Synchronous Motor

3/28/2015 SynchronousmotorWikipedia,thefreeencyclopedia

http://en.wikipedia.org/wiki/Synchronous_motor 1/10

AsynchronousmotorgeneratorsetforACtoDCconversion.

Smallsynchronousmotorandintegralstepdowngearfromamicrowaveoven

SynchronousmotorFromWikipedia,thefreeencyclopedia

AsynchronouselectricmotorisanACmotorinwhich,atsteadystate,[1]therotationoftheshaftissynchronizedwiththefrequencyofthesupplycurrenttherotationperiodisexactlyequaltoanintegralnumberofACcycles.SynchronousmotorscontainmultiphaseACelectromagnetsonthestatorofthemotorthatcreateamagneticfieldwhichrotatesintimewiththeoscillationsofthelinecurrent.Therotorwithpermanentmagnetsorelectromagnetsturnsinstepwiththestatorfieldatthesamerateandasaresult,providesthesecondsynchronizedrotatingmagnetfieldofanyACmotor.AsynchronousmotorisonlyconsidereddoublyfedifissuppliedwithindependentlyexcitedmultiphaseACelectromagnetsonboththerotorandstator.

ThesynchronousmotorandinductionmotorarethemostwidelyusedtypesofACmotor.Thedifferencebetweenthetwotypesisthatthesynchronousmotorrotatesinexactsynchronismwiththelinefrequency.Thesynchronousmotordoesnotrelyoncurrentinductiontoproducetherotor'smagneticfield.Bycontrast,theinductionmotorrequires"slip",therotormustrotateslightlyslowerthantheACcurrentalternations,toinducecurrentintherotorwinding.Smallsynchronousmotorsareusedintimingapplicationssuchasinsynchronousclocks,timersinappliances,taperecordersandprecisionservomechanismsinwhichthemotormustoperateataprecisespeedspeedaccuracyisthatofthepowerlinefrequency,whichiscarefullycontrolledinlargeinterconnectedgridsystems.

Synchronousmotorsareavailableinsubfractionalselfexcitedsizes[2]tohighhorsepowerindustrialsizes.[1]Inthefractionalhorsepowerrange,mostsynchronousmotorsareusedwherepreciseconstantspeedisrequired.Inhighhorsepowerindustrialsizes,thesynchronousmotorprovidestwoimportantfunctions.First,itisahighlyefficientmeansofconvertingACenergytowork.Second,itcanoperateatleadingorunitypowerfactorandtherebyprovidepowerfactorcorrection.

Thesemachinesarecommonlyusedinanalogelectricclocks,timersandotherdeviceswherecorrecttimeisrequired.

Contents

1Type1.1Nonexcitedmotors

1.1.1Reluctancemotors

http://en.wikipedia.org/wiki/Steady_statehttp://en.wikipedia.org/wiki/AC_motorhttp://en.wikipedia.org/wiki/Power_factorhttp://en.wikipedia.org/wiki/Electromagnethttp://en.wikipedia.org/wiki/Electric_clock#Synchronous_clockhttp://en.wikipedia.org/wiki/Utility_frequencyhttp://en.wikipedia.org/wiki/AC_motorhttp://en.wikipedia.org/wiki/Induction_motorhttp://en.wikipedia.org/wiki/Electromagnethttp://en.wikipedia.org/wiki/Timerhttp://en.wikipedia.org/wiki/Brushless_wound-rotor_doubly_fed_electric_machinehttp://en.wikipedia.org/wiki/Magnetic_fieldhttp://en.wikipedia.org/wiki/Slip_(motors)http://en.wikipedia.org/wiki/File:Synchronous_motor-generator_set_for_AC_to_DC_conversion_(Rankin_Kennedy,_Electrical_Installations,_Vol_II,_1909).jpghttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Electromagnethttp://en.wikipedia.org/wiki/Statorhttp://en.wikipedia.org/wiki/Utility_frequencyhttp://en.wikipedia.org/wiki/File:Synchronmot.jpghttp://en.wikipedia.org/wiki/Rotor_(electric)http://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Servomechanismhttp://en.wikipedia.org/wiki/Alternating_currenthttp://en.wikipedia.org/wiki/Tape_recorder



