfrom the author’s part an action for analytic and selection of kinetic modelspresented in literature. Taking into account the performance criterion, it waschosen the Weekman kinetic model, for the total description of the overall. Therates of the three reactions from kinetic diagram are definition on these relations:

233

22

211

C

B

A

YkrYkrYkr

. (2)

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FCC model predictive control-300-

Constant rates reaction k1, k2, k3 are dependent for base material quality, risertemperature, activity equilibrium catalyst and condition operating.

Material balance. The riser is considered a tube reactor with a totaldisplacement operated in an adiabatic regime. The material balance equationshave the form

2A3B2

v

C

B22A1

v

B

2A31

v

A

Y*kY*k*U1

dzdY

)Y*kY*k(*U1

dzdY

Y)kk(*U1

dzdY

. (4)

where Uv represents vapor’s rate.

Heat balance .The heat balance lengthways riser is represented by differentialequation

pcatCcatRpaburCaburRpACAYQrAQ1rΔH

dzdT

mp

(5)

where AQ is raw material, BQ - gasoline mass flow, catQ - catalyst mass flow, aburQ -steam mass flow.

2.3. The reactor -stripper subsystem.

The mathematical model of the reactor stripper subsystem is based on the hypothesisof the perfect mixing. The dynamic model has two components: the material balance associatedto the co*ke deposed on the catalyst and the energy balance in the strippers:

R2catr1catR

s TQTQdt

dTW ; (6)

2cocs2cat1cocs1cat2cocs

s CQCQdt

dCW , (7)

where Ccocs1 mass fraction of co*ke on spent catalyst; Ccocs2 mass fraction of co*ke oncatalyst in separator; Ws – holdup catalyst in separator.

2.4. The regenerator model

The authors adapted the model developed by Erazu, model that treats thematerial balance associated to the co*ke, the material balance associated to the oxygenand the energy balance (Erazu ,1978).

The model is sufficiently complex to capture the major dynamic effects thatoccur in an actual FCCU system. It is multivariable, strongly interacting and highlynonlinear. The model is implemented in Matlab (SIMULINK) programming languageand was used for the study of different operating regimes induced both by design

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Popa, C., Patrascioiu, C -301-

changes and by changing operation strategies but also for investigating which controlstrategies may by implemented.

3. MPC FOR THE FCC

The catalytic cracking process is complex both from modeling and from thecontrol point of view. The FCCU is difficult to control due to the nonlinear behavior,the strong interactive feature coupled with the presence of equipment, and operatingconstrains. The complex dynamic behavior of the process was used in the MPCalgorithm scheme based on nonlinear model.

The controlled variables have been selected to provide, through control, a safeand economic operation. The controller variables are regenerator temperature Treg, andreactor temperature Tr. The regenerator temperature, Treg has to be maintained at acertain value to allow a stable removal co*ke from the catalyst. Overriding a hightemperature limit produces a permanent catalyst deactivation; a reduction under alower limit leads to co*ke accumulation on the regenerated catalyst. The reactortemperature Tr, has to be maintained at certain level to a desired maximum conversionof the fee oil.

The manipulated variables are Qcat1 – regenerated catalyst flow rate; Qair –mass flow rate of air to regenerator. The disturbances variables are Qmp, Tmp – feedstock flow and temperature.

Process identification test. Elaboration an MPC controller Matlab(Simulink)suppose the linierized the model of the catalytic cracking, for the obtain the simplifiedmodel of the process. The model simplified is obtained used the process identificationtest.

The process identification test the methods presented by Coleman and Seborgin their papers. The scope of the process identification test was to capture the plantdynamic in the models to develop linear controller. The first step in this test isdetermination the inputs-outputs structure of the process, figure 1. The inputs variablesof the process are Qmp, Tmp – feed stock flow and temperature, Qcat1 – regeneratedcatalyst flow rate; Qair – mass flow rate of air to regenerator. The outputs variables areregenerator temperature Treg, and reactor temperature Tr.

Process identification tests were carried out variables by making step changeson each input variable. The magnitude of the steps was selected to ensure that a clearresponse of the outputs variables was observed. The transfer function models of theFCC process are given in table 1.

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FCC model predictive control-302-

Fig. 2. Inputs –Outputs structures of the FCC.

4. SIMULATION RESULTS

The control objective is to maintain the controlled variables at predeterminedset points in the presence of typical process disturbances while maintaining safe plantoperation. The figure 2 presents the MPC controller response to 10% increases feedstock temperature. The figure 3 it can be observed the closed loop response of thesystem with MPC controller for 10% step increase the regenerated catalyst flow rate.Figure 4 show closed loop response of the system with MPC controller for 10 % stepincrease in the reactor temperature set point at 10s.

Table 1.The transfer function model of the FCC.Inputs

OutputsTmp Qmp Qcat Qaer

Tr 103.01775.0s 1025.0

0007913.0

s 1003.0

0001751.0s

Treg 135.01655.0s 135.0

0007153.0

s 11.0

00005791.0

s 12.0

002756.0s

FCC

12

1

Qcat

Qmp

Tmp

Treg

Tr

Qaer

232

4

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Popa, C., Patrascioiu, C -303-

Fig 2. Closed loop response of the system with MPC controller for 10% step increase the feedstock temperature.

Fig . 3. Closed loop response of the system with MPC controller for 10% step increase theregenerated catalyst flow rate.

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FCC model predictive control-304-

Fig 4. Closed loop response of the system with MPC controller for 10 % step increase in thereactor temperature set point at 10s.

From this graphs, it was observed that the MPC controller is powerful enoughto bring the severe nonlinear, strong coupling, time varying process under control,making the operation smooth and stable, reducing products.

4. CONCLUSIONS

The linearized model was used to design an MPC controller, which was successfully, applied to original nonlinear model. From the graphs of the outputs and inputvariables, it is clear that MPC strategy is far more effective to handle the thornie*stsituations found in oil industrial. Based on the success of the MPC simulation on theFCC model, following objectives will be achieved in an industrial practice :

i) improving the product quality- the MPC stabilizes the process operation,reducing the impact of control oscillations on the process;

ii) minimizing energy consumption;iii) improving process economic performance;

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Popa, C., Patrascioiu, C -305-

iv) improving the process operating stability, since the MPC reduces theprocess overshoot, it carries the process outputs to their set points in asmoother and faster manner in the presence of disturbances;

v) maximizing the process throughput and desirable products yield.Traditional operation keeps the unit at some distance from the constraints(optimum conditions) to ensure equipment and unit safety.

The MPC technology minimizes the distance between operating points and theoptimum, significantly increasing the processing capacity and desirable products yield.

BIBLIOGRAPHY

[1] Ali, H., and Rohani, S., Dynamic modeling and simulation of a riser-type fluidcatalytic cracking unit. Chemical Engineering Technology, 20, 118, 1997;

[2] C. Popa, C. Pătrăşcioiu , The adaptation of the control model for FCCU, The 5th

International symposion on process control, UPG, 2006;[3] C.Pǎtrǎşcioiu Popa C , Modeling a riser-Type reactor of fluid catalytic cracking

unit, The International Symposium and Modeling, Simulation and System’s Identification,Universitatea Dunarea de jos , 2004;

[4] Errazu A.F. , H. I. DeLasa and F. Sarti, A Fluidized bed catalytic CrackingRegenerator Model, Grid Effects, Canadian Journal of Chemical Engineering, 57, 191-197,1978;

[5] Coleman B., Babu J., Techniques of Model Based Control, Pentice Halll, 2004;[6] Seborg D, Edgard T, Duncan M, Process Dynamic and Control, John Wiley&

Sons Inc, 2004.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 306-311

GAS MONITORING SYSTEM BASED ON MODBUSPROTOCOL AND VIRTUAL INSTRUMENTATION

NICOLAE PĂTRĂŞCOIU, ADRIAN MARIUS TOMUŞ

Abstract: Major coal mine explosion disasters have always involved the combustionof coal dust, originally triggered by methane. So that is necessary to use monitoring and datalogger systems to control the underground environmental methane concentration. In this paperwe propose such system based on specific sensors to collect data from different measurementpoints, a serial data transmission based on Modbus protocol and a virtual instrumentation todata receiving, processing and visualization.

