ModernfrequencychangertechnicalanalysisChengXi(Heilongjianglongmaymininggroupco.,ltd.)Thegeneralfrequencychangerbyitsmeritsandsoonintellectualization,digitization,networkreceivespeoplesfavormoreandmore,butalongwiththegeneralfrequencychangerapplicationscopesexpansion,exposessomequestions.Inviewofthesequestions,thisarticlecarriedonhasanalyzedandproposedthecountermeasure.First,overtonequestionandcountermeasure.Thegeneralfrequencychangersmaincircuitformgenerallybytherectificationpart,thecontravariantpartandthefilterpartiscomposed.Therectificationpartforthethree-phasebridge-typeuncontrolledrectifier,theinvertorspartistheIGBTthree-phasebridge-typeinvertors,andtheoutputisthePWMprofile.Becausethegeneralfrequencychangersrectificationpartusesthediodeuncontrolledbridge-typelevelingcircuit,themiddlefilterpartusesthebigelectriccapacitytotakethefilter,thereforerectifiersinputcurrentinfactiscapacitorschargingcurrent,assumesahighermoreandprecipitouspulsewave,itsharmoniccomponentisbig.Fortheharmoniccancellation,mayuse:1,Increasesthefrequencychangerelectricpowersupplyinternalresistance.Usuallyinthesituation,powerequipmentsinternalresistancemayplaythecushionfrequencychangerconcurrentfilterelectriccapacitysreactivepowerrole.Thiskindofinternalresistanceistransformersshort-circuitimpedance.Whenpowersourcecapacityrelativefrequencychangercapacityhour,thentheinternalresistancevaluerelativelyisbigger,theharmoniccontentissmaller；Whenthepowersourcecapacityrelativefrequencychangercapacityisbigger,thentheinternalresistancevaluerelativelyisbigger,theharmoniccontentisbigger.Thereforebestchoiceshort-circuitimpedancebigtransformer.2,Installsthereactor.Installsthereactorisactuallyincreasesthefrequencychangerelectricpowersupplysinternalresistancefromexterior.Installsthedirect-currentreactorinfrequencychangersexchangesideinstallmentexchangereactororinfrequencychangersdirect-currentside,alsoorinstalls,suppressestheharmoniccurrent.3,Transformerheterogeneitymovement.Thegeneralfrequencychangersrectificationpartissixpulsewaverectifiers,thereforeproducestheovertoneisbig.Ifusingtransformersheterogeneitymovement,causesphaseanglemutualdeviation30likeY-,-thecombinationtwotransformerconstitutiontobeequalto12pulsewaveeffects,thenmayreducetheloworderharmoniccurrent28%,playstheharmonicsuppressionrole.4,Adjustsfrequencychangerscarrierratio.Solongascarriercomparedtoenoughbig,isinferiortheovertonetobepossibletosuppresseffectively,speciallythereferencewavepeak-to-peakvalueandthecarrierpeak-to-peakvaluearesmallerthan1:00,13followingoddnumberovertonesnolongerappear.5,Special-purposefilter.Thespecial-purposefilteruseinexaminingthefrequencychangerharmoniccurrentthepeak-to-peakvalueandthephase,andproducesonewiththeharmoniccurrentpeak-to-peakvaluetobethesame,butthephasejustrightoppositeelectriccurrent,passesthroughinthefrequencychanger,absorptionharmoniccurrent.Second,matchingofloadquestionandcountermeasure.Producesmachinerystorquecharacteristicstodivideintothreetypesroughly:Permanenttorqueloading,airblowerpumpclassloadandpermanentpowertermination.Inviewofthedifferentloadtype,shouldchoosethedifferenttypethefrequencychanger.1,Permanenttorqueloading.Thepermanenttorqueloadingisreferstotheloadmomenttohavenothingtodowiththerotationalspeed,underanyrotationalspeed,thetorquemaintainsconstant.Butthepermanenttorqueloadingdividesintothefrictionclassloadandthepotentialenergytypecapacitytwokinds.2,Airblowerpumpclassload.Theairblowerpumpclassloadispresentindustryfieldapplicationmostequipment,althoughthepumpandairblowerscharacteristicaremanyandvaried,butmainlybythecentrifugalpumpandthecentrifugalfanapplication,thegeneralfrequencychangersareprimarilymostinthiskindofloadapplication.Thiskindofloadisnothightofrequencychangersperformancerequirement,onlyrequeststheefficiencyandthereliability,thereforethechoicehastheU/f=constcontrolmodelfrequencychangerthen,likeMitsubishifrequencychangerFR-F540(L)series.Airblowerloadinactualmovementprocess,becausetherotorinertiaisquitebig,thereforefrequencychangersrisetimeandthedecelerationtimeareaveryimportantquestion.Theairblowerloadssystemrotorinertiacomputationisveryimportant.Whenfrequencychangerconcretedesign,accordingtothecomputedresult,carriesonthesuitablerevision,whenthefrequencychangerstartsdoesnotoccurtheoverflowtripandthefrequencychangerdeceleratewhendoesnothaveintheovervoltagetripsituation,choiceshortesttime.Butthepumpclassloadintheactualmovementprocess,easytohavethebuzz,thebuildthepressureandthewaterhangstheeffect,thereforetimefrequencychangershaping,mustchooseissuitableforthepumpclassloadthefrequencychanger,andfrequencychangerinfunctionhypothesistimemustaimattheabovequestiontocarryonestablishesalone.3,Permanentpowertermination.Thepermanentpowerterminationreferstotheloadwhichthetorqueroughlyandtherotationalspeedisinreverseproportion,likecoiler,unwindingcoilerandsoon.Speakingofcertainspeedchangescope,whenactuatesthepermanentpowerterminationusingthefrequencychanger,usuallytheconsiderationselectsthepermanenttorquevelocitymodulationmethodbelowsomerotationalspeed,whenishigherthanthisrotationalspeedonlythenselectsthepermanentpowervelocitymodulationmethod.Usuallyiscalledthisrotationalspeedspotsthebasefrequency,butthispointcorrespondencesvoltageoutputstheratedvoltageforthefrequencychanger.Third,givesoffheatthequestionandthecountermeasure.Frequencychangersgivingoffheatisproducesbytheinternalloss.Carriesontheradiationtothefrequencychanger,usuallyuse:1,Usestheventilatorradiation.Frequencychangersinternalinstallationventilatormaycarryofffrequencychangersboxbodyinteriorradiation,iftheventilatorcannotthenormalwork,immediatelystopthefrequencychangermovement.2,Reducesinstallstheambienttemperature.Generalfrequencychangersenvironmentoperatingtemperaturegeneralrequestin-10to-50,ifcantakethemeasuretoreducethefrequencychangeroperatingtemperatureasfaraspossible,thenfrequencychangersservicelifelengthens,theperformanceisalsoquitestable.Mayadopttwomethodsregardingthisquestion:First,constructstheindependentfrequencychangerlowpressure,theinteriorinstallstheairconditioning,maintainsthelowpressurethetemperaturein+15to+20between；Second,frequencychangersinstallmentspaceneedstosatisfythefrequencychangerinstructionforusetherequest.Theabovetalksaboutthefrequencychangergivesoffheatisreferstothefrequencychangerintheratedrangethenormaloperationloss.Whenthefrequencychangerhastheunusualmovement(forexampleoverflow,whencrossespressure,thelosswhichoverloadandsoon)produces,mustavoidthiskindofphenomenonthroughthenormalshapingtheoccurrence.Regardingtheairblowerpumpclassload,takeMitsubishifrequencychangerFR-F540astheexample,whenthefrequencychangerisoppositeinitsratedload120%overloads,itsdurationis60seconds,anddoesnotallowwithin300secondstopresentthesecondoverload.Whenthefrequencychangerpresentstheoverload,becausethepowerunititwindsthroughtheexcesscurrentelevatestemperature,causesthefrequencychangeroverheated,bymustcauseitstemperaturedecreasetocausefrequencychangersoverheatedprotectionmovementassoonaspossibletoeliminate,thisundercookingisfrequencychangersoverloadcycle.Thedifferentfrequencychanger,itsoverloadmultiple,theoverloadtimeandtheoverloadcyclearenotsame,anditsoverloadmultipleisbigger,theoverloadtimeisshorter.Electricalmachinerywhichactuatesregardingthefrequencychanger,maydivideintotwokindsaccordingtoitsworkingcondition:Long-termworkingsystemandredundantshort-timeworkingsystem.Thelong-termworkingsystemselectricalmachinerymayaccorditsnamebrandstipulationdatalong-termmovement.Inviewofthiskindofload,thefrequencychangermaycarryontheshapingaccordingtotheelectricalmachinerydataplatedata,likecontinuousrunningoilpump,ifitselectricalmachinerypoweristime22kW,maychoosetheFR-F540-22kfrequencychangerthen.Theredundantshort-timeworkingsystemelectricalmachinery,itscharacteristicistheduplicationandshort-time,namelyelectricalmachinerysoper