Key Points of Motor Rotor Dynamic Balancing Process Control

2020-02-25

Rotordynamicbalanceisanextremelyimportantprocessinthemotorproductionandmanufacturingprocess,whichisdirectlyrelatedtowhetherthenoiseandvibrationperformanceofthemotorareuptostandard. Duetothedefectsinth

Summary of Industrial Application and Development Trend of Popular Science Motors

2017-12-28

Sciencepopularization,industrialapplicationanddevelopmenttrendsummaryofvariousmotors Electricmotor(English:electricmachine,commonlyknownas"motor")referstoanelectromagneticdevicethatconvertsortransferselectricenergyaccordingtothelawofelectromagneticinduction.itisindicatedbytheletterm(theoldstandardisd)inthecircuit. Itsmainfunctionistogeneratedrivingtorqueasapowersourceforelectricalappliancesorvariousmachines.  1,theuseofmotor   Controlmotorsinindustry,agriculture,transportationandotherfieldsmainlyincludeservomotors,steppingmotors,torquemotors,switchedreluctancemotorsandbrushlessDCmotors.  ThemostwidelyusedofallkindsofmotorsisACasynchronousmotor(alsocalledinductionmotor). Itiseasytouse,reliableinoperation,lowinpriceandfirminstructure,butithasalowpowerfactorandisdifficulttoregulatespeed. Synchronousmotorsarecommonlyusedinpowermachineswithlargecapacityandlowrotationspeed,becausesynchronousmotorsnotonlyhavehighpowerfactor,butalsotheirrotationspeedhasnothingtodowiththesizeoftheloadandonlydependsonthefrequencyofthepowergridandworkmorestably. DCmotorsareoftenusedinoccasionsrequiringwide-rangespeedregulation,buttheyhavecommutator,complexstructure,highprice,difficultmaintenanceandarenotsuitableforharshenvironments.  Sincethe1970s,withthedevelopmentofpowerelectronicstechnology,ACmotorspeedregulationtechnologyhasgraduallymaturedandtheequipmentpricehasbeendecreasing,thusithasbeenapplied. Themaximumoutputmechanicalpowerthatthemotorcanundertakeunderthespecifiedworkingsystem(continuous,short-termoperationandintermittentperiodicoperation)withoutcausingoverheatingofthemotoriscalleditsratedpower,andattentionshouldbepaidtotheregulationsonthenameplatewhenitisused.  Whenthemotorisrunning,attentionshouldbepaidtomatchingthecharacteristicsofitsloadwiththoseofthemotortoavoidrunawayorstalling. Therearemanymethodsofmotorspeedregulation,whichcanmeettherequirementsofdifferentproductionmachineryspeedchanges. Ingeneral,theoutputpowerofthemotorvarieswiththespeedofthemotor. Fromthepointofviewofenergyconsumption,speedregulationcanberoughlydividedintotwotypes:oneistokeeptheinputpowerunchangedandadjusttheoutputpowertoadjusttherotationspeedofthemotorbychangingtheenergyconsumptionofthespeedregulationdevice; Thesecondistocontroltheinputpowerofthemotortoadjusttherotationalspeedofthemotor.  