發(fā)輸變電復(fù)習(xí)進(jìn)度設(shè)計(jì)

一、原始依據(jù)（包括設(shè)計(jì)或的工作基礎(chǔ)、研究條件、應(yīng)用環(huán)、刷直流電機(jī)還具有電磁干擾小、運(yùn)行可靠方便、形狀和尺寸靈活多樣等諸、DSP的無刷直流電機(jī)，． ，．KIizuka,HUzuhashi，MKano. putercontrolforsensorlessbrushlessmotor[J].IEEETrans.Ind.Applicat，1985,21(3):595-601.KTaehyung.SensorlesscontroloftheBLDCmotorsfromnear-zerotofullspeed[D].Texas:TexasA&MUniversity,2003.選題是否合適：是選題是否合適：是□ 課題能否實(shí)現(xiàn)：能□ 審題小組組長（簽字 本文基于TI公司的DSP——TMS320LF2407A進(jìn)行了相應(yīng)的無位置傳介紹了TMS320LF2407A的結(jié)構(gòu)和功能并給出了相應(yīng)的和ADCPermanentmagnetBrushlessDCmotorwithexcitationhavefoundwideappicationinreallifeandproductionduttosimplestructure,higheffficiencyandlargemagneticfluxdensity,ButinbrushlessDCmotors,mechanicalpositionsensorsaffectoverallsystem’sreliability,costandvolume,eveninsomeoccasionstheycannotbeinstalledsimply.Thereforesensorlesscontrolisofgreatsignificance.Attaentofsensorlesscontrolnotonly esalotofdisadvantagesgeneratedbythesensor,butalsoexpandstheapplicationrangeofbrushlessDCmororfurther.Atpresent,sensorlesscontrolhas eadevelopmenttrendofcontroltechniqueforbrushlessDCmotor.ThisdissertationresearchessensorlessconrtolbasedonDSPchips—TMS320LF2407AofTIAtfiirst,developmentstatusanddevelopmenttrendofsensorlesscontrolisIntroducted,thenoperationalcharacteristicsofbrushlessDCmotorisyzed,andaginstoperationalcharacteristicsasensorlesscontrolmethodisIntroducted.HardwareofsensorlesscontrolcontrolcircuitisIntroducted.Implementmethodofthesignalprocessingchip,powerdevices,thecorrespondingcircuitcomponents,andtheintegratedfunctionareexined.TMS320LF2407A’structureandfunctionisintroducedandthecorrespondingADCandImplementtheoryandalgorithms,aswellasthecorrespondingsoftwareachieveingcontrol,aregived,Finallyysisofthetestresultsarepresented.:BrushlessDCMotor;Sensorlesscontrol;DigitalSignalProcessing第一章緒 第二章永磁無刷直流電機(jī)的結(jié)構(gòu)與工作原 第三章無位置傳感器無刷直流電動機(jī)控制方法的實(shí) 光耦............................................................................. A硬件的主要特 ADC中斷子程 致第一章2030年代，就有人研究以電子換向代替機(jī)械換向的直流電機(jī)，并直流電機(jī)僅停留在階段。1955年，的D.Harrison等人首次申請了應(yīng)用19621978MAC經(jīng)典無刷直流電動機(jī)及其驅(qū)動器的推出以后。之后，波無刷直流電機(jī)。20多年以來，隨著永磁新材料、微電子技術(shù)、自動控制技術(shù)以1968W1976年，西德R·哈尼特司等人試制成功借助數(shù)字式喚醒分配器和過零鑒別器的組合來實(shí)實(shí)現(xiàn)對無刷直流電機(jī)的控制當(dāng)前主要采用集成電路控制器單片機(jī)和DSP控制三種方式的控制的出現(xiàn)使得運(yùn)行速度處理能力有很大的提高。特別是到了20世紀(jì)80年代，DSP的推出，在信號處理鄰域引起了巨大的。DSPDSP成本的降低，使永磁無數(shù)直流電機(jī)的全數(shù)字控制成為了研究的熱點(diǎn)。DSP的固有計(jì)算能力可用在無DSP實(shí)現(xiàn)無位置傳感起控制成為研究的熱點(diǎn)，DSP無位置傳感起無刷電動機(jī)，成為無刷直流電動機(jī)的發(fā)展方向。、、 本文主要研究基于DSP的無位置傳感器無刷直流電機(jī)控制電路的設(shè)計(jì)，DSP程序設(shè)計(jì)。第四章介紹了基于TI公司的DSPTMS320LF2407A實(shí)現(xiàn)的無位置傳 第二章本章介紹了永磁無刷直流電機(jī)（PermanentMagnetBrushlessDCMotor）的基2-1

