直流电机速度控制SpeedControlofDC Motor中英文资料.docx

直流电机速度控制SpeedControlofDC Motor中英文资料.docx

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直流电机速度控制SpeedControlofDCMotor中英文资料

SpeedControlofDCMotor

RegulatorSystems

Aregulatorsystemisonewhichnormallyprovidesoutputpowerinitssteady-stateoperation.

Forexample,amotorspeedregulatormaintainsthemotorspeedataconstantvaluedespitevariationsinloadtorque.Eveniftheloadtorqueisremoved,themotormustprovidesufficienttorquetoovercometheviscousfrictioneffectofthebearings.Otherformsofregulatoralsoprovideoutputpower;Atemperatureregulatormustmaintainthetemperatureof,say,anovenconstantdespitetheheatlossintheoven.Avoltageregulatormustalsomaintainmustoutputvoltageconstantdespitevariationintheloadcurrent.Foranysystemtoprovideanoutput,e.g.,speed,temperature,voltage,etc,anerrorsignalmustexistundersteady-stateconditions.

ElectricalBraking

Inmanyspeedcontrolsystem,e.g.,rollingmillsminewinders,etc.,theloadhastobefrequentlybroughttoastandstillandreversed.Therateatwhichthespeedreducesfollowingareducedspeeddemandisdependentonthestoredenergyandthebrakingsystemused.Asmallspeedcontrolsystem（sometimesknownasavelodyne）canemploymechanicalbraking,butthisisnotfeasiblewithlargespeedcontrollerssinceitisdifficultandcostlytoremovetheheatgenerated.

Thevariousmethodsofelectricalbrakingavaiableare:

（1）Regenerativebraking.

（2）Eddycurrentbraking.

（3）Dynamicbraking.

（4）Reversecurrentbraking（plugging）.

Regenerativebrakingisthebestmethod,thoughnotnecessarilythemosteconomic.Thestoredenergyintheloadisconvertedintoelectricalenergybytheworkmotor（actingtemporarilyasagenerator）andisreturnedtothepowersupplysystem.Thesupplysystemthusactsasa“sink”intowhichtheunwantedenergyisdelivered.Providingthesupplysystemhasadequatecapacity,theconsequentriseinterminalvoltagewillbesmallduringtheshortperiodsofregeneration.IntheWard-LeonardmethodofspeedcontrolofDCmotors,regenerativebrakingisinherent,butthyristordriveshavetobearrangedtoinverttoregenerate.Inductionmotordrivercanregenerateiftherotorshaftisdrivenfasterthanspeedoftherotatingfield.Theadventoflow-costvariablevariable-frequencysuppliesfromthyristorinvertershavebroughtaboutconsiderablechargesintheuseofinductionmotorsinvariablespeeddrives.

Eddycurrentbrakingcanbeappliedtoanymachine,simplybymountingacopperoraluminiumdiscontheshaftandrotatingitinamagneticfield.Theproblemofremovingtheheatgeneratedissevereinlargesystemasthetemperatureoftheshaft,bearing,andmotorwillberaisedifprolongedbrakingisapplied.

Indynamicbreaking,thestoredenergyisaresistorinthecircuit.WhenappliedtosmallDCmachines,thearmaturesupplyisdisconnectedandaresistorisconnectedacrossthearmature（usuallybyarelay,contactor,orthyristor）.Thefieldvoltageismaintained,andbrakingisapplieddowntothelowestspeed.Inductionmotorsrequireasomewhatmorecomplexarrangement,thestatorwindingsbeingdisconnectedfromtheACsupplyandreconnectedtoaDCsupply.Theelectricalenergygeneratedisthendissipatedintherotorcircuit.DynamicbrakingisappliedtomanylargeAChoistsystemwherethebrakingdutyisbothsevereandprolonged.

Anyelectricalmotorcanbebroughttoastandstillbysuddenlyreconnectingthesupplytoreversethedirectionofrotation（reversecurrentbraking）.Appliedundercontrolledconditions,thismethodofbrakingissatisfactoryforalldrivers.Itsmajordisadvantageisthattheelectricalenergyconsumedbythemachinewhenbrakingisequaltothestoredenergyintheload.Thisincreasestherunningcostsignificantlyinlargedrives.

EqualpulsewidthPWMlaw

VVVF（VariableVoltageVariableFrequency）installsintheearlytimeisusesPAM（PulseAmplitudeModulation）tocontrol,itsinventorpartwhichthetechnologyrealizesbutonlycanoutputthefrequencyadjustablesquare-wavevoltagenottobeabletoadjustthepressure.ThepulsewidthPWMlawarepreciselyinordertoovercome,isinthePWMlawwhichthePAMlawthisshortcomingdevelopmentcomesthesimplestonekind.ItiseachpulsewidthequalpulserowtookthePWMwave,throughachangepulserowcyclemaythefrequencymodulation,thechangepulsewidthorthedutyfactormayadjustthepressure,usesthesuitablecontrolmethodthentocausethevoltageandthefrequencycoordinationchange.IsoppositeinthePAMlaw,thismethodmeritsimplifiedtheelectriccircuitstructure,enhancedtheinputendpowerfactor,butsimultaneouslyalsohasintheoutputvoltagebesidesthefundamentalwave,butalsocontainsthebigharmoniccomponent.

