Optimum Pole Configuration of A-C Induction Motors .pdf

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1、OptimumPoleConfigurationofA-CInductionMotorsUsedOnAdjustableFrequencyPowerSuppliesbyMichaelJ.MelfiProductDevelopmentEngineerB-7100-1PresentedatTheIEEEPCICTechnicalConferenceofTheIndustryApplicationSocietyInDenver,COonSeptember13,1955OPTIMUMPOLECONFIGURATIONOFACINDUCTIONMOTORSUSEDONADJUSTABLEFREQU

2、ENCYPOWERSUPPLIESMICHAELJ.MELFI-Member,IEEEPRODUCTDEVELOPMENTENGINEERINGRELIANCEELECTRICROCKWELLAUTOMATIONCLEVELAND,OHIO44117ABSTRACTmotorsisthatitallowsanessentiallyinfinitenumberofpossible“basespeeds,”Fora"fixedfrequency"(linepowered)ACincludingbasespeedsinexcessof3600RPM.inductionmotor,asimple

3、relationshipexistsbetweenthenumberofmagneticpolesandtheII.FIXEDFREQUENCYAC-POLENUMBERSsynchronousspeed.Specificchoicesofpolenumberandthecommonlinefrequenciesof50Intheworldoffixedfrequency,“linepower”and60Hzresultindiscreteavailablespeedsapplications,ACinductionmotorsoperatingonforthesemotors.50or

4、60HzpowerarerestrictedtoasetofsynchronousspeedsasdefinedbythenumberofWhenmatchingACinductionmotorstovariablemotorpoles(TableI).Thesespeedssimplyspeedapplicationsusingadjustablefrequencyaretheresultofthe“physics”ofACpowersupplies,thereisatemptationtoinductionmotorsasdescribedinEquation(1).assumeth

5、at50or60Hzwillbethe"baseThemotordesignerdoesnothaveany“choice”frequency,"andthereforethe"basespeeds"astothenumberofpolestouseforaachievablearethoseprovidedbyvaryingthespecificmotorspeed.numberofmotorpoles.Thatassumptionnotonlylimitsthechoicesofbasespeeds,butfalsoresultsinsuboptimalperformancefrom

6、N=´120(1)themotor.ThispaperwillexplainthePphysicsofwhytheoptimalchoiceofthewhereN=speedinRPMnumberofmotorpolesismoreafunctionofthemotortorque(size),ratherthanthemotorf=appliedfrequencyinHzspeed,whenconsideringadjustablefrequencyP=numberofmagneticpolesapplications.Infact,theexclusiveuseofafourpole

7、configurationresultsinoptimalperformanceforasignificantrangeofratings.TheparameterswhichcanbeTABLEIoptimizedviathecorrectchoiceofpoleACMOTORSYNCHRONOUS(NOLOAD)SPEEDSconfigurationinclude-torquedensity,speedAT50AND60HzIN