XMX

圖2- 電動機(jī)本體是一裝式的普通永磁直流電動機(jī)，它的電樞放在定子上，永2-2所示。SNNSNNS NSNS NSSN

(a)2-3要有正弦和梯形兩種形式，故習(xí)慣上又把它們分為正弦型永磁同步電機(jī)和型無刷直流電機(jī)與正弦型永磁同步電機(jī)相比型永磁無刷直流電機(jī)控制簡單、出力大得到了更廣泛的應(yīng)用本文研究的對象就是型永磁無刷直流電動機(jī)。對轉(zhuǎn)子部分，永磁體和導(dǎo)磁體是產(chǎn)生磁場的2-3 圖2-3 以三相星形六狀態(tài)[2-3(b)]和三相星形三狀態(tài)[2-3(a)]使用最廣泛。90°角，以保持電機(jī)轉(zhuǎn)矩的最大值。在本中的研究中，使用星形三相全控式主繞組接線方式。為了減少轉(zhuǎn)矩2-1所示。2-4(a)所示位置時(shí)，轉(zhuǎn)子位置傳感器發(fā)出磁極位置信號，經(jīng)過控制電路邏輯1AV6截至，V2V1仍導(dǎo)3→4→4→6→1SnNSnNSnN圖2- 2-1。2-1ABCBCAB對于永磁無刷直流電動機(jī)，大量使用形狀的氣隙磁場，其理想波形如圖2-5所示這種具有氣隙磁感應(yīng)強(qiáng)度分布梯形波反電動勢的無刷直流電機(jī)稱為電動機(jī)。電動機(jī)在控制時(shí)常采用電流驅(qū)動，即與120°導(dǎo)通型三相逆變器相匹配，由逆變器向電動機(jī)提供三相對稱的，寬度為120°電角度的電流。ππ圖2- B2-6。π圖2- 2-7圖2- 仍以空載時(shí)的反電動勢為依據(jù)。由此在某一固定轉(zhuǎn)速下按時(shí)間軸建立的如圖2-8圖2- 的。調(diào)解方式有兩種：一種為PAM方式，一種為方式。在PAM方式中，直流母線電壓Us可調(diào)，逆變器功率開關(guān)器件只負(fù)責(zé)電機(jī)換向控制，通過調(diào)節(jié)直流母線電壓Us的大小調(diào)解電機(jī)轉(zhuǎn)速。在方式中，直流母線電壓不可調(diào)，逆變電壓的平均值，從而達(dá)到調(diào)節(jié)轉(zhuǎn)速的目的。當(dāng)然，逆變器也可采用S技術(shù)或室內(nèi)風(fēng)機(jī)用無刷直流電機(jī)。當(dāng)母線電壓為310V左右時(shí)，多用調(diào)解方式，傳統(tǒng)電機(jī)中，由于位置傳感器體積較大，維修，設(shè)計(jì)復(fù)雜難以適應(yīng)惡劣120°導(dǎo)通型時(shí)，在每一時(shí)刻只有兩相導(dǎo)通，而未導(dǎo)通的一相可2-8262-9給出了電動機(jī)某一相的模型。圖中，L為相電感，R為相電阻，Ex為相感應(yīng)電動勢，Ix為相電流，Vx為星形連接中性點(diǎn)電壓。LRLRE2-9U=Ri+Ldia+e+

(2- U=

+Ldib+e+

(2- U=Ri+Ldic+e+

(2-

項(xiàng)和LdIx項(xiàng)相抵消，可Ua+Ub+Uc=ea+eb+ec+ (2-2-8可見，無論哪個(gè)相感應(yīng)電動勢的過零點(diǎn)，都存在eaebec=0的Ua+Ub+Uc= (2-對于斷電那一相，Ix=0，因此根據(jù)式(2-1,2-2,2-3)，其感應(yīng)電動勢為ex=Ua? (2-第三章XMZY功率路隔路123456圖3- DSP的控制和驅(qū)動電分別與TMS320LF2407AACDIN00～ADCIN03通道相連通。 圖3- 2通方式，調(diào)速時(shí)各橋臂上管采用調(diào)制電機(jī)的輸入電壓，下管恒通，調(diào)制6-1-6-1- 2-3-4-5-TaT-TaT+TbT-TbT+TcT-Tc 240° 圖3-3兩兩導(dǎo)通上管調(diào)制方式示意U=Ri+Ldia+e+

