第10章 直流無刷電機(jī)

IntroductionBLDCmotorsareoneofthemotortypesrapidlygainingpopularity.BLDCmotorsareusedinindustriessuchasAutomotive,Aerospace,Consumer,Medical,IndustrialAutomationEquipmentandInstrumentation.Asthenameimplies,BLDCmotorsdonotusebrushesforcommutation;instead,theyareelectronicallycommutated.BrushlessDCelectricmotor(BLDCmotors)alsoknownaselectronicallycommutatedmotorsaresynchronousmotorsthatarepoweredbyaDCelectricsourceviaaninverter,whichproducesanACelectricsignaltodrivethemotor(AC,alternatingcurrent,doesnotimplyasinusoidalwaveformbutratherabi-directionalcurrentwithnorestrictiononwaveform);additionalsensorsandelectronicscontroltheinverteroutputamplitudeandwaveformandfrequency(i.e.rotorspeed).ABrushlessDCmotorconsistsofthreeparts,amotor,therotorpositionsensorsandelectronicswitchingcircuit.principleblockdiagramofabrushlessDCmotorisshowninfig.10-1.DCpowersupplySwitchingcircuitMotorPositionSensorOutputFig.10-1principleblockdiagramofbrushlessDCmotors翻譯直流電機(jī)的電機(jī)類型之一的迅速普及。BLDC電機(jī)應(yīng)用在如汽車，航空航天，消費(fèi)，醫(yī)療行業(yè)，工業(yè)自動化設(shè)備及儀表。顧名思義，BLDC電機(jī)不使用電刷換向；相反，它們是電子換向。無刷直流電機(jī)（BLDC電機(jī)）也被稱為電子換向電機(jī)同步電機(jī)，由直流電源通過逆變器驅(qū)動電機(jī)，產(chǎn)生交流電信號（交流，交流，并不意味著一個正弦波形而對波形沒有限制雙向電流）；附加傳感器和電子控制的逆變器輸出的幅值、波形和頻率（即轉(zhuǎn)速）。BLDCmotorshavemanyadvantagesoverbrushedDCmotorsandinductionmotors.Afewoftheseare:直流電機(jī)在直流有刷電機(jī)和感應(yīng)電機(jī)有許多優(yōu)點(diǎn)。這些都是一些：?Betterspeedversustorquecharacteristics更好的速度和轉(zhuǎn)矩特性?Highdynamicresponse高動態(tài)響應(yīng)?Highefficiency效率高?Longoperatinglife壽命長?Noiselessoperation無聲運(yùn)行?Higherspeedranges?高速范圍Inaddition,theratiooftorquedeliveredtothesizeofthemotorishigher,makingitusefulinapplicationswherespaceandweightarecriticalfactors.Wewilldiscussindetailtheconstruction,workingprinciple,characteristicsandtypicalapplicationsofBLDCmotors.此外，通過向電動機(jī)轉(zhuǎn)矩的大小比例較高，使得它在空間和重量是關(guān)鍵因素的應(yīng)用。我們將詳細(xì)討論的結(jié)構(gòu)，工作原理及典型應(yīng)用，直流電機(jī)的特點(diǎn)。10.2FUNDAMENTALCONSTRUCTIONANDOPERATINGPRINCIPLE基本結(jié)構(gòu)和工作原理BLDCmotorsareatypeofsynchronousmotor.Thismeansthemagneticfieldgeneratedbythestatorandthemagneticfieldgeneratedbytherotorrotatesatthesamefrequency.BLDCmotorsdonotexperiencethe“slip”thatisnormallyseenininductionmotors.BLDCmotorscomeinsingle-phase,2-phaseand3-phaseconfigurations.Correspondingtoitstype,thestatorhasthesamenumberofwindings.Outofthese,3-phasemotorsarethemostpopularandwidelyused.直流電機(jī)是一種同步電機(jī)。這意味著由轉(zhuǎn)子產(chǎn)生的磁場與定子所產(chǎn)生的磁場，在相同的頻率旋轉(zhuǎn)。BLDC電機(jī)不經(jīng)歷“滑”即是在感應(yīng)電動機(jī)通常看到的。直流電機(jī)是單相，兩相和三相配置。相應(yīng)的類型，定子繞組相同數(shù)量。從這些，三相異步電動機(jī)是最流行和廣泛使用的。10.2.1CONSTRUCTIONFigure10-2Construction1)StatorThestatorofaBLDCmotorconsistsofsteellaminationswithwindingsplacedintheslotsthatareaxiallycutalongtheinnerperiphery.Traditionally,thestatorresemblesthatofaninductionmotor;however,thewindingsaredistributedinadifferentmanner.MostBLDCmotorshavethreestatorwindingsconnectedinstarfashion.Eachofthesewindingsareconstructedwithnumerouscoilsinterconnectedtoformawinding.OneormorecoilsareplacedintheslotsandtheyareFigure10-3Statorinterconnectedtomakeawinding.Eachofthesewindingsaredistributedoverthestatorperipherytoformanevennumbersofpoles.Figure10-3一臺電機(jī)的定子由鋼疊片放置在沿內(nèi)周軸向切槽繞組。