2.DevelopmentofMotor   Accordingtothecurrentdevelopmentofmotor,energysavingisthedevelopmentgoal,intelligentcontrolisthedevelopmenttrend,andbrushlessDCmotoristhedevelopmenthotspot.   Energyconservationisthekeytodevelopment   Withtheglobalenergycrisisbecomingmoreandmoreprominent,governmentsandenterprisesallovertheworldaretryingtofindwaystoachievesustainableenergydevelopment.Increasingsourcesofincomeandreducingexpenditureisthecurrentcommonmethod. Atpresent,ourcountryalsofacesmanyproblemsinenergyrestriction,anditisparticularlyurgenttobalancetherelationshipbetweenenergyandeconomicdevelopment.  Fromtheperspectiveofenergyconservationandenvironmentalprotection,highefficiencymotorsarethecurrentinternationaldevelopmenttrend.EuropeanCEMEPstandards,basedontherunningtimeofmotors,dividedtheefficiencyintoeff1(highest),eff2andeff3(lowest)levels,whichwereimplementedstepbystepfrom2003to2006. IEC60034-30dividesmotorefficiencyintofourgrades:IE1(correspondingtoeff2),IE2(correspondingtoeff1),IE3andIE4(highest). ChinaiscommittedtoimplementingIE2andabovestandardsfromJuly1,2011. Boththeinternationalrequirementsandthedomesticenergyshortagesituationneedtotaketheenergy-savingdevelopmentofmotorsasthefirsttask.   Intelligentcontrolisthetrend   Withthedevelopmentofcommunicationtechnology,intelligentcontrolhasalsobecomeahottopicinthefieldofmotors.Thefullyautomaticwashingmachinesandautomaticcurtainsusedinourlifealltransmitintelligentsignals.Motorcontroltendstobesimplifiedandintelligent.PLC,FPGAandDSPareincreasinglyintegratedintothemotorindustrychain.  Thefunctionofintelligentmotorcontrolismuchmorethanthatoftraditionalmotorcontrol.Intelligentmotorrealizeslow-carbonoperation,andthefailureprobabilityanddowntimearegreatlyreduced.Ithasbecometheinevitabletrendofmotorcontroldevelopment. Forexample,anintelligentpowermodulecanbeusedtoformapowerinterfacebetweenthemicrocontrollerorDSPandthemotor,whichcanreducethesizeofthemotorandsimplifythedesign.  Comparedwithpreviousdiscretesolutions,thismodulehastheadvantagesofsmallerparasiticinductanceandhigherreliabilitybecauseallpowerdevicesinthemoduleusethesamebatchofchipsandhaveconsistenttestperformance. Thisintelligentpowermodulecaninterfacedirectlywiththemicrocontroller'slowvoltageTTLorCMOSoutputandhasaprotectioncircuit.  Themoduleisinternallyprovidedwithathermistorformonitoringjunctiontemperature,alogicprotectioncircuitforpreventingupperandlowerbridgearmsfrompassingthrough,deadtimecontrol,andadrivewaveformshapingcircuitforminimizingEMI,etc. Inthemodule,eachdrivingICcanbeoptimizedtocompletetheswitchingactionofthepowerdevicewithminimumEMIanddrivingloss. Itisagreatpromotiontoenergyconservation.  BrushlessDCmotorisahotspot  Afteryearsofdevelopmentandapplication,the