(3- U=

+Ldib+e+

(3- U=Ri+Ldic+e+

(3- 603-36-1AB相導(dǎo)通，且A+，B-3-4eb3-46-1A、B兩相電流大小相等，方向相反，C相電流為零，則(3-3)為Uc=ec+ (3-或ec=Uc? (3-由于ia=?ib，ea=?eb,將(3-1)式和(3-2)U=1(U+U (3- 再將(3-6)式代入(3-5)式，得Ce=U?1(U+U 同理，ABe=U?1(U+U e=U?1(U+U 由于系統(tǒng)采用調(diào)制方式，所以實(shí)際應(yīng)用中將端電壓Ua,b,c分壓后，Ua0、Ub0Uc03-5所示。O圖3- 此時(shí)，檢測電路的O點(diǎn)與Us負(fù)極相連。因此式(3-7)、(3-8)和(3-9) =

?1 + (3-

=

?1 +U (3-

=

?1 + (3-

3-63-1所6-1-6-1- 2-3-4-5- 240° 圖3- 3-1本課題采用單極性控制方式，即受控的兩個(gè)開關(guān)管中的上橋臂開關(guān)采用定頻控制，另一個(gè)開關(guān)管常開。這樣使開關(guān)管的工作狀態(tài)與換相的3-2所示。3-2前AYAYqCdXB圖3- 3-8V1V6Frd軸夾角1803-7所示位置，定位失敗。AYqAYqdCXB圖3- AX AXCB3-93-10。03-10U=U0+k× (3-f=f0+k× (3-其中，U0-f0-△U、△f他控同步運(yùn)行過程中每電周期內(nèi)電壓和頻率增量，且k=0,1,2f=fs時(shí)進(jìn)行他控同步運(yùn)行方式到自控同步運(yùn)行方式的切換，同時(shí)，在切換瞬間適當(dāng)加大切換電壓Ue至Us，以保證正確切換。無刷直流電機(jī)的驅(qū)動電路采用了三相橋式全控電路，逆變器采用六片MOSFET——IRF530NMOSFET20VRC抑制電路等保護(hù)電機(jī)控制的驅(qū)動器采用IR2130。IR2130是IR公司繼IR2110之后推出的一款MOSFET功率器件柵極驅(qū)動集成電路。一片IR2130可以代替三個(gè)輯輸入與COMS或LSTTL2.5V邏輯電壓。TMS320LF240A的輸出信號通過光耦合后送給IR2130，由IR2130IR2130直接可用于母線電壓為-4～+500V的系統(tǒng)，進(jìn)而來驅(qū)動功率MOSFET3個(gè)橋的三個(gè)高壓側(cè)功率管的導(dǎo)通關(guān)斷。3個(gè)下半橋功率管與共用一個(gè)電源，通過L01、L02、L03分別控制下半橋的三個(gè)低壓側(cè)功率管的導(dǎo)通關(guān)斷，從而來控制3-11所示。1111113-11IR2130功率開關(guān)的柵極驅(qū)動要求和功率開關(guān)的最大“開通”時(shí)間有關(guān)；R3—R6、RS為過極電阻，R7—R92、3、4為驅(qū)動逆變器中三個(gè)TMS320LF2407A器輸出端已連至相應(yīng)高、低壓側(cè)的六個(gè)N溝道功率MOSFET；中ITRP是過其工作原理為：從TMS320LF2407A脈沖形成部分(或波形發(fā)生器)來MOSFETH1、H2、H3先經(jīng)片內(nèi)三個(gè)脈沖處理和電平移位器中的自舉電路進(jìn)行電位轉(zhuǎn)換，變?yōu)闆_欠電壓與否檢驗(yàn)之后，送到輸出驅(qū)動器進(jìn)行功率放大，最后才加到高壓側(cè)的MOSFET的柵源極。一旦外電路發(fā)生過電流或直通、IR2130的工作電源欠電壓、另一方面經(jīng)FAULT端輸出一故障信號經(jīng)光電輸入到TMS320LF2407A的PDPINTPDPINT引腳為低電平時(shí)，DSP內(nèi)部定時(shí)器立即停止計(jì)數(shù)，所有輸出管腳成高阻狀態(tài)，并產(chǎn)生中斷信號，通知CPU有異常情況發(fā)生。部分。6N137能避免光耦連接的兩端電器上存在可能造成損壞的電勢電壓差，以6N137通過光耦合來取代電氣量的直接聯(lián)系，因此可以數(shù)字部分與模擬部分，實(shí)現(xiàn)作用。6N137為高速光耦合元件，性能較好，反應(yīng)較快，使在本NOINTERNALNOINTERNAL