1.1.2Hysteresismotors1.1.3Permanentmagnetmotors

1.2DCexcitedmotors2Synchronousspeed

2.1Example3Construction4Operation5Startingmethods6Applications,specialproperties,andadvantages

6.1Useassynchronouscondenser6.2Steadystatestabilitylimit6.3Other

7Subtypes8Seealso9References10Externallinks

Type

Synchronousmotorsfallunderthemoregeneralcategoryofsynchronousmachineswhichalsoincludesthesynchronousgenerator.Generatoractionwillbeobservedifthefieldpolesare"drivenaheadoftheresultantairgapfluxbytheforwardmotionoftheprimemover".Motoractionwillbeobservedifthefieldpolesare"draggedbehindtheresultantairgapfluxbytheretardingtorqueofashaftload".[1]

Therearetwomajortypesofsynchronousmotorsdependingonhowtherotorismagnetized:nonexcitedanddirectcurrentexcited.[3]

Nonexcitedmotors

Innonexcitedmotors,therotorismadeofsteel.Atsynchronousspeeditrotatesinstepwiththerotatingmagneticfieldofthestator,soithasanalmostconstantmagneticfieldthroughit.Theexternalstatorfieldmagnetizestherotor,inducingthemagneticpolesneededtoturnit.Therotorismadeofahighretentivitysteelsuchascobaltsteel,Thesearemanufacturedinpermanentmagnet,reluctanceandhysteresisdesigns:

[4]

Reluctancemotors

Thesehavearotorconsistingofasolidsteelcastingwithprojecting(salient)toothedpoles.Typicallytherearefewerrotorthanstatorpolestominimizetorquerippleandtopreventthepolesfromallaligningsimultaneouslyapositionwhichcannotgeneratetorque.[2][5]Thesizeoftheairgapinthemagneticcircuitandthusthereluctanceisminimumwhenthepolesarealignedwiththe(rotating)magneticfieldofthestator,andincreaseswiththeanglebetweenthem.Thiscreatesatorquepullingthe

http://en.wikipedia.org/wiki/Electric_motorhttp://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/Electrical_loadhttp://en.wikipedia.org/wiki/Prime_mover_(engine)http://en.wikipedia.org/wiki/Cobalthttp://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Retentivityhttp://en.wikipedia.org/wiki/Hysteresishttp://en.wikipedia.org/wiki/Reluctancehttp://en.wikipedia.org/wiki/Electric_generatorhttp://en.wikipedia.org/wiki/Reluctance_motor



Singlephase60Hz1800RPMsynchronousmotorforTeletypemachine,nonexcitedrotortype,manufacturedfrom19301955.

rotorintoalignmentwiththenearestpoleofthestatorfield.Thusatsynchronousspeedtherotoris"locked"totherotatingstatorfield.Thiscannotstartthemotor,sotherotorpolesusuallyhavesquirrelcagewindingsembeddedinthem,toprovidetorquebelowsynchronousspeed.Themachinestartsasaninductionmotoruntilitapproachessynchronousspeed,whentherotor"pullsin"andlockstotherotatingstatorfield.[6]

Reluctancemotordesignshaveratingsthatrangefromfractionalhorsepower(afewwatts)toabout22kW.Verysmallreluctancemotorshavelowtorque,andaregenerallyusedforinstrumentationapplications.Moderatetorque,integralhorsepowermotorsusesquirrelcageconstructionwithtoothedrotors.Whenusedwithanadjustablefrequencypowersupply,allmotorsinthedrivesystemcanbecontrolledatexactlythesamespeed.Thepowersupplyfrequencydeterminesmotoroperatingspeed.