Keywords: methane sensor, modbus protocol, virtual instrumentation

1. METHANE GAS SENSORS SIGNAL TRANSMISSION

Many models of gas detectors are available to measure methaneconcentrations, as well as most of the other contaminant gases found in mines andtunnels. Most methane detectors used in mining use a catalytic heat of combustionsensor to detect methane and other combustible gases. These have been proven throughmany years of reliable operation.

To transmit sensors output signal from different systems like system gasmonitor exists many methods and one of this is serial transmission based on the RS –485 standard and the Modbus communication protocol.

Here are some gas sensors that are using catalytic heat of combustion orinfrared absorption like operating method but the same the same signal transmissionmethod namely serial transmission based on the RS – 485 standard and the Modbuscommunication protocol: S4100C Combustible Gas Addressable Transmitter from General Monitors

designed to measure and display concentrations of combustible gases in therange of 0 – 100% LEL, but will continue to display concentrations up to

Assoc.Professor at the University of Petroşani Assist.univ. at the University of Petroşani

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Patrascioiu, N., Tomuş A., M. -307-

120% LEL with the instrument addressed via the Dual Modbus RTU serialinterface.

Ultra 1000 Addressable Sensor for Combustible Gases from PEM –TECH, Inc. designed to provides a 4–20mA signal proportional to 0 – 100%of the detection range.

5100-02-IT Combustible Gas Sensor Module from Sierra Monitor thatmeasure concentrations of combustible gases in the range of 0 – 100% LEL.

Model D12-IR Gas Transmitter from AFC International, Inc that measure themethane in range 0 – 100 V/V.

MC-4210-CH4 Modbus Addressable Sensor from American Mine Research(AMR). Inc.

SEC 3000 Gas Detector from Sensor Electronics Corporation (SE).

2. GAS SENSOR S4100C MODBUS PROTOCOL

2.1. Modbus Protocol

The Modbus Serial Line protocol is a Master-Slaves protocol so that only onemaster (at the same time) is connected to the bus, and one or several (247 maximumnumber) slaves nodes are also connected to the same serial bus. A Modbuscommunication is always initiated by the master. The slave nodes will never transmitdata without receiving a request from the master node. The slave nodes will nevercommunicate with each other. The master node initiates only one Modbus transactionat the same time.

The master node issues a Modbus request to the slave nodes in two modes: In unicast mode, the master addresses an individual slave. After receiving and

processing the request, the slave returns a message (a 'reply') to the master. Inthat mode, a Modbus transaction consists of 2 messages: a request from themaster, and a reply from the slave. Each slave must have a unique address(from 1 to 247) so that it can be addressed independently from other nodes.

In broadcast mode, the master can send a request to all slaves.The drawing presented in fig.1 explains the master behavior:

Fig.1. The Master state diagram

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Gas monitoring system based on modbus protocol and virtual instrumentation-308-

State "Idle" is the initial state after power-up. A request can only be sent in"Idle" state. After sending a request, the Master leaves the "Idle" state, and cannot senda second request at the same time. When a unicast request is sent to a slave, the mastergoes into "Waiting for reply" state, and a “Response Time-out” is started. It preventsthe Master from staying indefinitely in "Waiting for reply" state. Value of theResponse time-out is application dependant. When a reply is received, the Masterchecks the reply before starting the data processing. The checking may result in anerror, for example a reply from an unexpected slave, or an error in the received frame.In case of a reply received from an unexpected slave, the Response time-out is keptrunning. In case of an error detected on the frame, a retry may be performed. If noreply is received, the Response time-out expires, and an error is generated. Then theMaster goes into "Idle" state, enabling a retry of the request. The maximum number ofretries depends on the master set-up.

In unicast mode the Response time out must be set long enough for any slaveto process the request and return the response. Therefore the Turnaround delay shouldbe shorter than the Response time-out. Typically the Response time-out is from 1s toseveral second at 9600 bps; and the Turnaround delay is from 100 ms to 200 ms.

The drawing presented in fig.2 explains the master behavior:

State "Idle" is the initial state after power-up. When a request is received, theslave checks the packet before performing the action requested in the packet. Differenterrors may occur : format error in the request, invalid action, … In case of error, areply must be sent to the master. Once the required action has been completed, aunicast mode message requires that a reply must be formatted and sent to the master. Ifthe slave detects an error in the received frame, no respond is returned to the master.Modbus diagnostics counters are defined and should be managed by any slave in orderto provide diagnostic information.

Fig.2. The Slave state diagram

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Patrascioiu, N., Tomuş A., M. -309-

2.2. Gas sensor S4100C

In this paper we deals with an application that use twelve S4100C sensorsconnected by an serial transmission line and from these the information is collected byan PC computer whereon run a program called virtual instrument (VI) written inLabVIEW.

The General Monitors Model S4100C Smart Transmitter is a highly reliable,self contained, microprocessor controlled, hydrocarbon gas monitor can be addressedvia the Dual Modbus RTU serial interface. The Modbus communications interface isbased on the RS485 standard, is implemented as a 2 wire, half-duplex, and conforms tothe EIA-485 specification. The interface implements the RTU protocol that is anasynchronous NRZ format and the factory defaults are set to 19K2 baud, no parity and1 stop bit.

For the S4100C sensor the Modbus register configuration is presented byfollowing table 1

Table 1 The Modbus register configuration

Here it can be observe that to collect information about gas concentration andabout sensor status is necessary to read the registers #2 and respectively #3. To do thison the communication bus the master that is the PC computer must deliver the readcommand:

sensor address function code register address number of registers to be read1 byte 1 byte 2 byte 2 byte

01 … 0C 03 0001 0002

The addressed sensor after receive the request and processing the requiredaction sent a replay that has the format:

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Gas monitoring system based on modbus protocol and virtual instrumentation-310-

sensor address function code number of bytes data1 byte 1 byte 1 byte 4 byte

01 … 0C 03 02 R2HR2LR3HR3L

3. VIRTUAL INSTRUMENT

To generate query for sensors and to receive and processing the sensor’sanswer is used a program written in graphical language LabVIEW named virtualinstrument. This has two basic components: front panel that include the controlsnecessary to generate commands and indicators used to display measured values,

messages and others necessary information and block diagram.On the front panel, figure 3, are dispose:

in MODBUS SETTINGS section controls necessary to set the Modbusprotocol parameters;

in MEASUREMET ERROR MESSAGES section a display area formiscellaneous messages generated for corresponding errors that can appear inmeasurement and data acquisition process like over limit gas concentration,sensor short circuit, sensor open circuit;

in MEASUREMET POINTS section, twelve indicators that display the gasconcentration current value, the time for over limit gas concentration and forthe nonce is changed the indicator color from green to red simultaneous withdisplay the right message.

Fig. 3. Front panel of the virtual instrument

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The block diagram, figure 4, represent the proper application program whereare used the programming elements and one of these is Staked Sequence Structure bythe medium of this are build the sequences for generate the queries and also forprocessing the answers.