8 3-12DSP本章介紹了基于TI公司的DSPTMS320LF2407A實(shí)現(xiàn)的無位置傳感器TMS320LF2407A的功能結(jié)構(gòu)，然后介紹了基TMS320LF2407A是TI公司專門針對電機(jī)、逆變器、機(jī)器人、數(shù)控機(jī)床等控元和片內(nèi)外設(shè)集中到了一個(gè)內(nèi)，極大地提高了數(shù)據(jù)處理和操作控制的性能 ACMOS3.3V；30MIPS的執(zhí)行速度使得頻30MHz33ns。TMS320LF2407A含有可擴(kuò)展的外部器總共192KB空間包括程序器空間，54KBI/O尋址空間TMS320C2XXCPUTMS320LF2407ADSPTMS320DSP含有高達(dá)32KB的FLASH程序器，1.5KB的數(shù)據(jù)/程序的雙口RAM2KB的單口RAM含有可以實(shí)現(xiàn)半雙工或全雙工通信的串行通行借口（SCI）含有可單獨(dú)編程或復(fù)用的通用輸入/40含有兩個(gè)電動機(jī)驅(qū)動保護(hù)中斷、復(fù)位中斷和兩個(gè)可外部中斷可以與帶有SPI接口的連接。3它的10位A/D轉(zhuǎn)換器最小時(shí)間為500ns，可選擇有兩個(gè)管理起來觸8A/D16A/D轉(zhuǎn)換器。含有控制器局域網(wǎng)絡(luò)（CAN）2.0BTMS320LF2407A的內(nèi)部結(jié)構(gòu)、器和I/O空（CPU（CALU32位累加器。16×16的乘法器。數(shù)據(jù)產(chǎn)生邏輯，包括8個(gè)輔助寄存器以及一個(gè)輔助寄存器算術(shù)邏輯單此外，TMS320LF2407A的設(shè)計(jì)基于增強(qiáng)的哈佛結(jié)構(gòu)。它可以通過并行總線（AB（DAB個(gè)給定的機(jī)器周期內(nèi)，CALU可以執(zhí)行多達(dá)3次的并行器操作。（64K（64KDSP圖4- 180°而造成的定位失敗。準(zhǔn)備第一次磁定位;; 1高有效 6高電平,其它 ;A相入，B相出,C ; ;1高有效,4高電平,其它 ;A相入，C相出,B ;本課題采用單極性控制方式，即受控的兩個(gè)對角開關(guān)管中的上橋壁關(guān)管采用定頻控制，另一個(gè)開關(guān)管常開。這樣使開關(guān)管的工作狀態(tài)與換4-2所列。為了對應(yīng)程序中的分支關(guān)系（跳轉(zhuǎn)關(guān)系，換相控制字依次取2、4、6、8105-12468例如，若使CB相流出，A COMP; #0E00H,ACTRA;5高有效，4強(qiáng)制 333倍的感應(yīng)電動勢值。ASYM，，假設(shè)在5高有效6強(qiáng)制高，即電流從C相入，B相出時(shí)，檢測感， END,NEQ;變了，則退出 V1,1;沒變，則使V1左移一位，即V1×2 3-630°。這就是說在測的過零點(diǎn)后，1230°所有的平均時(shí)間，用這個(gè)平均時(shí)間作為ADC20kHz1ADC50μsNNNNNNY磁定位計(jì)數(shù)器4-2ADC4-3。4-311.8mNm/A18V，感應(yīng)電動勢波形為梯形。路率MOSFET的開關(guān)性能不是很理想所導(dǎo)致的從實(shí)驗(yàn)中電機(jī)運(yùn)行的整體[J]．電機(jī)與控制學(xué)報(bào)，2002(3)：6-KIizuka,HUzuhashi，MKano. putercontrolforsensorlessbrushlessmotor[J].IEEETrans.Ind.Applicat，1985,21(3):595-601.KTaehyung.SensorlesscontroloftheBLDCmotorsfromnear-zerotofullspeed[D].Texas:TexasA&MUniversity,2003.，任軍軍，張仲超．三次諧波檢測無刷直流電機(jī)轉(zhuǎn)子位置的研究[]．中國電機(jī)工程學(xué)報(bào)．2004，24(5)：163-16.[J]，零檢測算法及其相位修正[J]．電氣傳動，2001(2)：14-16．，，，，等．無刷電機(jī)中電樞反應(yīng)對換向電動勢的影響[J]．，，CHAPTER PRINCIPLESOFTHEBLDCMOTORNewadvancesinthedevelopmentoffastsemiconductorswitchesandcost-effectiveDSPprocessorshaverevolutionizedtheadjustablespeedmotordrives.Thesenewopportunitieshavecontributedtothefieldofmotordrivesbyintroducingnovelconfigurationsforelectricmachinesinwhichtheburdenisshiftedfromcomplicatedhardwarestructuresontosoftwareandcontrolalgorithms.ThisinturnhasresultedinconsiderableimprovementincostwhileupgradingtheperformanceoftheoveralldriveTheBLDCmotordrivesystemisthemostillustrativeexampleofthistrend.Verycompactgeometryandanimpressiveefficiency,alongwithaverysimplecontrolareamongthemainattractionsforrecingmanyadjustablespeedapplicationswiththisemergingtechnology.Inthischapter,fundamentalsoftheBLDCmotordrivearedescribed.ThedetailedstructureoftheBLDCmotor;advantagesanddisadvantagesofthemotor;controlstrategy;powerconvertersfortheBLDCmotordrive;torquegenerationmechanism;anddynamicsoftheBLDCmotorareincluded.A.MechanicalStructureoftheBLDCThebrushlessDC(ELDC)motorisarotatingself-synchronousmachinewithapermanentmagnetrotorandwithknownrotorshaftpositionsforelectroniccommutation.IntheDCmotor,thepolarityreversalisperformedmechanicallybythecommutatorandbrushes.Sincethemechanicalcommutatorisfixedtotherotor,theswitchinginstantsareautomaticallysynchronizedwiththealternatingpolarityofthemagneticfield.However,inthebrushlessDCmotor,thepolarityreversalisperformedelectronicallybyswitches,Theresultingperformanceequationsandspeed/torquecharacteristicsforBLDCmotorsarealmostidenticalwithDCmotors[9].Fig.1showstheconventionalDCmotorandBLDCmotorconfigurations.TheDCmotorhasmechanicalswitchessuchascommutatorandbrush.However,theBLDCmotorrecesthemechanicalswitcheswithelectronicFig.1.DifferencebetweenDCandBLDCThepermanentmagnetBLDCmotorscanbecategorizedaccordingtothewaythepermanentmagnetsaremountedontherotorandtheshapeoftheback-EMF.Thepermanentmagnetscaneitherbesurfacemountedorinteriormountedandtheback-EMFshapecaneitherbesinusoidalortrapezoidal.Surface-MountedPermanentMagnetTypeofFig.2(a)showsthesurface-mountedpermanentmagnetrotor.Eachpermanentmagnet(PM)ismountedontheroundsurfaceoftherotor,itiseasytobuildand,inthemachinedesignpointofview,skewedpolescanbeeasilymagnetizedonthisroundrotortominimizecoggingtorque.ButthereisapossibilityfortheattachedPMtoflyapartduringhigh-speedoperation.Typically,forthistypeofmotor,theinductancevariationbyrotorpositionisnegligiblysmall.Fig.2.CrosssectionalviewofthepermanentmagnetInterior-MountedPermanentMagnetTypeofFig.2(b)showstheinterior-mountedPMrotor,Eachpermanentmagnetisinsidetherotor.Theuscoftheinterior-mountedPMisnotascommonasthesurface-mountedtype,buttheinterior-mountedPMisagoodcandidateforhigh-speedoperation.Itisnotedthatthereisaninductancevariationforthistypeofmotorbecausetheeffectiveair-gapvariesbyrotorposition.TrapezoidalShapeBack-EMFTypeofThetrapezoidalback-EMFtypeofmotorisdesignedtoutilizethetrapezoidalback-EMFswithsquarewavecurrentstogenerateconstanttorque.IthasthefollowingRectangulardistributionofmagnetfluxintheairRectangularcurrentConcentratedstatorLowermanufacturingSimpleSixcommutationpointsarerequiredforoneelectricalCommutationtorquerippleForthistypeofBLDCmotor,theexcitedcurrenttakestheformofquasi-squarecurrentwaveformwithtwo60’electricalintervalsofzerocurrentexcitationpercycle.Thenatureoftheexcitationwaveformsfortrapezoidalback-EMEFpermitssomeimportantsystemsimplificationscomparedtosinusoidalback-EMFmachine.Inparticular,theresolutionrequirementsfortherotorpositionsensoraremuchlowersinceonlysixcommutationinstantsarenecessaryforoneelectricalcycle.Fig.3showsthewindingconfigurationofthetrapezoidalbaek-EMFtypeofBLDCmachine,Fig,3.Structureofthetrapezoidalback-EMFtypeofBLDCSinusoidalShapeBack-EMFTypeofFig.4showsthewindingconfigurationofthesinusoidalback-BMFtypeofTheyhavethefollowingSinusoidaldistribution,ofmagnetfluxintheSinusoidalcurrentSinusoidaldistributionofstatorUseforservoNocommutationtorqueHighermanufacturingOpticalencoderorresolverisusuallyrequiredasapositionFig.4.Structureofthetwo-pole,sinusoidalback-EMFtypeofBLDCThemostfundamentalaspectofthesinusoidalback-EM.Ftypeofmotoristhattheback-EMFgeneratedineachphasewindingbytherotationofthemagnetshouldbeasinusoidalwavefunctionofrotorangle.Thebasicoperationofasinusoidalback-EMFtypeofBLDCmotorisverysimilartotheACsynchronousmotor.IthasarotatingstatorMMFwavethesameasasynchronousmotor,andthereforecanbeyzedwithaphasordiagram.Typically,thesinusoidalback-EMFtypeofmotorisnotconsideredasaBLDC,butratheraPMSM(penuanentmagnetsynchronousmachine).Inthisdissertation,thepositionsensorlesscontrolmethodfortheBLDCmotorsthathavetrapezoidalback-EMPispresented.BAdvantagesandDisadvantagesoftheBLDCMotorTheBLDCmotoroffersmanyadvantagessuchas:Highefficiency:BLDCmotorsarethemostefficientofallelectricmotors.Thisisduetotheuseofpermanentmagnetsfortheexcitation,whichconsumesnopower.Theabsenceofmechanicalcommutatorandbrushesmeanslowmechanicalfrictionlosses.Compactness:Therecentintroductionofhigh-energydensitymagnets(rare-magnets)hasallowedachievementofveryhighfluxdensitiesintheBLDCmotor,Thisachieveshightorques,whichinturnsallowsmakingthemotorsmallandlight.thecontrolvariablesareeasilyaccessibleandconstantthroughouttheoperationoftheEaseofcooling:Thereisnocurrentcirculationintherotor.Therefore,therotorofaBLDCmotordoesnotheatup.Theonlyheatproductionisonthestator,whichiseasiertocoolthantherotorbecauseitisstaticandontheperipheryofthemotor.Lowmaintenance,greatlongevity,andreliability:Theabsenceofbrushesandmechanicalcommutatorsuppressestheneedforassociatedregularmaintenanceandsuppressestheriskoffailureassociatedwiththeseelements.Thelongevityisbasedonlyonthewindinginsulation,bearing,andmagnetlife-length.Lownoise:Thereisnonoiseassociatedwiththecommutationbecauseitiselectronicandnotmechanical.thedrivingconverterswitchingfrequencyishighenoughsothattheharmonicsarenotaudible.Also,asinallmodernmachines,theBLDCmotorhassomeinherentdisadvantagessuchas:Cost:Rare-earthmagnetsaremuchmoreexpensivethanothermagnetsandresultinanincreasedmotorcost,Thecostofhigherenergydensitymagnetsprohibitstheiruseinapplicationswhereinitialcostisamajorconcern.Limitedconstantpowerrange:ThefieldweakeningoperationfortheBLOCmotorissomewhatdifficultduetotheuseofpermanentmagnets.Alargeconstantpowerrangeiscrucialforseveralapplications.ThepermanentmagnetBLDCmotorisincapableofachievingaumspeedgreaterthantwicethebasespeed.Demagnetizationofthepermanentmagnet:Magnetscanbedemagnetizedbylargeopposingmagnetomotivesandhightemperatures.Thecriticaldemagnetizationisdifferentforeachmagnetmaterial.Extremecaremustbetakentocoolthemotor,especiailyifitisbuiltcompact.High-speedcapability:Thesurface-mountedpermanentmagnetmotorscannotreachhighspeedsbecauseofthelimitedmechanicalstrengthoftheassemblybetweentherotoryokeandthepermanentmagnets.InverterfailuresinBLDCmotordrives:Becauseofthepennanentmagnetsontherotor,BLDCmotorspresentmajorrisksincaseofshortcircuitfailuresoftheinverter.Indeed,therotatingrotorisalwaysenergizedandconstantlyinducesanintheshort-circuitedwindings.Averylargecurrentcirculatesinthosewindingsandanaccordinglylargetorquetendstoblocktherotor.Especiallyforvehicleapplications,thedangersofblockingoneorseveralwheelsofavehiclearenon-PermanentMagnetsoftheBLDCThecharacteristicofthepermanentmagnetthroughallfourquadrantsoftheB-jiollneisactuallyalargehysteresisloop.Permanentmagnetsaremagneticmaterialswithalargehysteresisloop.ThusthestatingpointforunderstandingpermanentmagnetsistheirhysteresiscurveshowninFig.5.Theintersectionofacharacteristicwiththep0Haxisiscalledcoercivityofthemagneticmaterial.Also,theBaxisintersectioniscalledtheremanence,BrFig.5.HysteresisloopofapermanentThehysteresisloopshowninFig.5isformedbyapplyingthelargestpossibleexternalmagneticfieldtoanunmagnetizedmaterial,thenshuttingitoff.Thisallowsthematerialtorelax,orrecoil,alongtheuppercurveshowninFig.5,Thefinalpositionattainedisafunctionofthemagneticcircuitexternaltothemagnet.Ifthetwoendsofthemagnetareshortedtogetherbyapieceofinfiniypermeablematerial,themagnetissaidtobekeepered,andthefinalpointattainedisH=0.Thefluxdensityleavingthemagnetatthispointisequaltotheremanence,denotedB,.Theremanenceistheumfluxdensitythatthemagnetcanproducebyitself.Ontheotherhand,ifthepermeabilitysurroundingthemagnetiszero,nofluxflowsoutofthemagnetandthefinalpointattainedisB=0.Atthispoint,themagnitudeofthefieldintensityacrossthemagnetisequaltothecoercivity,denotedH.Forpermeancevaluesbetweenzeroandinfinity,theoperatingpointliessomewhereinsecondquadrantregion,betweentheremanenceandcoercivity.Normally,inmachinedesignanddriveconsiderations,onlythesecondquadrantportionisconsidered,asthisiswheredesirableoperatingpointsarelocated.PermanentmagnetsareessentialingredientstotheBLDCmotors.Inlasttwodecadespermanentmagnettechnologyhasimprovedsubstantially.Manydifferenttypesofpermanentmagnetmaterialsareavailabletoday.ThetypesavailableincludeAlnico,Ferrite(ceramic),Rare-earthsamarium-cobalt,andNeodymium-iron-boron(NdFeB).TheNdFeBmagnetshavethehighestpowerproduct,whichhavebeendevelopedrecently.Ferritemagnetsarethemostconnuonlyusedduetotheircosteffectiveness.EachmagnettypehasdifferentpropertiesleadingtodifferentconstraintsanddifferentlevelsofperformanceinBLDCmotors.ThecharacteristicsofthepermanentmagnetmaterialsarecomparedinTable1.ThetypicaldemagnetizationcharacteristicsofthemostcommontypesofpermanentmagnetsareshowninFig.6.Theferritemagnetischeap,buthasmuchlowerremanencefluxdensity,coercive andpowerproduct.TheNdFeBmagnethasthehighestrernanenceandcoerciveasshowninFig.6.Fig.6.DemagnetizationcharacteristicsofthecommonpermanentmagnetTable-1CharacteristicsofthepermanentHighBandlowHExcellentmechanicalstrengthGoodforlarge-sizepermanentLowBrandmidHRelativelyinexpensiveandlightHighBrandHVeryexpensiveSmalltemperatureHighBrandHExcellentperformanceRelativelyControlPrinciplesandStrategyoftheBLDCAtypicalBLDCmotordrivesystemconsistsoftheBLUCmotor,thepowerconverter,andadigitizedcontrolsystem.TheinverterisconnectedtoaDCpowersupplywhichcanbederivedfromtheutilitylinesthroughafront-enddioderectifierorfrombatteries.ThedigitalcontrollerenergizeseachphaseoftheBLDCmotorinasequenceandtheenergizationissynchronizedwiththerotorpositioninordertoproduceconstanttorque.Therefore,thesystemrequiresamechanicalpositionsensorthatisusuallyattachedinsideoftheBLDCmotorinordertoproviderotorpositionfeedbackforthecontroller.ThepositionHallsensorsareusuallyusedtodrivetheBLDCmotorwiththesquarewaveformofcurrent.ThetypicalBLDCmotordrivesystemwithpositionfeedbackisshowninFig.7.Thecontrollerreadsthemechanicalpositionanddecidestheappropriatephasetobecommutated.Ideally,eachstatorphaseisexcitedwithasquarepulseofcurrent.Themagnitudeofthecurrentpulseandtimingofcommutationinstance,incombinationwiththemachineparameters,hasadirecteffectonthemagnitudeofthetorquedeveloped.Fig.8(a)showstheequivalentcircuitand(b)showstrapezoidalback-EMF,currentprofiles,andHallsensorsignalsofthethree-phaseBLDCmotordrive.Thevoltagesseeninthisfigure,ea,eb,andearetheline-to-motorneutralback-EMFvoltages,whicharetheresultofthepermanent-magnetfluxcrossingtheairgapinaradialdirection,cuttingthecoilsofthestatoratarateproportionaltotherotorFig.7.AtypicalBLDCmotordrivesystemwithpositionThecoilsofthestatorarepositionedinthestandard3-phasehill-pitch,concentratedarrangement,andthusthephasetrapezoidalback-EMFwaveformsarediscedby120oelectricaldegrees,Thecurrentpulsegenerationisa“120oonand60ooff”type,meaningeachphasecurrentisflowingfor2/3ofanelectrical360operiod,120opositivelyand120onegatively.Todrivethemotorwithumandconstanttorque/ampere,itisdesiredthatthelinecurrentpulsesbesynchronizedwiththelineneutralbaek-EMFvoltagesoftheparticularphase.Fig.8.