Hysteresismotors

Thesehaveasolidsmoothcylindricalrotor,castofahighcoercivitymagnetically"hard"cobaltsteel.[5]Thismaterialhasawidehysteresisloop(highcoercivity),meaningonceitismagnetizedinagivendirection,itrequiresalargereversemagneticfieldtoreversethemagnetization.Therotatingstatorfieldcauseseachsmallvolumeoftherotortoexperienceareversingmagneticfield.Becauseofhysteresisthephaseofthemagnetizationlagsbehindthephaseoftheappliedfield.Theresultofthisisthattheaxisofthemagneticfieldinducedintherotorlagsbehindtheaxisofthestatorfieldbyaconstantangle,producingatorqueastherotortriesto"catchup"withthestatorfield.Aslongastherotorisbelowsynchronousspeed,eachparticleoftherotorexperiencesareversingmagneticfieldatthe"slip"frequencywhichdrivesitarounditshysteresisloop,causingtherotorfieldtolagandcreatetorque.Thereisa2polelowreluctancebarstructureintherotor.[5]Astherotorapproachessynchronousspeedandslipgoestozero,thismagnetizesandalignswiththestatorfield,causingtherotorto"lock"totherotatingstatorfield.

Amajoradvantageofthehysteresismotoristhatsincethelagangleisindependentofspeed,itdevelopsconstanttorquefromstartuptosynchronousspeed.Thereforeitisselfstartinganddoesn'tneedaninductionwindingtostartit,althoughmanydesignsdohaveasquirrelcageconductivewindingstructureembeddedintherotortoprovideextratorqueatstartup.

Hysteresismotorsaremanufacturedinsubfractionalhorsepowerratings,primarilyasservomotorsandtimingmotors.Moreexpensivethanthereluctancetype,hysteresismotorsareusedwherepreciseconstantspeedisrequired.

Permanentmagnetmotors

Apermanentmagnetsynchronousmotor(PMSM)usespermanentmagnetsembeddedinthesteelrotortocreateaconstantmagneticfield.ThestatorcarrieswindingsconnectedtoanACsupplytoproducearotatingmagneticfield.Atsynchronousspeedtherotorpoleslocktotherotatingmagneticfield.These

http://en.wikipedia.org/wiki/Torquehttp://en.wikipedia.org/wiki/Squirrel-cage_rotorhttp://en.wikipedia.org/wiki/AC_motor#Hysteresis_synchronous_motorhttp://en.wikipedia.org/wiki/Coercivityhttp://en.wikipedia.org/wiki/Hysteresis_loophttp://en.wikipedia.org/wiki/RPMhttp://en.wikipedia.org/wiki/Teletypehttp://en.wikipedia.org/wiki/Coercivityhttp://en.wikipedia.org/wiki/File:Synchronous_motor_from_Teletype_machine.jpghttp://en.wikipedia.org/wiki/Permanent_magnet



DCexcitedmotor,1917.Theexciterisclearlyseenattherearofthemachine.

motorsarenotselfstarting.Becauseoftheconstantmagneticfieldintherotorthesecannotuseinductionwindingsforstarting.[7][8][9][10][11]

Themaindifferencebetweenapermanentmagnetsynchronousmotorandanasynchronousmotoristherotor.SomestudiesseemtoindicatethatNdFeBpermanentmagnetsynchronousmotorsarearound2percentmoreefficientthanthehighestefficiency(IE3)asynchronousmotorsusingthesamestatorlaminationsandsimilarvariablefrequencyspeedcontrollers.[12]

DCexcitedmotors

Usuallymadeinlargersizes(largerthanabout1horsepoweror1kilowatt)thesemotorsrequiredirectcurrentsuppliedtotherotorforexcitation.Thisismoststraightforwardlysuppliedthroughsliprings,butabrushlessACinductionandrectifierarrangementmayalsobeused.[13]ThedirectcurrentmaybesuppliedfromaseparateDCsourceorfromaDCgeneratordirectlyconnectedtothemotorshaft.

Synchronousspeed

Thesynchronousspeedofasynchronousmotorisgiven:[14]inrpm,by:

andinrads1,by:

where:isthefrequencyoftheACsupplycurrentinHz,isthenumberofpolesperphase.

If isthenumberofpolepairsperphase(rarelycalled'planesofcommutation')instead,simplymultiplybothformulasby2.