The program starts with Modbus initialization (INIT SubVI), generatecommand and receive the answer (abcWR SubVI) followed by the function IndexArray that extract from registers the gas concentration value (index 1) and sensor status(index 2). These information are represented by corresponding bytes with MSB first sothat these hexa format bytes are converting into decimal number for display throughthe function Cast Unit Bases. From data extract by index 2 are forwards extract the bitsthrough are generated the messages about sensor’s status

BIBLIOGRAPHY

[1] Pătrăşcoiu, N. Sisteme de achizitie si prelucrare a datelor. InstrumentatieVirtuala. Editura Didactica si Pedagogica, Bucuresti, 2004, pp 250-256, ISBN 973-30-2622-0

[2] * * *. MODEL S4100C Hydrocarbon Smart Transmitter. Instruction Manual. PartNo. MANS4100C-EU, Revision K08/05

[3] * * *. MODBUS over Serial Line. Specification and Implementation Guide V1.01.Modbus.org. Aug. 30/2006

[4] * * *. LabVIEWTM 8.2. LabVIEW Fundamentals. National Instruments August2005 374029A-01

Fig. 4. Diagram block of the virtual instrument

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 312-319

HYBRID NEURAL NETWORK FOR PREDICTION OFPROCESS PARAMETERS IN INJECTION MOULDING

POPESCU MARIUS-CONSTANTIN

Abstract. In this paper, the attempts made by the authors to develop an artificial neuralnetwork system for prediction of injection moulding process parameters is presented. In thiswork, attempts have been made to determine the process parameters that could affect injectionmoulding process based on governing equations of the filling process.

Keywords: Hybrid neural networks; Injection moulding; Back propagation algorithm

1. INTRODUCTION

The industrial production process as practised in today's injection mouldingindustry is based on the interaction between regulation technology, industrial handlingapplications and computer science. Computer-integrated manufacturing has become arealistic prospect for injection moulding firms where maximum reproducibility andavailability are necessary to guarantee the competitiveness. In injection moulding, thetrial and error methods have always been as a practice to determine the optimuminjection moulding process parameters. Experts of the trade often refer to previousmould design similar to the current design and use its successful moulding processparameters. Injection moulding is a cyclic process whereby a heat-softened plastic isinjected into a mould from which it is ejected after it has set to the shape of the cavity.Thus, an injection moulding machine is one that discontinuously produces formedarticles primarily from polymeric materials.

2. NEURAL NETWORKS

An artificial neural network is a massively parallel array of simplecomputational units that models some of the functionality of the human brain andattempts to capture some of its computational strength [1]. In other words, it is a

University of Craiova, Faculty of Electromechanics, Craiova, Romania

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Popescu M., C. -313-

system of interlinked but very simple data processors. Neural computing is defined asthe study of networks of adaptable nodes which, through a process of learning fromexamples, store experimental knowledge and make it available for use.

Error-back-propagation is a particular example of a larger class of learningalgorithms, which are classified as 'supervised learning', because at each step thenetwork is comparing the actual output with the desired output [7]. Not only suchalgorithms are probably not implemented in biological neural networks, but also sufferbecause they are applicable only when the desired output is known in advance. Najmiand Lee [5] analysed the mould-filling process for injection moulding. Hung and Shen[2] believed that mechanical properties of fibre-reinforced polymer depend strongly onorientation patterns of fibres.

Liu and Manzione [4] developed a moulding technology that could deliver themicron-level precision in injection moulding process. Shelesh-Nezhad and Siores [13]developed an intelligent system for obtaining the magnitude of process parameters inplastic injection moulding operation. Rao and Yarlagadda [12] developed a four-layerback-propagation network to acquire and apply knowledge from the flow-stress dataobtained from experimentation. Popescu [6] also developed a similar artificialintelligence system for metal injection moulding. Yarlagadda and Cheng [14]developed a network to predict the process parameters in pressure die-casting. It wasbased on the governing equations of the filling stage for the die-casting process and thenetwork was trained with data collected from experts in this field. The trained neuralnetwork functions as a mapping mechanism and it is capable of predicting injectiontime when presented with unfamiliar data pair such as melt temperature, mouldtemperature, weight of casting and injection pressure. The Levenberg-Marquardtapproximation algorithm was used as it reduced the sum-squared error to a very smallvalue thus generating better accuracy of predictions. With the development of thisnetwork, a novice user can determine the injection time of the die-casting process. Therange of the applications of neural networks is colossal ranging from speechrecognition to flight control simulations. In the manufacturing field involving injectionmoulding, moulding parameters still remain an uncertainty without the assistance fromexperts. Hence, the neural network approach is used to overcome these uncertainties bypredicting the injection moulding process parameters [10].

3. CONSIDERATION OF INJECTION MOULDING

Injection moulding is a high volume production process with high tooling andset-up cost. The four main moulding parameters that affect the properties of themoulded product are melt temperature, mould temperature, injection pressure andinjection time. A successful moulding process is one, which optimises all theparameters to achieve mouldability. The characteristics of melt temperature are shownin Fig. 1 [11]. Fig. 2 shows the characteristic of mould temperature with injection timeand characteristics of injection pressure. Injection pressure is the theoretical pressuredue to the forces acting on the injection piston screw against the material, assuming nolosses. In a rectangular channel, it is given by the expression

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Hybrid neural network for prediction of processparameters in injection moulding-314-

3

12TH

QLp , (1)

where is the viscosity of the melt in poise, Q the volumetric filling rate in cubiccentimetre per second, L the channel length in centimetres. As for the rectangularchannel, T is the length of the slit in centimetres and H the thickness of the slit incentimetres. Fig. 3 shows the characteristics of injection pressure [3]. Injection time isthe time required for the injection moulding machine to fill the part. The combinedeffect of high temperature and high shear rate (resulting from high flow rate) reducesthe melt viscosity, and therefore offsets the pressure requirement. An estimation wasbased on the assumption that the mould be filled before half of the available gap hasbeen taken up with solidified material. This results in the equation:

3

3

8

/

C

PPdt frtw , (2)

where dw is the minimum wall thickness of the moulding in millimetres, Pt the flowpath in millimetres. Pfr is equal to the flow path ratio. The freeze-off constant, C, isproportional to the ratio given by:

mc

mx

TTTT

C

, (3)

where Tx is the heat distortion of the material, Tm the mould temperature and Tc thecylinder temperature. Fig. 3 shows the relationship of injection time and pressure.

Fig. 1. Characteristics of melt temperature w.r.t screw speed, pressure and flow length.

Fig. 2. Characteristics of mould temperature with injection time and injection pressure.

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Popescu M., C. -315-

Fig. 3. Characteristics of injection pressure, flow rate and part thickness

4. CONFIGURATION OF THE NEURAL NETWORK

Neural networks are the family of artificial intelligence and can be defined as"massive parallel interconnected networks of simple (usually adaptive) elements andtheir hierarchical organisations which are intended to interact with objects of the realworld in the same way as biological nervous systems do". Neural computation isperformed by a dense mesh of computing nodes and connections. The neurons areoften organised in layers and feedback connections both within the layer and towardadjacent layers are allowed. Each connection strength is expressed by a numerical

value called a weight,which can bemodified. Theseadjustable weightscorrespond tobiological synapses.The weighted inputsto a neuron areaccumulated and thenpassed to anactivation function,which determines theneuron's response.One of the mostattractive features ofneural networks is theability to produce anapproximate solutionrather than one,which is not correctwhen, presented withnoisy or incompleteinformation or data.

When presented with such data, which lies within or outside the range of training data,the network will generally interpolate and degrade (properties of fuzzy logic) to

Fig. 4. Two-stage neural network system for prediction ofinjection time and pressure

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provide the best approximation [8]. The schematic representation of two-stage multi-layered feed-forward neural network for predicting injection time and injectionpressure in injection moulding process is shown in Fig. 4.

In this work two specific neural network training algorithms namely, error-back-propagation, and Levenberg-Marquardt approximation (Gauss Newton) algorithmwere used to train the network. The neural network in this work serves as a mappingfunction for injection time and injection pressure. Experts on the production floor oftenapproximate these two parameters and with little trial and error, in order to determinethe optimum operating parameters. However, the new designers rely on experts or useof simulation software for assistance. In this work, two networks were developedwhich were capable of approximating the function of the simulated data. The error-back-propagation and the Levenberg-Marquardt approximation algorithms were usedduring the training phase. However, the latter is often used due to its betterconvergence. The input parameters considered for the first network were melttemperature of the alloy, mould temperature, flow length, inverse function of partthickness, function of melt and mould temperatures and the output parameter predictedis injection pressure. The input parameters considered for the second network were theoutput of the first network, i.e. injection pressure, flow length and part thickness.

