版权说明:本文档由用户提供并上传,收益归属内容提供方,若内容存在侵权,请进行举报或认领
文档简介
Chapter5SynchronousMachines7/10/2024SynchronousMachines1IntroductionTheDCfieldisnormallyontherotorandACarmaturewindingisonthestatorDCfieldcurrentsetsupmainair-gapfluxandACarmaturehandlestheelectricalpowerRotorrotatesinsynchronismwiththemagneticfieldsetupbythearmaturewindingsRotorspeedisproportionaltothefrequencyofthearmaturecurrentsinsteadystate7/10/2024SynchronousMachines2Stator-rotormutualinductanceis
Laf
cos(qme)Insteadystate
qme=wet+de0Open-circuitarmaturevoltageis 7/10/2024SynchronousMachines3Simplifiedthree-phasesynchronousmachineStatormutualinductanceis Lab=Laa0cos(120˚)=-½Laa0Statorselfinductanceis La=Laa0+Lal
Balancedthree-phasecurrentsia+ib+ic=0 7/10/2024SynchronousMachines47/10/2024SynchronousMachines5Motorsignconventionsimplymeansthereferencedirectionsarechosenfornormalmotoroperation7/10/2024SynchronousMachines6Synchronous-machineequivalentcircuits:(a)motorreferencedirectionand(b)generatorreferencedirection.7/10/2024SynchronousMachines7IaVa(Ra+jXs)IaEafIaEaf(Ra+jXs)IaVaSynchronousmotorandgeneratorphasordiagramsbothhavinglaggingpowerfactorattheterminals(IalaggingVa)MotorGenerator5.3Open-andShort-CircuitCharacteristicsTheopen-circuitarmaturevoltageandshort-circuitarmaturecurrent,bothplottedversusthefieldcurrent,allowcomputationofthesynchronousreactanceXsOpen-circuitcharacteristicwillshowsignificantsaturationandisoftencalledopen-circuitsaturationcurveShort-circuitcharacteristic(plotteduptoslightlyaboveratedcurrent)willnot,sincetheexcitationislowtheseconditions7/10/2024SynchronousMachines87/10/2024SynchronousMachines9Open-andshort-circuitcharacteristicsshowingequivalentmagnetizationlineforsaturatedoperatingconditions7/10/2024SynchronousMachines10SaturatedandunsaturatedvaluesofXs:SaturatedandunsaturatedvaluesofXsinperunit:Inlargesynchronousmachines,thearmatureresistanceismuchsmallerthanthesynchronousreactance.5.4Steady-StatePower-AngleCharacteristic7/10/2024SynchronousMachines11(a)Impedanceinterconnectingtwovoltages(b)phasordiagramMaximumpowerdeliveredbyasynchronousmachineisaspecialcaseofpower-anglecharacteristicforpowertransferthroughaseriesimpedanceZ=R+jX,fromE1toE2ForsimplicityZjX7/10/2024SynchronousMachines125.5Steady-StateOperatingCharacteristics7/10/2024SynchronousMachines13Constructionusedforderivationofasynchronousgeneratorcapabilitycurve.7/10/2024SynchronousMachines14ThisequationgivesthefieldheatinglimitThearmatureheatinglimitissimplythemachinevolt-ampererating(ratedcurrentatratedterminalvoltage)7/10/2024SynchronousMachines15Phasordiagramforconstant-poweroperationatconstantterminalvoltage.NotethatlesslaggingormoreleadingcorrespondstosmallerexcitationvoltagemagnitudeEafandsmallerfieldcurrentIfIa3VajXsIa2Eaf1Ia2Ia1Eaf3Eaf2jXsIa3jXsIa17/10/2024SynchronousMachines16SynchronousGeneratorVCurves5.6EffectsofSalientPolesIntroductiontosynchronouslyrotatingdqaxistheoryResolvearmaturephasorsintodandqaxiscomponentsDirect(d)axisisalignedwithfieldpoles,quadrature(q)axisismidwaybetweenpoles7/10/2024SynchronousMachines177/10/2024SynchronousMachines18Inductanceisfluxlinkageperunitampere:Thed-axiscurrentproducesMMFthatseesashortairgap(acrosspolefaces)sothed-axisinductanceislargeTheq-axiscurrentproducesMMFthatseesalongairgap(interpolarregion)sotheq-axisinductanceisrelativelysmallSalient-polemachinesareanalyzedwithaphasordiagramrepresentingd-andq-axisquantitiesseparately:IdseesXdandIqseesXqwhereXd>XqNosimpleequivalentcircuitisavailable7/10/2024SynchronousMachines197/10/2024SynchronousMachines20Phasordiagramforasalient-polesynchronousgenerator.7/10/2024SynchronousMachines21Phasordiagramillustratingthetechniqueforlocatingthequadratureaxisgivenarmatureterminalvoltage,currentandpowerfactorPermanent-MagnetACMachinesPolyphasesynchronousmachineswithpermanent-magnetrotorsareuseful,withmanyapplicationsparticularlyasmotorsTheanalysisissimilartothatalreadydiscussed,excepttheexcitationisnotadjustablePermanent-magnetmotorsareusuallyoperatedfromvariable-frequencymotordrives7/10/2024SynchronousMachines227/10/2024SynchronousMachines23Schematicdiagramofthree-phasepermanent-magnetacmachine.Thearrowindicatesthedirectionofrotormagnetization.Thismachinecanbeanalyzedasifitwereawound-fieldmachinewithconstantfieldcurrent.Thecontrolofapermanent-magnetacmotoroftenusesarotorpositionsensor.SummaryThesynchronousmachineisanalyzedundersteady-stateoperatingconditionsPolyphasecurrentsonthestatorproducearotatingMMFthatinteractswiththatoftherotatingfieldwindingtoproduceasteadytorqueTheequivalentcircuitandthephasordiagramareusefulforperformancecalculationsunderawidevarietyofoperatingconditions7/10/2024SynchronousMachines24Chapter6PolyphaseInductionMachines7/10/2024PolyphaseInductionMachines25IntroductionRotorrotationisnotsynchronouswiththemagneticfieldsetupbythearmaturewindingsInductionmachinesarealsocalledasynchronousmachinesAnalysisissimilartothatofatransformer,sincestatorandrotorwindingsaresimilartoprimaryandsecondarywindings,butwithrotationRotorconstructionisusuallyasquirrel-cagedesign7/10/2024PolyphaseInductionMachines267/10/2024PolyphaseInductionMachines27(a)Therotorofasmallsquirrel-cagemotor.(b)Thesquirrel-cagestructureaftertherotorlaminationshavebeenetchedawayRotorcurrentshavefrequencyofsfe
whichproducefluxwaverotatingatsnsr/minfasterthantherotorspeedWithrespecttothestator,therotorfluxwaverotatesatsynchronousspeed:7/10/2024PolyphaseInductionMachines28Boththestatorfluxwaveandtherotorfluxwaverotateatsynchronousspeed,sotheycaninteracttoproducetorque7/10/2024PolyphaseInductionMachines29Typicalinduction-motortorque-speedcurveforconstant-voltage,constant-frequencyoperationAtnormalload,theslipisabout2to10%RotorelectricalfrequencyislowAstheslipincreases,thespeeddropsandthetorqueincreasesTorqueisnearlyproportionaltoslipforloadsuptoratedtorqueMaximumtorqueorbreakdowntorqueisabouttwiceratedtorqueOnstartup,thespeedisinitiallyzeroandtheslipis1Thestartingcurrentislargeaswewillsee7/10/2024PolyphaseInductionMachines30CurrentsandfluxesininductionmotorsBothrotorandstatorcurrentssetuprotatingmmfwaveswithconstantamplitudethatrotateatsynchronousspeedTheresultantfluxwaveisduetobothstatorandrotormmf’sInteractionsareshowninthefigurebelowinadevelopment(asifthecylindricalgeometrywererolledoutflat)7/10/2024PolyphaseInductionMachines317/10/2024PolyphaseInductionMachines32Developedrotorwindingofaninductionmotorwithrotormmfandresultantfluxdensitywavesfor(a)zeroand(b)nonzerorotorleakagereactance.Noticethatthetorqueisinthedirectionofrotation,asexpectedforamotor.InductionmotorequivalentcircuitStator:Synchronouslyrotatingair-gapfluxgeneratescounteremf’sineachphaseStatorcurrentsproducevoltagedropduetoresistanceandleakagereactances7/10/2024PolyphaseInductionMachines33StatorequivalentcircuitisexactlylikethatoftheprimaryofatransformerRotorpresentsanimpedanceZ2tothestatorRotorimpedanceZrotordiffersfromZ2byaturnsratio(likethetransformer)andbyaspeeddifference(therotorrotateswhilethestatordoesnot)7/10/2024PolyphaseInductionMachines34Notethatthesubscript2sindicatesthatthequantityisslipfrequency,whiletherotorleakagereactanceX2isthevalueatstatorfrequency:7/10/2024PolyphaseInductionMachines35Next,weneedtoreferthisimpedancetostatorfrequencyusingAmpere’sandFaraday’slaws7/10/2024PolyphaseInductionMachines36TheimpedanceZ2isreferredtothestatorfrequencyandcompletestheequivalentcircuitAnalysisoftheequivalentcircuit7/10/2024PolyphaseInductionMachines37Numberofphases=qPowertransferredacrosstheairgap=PgapRotorI2Rloss=ProtorElectromagneticpower=Pmech7/10/2024PolyphaseInductionMachines38Alternativeformofpolyphaseinductionmotorequivalentcircuitdisplaystherotorresistanceseparatedintotwoseriesresistances:7/10/2024PolyphaseInductionMachines39ElectromagnetictorqueTmechcorrespondingtoPmechis:Corelossesmaybeneglectedorlumpedwithrotationalloss,simplifyingthecircuit7/10/2024PolyphaseInductionMachines40UseofThevenin’stheoremUseThevenin’stheoremata-binthesimplifiedequivalentcircuit:7/10/2024PolyphaseInductionMachines417/10/2024PolyphaseInductionMachines42Torque-slipcurveofinductionmotorshowingbraking,motor,andgeneratorregions.Normalmotoroperationisjustbelowsynchronousspeed.7/10/2024PolyphaseInductionMachines43Themaximumtorque,orbreakdowntorque,occursatmaximumair-gappower7/10/2024PolyphaseInductionMachines44Torque-slipcurvesforseveraldifferentvaluesofrotorcircuitresistance.Thisisexploitedtocontrolthespeedofwound-rotormotorsbyinsertingexternalresistanceinserieswiththerotorterminals.7/10/2024PolyphaseInductionMachines45ParameterdeterminationfromtestsNo-loadtestgivesrotationalloss(friction,windageandcoreloss)excitingcurrentProcedurediscussedinthetextallowsaccuratecomputationofcorelossesandXmApproximatevalue:Xm
Xnl
=V1,nl/I1,nlBlocked-rotortestgivesleakagereactancesProcedurediscussedinthetextallowsaccuratecomputationofX1+X2andR2
R1isfoundfromdcmeasurementsTable6.1givesanempiricaldistributionofleakagereactances7/10/2024PolyphaseInductionMachines467/10/2024PolyphaseInductionMachines47Table6.1Empiricaldistributionofleakagereactances(IEEEStd.112)FractionofX1+X2MotorClassDescriptionX1X2ANormalstartingtorque,normalstartingcurrent0.50.5BNormalstartingtorque,lowstartingcurrent0.40.6CHighstartingtorque,lowstartingcurrent0.30.7DHighstartingtorque,highslip0.50.5WoundrotorPerformancevarieswithrotorresistance0.50.5RotorcircuitparametervariationAsthemotorstarts,therotorcircuitparametersR2andL2mayvarywithslipfrequencyduetotheskineffectThiseffectispro
温馨提示
- 1. 本站所有资源如无特殊说明,都需要本地电脑安装OFFICE2007和PDF阅读器。图纸软件为CAD,CAXA,PROE,UG,SolidWorks等.压缩文件请下载最新的WinRAR软件解压。
- 2. 本站的文档不包含任何第三方提供的附件图纸等,如果需要附件,请联系上传者。文件的所有权益归上传用户所有。
- 3. 本站RAR压缩包中若带图纸,网页内容里面会有图纸预览,若没有图纸预览就没有图纸。
- 4. 未经权益所有人同意不得将文件中的内容挪作商业或盈利用途。
- 5. 人人文库网仅提供信息存储空间,仅对用户上传内容的表现方式做保护处理,对用户上传分享的文档内容本身不做任何修改或编辑,并不能对任何下载内容负责。
- 6. 下载文件中如有侵权或不适当内容,请与我们联系,我们立即纠正。
- 7. 本站不保证下载资源的准确性、安全性和完整性, 同时也不承担用户因使用这些下载资源对自己和他人造成任何形式的伤害或损失。
最新文档
- 2024上半年连锁零售品牌门店发展趋势分析报告
- 保育员的职业道德课件
- 八年级物理上册认识运动教科版课件
- 莆田市仙游县鲤城街道社区工作者招聘考试试题及答案2024
- 荆门市东宝区漳河镇社区工作者招聘考试试题及答案2024
- 绍兴市新昌县东茗乡社区工作者招聘考试试题及答案2024
- 聊城市高唐县人和街道社区工作者招聘考试试题及答案2024
- 土地项目施工方案
- 防汛、生态、景观建设新型标准河道
- 第四章施工总进度计划
- 三坐标测量机MSA分析
- 传统节日中秋节介绍PPT课件(带内容)
- 急性肾小球肾炎ppt图文ppt(ppt)课件
- 诸暨联合村镇银行
- 基建一体化管理配网示范工程精细化设计施工工艺标准(电缆部分)2012年发布
- 中国传统文化介绍PPT模板课件
- 苏教版三年级数学上册《1-3 倍的认识练习》课堂教学课件PPT小学公开课
- 西方现代人文地理学思潮
- 《师德与教师礼仪》全册配套优质PPT教学课件
- 驾校管理制度管理办法和岗位职责(全)
- 九年级物理北师大版全一册教学计划上
评论
0/150
提交评论