Example

A3phase,12pole(6polepair)synchronousmotorisoperatingatanACsupplyfrequencyof50Hz.Thesynchronousspeedis:

Construction

http://en.wikipedia.org/wiki/File:Electrical_Machinery_1917_-_Westinghouse_motor.jpghttp://en.wikipedia.org/wiki/Brushless_DC_electric_motorhttp://en.wikipedia.org/wiki/Radian_per_secondhttp://en.wikipedia.org/wiki/Slip_ringhttp://en.wikipedia.org/wiki/Hertzhttp://en.wikipedia.org/wiki/Synchronous_speedhttp://en.wikipedia.org/wiki/3-phasehttp://en.wikipedia.org/wiki/Magnethttp://en.wikipedia.org/wiki/Asynchronous_motorhttp://en.wikipedia.org/wiki/Asynchronous_motorhttp://en.wikipedia.org/wiki/Rpmhttp://en.wikipedia.org/wiki/Frequency



Rotorofalargewaterpump.Theslipringscanbeseenbelowtherotordrum.

Statorwindingofalargewaterpump

Therotatingmagneticfieldisformedfromthesumofthemagneticfieldvectorsofthethreephasesofthestatorwindings

Theprincipalcomponentsofasynchronousmotorarethestatorandtherotor.[15]Thestatorofsynchronousmotorandstatorofinductionmotoraresimilarinconstruction.[16]Withthewoundrotorsynchronousdoublyfedelectricmachineastheexception,thestatorframecontainswrapperplate.[17]Circumferentialribsandkeybarsareattachedtothewrapperplate.[17]Tocarrytheweightofthemachine,framemountsandfootingsarerequired.[17]WhenthefieldwindingisexcitedbyDCexcitation,brushesandslipringsarerequiredtoconnecttotheexcitationsupply.[18]Thefieldwindingcanalsobeexcitedbyabrushlessexciter.[19]Cylindrical,roundrotors,(alsoknownasnonsalientpolerotor)areusedforuptosixpoles.Insomemachinesorwhenalargenumberofpolesareneeded,asalientpolerotorisused.[20][21]Theconstructionofsynchronousmotorissimilartothatofasynchronousalternator.[22]

Operation

Theoperationofasynchronousmotorisduetotheinteractionofthemagneticfieldsofthestatorandtherotor.Itsstatorwindingwhichconsistsofa3phasewindingisprovidedwith3phasesupplyandrotorisprovidedwithDCsupply.The3phasestatorwindingcarrying3phasecurrentsproduces3phaserotatingmagneticflux(andthereforerotatingmagneticfield).Therotorlocksinwiththerotatingmagneticfieldandrotatesalongwithit.Oncetherotorlocksinwiththerotatingmagneticfield,themotorissaidtobeinsynchronization.Asinglephase(ortwophasederivedfromsinglephase)statorwindingispossible,butinthiscasethedirectionofrotationisnotdefinedandthemachinemaystartineitherdirectionunlesspreventedfromdoingsobythestartingarrangements.[23]

Oncethemotorisinoperation,thespeedofthemotorisdependentonlyonthesupplyfrequency.Whenthemotorloadisincreasedbeyondthebreakdownload,themotorfallsoutofsynchronizationandthefieldwindingnolongerfollowstherotatingmagneticfield.Sincethemotorcannotproduce(synchronous)torqueifitfallsoutofsynchronization,practicalsynchronousmotorshaveapartialorcompletesquirrelcagedamper(amortisseur)windingtostabilizeoperationandfacilitatestarting.Becausethiswindingissmallerthanthatofanequivalentinductionmotorandcanoverheatonlongoperation,andbecauselargeslipfrequencyvoltagesareinducedintherotorexcitationwinding,synchronousmotorprotectiondevicessensethisconditionandinterruptthepowersupply(outofstepprotection).[23][24]

Startingmethods

http://en.wikipedia.org/wiki/File:Rotor_of_an_electric_water_pump.jpghttp://en.wikipedia.org/wiki/File:3phase-rmf-180f-airopt.gifhttp://en.wikipedia.org/wiki/File:Stator_of_an_electric_water_pump.jpghttp://en.wikipedia.org/wiki/Direct_currenthttp://en.wikipedia.org/wiki/Brushless_wound-rotor_doubly-fed_electric_machine



Vcurveofasynchronousmachine

Aboveacertainsize,synchronousmotorsarenotselfstartingmotors.Thispropertyisduetotheinertiaoftherotoritcannotinstantlyfollowtherotationofthemagneticfieldofthestator.Sinceasynchronousmotorproducesnoinherentaveragetorqueatstandstill,itcannotacceleratetosynchronousspeedwithoutsomesupplementalmechanism.[2]