These input parameters are inter-dependent and are constantly in conflict in avery complex way. In practice, the process starts by setting up both the melttemperature and the mould temperature, then the expert will experimentally determinethe injection time for the process based on the material characteristics and complexityof the part to be moulded. To eliminate the efforts of an expert, this work attempted tofind the optimum injection time and injection pressure associated with a certain meltand mould temperatures by using a neural network approach. With the inputparameters, the system predicts the injection time with an accuracy of 0.87% and adeviation of 3.52%, the injection pressure with an accuracy of 0.93% and a deviationof 3.93%. Fig. 5 shows a comparison of the simulated and the actual output. Initiallythe network was trained by considering flow length, part thickness, melt temperatureand mould temperature as the input parameters and the injection time as the outputparameter. After several attempts, it was found that the combination of flow length, theinverse of minimum part thickness, melt temperature, mould temperature, difference ofmelt and mould temperatures as the input parameters provide the best convergence.The training started with two sets of training data and finally increased to four sets oftraining data. Attempts to use more sets of training data and hidden-layers were made,but both did not yield better results. Instead, training cycles were longer than the initialconfiguration.

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5. RESULTS

The initial process prior to training the network includes the analysis ofgoverning equations of the filling stage. This is important in determining the inputparameters to be collected for training the network. Training data could either becollected from experts from the industries or by simulation software packages. A totalof 120 simulations were carried out, but only 114 were applicable, as six were foundfaulty due to incomplete filling. Out of the 114 data simulated, 94 were used for

training and 20were used to testthe network. Theinitial intentionwas to develop a5-input and 2-output network.With this

proposedconfiguration, itwas found thatthe network wasable to predict theinjection time toa certain level ofaccuracy, but itwas giving somearbitrary numbersfor the injectionpressure output.This led to arevision of thestructure of theentire network.

Fig. 5. Comparison of actual and simulated outputs or the injection time and pressure

The network was then changed to a two-stage neural network with the firstnetwork predicting injection time and the second network for injection pressure. Howlength, the inverse of minimum part thickness, melt temperature, mould temperature,the difference of melt and mould temperatures are the inputs for the first network. Theoutput of the first network, injection time, together with flow length and the inverse ofminimum part thickness are then carried over as inputs for the injection pressurenetwork. Two algorithms were used during the training phase, namely the error-back-propagation algorithm and the Levenberg-Marquardt approximation algorithm [9].Results show that the advanced algorithm Levenberg-Marquardt approximation wasable to converge at a faster speed with lesser training cycles as compared to the error-

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back-propagation algorithm. The Levenberg-Marquardt approximation algorithm couldalso achieve a lower sum-squared error. The scale of the input and output parameters isan important factor to consider when using the MATLAB [16]. Improperly-scaledvalues causing incompatibility may result in the network being inaccurate. During thetraining phase, the input and output parameters were converted to a smaller unit forcompatibility. The number of repetitions for a set of data to be used during training wasdetermined using the trial and error approach. In the case of the injection pressurenetwork, the optimum solution was obtained by using the data set once, but randomlyarranged in the matrix. On the other hand, the optimum result for the injection timenetwork was obtained from using four repetitions of data. However, with eightrepetitions of data, the results achieved were not as desirable as those obtained earlier.Table 1 shows the configuration of the network that was used in the training phases byusing Levenberg-Marquartdt algorithm. The optimum results were achieved by usingthe Levenberg-Marquardt approximation algorithm for both the networks. The firstnetwork was able to predict injection time to an accuracy of 0.91% with a deviation of4.62% using four sets of training data and five neurons in the hidden-layer. The secondwas able to predict injection pressure to an accuracy of 0.93% with a deviation of3.93% using two sets of data and 15 neurons in the hidden-layer. The graph belowshows the proximity of the actual output and the simulated output of the injection timenetwork and injection pressure network.

Table 1. Network configuration for training with Levenberg-Marquartdt algorithm

2-Layer network 1st layer: hidden (Logsig), 2nd layer: output (Purelin)Max. epochs 1000Initial value for MU 0,001Multiplier for increasing MU 10Multiplier for decreasing MU 0,1Maximum value for MU 1e10Error goal Number of neurons 0,001Number of training 05 input neurons, 05-20 neurons in hidden layer, 01 output neurondata (94 data pairs per set) 2 and 4 sets

6. CONCLUSIONS

The application of artificial intelligence has assisted many operations in manyfields. In this work, a neural network was developed to predict plastic injectionmoulding process parameters. Initially, the governing equations for mould-filling stagewere analysed in order to identify the input parameters for the proposed network. Theoutput parameters of the network developed are injection time and injection pressure.Based on the present work the following conclusions can be drawn. Mouldingconditions such as melt temperature, die temperature, injection pressure and injectiontime dominate the quality of the part produced. The trained neural network functions asa mapping mechanism and it is capable of predicting injection time when presentedwith totally new operating conditions. The slow convergence and the tendency of thenetwork to get stuck in local minima makes the gradient-descent method unsuitable forthis kind of application. The Levenberg-Marquardt approximation, with its

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sophisticated training algorithm, was found suitable for this application as it can reducethe sum-squared error to a very small value thus generating better accuracy of pre-dictions. With the development of this network, any novice user without priorknowledge of the injection moulding process can carry out the selection of processparameters for injection moulding.

BIBLIOGRAPHY

[1] Bown J., Injection Moulding of Plastic Components, McGraw-Hill, Maidenhead,UK, 1979.

[2] Hung C.F., Shen Y.K., Numerical simulation of fiber orientation in injection moldfilling, Int. Comm. Heat Mass Transfer 22, 1995.

[3] Johannber F., Injection Moulding Machines, A User's Guide, Hanser Publishing,1985.

[4] Liu C., Manzione L.T, Process Studies in Precision Injection Molding, PolymerEngineering and Science, University of Massachusetts, 1996.

[5] Najmi L.A., Lee D., Simulation of mould filling for powder injection moldingprocesses, Adv. Powder Metall. 3, 1990.

[6] Popescu M.C., Reţele neuronale şi algoritmi genetici utilizaţi în optimizareaproceselor, Sesiunea Naţională de Comunicări Ştiinţifice, Ediţia a IX-a, Târgu-Jiu, 2001.

[7] Popescu M.C., Optimizari în instalatiile de climatizare utilizate în incinte cudegajari de nocivităti, Ph.D. Thesis, University of Craiova, 2002.

[8] Popescu M.C., Neuro-fuzzy control of induction driving, 6th InternationalCarpathian Control Congress, Miskolc-Lillafured, Budapesta, 2005.

[9] Popescu M.C., Tracking Performance of a Quantized Adaptive Filter Equippedwith the Sign Algorithm, 7th International Carpathian Control Congress, Roznov podRadhostem, Czech Republic, 2006.

[10] Popescu M.C., Estimarea şi identificarea proceselor, Editura Sitech, Craiova,2006.

[11] Rosato D.V., Injection Moulding Handbook, 2nd Edition, International ThomsonPublishing, 1990.

[12] Rao K.P., Yarlagadda P.K.D.V., Neural network approach to flow stressevaluation in hot deformation, J. Mater. Process. Technol. 53, 1995.

[13] Shelesh-Nezhad K., Siores E., An intelligent system for plastic injectionmoulding process design, J. Mater. Process. Technol. 63, 1996.

[14] Yarlagadda P.K.D.V., Cheng W.C., Artificial intelligent neural networksystem for pressure die-casting, J. Mater. Process. Technol. 89-90, 1999.

[15] Zurada J.M., Introduction to Artificial Neural Systems, West PublishingCompany, 1992.