傳統(tǒng)上，定子類似于一個感應(yīng)電動機(jī)；然而，繞組分布在不同的方式。大多數(shù)的BLDC電機(jī)有三個定子繞組的星形連接方式。這些眾多的線圈繞組連接成一個繞組構(gòu)造。一個或多個線圈被放置在插槽中，他們相互連接，使繞組。這些繞組分布在定子的外圍形成一個偶數(shù)極。圖10-3Thearmaturewindingconnectionsareshowninfigure10-4.(a)3-phase,star,3-state;(b)4-phase,star,4-state(c)3-phase,star,6-state(d)2-phase,orthogonal,4-state

Figure10-4Armaturewindingconnection (e)3-phase,delta,6-state;(f)4-phase,closed,4-state2)RotorThefollowingfigure10-6showscrosssectionsofdifferentarrangementsofmagnetsinarotor.Figure10-6UnlikeabrushedDCmotor,thecommutationofaBLDCmotoriscontrolledelectronically.TorotatetheBLDCmotor,thestatorwindingsshouldbeenergizedinasequence.Itisimportanttoknowtherotorpositioninordertounderstandwhichwindingwillbeenergizedfollowingtheenergizingsequence.RotorpositionissensedusingHalleffectsensorsembeddedintothestator.不像有刷直流電機(jī)，一臺電機(jī)的換相控制電子。對BLDC電機(jī)旋轉(zhuǎn)，定子繞組應(yīng)在順序通電。重要的是要知道為轉(zhuǎn)子位置，了解哪些繞組將通電后，通電順序。轉(zhuǎn)子位置檢測采用霍爾傳感器嵌入定子。3)HallSensorsMostBLDCmotorshavethreeHallsensorsembeddedintothestatoronthenon-drivingendofthemotor.WhenevertherotormagneticpolespassneartheHallsensors,theygiveahighorlowsignal,indicatingtheNorSpoleispassingnearthesensors.BasedonthecombinationofthesethreeHallsensorsignals,theexactsequenceofcommutationcanbedetermined.大多數(shù)的BLDC電機(jī)有三個霍爾傳感器嵌入定子在電機(jī)的非驅(qū)動端。當(dāng)轉(zhuǎn)子的磁極通過附近的霍爾傳感器，他們給一個高或低信號，指示的N或S極附近時，傳感器。基于這三個霍爾傳感器信號的組合，變換的精確序列可以確定。(4)Electro-magneticpositionsensor10.2.2TheoryofOperation1)Theoperationprincipleof3-phase,star,3-statesystemisexplainedwithfigure8.Figure10-8OperationprincipleTable10-1Conductionsequencetableof3-phase,star,3-statesystemFigure10-9PhasevoltageswaveformsofBLDCFig.10-10Torquewaveform2)3-phase,star,bridgeconnectionFig.10-123-phase,star,bridgeconnectionV1V6(A+C-)→V6V2(B+C-)→V2V4(B+A-)→V4V3(C+A-)→V3V5(C+B-)→V5V1(A+B-)→V1V6(A+C-)Table10-2Conductionsequencetableof2-phase,star,3-phase,6-statesystemFigure10-13Torquevectordiagram3)3-phase,closed,bridgeconnection.Figure10-143-phase,closed,bridgeconnectionV1V6[A//(C→B)]→V6V2[B//(C→A)]→V2V4[C//(B→A)]→V4V3[A//(B→C)]→V3V5[B//(A→C)]→V5V1[C//(A→B)]→V1V6[A//(C→B)]Table10-3Conductionsequencetableofclosed,star,6-statesystem10.3COMPARINGBLDCMOTORSTOOTHERMOTORTYPESComparedtobrushedDCmotorsandinductionmotors,BLDCmotorshavemanyadvantagesandfewdisadvantages.Brushlessmotorsrequirelessmaintenance,sotheyhavealongerlifecomparedwithbrushedDCmotors.BLDCmotorsproducemoreoutputpowerperframesizethanbrushedDCmotorsandinductionmotors.Becausetherotorismadeofpermanentmagnets,therotorinertiaisless,comparedwithothertypesofmotors.Thisimprovesaccelerationanddecelerationcharacteristics,shor