StochasticPWM

ThattimethehighefficiencytransistormainlyforthebipolarityDaringtontriode,thecarrierfrequencygenerallydidnotsurpass5kHz,thevibrationwhichtheelectricalmachinerywindingelectromagnetismnoiseandtheovertonecreatedhasarousedpeople'sinterest.Inordertoobtaintheimprovement,thestochasticPWMmethodarisesatthehistoricmoment.Itsprincipleisthestochasticchangeturn-onfrequencycausestheelectricalmachineryelectromagnetismnoisetobelimitedtoapproximatelythebeltwhitenoise（inlinearfrequencycoordinatesystem,variousfrequenciesenergydistributioniseven）,althoughthenoiseadecibelnumberhasnotalwayschanged,butweakensgreatlytakethefixedturn-onfrequencyasthecharacteristiccolorednoiseintensity.Becauseofthis,evenifinIGBTbywidespreadapplicationtoday,hashadtolimitregardingthecarrierfrequencyiscomparingthelowfrequencythesituation,stochasticPWMstillhaditsspecialvalue;Ontheotherhandexplainedeliminatesthemachineryandtheelectromagnetismnoisebestmethodenhancestheoperatingfrequencyblindly,thestochasticPWMtechnologywaspreciselyprovidesananalysis,hassolvedthiskindofquestionbrand-newmentality.

SpatialvoltagevectorcontrolPWM

SpatialvoltagevectorcontrolPWM（SVPWM）alsocallsthemagneticfluxsinePWMlaw.Ittakethethree-phaseprofilewholeproductioneffectasthepremise,takeapproachestheelectricalmachineryairgaptheidealcircularrotaryfieldpathasthegoal,hastheactualmagneticfluxwiththeinventordifferentswitchpatterntoapproachthebasedirectorcirclemagneticflux,bytheirscomparisonresultdecidedtheinventortheswitch,formsthePWMprofile.Thislawembarksfromtheelectricmotorangle,regardsastheinventorandtheelectricalmachineryawhole,inscribesthepolygontoapproachthecirclethewaytocarryonthecontrol,causestheelectricalmachinerytoobtainthepeak-to-peakvalueconstantcircularmagneticfield（sinemagneticflux）.

Theconcretemethoddividesintothemagneticfluxsplit-ringtypeandthemagneticfluxclosedlooptype.Themagneticfluxsplit-ringlawsynthesizesanequivalentvoltagevectorwithatwonon-vanishingvectorsumnullvector,ifthesamplingtimeenoughissmall,maysynthesizetherandomvoltagevector.Whenthislawoutputratio-voltagesine-wavemodulationenhances15%close,sumoftheharmoniccurrenteffectivevaluesmallest.Themagneticfluxclosedlooptypeintroducesthemagneticfluxfeedback,controlsthemagneticfluxthesizeandthechangespeed.Estimatesthemagneticfluxafterthecomparisonandassignsthemagneticflux,accordingtotheerrordecidedhasthenextvoltagevector,formsthePWMprofile.Thismethodhasovercomethemagneticfluxsplit-ringmethodinsufficiency,whenhassolvedtheelectricalmachinerylowspeed,thestatorresistanceaffectsthemajorproblem,reducedtheelectricalmachinerypulsationandthenoise.Butbecausehasnotintroducedthetorquetheadjustment,thesystemperformancehasnothadthefundamentalimprovement.

VectorControlPWM

Thevectorcontrolalsocalledthemagneticfielddirectiondetectioncontrol,itsprincipleisasynchronousmotorunderthree-phasecoordinatesystemstatorcurrentIa,IbandIc,throughthethree-phase/twophasetransformation,equivalentbecomesundertwostaticcoordinatesystemsalternatingcurrentIa1andIb1,againthroughpressestherotormagneticfielddirectiondetectionrevolvingtransformation,equivalentbecomesunderthesynchronizedrevolvingcoordinatesystemdirectcurrentIm1andIt1（Im1isequaltothedirectcurrentmotorexcitingcurrent;It1isequaltothearmatureelectriccurrentwhichisproportionalwiththetorque）,thentheimitationdirectdischargemotivecontrolmethod,realizestothemotorcontrol.Itsessenceisthemotorequivalentisthedirectcurrentmotor,separatelytothespeed,themagneticfieldtwocomponentscarriesontheindependentcontrol.Throughthecontrolrotorfluxlinkage,thenthedecompositionstatorcurrentobtainsthetorqueandthemagneticfieldtwocomponents,aftercoordinatetransformation,realizationorthogonalordecouplingcontrol.

But,becausetherotorfluxlinkageaccuratelyobserveswithdifficulty,aswellasthevectortransformationcomplexity,causestheactualcontroleffectoftenwithdifficultytoachievetheoreticalanalysiseffect,thisisthevectorcontroltechnologyinthepracticeinsufficiency.Inaddition,Itmustdirectlyorindirectlyobtainstherotorfluxlinkagetobeabletorealizethestatorcurrentdecouplingcontrolinspaceposition,needstodisposetherotorpositionorthevelocitygeneratorinthiskindofvectorcontrolsystem,thisgivesmanyapplicationsituationstobringinconvenientlyobviously.

TheanalyticalfunctionsofthearmaturereactionofpermanentmagnetbrushlessDCmotorwithconcentratedcoilsareproposedbyusingthemethodofimage,concerningwiththeconfigurationofthesemachines.Thisapproac