[16] *** User Guide Matlab for Simulink

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 320-325

INFORMATIC VIRUSES DETECTION USING HEURISTICALGORITHMS

OTILIA CANGEA

Abstract:. The paper deals with the problem of preventing electronic attacks againstindustrial systems, essentially referring to the problem of informatic viruses. The goal isunderstanding the concept of “informatic virus” and detecting the conventional informaticviruses using static and dynamic methods, as well as intelligent methods based on heuristicalgorithms. A system designed for informatic viruses is software implemented in “VirusInspector”, an original software product that verifies the characteristics of the program andestimates if that program is an informatic virus.

Keywords: informatic virus, heuristic algorithm, virus detection.

1. INTRODUCTION

In less than a generation, virtual introduction of computers has changed theway in which people and organizations obtain and exchange informations, allowing anincreased efficiency, a greater operational control and a more efficient access toinformations. Because computerized systems are essential for an adequate developmentof the majority of modern industrial activities, their security has to be an importantconcern for all the organizations dealing with them. Among the factors that may beconsidered responsible for the increase of the electronic attack risk are: inherent security difficulties; increased globalization; inadequate specific knowledge of the users of industrial systems [1], as well as

ignoring the use of specific procedures.Electronically stored information has a certain value. An incident that affects

this information will consequently affect the industrial entity, the industrial system orthe person that depends on or uses the respective informations. This is the reason whyinformation is evaluated in relation with the possible impact of an incident that will

Lecturer, Ph.D. at the “Petroleum-Gas” University of Ploiesti

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negatively affect it. The threats, the vulnerabilities and the possible impact have to becombined in order to obtain an estimate of the risk the information is submitted to.

2. HEURISTIC ALGORITHMS FOR INFORMATIC VIRUSESDETECTION

The informatic virus represents [2] a program that has the ability to insert hisown copies in other programes and to cause varied effects, that range from harmless tovery distructive ones. A program is considered to be a virus if : it modifies user programes by inserting his own structures; the alterations caused refer not only to a programe, but to groups of

programes, as well; it recognizes an already infected program; if it finds an already infected programe, it forbidens another modification; the infected programe has the same properties.

A virus is made of three components, namely the contamination part, the self-recognition part and the destructive part.It is important to emphasize that the evolution of a virus is characterized by two stages: the latent stage, when the virus spreads itself in the system and may be

detected and eliminated by specialized programes; the active stage, when the virus is in action, fullfiling the tasks it was

programmed to achieve.Detection –or scanning- is finding viruses by means of checking every file.

There are two detection methods: classic and heuristic.The classic method [3] generates a list of signatures -fingerprints- that define

the known viruses. This list has to be daily modified, in order to recognize the newviruses. Classic detection means searching in every file of all known virusesfingerprints.

A heuristic method is a method that solves a problem using rules based onexperience or intuition. The heuristic analysis is a small expert system that uses a set ofrules that describe viruses and applies these rules to the analyzed programes. Everyanalyzed file is being disassembled in order to search code sequences that mayrepresent instructions specific to viruses, such as a request to remain memory residentor files searching. In the same time, there is a great probability that these may be falsealarms –some programes have to execute these operations, so that these are notinformatic viruses.

Genetic algorithms are evolutive searching algorithms, designed in order toidentify aproximative solutions of difficult problems, by means of principles derivedfrom evolutive biology –mutation, heritage, natural selection, and crossing.Genetic operators are those procedures that operate on the elements of the populationarray. There are two main genetic operators: a transforming mi operator, named mutation, that creates a new individual by

means of a small change of a chosen individual (mi:s->s);

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Informatic viruses detection using heuristic algorithms-322-

a more powerful operator cj, named crossing, that creates new individuals bycombining two or more individuals (cj:sxs...xs->s) (one usually uses twoparents).

After a certain number of generations, the algorithm converges, that is the mostpromising individual reaches a value as close as possible to the optimum solution.

In order to describe the structure of a genetic algorithm one has to settle thefollowing: the used chromosomes have a constant lenght; the population (generation) P(t+1) is obtained by retaining all the descendants

of the P(t) population and by subsequently erasing of all the chromosomes ofthe precedent P(t) population;

the number of chromosomes is constant.In these circ*mstances, the structure of the fundamental genetic algorithm is as

follows:1. t<- 02. the P(t) population is randomly initialized3. the chromosomes of the P(t) population are evaluated4. as long as the finish condition is not fullfilled, there are executed the next steps: 4.1. one selects the P(t) chromosomes that will contribute to forming the new

generation; let them be P1 4.2. the P1 chromosomes are submitted to the genetic operators (preponderant

mutation and crossing operators) and the obtained population is P2 4.3. one erases from P1 the parents of the obtained descendants and the

chromosomes left in P1 are included in P2 4.4. a new generation is built: P(t+1)<-P2; all chromosomes from P(t) are erased;

t<- t+1; one evaluates P(t).The finishing condition refers to obtaining the given number of generations. If themaximum admitted number of generations is N, then the condition is t>N. Oneconsiders that the algorithm result is given by the most promising individual from thelast generation.

4. SOFTWARE PROGRAMS FOR INFORMATIC VIRUSESDETECTION

The software implementation of an informatic viruses detection system hasbeen achieved using C++ Builder. „Virus Inspector” verifies the characteristics of theprogram and estimates if that program is an informatic virus.

In order to create an intelligent heuristic program, the genetic algorithms have beenused, with the following characteristics: genetic representation: an individual representation is (g1, g2,…g10), where gi

may be 1, if i is a vulnerability, and 0, if i doesn’t represent a risk; individual representation: the quality of an individual, C, is given by the value

of the objective function that has to be maximized :

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k

iPiCi

1)*( , k=10 (1)

heuristic algorithm parameters: dimension of the initial population (n0),maximum dimension of the population (nmax), maximum number ofgenerations (gmax), crossing rate (cr) and mutation rate (mr).

The interface of the heuristic scanning module is presented in figure 1.

Fig. 1. Heuristic scanning interface module

The input data are the program characteristics, the weights associated to eachcharacteristic, and the genetic parameters. One may choose the program characteristics,may modify the associated weights, as well as the parameters of the genetic algorithm.

Figure 2 presents an example for a virus program, having as input data thefollowing characteristics: affecting the subroutines of the operating system modifying the registry of the operating system infiltration in the electronic mail applications

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Informatic viruses detection using heuristic algorithms-324-

Fig. 2. An example for a virus program

In these circ*mstances, the scanned program is a virus. The obtained outputfile “c:\rezultate.txt.” is presented below. Fitness is the value of the criterion functionfor each generated program, that reflects the performances of the respective program.

Population at 0 generation:

0 individual: (0010000111)

1st individual: (1010111001)

2nd individual: (1001000010)

3rd individual: (1110111011)

4th individual: (0010110000)

0 generation maximum fitness = 36

Population at 1st generation:

0 individual: (0010000111) fitness=0

1st individual: (1010111001) fitness=24

2nd individual: (1001000010) fitness=36

3rd individual: (1110111011) fitness=24

4th t individual: (0010110000) fitness=4

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1st generation maximum fitness = 36

Population at 3rd generation:

0 individual: (0010000111) fitness=0

1st individual: (1010111001) fitness=24

2nd individual: (1001000010) fitness=36

3rd individual: (1110111011) fitness=24

4th individual: (0010110000) fitness=4

3rd generation maximum fitness = 36

Population at 5th generation:

0 individual : (0010000111) fitness=0

1st individual : (1010111001) fitness=24

2nd idividual : (1001000010) fitness=36

3rd idividual : (1110111011) fitness=24

4th individual : (0010110000) fitness=4

5th generation maximum fitness = 36

---------------------------------------

5. CONCLUSIONS

Using “Virus Inspector”, one may analyze the main problems of the heuristicalgorithms. Some of the conclusions are presented below: the solution found by the heuristic algorithms it is not always the best one, but

it is located in the proximity of the optimum solution; an efficient antivirus system has to be implemented in an assembling

environment, that allows pursuing the effects and counteracts the disturbancesthat occur in the system as a result of the presence of the viruses;

a multithreading or multitasking system may be implemented in order tosignificantly reduce the answer time.