Largemotorsoperatingoncommercialpowerfrequencyincludea"squirrelcage"inductionwindingwhichprovidessufficienttorqueforaccelerationandwhichalsoservestodamposcillationsinmotorspeedinoperation.[2]Oncetherotornearsthesynchronousspeed,thefieldwindingisexcited,andthemotorpullsintosynchronization.Verylargemotorsystemsmayincludea"pony"motorthatacceleratestheunloadedsynchronousmachinebeforeloadisapplied.[25]Motorsthatareelectronicallycontrolledcanbeacceleratedfromzerospeedbychangingthefrequencyofthestatorcurrent.[26]

Verysmallsynchronousmotorsarecommonlyusedinlinepoweredelectricmechanicalclocksortimersthatusethepowerlinefrequencytorunthegearmechanismatthecorrectspeed.Suchsmallsynchronousmotorsareabletostartwithoutassistanceifthemomentofinertiaoftherotoranditsmechanicalloadissufficientlysmall[becausethemotor]willbeacceleratedfromslipspeeduptosynchronousspeedduringanacceleratinghalfcycleofthereluctancetorque."[2]Singlephasesynchronousmotorssuchasinelectricwallclockscanfreelyrotateineitherdirectionunlikeashadedpoletype.SeeShadedpolesynchronousmotorforhowconsistentstartingdirectionisobtained.

Applications,specialproperties,andadvantages

Useassynchronouscondenser

Byvaryingtheexcitationofasynchronousmotor,itcanbemadetooperateatlagging,leadingandunitypowerfactor.Excitationatwhichthepowerfactorisunityistermednormalexcitationvoltage.[27]Themagnitudeofcurrentatthisexcitationisminimum.[27]Excitationvoltagemorethannormalexcitationiscalledoverexcitationvoltage,excitationvoltagelessthannormalexcitationiscalledunderexcitation.[27]Whenthemotorisoverexcited,thebackemfwillbegreaterthanthemotorterminalvoltage.Thiscausesademagnetizingeffectduetoarmaturereaction.[28]

TheVcurveofasynchronousmachineshowsarmaturecurrentasafunctionoffieldcurrent.Withincreasingfieldcurrentarmaturecurrentatfirstdecreases,thenreachesaminimum,thenincreases.Theminimumpointisalsothepointatwhichpowerfactorisunity.[29]

Thisabilitytoselectivelycontrolpowerfactorcanbeexploitedforpowerfactorcorrectionofthepowersystemtowhichthemotorisconnected.Sincemostpowersystemsofanysignificantsizehaveanetlaggingpowerfactor,thepresenceofoverexcitedsynchronousmotorsmovesthesystem'snetpowerfactorclosertounity,improvingefficiency.Suchpowerfactorcorrectionisusuallyasideeffectofmotorsalreadypresentinthesystemtoprovidemechanicalwork,althoughmotorscanberunwithoutmechanicalloadsimplytoprovidepowerfactorcorrection.Inlargeindustrialplantssuchasfactoriestheinteractionbetweensynchronousmotorsandother,lagging,loadsmaybeanexplicitconsiderationintheplant'selectricaldesign.

http://en.wikipedia.org/wiki/Single-phase_electric_powerhttp://en.wikipedia.org/wiki/Moment_of_inertiahttp://en.wikipedia.org/wiki/File:V_curve_synchronous_motor.svghttp://en.wikipedia.org/wiki/Power_factor_correctionhttp://en.wikipedia.org/wiki/Shaded-pole_synchronous_motor



Steadystatestabilitylimit

where,

isthetorqueisthetorqueangle

isthemaximumtorque

here,

Whenloadisapplied,torqueangle increases.When =90thetorquewillbemaximum.Ifloadisappliedfurtherthenthemotorwillloseitssynchronism,sincemotortorquewillbelessthanloadtorque.[30][31]Themaximumloadtorquethatcanbeappliedtoamotorwithoutlosingitssynchronismiscalledsteadystatestabilitylimitofasynchronousmotor.[30]

Other

Synchronousmotorsareespeciallyusefulinapplicationsrequiringprecisespeedand/orpositioncontrol.

