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Key Points of Motor Rotor Dynamic Balancing Process Control
2020-02-25
Rotordynamicbalanceisanextremelyimportantprocessinthemotorproductionandmanufacturingprocess,whichisdirectlyrelatedtowhetherthenoiseandvibrationperformanceofthemotorareuptostandard. Duetothedefectsinth
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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
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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.
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