BIBLIOGRAPHY

[1] Amor, D., The E-Bussiness (R)evolution: Living and Working in anInterconnected World, Prentice Hall, 2001.

[2] Castano, S., Fugini, M., Martella, G., Samarati,P., Database Security, Addison-Wesley, 1995.

[3] Austin, R., Darby, C., The Myth of Secure Computing, Harvard Business Review,2003.

[4] Dimitriu, G., Programe antivirus, Editura Teora, Bucuresti, 1997.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 326-331

MODELING FOR INDUSTRIAL AND MANUFACTURINGSYSTEMS

EGRI ANGELA, SIRB VALI CHIVUŢA

Abstract: Simulation modeling and analysis the process of creating and experimentingwith a o computerized mathematical model of a physical system. For the purposes of thishandbook, a system is defined as a collection tiled are traditional simulation and training simulators.In general, the distinction is as follows.. Examples of manufacturing systems include: machiningoperations, assembly operations, materials-handling equipment and warehousing. Machiningoperation simulations can include processes involving either manually or computer numericallycontrolled factory equipment for machining, turning, bending, cutting welding, and fabricating.Assembly operations can cover any type of assembly line or manufacturing operation that requiresthe assembly of multiple components into a single- piece of work. Material-handlingsimulations have included analysis of cranes, for klifts, and automatically guided vehicles,Warehousing simulations have involved the manual or automated storage and retrieval of rawmaterials or finished goods.

Keywords: manufacturing systems, Fishbone chart, Pareto chart.

1. OTHER TYPES OF SIMULATION MODELS

The types of simulation models previously discussed are not the only types ofsimulation model practit ioner may encounter or have a need for. Another type ofcomputer simulation mode computer simulator. Though the distinction betweensimulation models and computer simulate differ somewhat among practitioners, thefollowing discussion may help differentiate these two simulation. Models of thesystems are normally created with different resource or operating polis have beenpreviously determined to be of interest. After the simulation runs, the output meaperformance are compared between or among the models. Thus, the ul t imate use orthe mod make resource or operating policy decisions concerning the system. Simulators

Assoc.prof. univ. dr. Eng at the University of Petrosani Lecturer.ph at the University of Petrosani

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are also models of existing or proposed systems. In contrast to simulation models, andoperating policy decisions are not made beforehand These types of decisions are actualdur ing the simulation run. Thus, the output measures are observed not only at the endof the more importantly, during the simulation run.

2. PURPOSES OF SIMULATION

The simulation modeling and analysis of different types of systems are conductedfor the purposes of (Pedgen et al., 1995): Gaming insight into the operation of a system,Developing operating or resource policies to improve system performance, Testing newconcepts and/or systems before implementation and Gaining information withoutdisturbing, the actual system.Advantages to simulation:

In addition to the capabilities previously described, simulation modeling hasspecific benefits. These include: Experimentation in compressed time, Reduced analyticrequirements and Easily demonstrated models.Disadvantages to Simulation:

Although simulation has many advantages, there are also some disadvantages ofwhich the simulation practitioner should be aware. These disadvantages are not really directlyassociated with the modeling and analysis of a system but rather with, the expectationsassociated with simulation protects.

These disadvantages include the following: Simulation cannot give accurate results when the input data are inaccurate; Simulation cannot provide easy answers to complex problems; Simulation cannot solve problems by itself.

3. BASIC SIMULATION MODEL COMPONENTS

For demonstration purposes, consider the simplest possible system that may be ofinterest to the practitioner. Examples of this simple type of system would include, but not be

Fig. 1. Basil simulation modelcomponents

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limited to: a customer service center with one representative, a barber shop with onebarber, a mortgage hem officer in a bank, a piece of computer-controlled machine in afactory and an ATM machine. Each of these simple systems insists of three types of majorcomponents: Entities, Queues and Resources. The relationships among the components areillustrated in Figure 1.

3.1 Entities

The first type of component is an entity; something that changes the state or the systemIn many cases, particularly those involving service systems, the entity may be a person. In thecustomer service center, the entities are the customers.

Entities do not necessarily have to be people; they can also be objects The entities that themortgage loan officer deals with arc loan applications. Similarly, in the factory example, theentities are components waiting to be machined.

3.1.1. Entity Batches

The number of entities that arrive in t he system at the same given time is knownas the batch size. In some systems, the batch size is always one. In others, the entities mayarrive in groups of different sizes. Examples of batch arrivals are families going to a movietheater. The batch sizes may be two, three, four, or more.

3.1.2. Entity Interarrival Times

The amount of time between batch arrivals is known as the interarrival time. It doesnot matter whether the normal batch size is one or more. We are interested only in theinterval from when the last batch at rived to when the cut rent batch arrives. The previousbatch may have had only one entity, whereas the next batch has more than one. Interarrivaltime is also the reciprocal of the arrival rate. In collecting entity arrival data it is usuallyeasier to collect the batch interarrival time.

3.1.2 Entity Attributes

Entities may also possess attributes. These are variables that have values unique toeach entity in the system. Even though the entity attribute will have the same name, there couldbe as many different values as there are entities. An example of an attribute of this type involvesthe entity's arrival time. Each entity's attribute ARRT1ME would store the simulation systemtime that the entity arrived in the system. So, unless a batch of entities arrived it the sametime, each entity would have a unique value in its attribute ARRTIME. Some entity attributesmay have the same value. En the case of airline passengers, the attribute PASSTYPE could holda value corresponding to the type of passenger the entity represents. A value of 1 inPASSTYPE could represent a first-class passenger, and a value of 2 could represent acoach-class passenger. Simulation programs may also, utilize global variables. Globalvariables are not to be confused with entity attributes. These variables differ from entityattributes in that each global variable can maintain only one value at a given time. A typical

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use of a global variable in a simulation program is the variable that keeps track of thesimulation run time.

4 TOOLS FOR DEVELOPING THE PROBLEM STATEMENT

There are two common tools available to the practitioner for assisting with theproblem statement. These are net actually problem-solving tools but rather are problemidentification tools. Although these tools were originally developed for themanufacturing environment, they can easily be adapted to other sectors of industry.These tools are:

Fishbone chart; Pareto chart.

4.1 Fishbone Chart

The Fishbone chart is also know as the cause-and-effect diagram, man-machine-material chart, and as the Isikawa chart (Suzaki, 1987). The purpose of thischart is to identify the cause of the problem or effect of interest. The Fishbone chartlooks similar to the bones of a fish. The head of the fish is labeled with the problem oreffect. Each major bone coming out of the spine is a possible source or cause of theproblem. For example, in a manufacturing process there are major bones for man,machine, material, and methods. This is illustrated m Figured 2.

Off each of the major bones the practitioner is to add additional subbones. Forthe man bone, this might include supervisors, shift 1, shift 2, etc. It may also includeother people such as maintenance or engineering. For the materials bone, the fish wouldinclude subbones for all of the raw materials that are present in the process. For themachine bone, the fish would have a subbone for each major piece of equipmentinvolved in the manufacturing process. Finally, the method bone would have subbonesfor the work methods for the different manufacturing processes.

4.2 Part-to Chart

The Pareto chart is a second technique tohelp the practitioner to develop theproblem statement (Nahmias, 1987).Interested in increasing the quality of amanufacturing operation. By performingthe wishbone diagram analysis, you havenarrowed down the quality problem to a

particular segment of the manufacturing process. Defects can be a result of variations intemperature, humidity, product age, or worker error. Depending on the severity of thedefect, the product may be reworked or have to be scrapped. It the product is reworked,additional cost is entailed to disassemble the product and repeal the defective part of theprocess If the product is scrapped, loss is associated stated with both the raw materials

Fig. 2. Fishbone chart

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and the work invested in the part up to the tune that it is declared defective. Toimplement a Pareto chart, you would need to know the number of defects, from eachsource and the cost associated with the detect. It these are multiplied together, the truecost of each defect can be determined. It is possible to end up with f our generalcombinations of true costs: Large number of inexpensive, easily repairable defects;Large number of expensive defects or a nonrepairable prouduct; Small number ofinexpensive, easily repairable detects; Small number of expensive defects or anonrepairable product.

