英语翻译原文Word下载.docx
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英语翻译原文Word下载.docx
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systemcan:
a)realizetheloadrelationshipofdirectelectromagnetictorquebetweenthemotorgroup;
b)getthecontinuouscontrolprocesseasilyforthereactionloadandpotentialenergyloadduringfourquadrant;
c)achievethetotalavailabilityoftheregeneratedenergyatanykindofload.Thesystem’spowerconsumptionmakesupunder30%ofactualloadpoweratanykindofload.
Keywords:
ACspeed-governing;
electromagneticload;
energysaving;
differencefrequency
1DevelopmentofACspeed–governing
Foralongtime,becauseDCMotorSpeedsuperiorperformanceandcoveruptheshortcomingsofcomplexstructures,andotherwidelyusedinengineeringprocesses.DCmotorratedspeedinthefollowingrun-time,maintainingaconstantcurrentexcitation,armaturevoltagecanbeusedtochangethemethodofachievingaconstanttorquespeedintheratedspeedoverrunningandmaintainingthearmaturevoltageconstant,canbeusedtochangethemethodexcitationconstantpowertransferSpeed.Usedspeed,double-loopDCconvertercurrentsystemwillbeanexcellentstaticanddynamicgovernorcharacteristics.
Therefore,duringthe1980sbeforethetransmissionspeedinthefield,DCconverterhasbeenthedominantposition.Inrecentyears,therapiddevelopmentofscienceandtechnologytospeedthedevelopmentoftheexchangecreatedaveryfavorabletechnicalconditionsandmaterialbasis.ACMotorSpeedControlsystemnotonlytheperformancewiththeperformanceofDCMotors,andthecostandmaintenancecostslowerthantheDCmotorsystems,higherreliability.
(1)ModerntypesofACDriveSystem
ModerncommunicationsystemsfromACMotorSpeed,powerelectronicpowerconverters,controllersanddetectors,andotherfourmajorcomponents.Powerelectronicpowerconverters,controllers,powerconsumptionisconcentratedinonetest,knownasthefrequencyconverter(VVVFdevices).ACMotordifferent,andmultiplytospeedtheexchangeofdifferentsystems.Sospeedofmoderncommunicationsystemscanbedividedintoasynchronousmotorspeedcontrolsystemandsynchronousmotorspeedregulationsystem.Atpresenttherearethreemorecommonprogramme,whichistheexchangeofasynchronousmotorspeedregulationsystem,SRMexchangesystemandspeedtheexchangeofpermanentmagnetsynchronousmotorspeedregulationsystem.Speedinthedesign,whichismoreappropriatetotheprogramme,whichrequiredfurtheranalysis.
Throughoutthedevelopmentofcommunicationtechnologiesspeed,wecanseethatmoderncommunicationtechnologiesspeedthedevelopmentoffuturetrendsanddevelopments.
1,intelligentcontrolsystemtospeedtheexchangeofimpactstudies.
2,speedcontrolsystemtoimprovetheefficiencyoftheexchangemethod.
3,thepressureFrequencyDeviceresearch.
4,systemreliabilitystudies.
(2)ACDriveSystemBenefits
Foralongtime,duetoDCconvertersystemperformanceisbetterthanACDriveSystem,DCconvertersystemhasbeeninareasdominatedbyspeed.However,theDCconvertersystemhasseveralshortcomingsbelow.
1,aDCmotordrag.DCMotorspronetofailure,maintenancedifficulties.
2,Useislimited.Inflammable,explosiveandapoorenvironmentwhereminingcannot.
3,theDCmotorofstructuralfactors,sothatsinglespeedandcapacityconstraints,resultinginDCconvertersystemdevelopmentwaslimited.
4,DCmotorprices,farhigherthanACmotors.
Withelectricity,electronictechnologydevelopment,especiallyinthedevelopmentofcontroltechnologyinrecentyears,exchangesspeedaccesstotheleapinthedevelopment.ACDriveSystembelowseveralmajoradvantages.
1,ACMotorparticularcageinductionmotorpricesmuchlowerthantheDCmotor.
2,ACMotordifficulttofailure,maintenanceissimple.
3,ACmotorthereisnorestrictionontheuseofoccasions.
4,ACmotorscanbemuchgreaterthanthecapacityofsingleDCmotor.
Let’sreviewforamomentsomeofthevarioustermsastheyareusedtodescribesolid-statefrequencycontrollers.Therearerigidtechnicaldefinitionsasgenerallyusdterminology.First,thetechnicaldefinitionsassuggestedbyorganizationssuchasIEC,NEMA,andIEEE(InstituteofElectronicsEngineers):
(1)Converter:
anoperativeunitforpowerconversioncomprisingoneormorevalvedevices(powersemiconductors,forexample).
(2)Self-commutatedconverter:
aconverterinwhichthecommutationvoltagesaresuppliedbycomponentswithintheconverters.
(3)Rectifier:
aconverterforconversionfromACtoDC.
(4)Inverter:
ainverterforconversionDCtoAC.
