8_Permanent magnet synchronous machine.pdf

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1、8.8.PermanentmagnetsynchronousmachinesPermanentmagnetsynchronousmachinesSource:SiemensAG,GermanyDARMSTADTDept.ofElectricalEnergyConversionUNIVERSITYOF8/1TECHNOLOGYProf.A.BinderPermanentmagnetmaterialsiB:RemanencefluxdensityRiH:CoercivefieldstrengthofB(H)-BCloopiMaterialdataB(

2、H):static”hysteresis"-loop(here:at20°C)iSoftmagneticmaterials(1):Iron,nickel,cobalt:BandHaresmall:ApplicationinRBCmagneticACfieldsiHardmagneticmaterials(2):=Permanentmagnetmaterials:BandHbig:RBCApplicationforgenerationofmagneto-staticfields1.Aluminium-Nickel-Cobalt-Magnets(Al

3、-Ni-Co)highB,lowH,cheapRBC2.Ferrite(e.g..Barium-Ferrite)ratherlowB,butincreasedHRBC3.Rare-EarthMagnetsSamarium-Cobalt:highB&H,smallinfluenceoftemperatureRBc4.Rare-EarthMagnetsNeodymium-Iron-Boron:veryhighB&H,decreasingwithin-RBCcreasingtemperatureiMagneticpointofoperationofPM

4、:in2.quadrantofB(H)-loopDARMSTADTDept.ofElectricalEnergyConversionUNIVERSITYOF8/2TECHNOLOGYProf.A.BinderRare-earthmagnets:LinearB(H)-Curvein2.quadrantiSelf-fieldofpermanentmagnetsiscalledmag-neticpolarizationJ,whichaddstotheexternalMfieldH,yieldingtheresultingfluxdensityB:MMr

5、rrB=µH+JM0MMiRare-earthmagnetsaredevelopedforhighsaturationpolarizationJ.siAfterturn-offofexternalfieldtheremanencefluxdensityB=J(H=0)=Jremains.RMMRiTwocoercivefieldstrengthsHdefined:Ca)At-HtheresultingmagneticfluxdensityBisCBMzero.b)At-HthemagneticpolarizationJwithintheCJMma

6、gnetiszero.B(H)-loopresultsfromaddingtheJ(H)-loopandthestraightlineB=µH.HenceitMMMMM0Misnearlylinearinthe2ndquadrant:B=B+µH,µ=ca.1.05µMRMMM0DARMSTADTDept.ofElectricalEnergyConversionUNIVERSITYOF8/3TECHNOLOGYProf.A.BinderPMsynchronousmachines:AirgapfluxdensityBpPMrotorwithsurf

7、acemountedmagnetsAir-gapfluxdensitydistributionatno-load(I=0)siNo-loadairgapflux-densityBp:ApproximationµM=µ0,BM≅BR+µ0andHMµFe→∞.-AMPERE´slawgives:No-load(I=0)=electricalAmpereturnsΘarezero;s2(Hδ+Hh)=Θ=0δMM-ConstancyoffluxbetweenfieldlinesΦ=BA=BAMMδδ-Identicalcrosssectionarea

8、sA=Ainmagnetsandinair-gapgive:B=BMδMδhMmagneticoperationallineB(H)B=