Speedisindependentoftheloadovertheoperatingrangeofthemotor.Speedandpositionmaybeaccuratelycontrolledusingopenloopcontrols,e.g.steppermotors.Lowpowerapplicationsincludepositioningmachines,wherehighprecisionisrequired,androbotactuators.TheywillholdtheirpositionwhenaDCcurrentisappliedtoboththestatorandtherotorwindings.Aclockdrivenbyasynchronousmotorisinprincipleasaccurateasthelinefrequencyofitspowersource.(Althoughsmallfrequencydriftswilloccuroveranygivenseveralhours,gridoperatorsactivelyadjustlinefrequencyinlaterperiodstocompensate,therebykeepingmotordrivenclocksaccurate(seeUtilityfrequency#Stability).)RecordplayerturntablesIncreasedefficiencyinlowspeedapplications(e.g.ballmills).

Subtypes

ThreephaseACsynchronousmotorsSynchronousbrushlesswoundrotordoublyfedelectricmachineSteppermotor(maybesynchronousornot)Reluctancemotor(maybesynchronousornot)

http://en.wikipedia.org/wiki/Brushless_wound-rotor_doubly_fed_electric_machinehttp://en.wikipedia.org/wiki/Robothttp://en.wikipedia.org/wiki/Reluctance_motorhttp://en.wikipedia.org/wiki/Utility_frequency#Stabilityhttp://en.wikipedia.org/wiki/Ball_millhttp://en.wikipedia.org/wiki/AC_motor#Three-phase_AC_synchronous_motorshttp://en.wikipedia.org/wiki/Stepper_motorhttp://en.wikipedia.org/wiki/Stepper_motorshttp://en.wikipedia.org/wiki/Phonograph#Turntable_technology



Seealso

ShortcircuitratioDoublyfedelectricmachine

References

1. Fitzgerald,A.E.CharlesKingsley,Jr.AlexanderKusko(1971)."Chapter6,Synchronousmachines,steadystate".ElectricMachinery,3rdEd.USA:McGrawHill.pp.283330.LibraryofCongressCatalogNo.70137126.

2. Fitzgerald,A.E.CharlesKingsley,Jr.AlexanderKusko(1971)."Chapter11,section11.2StartingandRunningPerformanceofSinglephaseInductionandSynchronousMotors,SelfstartingReluctanceMotors".ElectricMachinery,3rdEd.USA:McGrawHill.pp.536538.LibraryofCongressCatalogNo.70137126.

3. JamesGStallcup,Stallcup'sGenerator,Transformer,MotorandCompressor,page1513,Jones&Bartlett,2012ISBN1449695191.

4. WilliamYeadon(ed.),HandbookofSmallElectricMotors,McGrawHill2001ISBN007072332X,Chapter12"SynchronousMachines"

5. Gottlieb,IrvingM.(1997).Practicalelectricmotorhandbook,2ndEd.(http://books.google.com/books?id=Irj9w5IE31AC&pg=PA72&dq=shadedpole+synchronous+motor&hl=en&sa=X&ei=z9zyTuCVEuPMiQKgyKylDg&ved=0CE4Q6AEwAA#v=onepage&q=shadedpole%20synchronous%20motor&f=false)USA:Newnes.pp.7376.ISBN0750636386.

6. MichaelA.Laughton(2003),"19.2.5Reluctancemotors",ElectricalEngineer'sReferenceBook,Newnes,p.19/8,ISBN9780750646376

7. R.IslamI.HusainA.FardounK.McLaughlin."PermanentMagnetSynchronousMotorMagnetDesignsWithSkewingforTorqueRippleandCoggingTorqueReduction"(http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=4757411).IndustryApplications,IEEETransactionson.2009.doi:10.1109/TIA.2008.2009653(https://dx.doi.org/10.1109%2FTIA.2008.2009653)

8. KiChanKimSeungBinLimDaeHyunKooJuLee.TheShapeDesignofPermanentMagnetforPermanentMagnetSynchronousMotorConsideringPartialDemagnetization"(http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=1704668).Magnetics,IEEETransactionson.2006.doi:10.1109/TMAG.2006.879077(https://dx.doi.org/10.1109%2FTMAG.2006.879077)

9. P.PillayR.Krishnan."ApplicationcharacteristicsofpermanentmagnetsynchronousandbrushlessDCmotorsforservodrives"(http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=90357).IndustryApplications,IEEETransactionson.1991.doi:10.1109/28.90357(https://dx.doi.org/10.1109%2F28.90357)quote:"Thepermanentmagnetsynchronousmotor(PMSM)andthebrushlessDCmotor(BDCM)havemanysimilaritiestheybothhavepermanentmagnetsontherotorandrequirealternatingstatorcurrentstoproduceconstanttorque."