5 SIMULATION PROJECT NETWORK EXAMPLES

We use tin AOA approach to illustrate one possible network for part of asimulation project (Fig. 3). In this network, the are correspond to the following first-level project tasks:

A = Problem statement; B = Protect planning; C = System definition;D = Inputdata;E = Model translation; F = Verification; G = Validation; H = Experimental design;

In this particular simulation project network model, we begin by simultaneouslyworking on activity A, the problem formulation phase, and activity B, the project plan.We can begin the project planning before completing the problem formulation phasebecause we are already familiar with most of the simulation protect tasks However,before we can reach event node 3 to begin activity C, the system definition, we mustcomplete both activity A. the problem formulation, and activity B, the protect plan.Once both of these are completed at node 3, we can proceed with activity C, the systemdefinition, When we complete activity C, the system definition, we know what we needto model, and we know what data need to be collected. We can begin these tasks at thesame time as represented by activity D, input data, and activity E, model translation.While we are building the model, we can use dummy or estimate input data until theactual data are ready. When both activity D input data, and activity E, modeltranslation, are compete, we reach event node 6. With the initially complete, model, weare in the verification phase represented by activity F. On the completion of activity F,verification, we are at event node 7. With the verified model, we can begin the

validation process represented by activity are G.

Fig. 3. Simulation project network

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Egri A., Sirb V. C. -331-

6. CALCULATING TIN- CRITICAL PATH

Once we have developed our AOA network and have estimated the duration ofeach activity arc in the network, we can consider calculating the critical path throughthe network. As we have previously defined, the critical path is the list of activitiesthat, if delayed, will extend the overall length of time to complete the project.To compute the critical path, we will need to calculate the following values for eachactivity in the network: ES = Earliest start time, EF = Earliest finish time, LS = Lateststarting time, LF = Latest finish time. For each of the activities in the network, we caneasily calculate the earliest finish time as: EF = ES + task duration. Similarly the lateststart time for each of the activities in the network can be calculated with the followingequation: LS = IF - task duration In the simplest implementation of calculating thecritical path, we can use deterministic estimates of each of the activity durations (tablenr. 1.). For our activities we can use:

Table 1. Activity durationActivity Task Duration

A Problem formulation 5B Project planning 2C System definition 5D Input data collection and analysis 25E Model translation 20F Verification 10G Validation 5H Experimental design 2I Analysis 10J Conclusion, report, presentation 10

We now begin our calculations with a chart with the following headings:Activity, Duration, Predecessor, ES and EF. The critical path can be identified by theactivities with 0-day values in the slack column This means that the critical path is:Activity A- Problem formulation, Activity C- System definition, Activity D - Inputdata collection and analysis, Activity F- Verification, Activity G –Validation, ActivityH- Experimental design, Activity I- Analysis and Activity J- Report and presentation.

BIBLIOGRAPHY

[1]. Regh J. Introduction to robotics in CIM systems. Prentice Hall,U.S.A,2004.[2]. Pop E. Microcontrollere si automate programabile.E.D.P,Bucuresti,2003.[3].Nolfi, S. Floreano, D. Evolutionary Robotics: The Biology, Intelligence, and

Technology of Self-Organizing Machines, MIT Press, 2000 .[4]. Stout, B. The Basics of A* for Path Planning. In: Game Programming Gems,

2000.[5]. Calin S. Conducerea adaptiva si flexibila a proceselor industriale.E.T,

Bucuresti,1998.[6]. Levine, D.L. - Introduction to Neural and Cognitive Modeling, 2nd Edition,

Lawrence Erlbaum Associates, London, 2000

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 332-337

NEURAL NETWORK TECHNIQUES FOR MOBILE ROBOTNAVIGATION

CRISTINA POPESCU

Abstract: To control a dynamic system it may be necessary to use some knowledge ormodel of the system to be controlled. The kinematics and dynamics of the robot may becomplex and non-linear, and the interaction between the vechicle and the terrain may be hard tomodel in general. These problems determine to use neural network techniques for navigation.This paper presents some issues about neural network in general, and how these are used tocontrol the mobile autonomous robot. The control architecture based on neural network enablesthe robot to perform several basic operations like obstacle avoidance, target following and localnavigation in real world environments.

Key words: neural network, autonomous mobile robot, obstacle avoidance.

1. INTRODUCTION

One of the most important problems in the design of intelligent mobile robot isthe navigation problem. This dwell in ability of a mobile robot to plan and executemotion without collision within its environment. This environment may be dynamical,unknown or non-structured and the robot must be able to understand the structure ofthis environment. For these capabilities it is necessary that the robots have perceptions,recognition, data processing, learning and action capacities. To achieve autonomy therobot must have an onboard system that deduce information about robot corespondingto the environment and a control system based on the algorithms that process thisinformation in order to generate commands for robot. In this paper we give a briefoverview of common artificial neural networks and their applications to mobile robots.

Lecturer, at the Petroleum – Gas University of Ploiesti

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Popescu, C. -333-

2. NEURAL NETWORKS

Artificial Neural Networks are mathematical algorithms that are able to learnmappings between input and output states through supervised learning, or to clusterincoming information in an unsupervised manner.

Every neural network has two components: nodes, also known as neurons andconnections between nodes, also known as synapses. The neurons are connected witheach other via synapses. Each synapse has a weight attached. The output of a neuron isusually calculated with a function such as:

m

jjkjk xwfy

)*( (1)

where ky is the output of the neuron, f is an activation (transfer) function, kjw is theweight attached to synapse j for the neuron k, and jx is the input signal of the neuron.

In [4] is presented the McCulloch and Pitts Neurons and the Perceptronlearning rule and their implementation in obstacle avoidance behavior for mobile robotnavigation.

McCulloch and Pitts Neurons

The McCulloch and Pitts neuron is shown in figure 1.

Fig.1. McCulloch and Pitts neuron.

The neuron computes the weighted sum jkj xw of all m inputs. Thisweighted sum is then compared with a fixed threshold to produce a final output y .

If jkj xw exceeds , the neuron is “on” (y=1), if jkj xw is below the threshold,the neuron is “off” (y=0).

1x

2x

mx

1kw

2kw

kmw

jkj xw

ky

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Neural network techniques for mobile robot navigation-334-

Obstacle avoidance using McCulloch and Pitts Neurons:A robot as shown in figure 2 is to avoid obstacles when one or both of the

whiskers trigger, and move forward otherwise.

Whiskers LW and RW signal “1” when theyare triggered, “0” otherwise. The motors LMand RM move forward when they receive a“1” signal, and backwards when they receivea “-1” signal. The truth table for obstacleavoidance behaviour is shown in table 1.

Fig. 2. A simple robot.

Table 1 This function can be implemented usingMcCulloch and Pitts neuron for each motor, usingneurons whose output is either “-1” or “+1”. In thisexample it will be determined the necessary wights

RWw and LWw for the left motor neuron only. Itwas choosed for the threshold -0.01 value.

The first line of the truth table stipulates that both motor neurons must be “+1”if neither LW nor RW fire. Because it was choosed a threshold of 01.0 this isfulfilled.Line two indicates that RWw must be smaller than for the left motor neuron. It waschoosed 3.0RWw .Line three of the truth table indicates that LWw must be greater than and it waschoosed 3.0LWw .These weights already implement the obstacle avoidance function for the left motorneuron. The functioning network is shown in figure 3.

Fig.3. Left – motor node for obstacle avoidance

For more complicated functions determining weights is very hard and it is desirable tohave a learning mechanism that would determine those required weights automatically.

