河南科技學院機電學院-1-ThefrequencyconverterisusedanddiscussedlightlyTheasynchronousmotorissuchmainpowerequipmentofmanufacturingenterpriseaselectricity,chemicalindustry,etc.Asthehighenergyconsumptionequipment,itsoutputpowercantbeuptothechangeprorataofload,majoritycanonlyturnonthroughguardorvalvedegreeregulate,buttheenergythatthemotorconsumesdoesnotchangemuch,thuscauseverygreatenergytoloss.Inrecentyears,onethatiswiththematurityoftheproductiontechnologyofthefrequencyconverterandrangeofapplicationoffrequencyconverterisextensivedaybyday,usethefrequencyconvertertocarryontechnologytotransformtothemotorpowerintotheenergy-conserving,high-efficiencyimportantmeansofeveryenterprise.1.Frequencyconversionadjuststhespeedprinciplen60f(1s)/p(1)Inthetypen-Rotationalspeedoftheasynchronousmotor；f-Frequencyoftheasynchronousmotor；s-Themotoristransferedtothedifferencerate；p-Logarithmverymuchofthemotor。Canknowbytype(1)rotationalspeednindirectproportiontofrequencyf,onlyneedchangefrequencyfandchangetherotationalspeedofthemotor,motivepowerfrequencyrealizethatspeedregulate.Thefrequencyconverterismainlyadoptedandhandedin-frank-handoverthesidewhenfrequencyfchangesintherangeof0-50Hz,therotationalspeedofthemotorregulatestherangeverywidely.Frequencyconversiontransferspeedpasspersonwhochangeselectricity,exchangefrequentlyworkerpowerchangethroughtherectifierintoadirectcurrentsourcefirstjust,thenchangethedirectcurrentsourceintothefrequency,exchangepowercontrollableinvoltageinordertosupplythemotor.Thefrequencyconverteronethereisgenerallyfromrectificationcircuit,河南科技學院機電學院-2-inthemiddleofdirectcurrentlink,goagainstnotbecomingandcontrollingpartingof4piecesnottomakeup.Rectificationpartthree-phasebridgecontrolledrectifier,isitchangesomeintoIGBTthree-phasebridgetypegoagainstthengdevicetogoagainst,andoutputforPWMwaveform,middledirectcurrentforstrainwave,directcurrentenergystorageandbufferinactivepowerlink.ThewaveinharmonyissuppressedOutstandingproblemthatfrequencyconverterusewhetherinharmonywaveinterfere,asfrequencyconverterwhenworking,outputinharmonywaveelectriccurrentofelectriccurrentwillleadtothefactinterferingtothepower.Thougheveryfrequencyconverterproducertakemeasuresandreachtofrequencyconverterinharmonyadministrationofwavenationalstandardrequirebasically,questionneedingtopaycloseattentiontomostinbutthewaveinharmonyremainstheselectingtypeofthefrequencyconverteranduses.Containotherwavesinharmonybesidesbasewaveinthevoltageofoutputofthefrequencyconverter.Lowtimesofinharmonywaveusuallyexertagreatinfluenceonelectricalmachineryload,causethetorquetopulse,andhigherwaveinharmonymakesthefrequencyconverterexportleakingtheelectriccurrenttoincreaseofthecableagain,makeelectricalmachineryexertoneselfinsufficient,soleveltimesofinharmonywavethatfrequencyconverteroutputmustsuppress.Becausetherectificationpartofthefrequencyconverteradoptsthecontrolledbridgetyperectificationcircuitofdiode,themiddlestrainwavepartadoptlargeelectriccapacityaswavefilter,sointroductionofrectifierelectriccurrenttochargeelectriccurrentcondenserinfact,itisasteeperpulsewave,itswaveinharmonyisrelativelylargeinweight.Inordertodispelthewaveinharmony,adoptthefollowingcountermeasuremainly:a.Increasefrequencyconvertersupplypowerpowerimpedancegenerally,interiorimpedance,powerofequipmentcanisitbufferfrequencyconverterdirectcurrentstrainfunctionofinactivepower,waveofelectriccapacitytoplay.Impedanceisshortcircuitimpedanceofthevoltagetransformerinthiskind.Look河南科技學院機電學院-3-onpowercapacityrelativecapacitylittlefrequencyconverteras,interiorimpedancevaluerelativeandheavy,thelessthecontentofwaveinharmonyis；Therelativefrequencyconverterofcapacityofthepoweristhelargerincapacity,impedancevalueisrelativelow,thelargerthecontentofwaveinharmonyis.Choosefrequencyconverteratsupplyingpowerpowertransformering,hadbetterisitshortoutimpedanceheavyvoltagetransformertochoose.b.Installreactorinstallreactortoincreasefromoutsidefrequencyconvertersupplypowerinteriorimpedanceofpoweractually.Installsthereactororinstallsatthesametimeontheexchangesideofthefrequencyconverterorthedirectcurrentsideofthefrequencyconverter,cansuppresstheelectriccurrentofwaveinharmony.c.Therectificationpartofthefrequencyconverteris6pulsewaverectifiersthatthevoltagetransformerusuallyoperatesheterogeneously,sothewaveinharmonyproducedisrelativelybig.Useheterogeneousoperationofvoltagetransformer,suchasmakephaseplacecornerbadYof30eachotherY、2voltagetransformersmadeupareformedandequivalentto12pulsewaverectifiers,canreducetheelectriccurrentofwaveinharmony,playagoingtothewaveinharmonytosuppressrole.d.RegulateyearofthefrequencyconverterBobImproveBobinyearofthefrequencyconverter,cansuppresswaveinharmonyonceeffectivelylow.e.UsethewavefilterWavefiltercanmeasurefrequencyconverterinharmonywaveamplitudeandphaseplaceofelectriccurrent,producetheelectriccurrentcontrarytoelectriccurrentphaseplacethesameinamplitudeofwaveinharmony,thusabsorbeffectively.3.Matchofload3.1SquaretorqueloadAirblower,pumploadwhetherindustryuseequipmentmostlive,frequencyconverteratmostapplicationattheload.Itplantssquaretorqueload.Generallyspeaking,haveU/f=Constcontrolfrequencyconverterofmodecanmeetthe河南科技學院機電學院-4-demandofloadbasically,belowfoundationthemaincharacteristicquestionthatneednoticewhenintroducingpersonningwhoselectoffrequencyconverter.3.1.1HaveavoidedloadingAirblowerdifficultoverloadaswaterpump,guaranteeitgreaterthanormeanthecapacityofthemotorslightlyatthecapacitytochoosefrequencyconverter；Overloadcapacityoffrequencyconverterthatchooseatthesametimerequiretobelowereven,upto120%generally,1min.Butshouldnoticewhenthefunctionparameterofthefrequencyconverterischosenandpresetted,becausetheloadonehindersthetorqueindirectproportiontothesquareofrotationalspeed,whentheoperatingfrequencyishigherthanthespecifiedfrequencyofthemotor,tohindertorquecanexceedthespecifiedtorqueload,overfreightmotor.Soisitcontrolsupremeoperatingfrequencycanexceedthespecifiedfrequencyoftheelectricalmachinerystrictlytowant.3.1.2Matchthatthefrequencyconverteracceleratestimeandmoderatestimewhileopening/stoppingBecauseairblowerandloadofpumprotateinertiatobeheavy,itstartandwhenstoppingwithtoacceleratetimeandmoderatetimeitmatchestobeoneimportantproblemveryfrequencyconverter.Personwhoselectwhenusing,shouldc