(a)EquivalentFig.8(b)Back-EMFs,currents,andHallsensorTorqueProductionMechanisminBLDCMotorInordertoproducemotoringtorqueintheBLDCmotordrive,itisessentialtounderstandthecharacteristicsoftheback-EMFgeneratedintheBLDCmotors.Fig.9.BackEMFshapeofasingleturnFig.9showsthefluxlinkageandinducedback-EMFofasingleturncoilbythepositionvariation.Thefluxlinkageofasingleturncoilisderivedas:Where,1,B,and0arerotorlength,fluxdensityofthepermanentmagnet,androtorposition,respectively.Also,themagnitudeoftheinducedback-EMFis:Themagnitudeofthetotalinducedback-EMFwithconcentricwindingsisWhere,Ncisthenumberofturnsinaphasewinding.Basedontheinducedback-EMFandcurrentwaveformshowninFig.10,thetorqueisproduced.Fig.10.Back-EMFs,currents,andproducedtorqueThetorqueinBLDCmotorsisgeneratedbythetendencyoftherotorpolestogetinalignmentwiththeexcitedstatorphases.ytically,thetorqueinBLDCmotorsis Where,e,I,andw,standforthephaseback-EMF,phasecurrent,andspeed,respectively.From(2.4),itcanbeseenthati.nordertoproduceconstantmotoringtorqueinBLDCmotors,eachexcitedphaseshouldbesynchronizedwiththeflatpartsoftheback-EMF.Fig.10and(2.4)indicatethatthephaseturn-onandturn-offpositionaswellasthemagnitudeofthephasecurrentcanbeusedfortorquecontrol,Typically,thepositionHallsensorprovidesthephaseturn-onandturn-offinstants.Fig.10showstheidealproducedtorquewaveformneglectingrisingandfallingtimeofcurrentsandassumingtheback-EMFshapeisidealtrapezoidal.Inpracticalsystems,theproducedtorqueisnotideallyflat,buthasarippleforseveralreasons:1.)Commutationtorqueripple:Thecommutationtorquerippleisduetotherisingandfallingcurrentsthatarecommutatedduringthetransientperiod.Whenonephaseturnsoff(commutates),whileanotherturnson,theriseandfallratesofthephasecurrentsarenotthesame,andthusthetotal.torquegeneratedbythetwocurrentsduringcommutationisnotflat,buthasaripple.Severalpapers[lOj-[12jarepublishedtoeliminatethecommutationtorquepulsations.Instantaneoustorquerippleduetodistortionsintheback-EMF:Thedistortionofthephaseback-EMFduetomanyreasonsincludingmanufacturingimperfection,leakageflux,andlocalsaturationcausesinstantaneoustorqueripples.Toeliminatetheripple,newcurrentreferencesthatcompensatethedistortionofthebaek-EMFarepresentedbyseveralauthors[1l]-[l2J.Instantaneoustorquerippleduetocurrentripple:Whenthehysteresiscurrentcontrollerisused,instantaneouscurrentrippleexistsbasedonthehysteresisband.Theinstantaneouscurrentripplecancausethetorqueripple.ThecurrentcontrolusingtechniquebasedonthepopularP1orP11)controllercanproducelowercurrentripple,andhencelowerthetorqueripple.Coggingtorque:Thecoggingtorqueisapparentatlowspeeds,andisduetothetendencyoftherotortolineupwiththestatorinaparticulardirectionwherethereluctanceofthemagneticcircuitbythepermanentmagnetsisminimized.AtypicalcoggingtorqueprofileisafUnctionoftheangularposition.Coggingtorque b