Chapter7

SpaceVectorDescriptionandFieldOrientedControlofInductionMotors車用驅(qū)動(dòng)電機(jī)原理與控制基礎(chǔ)(第2版)PrincipleandControlFundamentalsofVehicleDriveMotorsa)

squirrelcagewindingb)

RotorstructureofwoundwindingFig.7-1Schematicdiagramofrotorstructureofinductionmotor27.1TheRotorStructureandWorkingPrincipleofIMThestatorstructureoftheinductionmotorisbasicallythesameasthatofthesynchronousmotor.Themaindifferenceliesintherotorstructureandthegenerationprincipleoftherotormagneticfield.Therotorstructureofinductionmotor(IM)mainlyincludestwoparts:rotorironcoreandrotorwinding.Thecommonwindingtypesaresquirrelcagetypeandwoundtype.1.SquirrelcagewindingAsquirrel-cagewindingisaself-closingshort-circuitwinding.Itconsistsofabarinsertedintoeachrotorslotandannularendringsatbothends.Iftheironcoreisremoved,theentirewindingislikea“circularsquirrelcage”.2.WoundwindingTheslotofthewoundrotorisembeddedwithathree-phasewindingcomposedofinsulatedwires.Thethreeoutgoingwiresofthewindingareconnectedtothethreecollectorringsmountedontheshaft,andareconnectedtotheexternalcircuitthroughbrushes.Thefeatureofthisrotoristhatanexternaladjustableresistorcanbeconnectedtotherotorwindingtoimprovethestartingandspeedregulationperformanceofthemotor.37.1.2WorkingPrincipleofThree-phaseIMThestatorisathree-phasesymmetricalwinding,anditsstructureisthesameasthatofathree-phasesynchronousmotor.Atthesametime,therotorisalsoequivalenttothree-phasesymmetricalwindingsa-x,b-yandc-z,andtheyareshort-circuited,thusformingabasicthree-phaseinductionmotor

Fig.7-2aTheequivalentphysicalmodelofthe

three-phaseinductionmotor4

7.1.2WorkingPrincipleofThree-phaseIM57.1.3Stator,RotorandMagneticFieldSynchronousCoordinateSystems

Table7-1Therepresentationandtransformationrelationshipsofcurrentvectorsinthreecoordinatesystems67.2VectorsEquationofIM7.2.1Stator/RotorInductanceandFluxLinkageofIM

Fig.7-3Theequivalentfour-coilprototypemotormodelofIM77.2.1Stator/RotorInductanceandFluxLinkageofIMFig.7-4Thestator/rotorcurrent,andrespectivefluxlinkagevectorsofthethree-phaseIM87.2.2SpaceVectorEquationsunderStationaryReferenceFrame

9

7.2.3SpaceVectorEquationsunderRotor-fixedabcReferenceFrame107.2.4SpaceVectorEquationunderArbitraryMagneticFieldSynchronousRotatingMTReferenceFrame

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7.2.4SpaceVectorEquationunderArbitraryMagneticFieldSynchronousRotatingMTReferenceFrame12

7.2.4SpaceVectorEquationunderArbitraryMagneticFieldSynchronousRotatingMTReferenceFrame13

7.2.4SpaceVectorEquationunderArbitraryMagneticFieldSynchronousRotatingMTReferenceFrame14Fig.7-5Steady-statevectordiagramofthethree-phaseIM7.2.4SpaceVectorEquationunderArbitraryMagneticFieldSynchronousRotatingMTReferenceFrame157.3RotorMagneticFieldEstablishmentProcessandItsOrientationFig.7-6Therotormagneticfieldisrepresentedasthecombinationoftheair-gapmagneticfieldandtherotorleakagemagneticfield

167.3RotorMagneticFieldEstablishmentProcessandItsOrientationFig.7-6Therotormagneticfieldisrepresentedasthecombinationoftheair-gapmagneticfieldandtherotorleakagemagneticfield