10. Y.HondaT.NakamuraT.HigakiY.Takeda."Motordesignconsiderationsandtestresultsofaninteriorpermanentmagnetsynchronousmotorforelectricvehicles"(http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=643011).IndustryApplicationsConference,1997.ThirtySecondIASAnnualMeeting,IAS'97.,ConferenceRecordofthe1997IEEE.1997.doi:10.1109/IAS.1997.643011(https://dx.doi.org/10.1109%2FIAS.1997.643011)

11. M.A.RahmanPingZhou."Analysisofbrushlesspermanentmagnetsynchronousmotors"(http://ieeexplore.ieee.org/xpl/login.jsp?tp=&arnumber=491349).IndustrialElectronics,IEEETransactions

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on.1996.doi:10.1109/41.491349(https://dx.doi.org/10.1109%2F41.491349)12. MarkusLindegger."Economicviability,applicationsandlimitsofefficientpermanentmagnetmotors"

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(http://books.google.co.in/books?id=RpmRb1fG8gYC&pg=PT47&dq=stator+frame&hl=en&sa=X&ei=_1vsULncFcvfkgXDhIHgBA&ved=0CD0Q6AEwAA)(Seconded.).Wiley.

18. GeraldB.Kliman,HamidA.Toliyat.HandbookofElectricMotors(http://books.google.co.in/books?id=4Kkj53fWTIC&pg=PA302&dq=synchronous+motor+field&hl=en&sa=X&ei=0RztUOnTD4enkQXuIGoAw&ved=0CDsQ6AEwAA#v=onepage&q=synchronous%20motor%20field&f=false)(Seconded.).p.302.

19. Jordan,HowardE.EnergyEfficientElectricMotorsandTheirApplications.B(Seconded.).Plenumpress.p.104.ISBN0306446987.

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(http://books.google.co.in/books?id=RpmRb1fG8gYC&pg=PT32&dq=synchronous+motor+salient+pole+rotor&hl=en&sa=X&ei=ZR7tUKv8BsuakgXu7oEI&ved=0CE0Q6AEwBA)(Seconded.).Wiley.

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principle/).25. JerryC.Whitaker,ACPowerSystemsHandbook,page192,CRCPress,2007ISBN0849340349.26. DavidFinney,VariableFrequencyACMotorDriveSystem,page32,IEE,1988ISBN0863411142.27. Bhattacharya,S.K.ElectricalMachinees(http://books.google.co.in/books?id=BN9rplPm

wAC&pg=PA481&dq=synchronous+motor+unity+power+factor&hl=en&sa=X&ei=FXPtUPalHcvukgX954DwCg&ved=0CE4Q6AEwBA#v=onepage&q=synchronous%20motor%20unity%20power%20factor&f=false)(thirded.).TataMcGrawHill.p.481.

28. ElectricMachineryAndTransformers(http://books.google.co.in/books?id=h965eTcjJEC&pg=PA229&dq=synchronous+motor+unity+power+factor&hl=en&sa=X&ei=F3HtUIbtDYiKkwXY2YGoCA&ved=0CDgQ6AEwAQ#v=onepage&q=synchronous%20motor%20unity%20power%20factor&f=false)(seconded.).Pearson.p.230.|first1=missing|last1=inAuthorslist(help)

29. Theraja,BL.Electricaltechnology.II(2010reprinted.).SChand.p.1524.30. Dubey,GK.Fundamentalsofelectricaldrives.Narosapublishingchennai.p.254.31. Pillai,SK.AFirstCourseOnElectricalDrives(seconded.).Newageinternational.p.25.

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