LW RW LM RM0 0 1 10 1 -1 11 0 1 -11 1 don’t

caredon’tcare

RM

LM

RWLW

LW

RW

LM-0.1

0.3

-0.3

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Popescu, C. -335-

The Perceptron is a network consisting of McCulloch and Pitts neurons that fulfils thisrequirement.

Perceptron

The Perceptron is a “single-layer” artificial neural network that is easy toimplement, low in computational cost and fast in learning. It consists of two layers ofunits: the input layer (which simply passes signals on) and the output layer ofMcCulloch and Pitts neurons (which performs the actual computation).

Fig. 4. Perceptron.

The perceptron learning rule

The rule for determining the necessary weights is very simple, it is given inequation (2).

xyttw kk )()()( (2)

kkk wtwtw )()1( (3)

with k being the target value for unit k (i.e. the desired output of output unit k), and

ky the actually obtained output of unit k. The speed of learning is determined by thelearning rate )(t . The learning rate is usually chosen to be constant, but may bevariable over time.

Obstacle avoidance using a perceptron

It will be consider the same example it has considered before: obstacleavoidance. The difference this time is that it will be use a Perceptron, and that will bedetermine the required weights using Perceptron learning rule (given in equations 2and 3).

x1

x2

xn

w11

wnk

y1

y2

y3

yk

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Neural network techniques for mobile robot navigation-336-

Let be 0.3 and be –0.01. The two weights of the left – motor node are zero tostart with. This initial configuration is shown in figure 5.

Fig. 5. Layout of a perceptron for obstacle avoidance.

It was applied equations (2) and (3) line by line through the truth table 1 and itwas obtained:

Line one00)11(3.0000)11(3.00

LWRM

LWLM

ww

Line two

01)11(3.006.01)11(3.00

01)11(3.0000)11(3.00

RWRM

RWLM

LWRM

LWLM

wwww

Line three

00)11(3.006.00)11(3.06.0

6.01)11(3.0001)11(3.00

RWRM

RWLM

LWRM

LWLM

wwww

The final network is shown in figure 6. A quick calculation shows that thisnetwork already performs the obstacle avoidance function.

Fig. 6. Final network for obstacle avoidance.

LW

RW

wLWLM

LM

RM

wRWRM

LW

RW

0LM

RM

-0.01

-0.01

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Popescu, C. -337-

3. CONCLUSIONS

Many functions robots have to learn are linearly separable, which means thatthe very fast learning Perceptron can be used for robot learning. In fact, its speed is themajor advantage of the Perceptron over networks such as the Multilayer Perceptron orBackpropagation Network.

This paper presents a very simple ways to implement and use neural networksfor the purpose of control a mobile robot for obstacle avoidance behavior. It isnecessary to find a neural network which perform more behaviors, like wall following,or achieve a target and to test different parameters in neural network with the aim ofreaching the optimal time for finding the safe path.

BIBLIOGRAPHY

[1]. Arkin, R.C., Behavior –Based Robotics, MIT Press, 1998.[2]. Janglova, D., Neural Networks in Mobile Robot Motion, pp.15-22, International

Journal of Advanced Robotic Systems, Volume 1, Number 1, 2004.[3]. Martin, P., Nehmzow, U., Programming by Teaching: Neural Networks Control

in the Manchester Mobile Robot, Intelligent Autonomous Vehicles 95, Helsinki, June1995.[4]. Nehmzow, U. (2000). Mobile Robotics: A Practical Introduction, Springer Verlag

London.

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Annals of the University of Petroşani, Electrical Engineering, 9 (2007) pages 338-342

PROGRAM CONCEIVED IN THE VISUAL STUDIO.NETMEDIU, FOR A CAPITAL DEVALUATION CALCULATION

AND DISPLAYING

VALENTIN CASAVELA

Abstract: The program contains both a graphic interface, where the user may input thedates referring to the capital, which he possesses, and calculations for its devaluation. Theformula may be modified, in accordance with the economical medium, in which you work andthe program may use it in a adequate manner. We suppose that the Visual Studio.Net packetwas installed on your computer.

Keywords. devaluation, deadtime, activevalue, percentage, textboxe

1. THE CONCEIVING OF THE PROGRAM

If we note with ActiveValue for the capital value to the initial moment, withPercentage of devaluation (abbreviated P%, being divided by 100) and with Deadtimefor the number of years, from the moment of the obtaining the capital, till its out of use(in the below formula it appears nr_years, but, in the program, Deadtime is the upperlimit of a cyclic sequence ), then the calculations for the dev devaluation formula is thenext::

dev=ActiveValue*(P%)*[(1-(P%))^( nr_years-1)] (1)

Execute double click on the icon with sign 8 overturned and you will obtain the mainmenu, and, after that, select File…New…Project, appearing another window, inwhich select Project Types ...Visual C# Projects…Templates… WindowsApplication…Name….and type Capital_Devalorization. Be continuing by selectingBrows,…Location..C:\Documents and Settings\valy\My Documents\Visual Studio

Lecturer, Ph.D. at the University of Petroşani

(PDF) ANNALS OF THE UNIVERSITY OF PETROŞANI 2007.pdf· Annals of the University of Petroşani, Electrical Engineering, 9 (2007)-3-CONTENTS Dašić Predrag, Nedeff Valentin, Curčić Srećko, - DOKUMEN.TIPS (339)

Casavela, V. -339-

Projects, or other convenient location. Execute click on O.K. It appears the windowwith the new project.

From the menu Proprieties select Text, in which write the name Devaluation,for the main form. Be continuing with ToolBox, where select and drag in the form fourcontrols: TextBox1, TextBox2, TextBox3, TextBox4. Select all four with thecombination Ctrl+Click, and, after that, from the menu Format…Align..Right, alignright. For the TextBox4 control you may select Proprieties…Multiline…True,obtaining the multi lines writing, inside this.

To be continuing, build other controls too. Three labels are obtained from:ToolBox…label1…Text…Active Value (the label name), then label2…Text…Devaluation Percent (the label name), respectively label3.,.. Dead Time (name).We need still a checkbox control, which selection will permit to print to a printer. So,select ToolBox…checkBox1..Text…Print to file (name).The last control needed is a button, from where we shell command the calculation. So,select again ToolBox…button1…Text…Calculation.

Till now, we used the drag-and-drop technique and we achieved the figurebelow -figure1. But we will clean the names from the textboxes, because here the userwill input the capital value, its percentage of devaluation and the number of years,while the capital is used, after which it is considered out of use (dead). It may beobserved that we enlarged the forth textbox, because it will contain more text lines,having, otherwise, set the multi lines propriety, as we have shown.

After we achieved that, in the main menu, we select View….Code and it willappear at once the code, offered by the Visual Studio.NET programming medium.,code which reflects all the operations, made till now. But we must added to this codesome programming lines too, for performing the calculations, mentioned above. Underthe figure1, it may be seen also the first added line code, highlighted with bold. It is thenamespace IO, which allows the performing of a text file, with the calculation results.

using System;using System.Drawing;using System.Collections;

Fig.1

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Program conceived in the visual studio.net mediu, for a capitaldevaluation calculation and displaying-340-

using System.ComponentModel;using System.Windows.Forms;using System.Data;using System.IO;

But come beck to the previous window, executing double click onForm1.cs[Design]. Select button1, then, in Proprieties, the yellow light (that is theevents icon), then double click on Click. It appears a program sequence, where it maybe added the code:

private void button1_Click(object sender, System.EventArgs e){

double ActiveValue;double Percentage;double Deadtime;double temp;double dev;//variables in double precision, utilized sequel.string st1,st2;string str="";string lc="\r\n";//string significant a CR and a LFstring forms;//string which will be used for concatenation of

the above//strings.

Double[]obj=new Double[1];//the double precision valuesarray //definition, which array, in fact, contains a single one.

ActiveValue=double.Parse(textBox1.Text);//it takes in the//ActiveValue capital, the value inputted by user in the first text