177.3.1Rotort-axisMagnetomotiveForceInducedbyMotionalElectromotiveForceFig.7-7Therotorequivalentcurrentvectorwhentherotormagneticfieldamplitudeisconstanta)Rotormagnetomotiveforcevectorformedbyrotorbarcurrent

b)Thespatialdistributionofmotionalelectromotiveforceandcurrentmagnitudeintheconductor18Fig.7-8

Therotorequivalentcurrentvectorwhentheamplitudeoftherotormagneticfieldisconstanta)Themagnetomotiveforcevectorsoftherotorcoilcurrentsandtheirsynthesisb)Theequivalentexcitationcurrentatt-axis

7.3.1Rotort-axisMagnetomotiveForceInducedbyMotionalElectromotiveForce

19Fig.7-9RotorcurrentvectorwhenrotormagneticfieldamplitudechangesDuringthedynamicoperationofthemotor,iftheamplitudeoftherotormagneticfieldchanges,transformerelectromotiveforcewillbeinducedineachrotorbar.AtthemomentshowninFig.7-9a,iftheamplitudeoftherotormagneticfieldisincreasing,accordingtoLenz'slaw,theelectromotiveforceineachbarwillbeshowninFig.7-9a.

7.3.1Rotorm-axisMagnetomotiveForceInducedbyInducedElectromotiveForcea)Rotorcurrentandrotormagnetomotiveforceb)Spatialdistributionoftransformerelectromotiveforceandcurrentmagnitudeinthebar207.3.3DefinitionandCharacteristicsofRotorMagneticField-OrientedCoordinateSystemFig.7-11RotorcagewindingisequivalenttoMTaxiscoilFig.7-12MagneticfieldorientedMTcoordinatesystem

217.3.4StatorandRotorFluxLinkageEquation

227.3.6StatorandRotorVoltageEquations

237.3.6StatorandRotorCurrentEquations

247.3.6StatorandRotorCurrentEquations

257.3.6StatorandRotorCurrentEquationsFig.7-13Vectordiagramofmagneticfluxandcurrentforathree-phaseinductionmotorafterfieldorientation

a)Dynamicvectordiagramoffluxlinkageandcurrent267.3.7TorqueEquation

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7.3.7TorqueEquation287.3.7TorqueEquation

297.4PrincipleofVectorControlbasedonCurrentPhasePlane7.4.1ControlConstraints

307.4.1ControlConstraintsonCurrentPhasePlane

317.4.1ControlConstraintsonCurrentPhasePlane

Fig.7-18Thediagramsofcontrolconstraintsandcontrollawforinductionmotor327.4.1ControlConstraintsonCurrentPhasePlane

337.4.2FieldWeakeningControlProcessonCurrentPhasePlaneFig.7-19OperatingregionoftheinductionmotoracrossthefullspeedrangeThefieldweakeningcontroloftheinductionmotorshouldaimforthemaximumtorqueoutput,takingintoaccounttheconstraintsofvoltageandcurrenttoallocatethecurrentreasonably.Duetothesevoltageandcurrentconstraints,theeffectivetorqueoutputoftheinductionmotordecreasesinthefieldweakeningregion.Tofullyutilizethemaximumtorquecapabilityofthedrivesystemundervoltageandcurrentlimitations,themostrationalutilizationofvoltageandcurrentisrequired.Theoperatingspeedrangeofaninductionmotorcanbedividedintothreeregions:constanttorqueregion,constantpowerregion,andconstantvoltageregion,asshowninFig.7-19.Whenthemotorspeedislessthanthebasespeedoffieldweakening,sincethegeneratedbackelectromotiveforceislessthanthemaximumvoltageoutputbytheinverter,themotoroperationisonlylimitedbythemaximumcurrentallowedbythemotor,andthemaximumoutputtorquecanremainunchanged.Therefore,thisareaisnamedasthe“constanttorquearea”.Abovethefieldweakeningbasespeed,themotorentersthefield