A Three-phase Induction Motor Problem

AnsoftRMxprtApplicationNoteApplicationNoteAP067-9911AThree-phaseInductionMotorProblemThisapplicationnotedescribeshowtosetup,solve,andanalyzetheresultsofatwo-pole,three-phaseinductionmotorusingRMxprt.ThemodelcreatedbyRMxprtwillthenbeusedasaninputforEMpulseasabasisforperformingmoredetailedanalysisandforincreasingtheaccuracyoftheperformancepre-dictions.RMxprtusesacombinationofanalyticalandmagneticcircuitequationstopredicttheperformanceofthisthree-phaseinductionmotor.EMpulseisanonlineartime-domainfiniteelementanalysis(FEA)softwarepackagethatsolveselectromagneticfieldequations,electriccircuitequations,andequationsofmotion.Youcancreatetheprojectfromscratchoropenthepre-solvedprojectcalled3ph.pjt,inthe/ansoft/exam-ples/rmxprt/directory.Ifyouarecreatingaprojectfromscratch,selectThreePhaseInductionMotorasthemotortypeinRMxprt.Thisprojectwascreatedusingversion2.3ofRMxprtandversion7.0oftheMaxwell2DFieldSimulator.Page2Three-phaseInductionMotorProblemGeneralDataUsetheGeneralwindowtospecifythemotorcharacteristics.➤Definethegeneraldata:1.Enter70.87kWintheRatedOutputPowerfieldforthistwo-polemotor.Thisisequaltoa95horsepowermotor.2.Enter460VinthedrivingRMSline-to-lineRatedVoltagefield.3.Enter60HzintheFrequencyfield.4.Enter3502rpmintheRatedSpeedfield.5.Enter1276WintheStrayLossfield.Ifthemeasuredstrayloadlossisunavailable,NEMAMG1[1],paragraph20.52,statesthatthisvalueshallbeassumedtobe1.2%oftheratedoutputformotorsratedlessthan2500hpand0.9%formotorsrated2500hpandgreater.IEEEStandard112[2]givesdifferentassumedstrayloadlossvaluesformotorsratedlessthan2500hp.Theyareasfollows:Inthisexample,followtheIEEEguidelinesanduse1.8%or1276watts.6.Enter700WintheFrictionLossfield.Thisvaluecontainsboththefrictionandwindlosses.7.ChooseTools/ModelUnits,andselectInchesastheunits.ChooseOKtoaccepttheunitsandclosethewindow.8.Enter9.5inchesintheIronCoreLengthfieldtodefinethelengthofthestator.9.Enter0.95intheStackingFactorfield.Thisgivesavalueof9.025inchesasthenetlengthofthesteel,aftertakinglaminationintoaccount.10.SelectD23asthenonlinearSteelTypeusedinthemanufacturingofthestatorlamination.ToexaminethematerialBH-curveforD23,chooseMaterials/BH,andthen,intheMaterialDatawindow,chooseOpen,andselectD23.h-b.Oncethedataisloadedintheleftwindow,youcanplottheB-Hcurveforthismaterial.Thestandardlossandspecificweightofthematerialarealsodisplayed.Thisinformationisnecessarytocalculatetheironcoreloss.Exitthiswindow,andcontinuethegeneraldatainput.11.SelectWyeastheWindingConnection.12.SelectConstantPowerastheLoadType.1-125hp1.8%126-500hp1.5%501-2499hp1.2%Three-phaseInductionMotorProblemPage3StatorDataUsetheStator1andStator2windowstodefinethestatordimensionsandstatorwindings.DefinetheDimensionsUsetheStator1windowtodefinethestatordimensions.➤Definethestator:1.Enter5.525inchesintheInnerDiameterfield.2.Enter10.125inchesintheOuterDiameterfield.3.Enter36intheNumberofSlotsfield.4.Select2astheSlotTypefortheshapeoftheslot.5.DeselectAutoDesignifitisselected,andenterthefollowingSlotDimensions(inch):•Enter0.055intheHr0field.•Enter0.065intheHs1field.•Enter0.698intheHs2field.•Enter0.16intheBs0field.•Enter0.309intheBs1field.•Enter0.432intheBs2field.Page4Three-phaseInductionMotorProblemDefinetheWindingsUsetheStator2windowtodefinethestatorwindings.➤Definethewindings:1.Select21intheWindingTypefield.Thewindingisadoublelayerlapwinding.2.Enter0inboththeTopSpareSpaceandBottomSpareSpacefields.Thesparespacesintheslotare0%oftheslot'sarea.3.Enter0.01inchesintheSlotInsulationfield.Theslotinsulationisthethicknessononesideofthestatorslot.4.Enter0intheEndAdjustmentfield.Theendadjustmentisthelengththatthestatorwindingsextendbeyondtheendofthestator.Forthismotor,thewindingsdonotextendbeyondthestator.5.Enter1inthenumberofParallelBranchesfield.Thismeansthecoilsmakinguponephaseareconnectedinseries.6.Enter11inthenumberofConductorsperSlotfield.7.Enter16intheCoilPitchfield.Hadthestatorusedafullpitchwinding,thenthecoilpitchwouldbe18slots(36slots/2poles).Thewindingiswound2slotsshorter,whichresultsinacoilpitchof16slots.8.Enter4.378inthenumberofWiresperConductorfield.Thisisnottheactualnumberbuttheequivalentnumberthatgivesthetotalwirecross-sectionalarea.(Oneconductorismadeupoftwo15AWGwiresandofthree16AWGwires.)9.Enter0.01inchesinthethicknessoftheWireWrapfield.10.Enter0.05708inchesintheWireDiameterfield.11.Enter15intheGaugefield.GaugesettingsaregiveninAWG.Three-phaseInductionMotorProblemPage5RotorDataUsetheRotor1andRotor2windowstodefinetherotor.DefinetheSlotDataUsetheRotor1windowtodefinetherotormeasurementsandthecharacteristicsoftherotorslots.➤Definetherotormeasurementsandrotorslotcharacteristics:1.Enter0.046inchesintheAirGapfieldtodefinethewidthoftheairgapbetweentherotorandthestator.2.Enter1.875inchesintheInnerDiameterfieldtodefinetheinnerdiameteroftherotor.Thisvalueisthesameasthediameteroftheshaft.3.Enter28intheNumberofSlotsfieldtodefinethenumberofrotorslots.4.Select6astheSlotType.DefinetheVentDataUsetheRotor2windowtodefinetherotorventcharacteristicsandotherrotormeasurements.➤Definetherotorventcharacteristicsandrotormeasurement