Key Points of Motor Rotor Dynamic Balancing Process Control

2019-08-26

Rotordynamicbalanceisanextremelyimportantprocessinthemotorproductionandmanufacturingprocess,whichisdirectlyrelatedtowhetherthenoiseandvibrationperformanceofthemotorareuptostandard. Duetothedefectsintheelectricaldesignofthemotor,thenoiseandvibrationwillalsoexceedthestandard,interwovenwiththemechanicalimbalance,resultinginextremelycomplexnoiseandvibrationproblemsofthemotor. Today,Msparticipatedinthediscussionontheunbalancedproblemofthemotorrotoritself,thatis,regardlessofelectromagneticfactors,toexplorethemechanicalcausesofnoiseandvibrationproblems.  Themotorrotoritselfbelongstoatypicalrotatingbody. Inthemanufacturingprocess,processingerrororuncertaintyofmanualoperationcausesunevenmassdistribution(i.e.eccentricity),resultinginimbalance. Iftheforcegeneratedbyunbalanceisnotcorrected,itwillnotonlycausedamagetothebearingandmotor,butalsocausecrackingofthemachinefoundationandcrackingoftheweldseamsofthestructuralparts.  Bymeansofweightingorde-weighting,reducingoreveneliminatingthisunbalancedfactoriscalledrotorbalance. Whentheunbalancedmassmomentexistsintheradialplaneofthecenterofmassandthereisnoforcemoment,itisdirectlyweightedorreducedbytheradialplaneofthecenterofmass,whichiscalledstaticbalancecorrection. Ifthecenterofmassoftherotorisexactlyontheaxis,thecenterofgravityoftherotoronthecrosssectionoftheaxisonbothsidesofthecenterofmassisnotontheaxis,andthetwocentrifugalforcesareequalinmagnitudeandoppositeindirectionwhenrotating,formingapairofforcecouples,thisforcecouplemomentcausesthetwoendbearingstogenerateaperiodicallychangingdynamicreactionforce,soitmustbeweightedorreducedintwoplanesatbothendsofthecenterofmass,whichiscalleddynamic-staticbalancecorrection. Ingeneral,thecentrifugalforcewhenthemotorrotorrotatesisaresultantforceandacouple,sotheoften-saidrotordynamicbalanceshouldactuallybethecorrectionoperationofthemixeddynamicandstaticimbalance.  Rotordynamicbalancingmethod Thecentrifugalforcecausedbyunbalancedependsontherotationspeedandweightoftherotor. Inordertofindthecorrespondingrelationshipbetweenunbalancedmassandamplitude,thetrialweightcanbeusedtochangethevibrationamplitudeandtoknowhowmuchamplitudechangetheunitunbalancedweightcauses. AssumingthatAistheoriginalamplitude(μm),Gistherotorweight(kg),Risthebalanceradius(mm),andtherotationspeedisn(r/min),thetrialweightisestimatedasfollows:Theweightingpositionmainlydependsontheaccumulationofexperiencetodeterminethebearingofthetrialweight,andgenerallytheunbalancedweightis15-45degreesaheadofthevibrationmeasuringpoint.  BalanceAccuracyandItsCalculation Balanceaccuracy,alsocalledbalancequality,isanindextomeasurethedegreeofrotorbalanceinmm/S. Iftheunbalancerate(unitg.mm/kg)oreccentricity(unitμm)oftherotorafterbalancingisE,thebalancingaccuracyG(unit:mm/s)is: G=ωe/1000 Whereωistherotorangularvelocity(rad/s)andtherelationshipwiththerotationalspeednisω=2πn/60 IfthebalanceradiusisR(unitmm),theformulaforcalculatingtheallowableresidualunbalancedmassm(unitg)isderivedasfollows: 2mω2R=Wω2e m=We/2R Wherewisthetotalmassoftherotorinkg Ifthereisamotorrotor,balanceaccuracyG6.3,rotorspeedn=800r/min,rotormass0.142kg,rotordiameter17mm,then: R=17/2=8.5(mm) e=1000G/ω=30000G/πn=75.2(μm) Allowedunbalancem=we/2r=0.63(g)  Atpresent,variousmotormanufacturersusedynamicbalancingequipmentofdifferentspecificationsandmodels. Accordingtothemeasuringprinciple,therearehardsupportdynamicbalancingmachineandsoftsupportdynamicbalancingmachine. Accordingtothetype,therearehorizontalandverticaldynamicbalancingmachines. Accordingtotheapplication,thereareuniversalandspecialdynamicbalancingmachines.  Intheactualbalancingprocess,wecanfindthatsomerotorsdonotfindproblemsinthebalancingprocess,ortherotorsthathavebeendeterminedtobebalancedbydynamicbalancingwillhavevibrationornoisecausedbytheproblemsoftherotorsthemselvesinactualoperation,especiallyforflexiblerotors. Inaddition,ifthedifferencebetweenthemotorspeedandthebalancingequipmentspeedislarge,thebalancingeffectwillnotbeconsistentwiththeactualoperationeffect. Itisbasedontheanalysisandsolutionofmanysimilarproblemsinthepast,andbasedoncontinuousexperienceaccumulationandtheoreticalinnovation,awidevarietyofimprovedandspecialdynamicbalancingequipmenthavebeenderived.