(5)IndirectACconverter:
aconvertercomprisingarectifierandaninverterwithaDClink.
Formoranther,anddefinition5coversthecompletesystem.However,generalusageintheUnitedStatesistocallit“inverter”:
PWMinverter,adjustablevoltageinverter,orcurrentsourceinverter.
PWMVersusAVIVersusCSI
Allthreeofthemostcommonlyusedadjustable-frequencycontrollersconsistofthreebasicsections.TheinputsectionconvertstheincomingACpowertoAC.Thecentersection,orDClinkorDCvoltage.TheoutputsectioninvertstheDCintoACofACofthedesiredfrequency.
Thedifferencesamongthesethreetypesofcontrollersarethemannerinwhichtheadjustablevoltageisobtained,andthetechniqueusedtocreatetheadjustablefrequency.
PWM
PulseWidthModulation(PWM)manytypesoftechnology,andisconstantlydeveloping.Canbasicallybedividedintofourcategories,namelywidthPWM,sinePWM,PWMflux-trackingmethodoftrackingPWMandcurrentlaw.PWMtechnologytoovercomethephasedapplicationoftheprincipleofalldefectssothatthemotorstatorexchangeshavebeenclosetosine-voltageandcurrent,improvingtheelectricalpowerfactorandthepoweroutput.MostmodernPWMcircuitgeneratedbyhighoutputHSOtheSCM(80,196)anddigitalsignalprocessors,softwareprogramminggeneratedbyPWM.Inrecentyears,newdigitalPWMgenerationchipsforHF4752,SLE4520,M18,andsoachievepractical,andhavepracticalapplications
Pulse-widthmodulation(PWM)utilizesdiodesintheinputstagetoprovideafixed-voltageDCbus.Theoutput,orinverterstage,createsaseriesofpulsesofconstantvoltagewiththepulsewidthsandquantitiesvaryingasrequiredbythedesiredbythedesignedoutputfrequencyandvoltage.Theoutputsectionsuppliesandcontrolsbothparameters,adjustablefrequencyandadjustablevoltage.
AVI
Adjustable-voltageinverters(AVI)usethyristorsinthestagetoobtainadjustablevoltageintheDClink.TheoutputstageswitchesthisDCvoltagewiththyristorsortransistorsorGTOstoobtainasquare-wavewhosewidthandtimingsequencecontrolisobtainedinthesecondstage.
CSI
Currentsourceinverters(CSIs)aresimilartoAVIs,exceptthatthecontrolisarrangedtoprovideaseriesofsquarewavesofcurrentoutput.
2 Thestructureandthefeatureofthesystem
Fig.1showstheprincipleandstructureofthisACexperimentsystem.TheworkprocessoftraditionalACspeed-governingisthatvariablevoltagefromfrequencyconverterdrivesaninductionmotorwhichmakesgeneratorsupplytosomeloadssuchasresistorandelectricheatingelement,andthenproducestheelectromagnetictorqueonthegeneratorasloadtorqueofmotor.Butthisloadtorqueisbalancedbyachievingthecurrentpowerfromfrequencyconverter.SothetraditionalACspeed-governingexperimentsystemisaprocessofenergyconsuming.
Fig.1 ACspeed-governingexperimentsystem
TheACspeed-governingexperimentsystem,whichisshowninFig.1,hasbeengreatlyimprovedatstructure.Normalmotor-generatorarechangedintotwomotorsatthesameshaftandthetwoinvertersareparallelatDCbus.Thentheoutputofvariablefrequencycurrentdrivesthetwomotorsseparately.Twoinverterscanbecontrolledbymeansofdifferencefrequency.Theadvantageofthisexperimentsystemisnotonlyinthechangeofstructure,butmoreimportantisthatthefunctionindex,controlfeaturearemuchmoreimproved,especiallyforitscharacteristicofeconomicalenergy.Ifthelossbeyondthemotorloadisnotconsidered,theexperimentresultsshowaprocessofregenerateenergybeingfeededbackandutilizedtotallyinfact.
3 Analysisofsystemprinciple
3.1 Formandfeatureofmotorload
TheworkingprincipleofthissystemisthatbothinductionmotorsfixedonsingleaxisaredrivenbyACdifferecefrequencyvoltagethataretheoutputsoftwoinvertersbymeansofsettingdifferencefrequency.Itcanbeprovedbytheanalysisoftorquefeatureandparameterexpressionthatthetorqueofmotorone(M1)producedbyhighfrequencyvoltageisbiggerthantorqueofmotor(M2)producedbylowfrequencyvoltage.SoM1worksatthestateofmotor(quadrantone)anditselectromagnetictorqueisasthemaintorquetodriveM2,whichworksatthestateofgenerator(quadranttwo)andoverstepsthesynchronousspeed(n>
n02).Itisobviouslythatifthesystemhasthepossibilitytorecoverregenerateenergy,M2willproducetheelectromagnetictorquewhichhastheoppositedirectiontoM1,andmakesmotor-generatorgroupgettheloadrelationshipofdirectelectromagnetictorque.Fig.2showseachmechanicalfeaturesoftwomotors
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