电机技术 电气电信 直流电源 外文翻译 外文文献 英文文献

电机技术（ELECTRICMOTORTECHNOLOGY）LESSONSINELECTRICCIRCUITS,VOLUMEIIACBYTONYRKUPHALDTSIXTHEDITION,LASTUPDATEMARCH07,2007THEORY,CONSTRUCTION,ANDREQUIREMENTSTTHEPRINCIPLESBEHINDELECTRICMOTORSHAVEBEENAROUNDFORALMOSTTWOCENTURIES，BUTTHETECHNOLOGYHASCOMEALONGWAYDURINGTHEPASTFEWYEARSALTHOUGHMICHAELFARADAYFIRSTSHOWEDTHERELATIONSHIPBETWEENCURRENTFLOWANDMAGNETICFIELDSIN1821，ITWASNTUNTIL11YEARSLATERTHATTHESEPRINCIPLESWEREUSEDTODEMONSTRATETHEFIRSTELECTRICMOTORACTUALLY，ITWASTHEINVENTIONOFTHECOMMUTATORTHATALLOWEDELECTROMAGNETICFORCESTOBECOAXEDINTOROTARYMOTIONONCEELECTRICALPOWERCOULDBETURNEDINTOMECHANICALPOWER，ITWASEASYTOSHOWHOWTHEREVERSEWASPOSSIBLEINNEEDOFASOURCEFORHISELECTRICLIGHT，THOMASEDISONPROPOSEDGENERATINGDCPOWERTOCUSTOMERSIN1882MEANWHILE，NIKOLATESLAINVESTIGATEDBRUSHLESSACINDUCTIONMOTORSBY1888，HEWASREADYTOOPPOSEEDISONBYPROPOSINGTHEUSEOFACFORPOWERDISTRIBUTIONDESPITESOMEDIRTYCAMPAIGNTACTICSBYEDISON，WEALLKNOWHOWTHATCONTESTTURNEDOUTBECAUSEOFTHEIMPORTANCEOFELECTRICMOTORS，IWILLSPENDSOMETIMETHISMONTHEXAMININGTHEIRCONSTRUCTION，THEORY，ANDWHATSREQUIREDTOUSETHEMWHATBEGANASAREALDISTINCTIONBETWEENDCANDACMOTORSHASBECOMEMUDDLEDDUETOTHEINTRODUCTIONOFELECTRONICSTOPROVIDESMARTCONTROLBUTLETSSTARTOFFWITHASIMPLELOOKATELECTROMAGNETICSELECTROMAGNETICFORCEATTHECENTEROFOURSOLARSYSTEM，THESUNGOESTHROUGHASUNSPOTCYCLEEVERY11YEARSSUNSPOTSAREAREASOFINTENSEMAGNETICFIELDSTHATPOKETHROUGHTHEPHOTOSPHEREANDAREEVENTUALLYDRAWNTOWARDITSATTRACTINGMAGNETICPOLEWHENTHISCOLLECTEDOPPOSITIONOVERPOWERSTHESUNSDIPOLESTATE，AFLUXREVERSALFLIPSTHEDIPOLESTATETHISISCONSISTENTWITHMAXIMUMSUNSPOTACTIVITYANDTHE11YEARCYCLETHEEARTHHASARECORDOFFLIPFLOPPINGMAGNETICPOLES，BUTTHEPERIODISMUCHLONGERTHELASTONEOCCURREDABOUT740，000YEARSAGONEEDLESSTOSAY，WEHAVENEVEREXPERIENCEDONE，ANDWEDONTKNOWHOWITMIGHTAFFECTLIFEASWEKNOWITTHEORIESSUGGESTTHATTHEEARTHSMOVINGMAGNETICFIELDMAYBEDUETOTHEUNEVENFLOWOFTHEOUTERLIQUIDCOREDEEPINTHEEARTHSLAYERSPLATETECTONICSSHOWUSHOWIRREGULARANDCONTINUOUSLYCHANGINGTHESURFACEIS，SOITSEASYTOSEETHATWERENOTDEALINGWITHSMOOTHSURFACESANDIDEALSPHERESROTATINGINPERFECTBALANCEONAXISHOWEVERLIFEWILLBEAFFECTEDBYTHISDRIFTINGMAGNETICFIELD（ANDINTERNALCURRENTS），WECANFINDCONSOLATIONINTHERELATIONSHIPBETWEENAMAGNETICFIELDANDANELECTRICCURRENTSOMEMATERIALSTHATARELARGELYMADEUPOFIRONORE（MAGNETITE）CANBECONVERTEDINTOALODESTONE（MAGNETIZEDMINERAL）BYHAVINGTHENORMALLYRANDOMMAGNETICFIELDSOFITSELECTRONSALIGNEDTHISCANCOMEFROMALARGECURRENTPASSINGTHROUGHTHECONDUCTIVEMATERIALEXTREMECURRENTSBRINGEXTREMEMAGNETICFIELDSTHATCANPERMANENTLYAFFECTELECTRONSPINWHENTHEEXTERNALFORCEHASSUBSIDED，THEMAGNETICALIGNMENTCANREMAIN，GIVINGTHEMATERIALAPERMANENTMAGNETICFIELDTHEFIRSTCOMPASSWASMADEBYFLOATINGTHISPERMANENTLYMAGNETIZEDMATERIALONWATERWITHTHEWATERACTINGASAFRICTIONLESSBEARING，THELODESTONECANROTATEANDALIGNITSELFWITHTHEMAGNETICFIELDOFTHEEARTH（NORTH/SOUTH）THERELATIONSHIPBETWEENMAGNETICFIELDSANDCURRENTWASDISCOVEREDBYHANSCHRISTIANSTEDIN1820WHENHENOTICEDACOMPASSNEEDLEDEFLECTINGFROMMAGNETICNORTHWHENHEAPPLIEDELECTRICCURRENTTOAWIRERUNNINGCLOSETOTHECOMPASSTHERIGHTHANDGRIPRULEDEMONSTRATESTHEDIRECTIONOFAMAGNETICFIELDAROUNDAWIREWHENTHEELECTRICCURRENTISFLOWINGINTHEDIRECTIONOFTHETHUMB（SEEFIGURE1）IN1825，BRITISHELECTRICIANWILLIAMSTURGEONSHOWEDHOWTHEMAGNETICFIELDPRODUCEDFROMACURRENTINAWIRECOULDBEINCREASEDWITHOUTADDITIONALCURRENTBYSTACKINGTHEWIREINPARALLEL。HISELECTROMAGNETWASAHORSESHOESHAPEDPIECEOFIRONTHATWASWRAPPEDWITHSEVERALTURNSOFTHEWIRETHEIRONCOREACTSASACONCENTRATORFORTHEMAGNETICFIELDPRODUCEDBYCURRENTFLOWINTHEWIREYOUCANCAUSETHENORTH/SOUTHORIENTATIONOFANELECTROMAGNETICCORETOSWAPPOLARITIESIFTHECOILISWOUNDINTHEOPPOSITEDIRECTIONORIFTHEDIRECTIONOFTHECURRENTTHROUGHTHEWIRESISREVERSEDFIGURE2SHOWSAREPRESENTATIONOFTHEATTRACTIONOFOPPOSINGMAGNETICPOLESANDTHEREPULSIONOFLIKEMAGNETICPOLESBYCONTROLLINGTHEDIRECTIONOFCURRENTFLOWINTHECOILOFANELECTROMAGNET，YOUDEFINEITSPOLEORIENTATIONTHERIGHTHANDGRIPRULECANALSOSHOWTHENORTHMAGNETICORIENTATION（THUMB）WHENTHEFINGERSSIMULATETHECURRENTFLOWDIRECTIONINTHEWIRESOFACOILTHEDCSOURCENNOTCOUNTINGLEYDENJARCAPACITORS（CIRCA1745），EARLYSCIENTISTSWERERESTRICTEDTOONESOURCEOFPOWER，THEELECTRICPILE，ORBATTERYALESSANDROVOLTAEXPERIMENTSWITHTHERTIFICIALELECTRICALORGANNAMEDFROMTHETORPEDOFISHABILITYTOPRODUCEANELECTRICSHOCK（THEELECTRICEELCOUSIN）IVEUSTHEBASICSOFCREATINGADIRECTCURRENTFROMDISSIMILARMETALSWITHOUTMEASUREMENTDEVICES，VOLTARESEARCHWASLIMITEDTOSENSORYCOMPARISONSHOWMANYOFYOUHAVETESTEDA9VBATTERYWITHYOURTONGUEWHILETHEBATTERYANDTHEELECTROMAGNETHAVELEDTODIVERGINGADVANCES，THISCOLUMNWILLPASSOVERMOSTINFAVOROFTHEELECTRICMOTORBUTADCSOURCEANDANELECTROMAGNETBYTHEMSELVESDONOTMAKEAMOTOREXPERIMENTSUSINGBATTERIESANDELECTROMAGNETSWEREABLETOPRODUCEONLYPARTIALMOTIONWITHOUTTHENEXTINVENTIONAPERMANENTMAGNETAFFIXEDTOTHEDIAMETEROFATURNTABLEWILLDEMONSTRATEROTATIONALMOTIONWHENANELECTROMAGNETORIENTEDATTHETURNTABLEPERIMETERISENERGIZEDANDITSPOLEOPPOSESTHEPERMANENTMAGNETPOLETHEREPELLINGMAGNETSPUSHAWAY，SPINNINGTHETURNTABLEUNTILTHEOPPOSITEPOLEOFTHEPERMANENTMAGNETISATTRACTEDTOTHEELECTROMAGNETTHEOPPOSITEPOLEOFTHEPERMANENTMAGNETONTHETURNTABLEISHAPPYTOREMAINATTRACTEDTOTHEELECTROMAGNETANDTHEROTATIONCEASES（NOTONLYDOESTHEROTATIONCEASE，BUTTHEATTRACTINGPOLESPROVIDEAFORCETHATPREVENTSROTATION）THENEEDHEREISTOBEABLETOREVERSETHECURRENTFLOWINTHEELECTROMAGNETEVERYTIMETHETURNTABLEISROTATED180。WITHTODAYSELECTRONICS，YOUCANDOTHIS，BUTTHATSGETTINGAHEADOFTHESTORYYOUCANIMAGINETHATWITHATURNTABLEOFSUFFICIENTWEIGHT，IFYOUJUSTTURNOFFTHEELECTROMAGNETFOR180，MOMENTUMMIGHTALLOWTHETURNTABLETOCONTINUEROTATINGUNTILTHEELECTROMAGNETCOULDPROVIDEANOTHERPUSHAFTERALL，MANYONECYLINDERENGINESUSEDFLYWHEELMOMENTUMBEFOREELECTRONICS，MECHANICSPLAYEDAMAJORROLEINADVANCINGTECHNOLOGYTHOMASDAVENPORTRECEIVEDTHEFIRSTPATENT（USPATENTNO132）FORANELECTRICMACHINETOUSEACOMMUTATOR（MECHANICALMEANSOFREVERSINGCURRENT）IN1837NOTETHATTHOUSANDSOFPATENTSISSUEDBETWEEN1790AND1835WERENOTNUMBEREDMOTORS（ORGENERATORS）AREMADEUPOFTWOPARTSASTATOR（THESTATIONARYPART）ANDAROTOR（THEMOVINGPART）。MY“TURNTABLE“HASAPERMANENTMAGNETASTHEROTORANDANELECTROMAGNETASTHESTATORICOULDHAVEJUSTASEASILYUSEDTHEPERMANENTMAGNETASTHESTATORANDANELECTROMAGNETASTHEROTORINFACT，BECAUSEOFTHECOMMUTATORSCONSTRUCTION，THISISTHEPREFERREDMETHOD，ASINDAVENPORTSPATENT（SEEFIGURE3）BEFOREMOVINGON，LETSLOOKATAPROBLEMWITHASINGLECOILDCMOTOR（SEEFIGURE4）。THETORQUEONTHEROTORBEGINSATZEROWHENTHEELECTROMAGNETICANDPERMANENTMAGNETCORESAREPARALLELTHEMOTORWILLNOTBEABLETOSELFSTARTIFTHEROTORANDSTATORAREALIGNEDTHISPROBLEMCANBEPREVENTEDIFTWOELECTROMAGNETSAREUSEDINTHEROTORATRIGHTANGLESTOONEANOTHERTWICEASMANYCOMMUTATORSEGMENTSAREUSED，WHICHALTERNATELYPOWERSTHECOILSEACHCOILISPOWEREDDURINGTHEUPPERPORTIONOFITSTORQUECURVESOMEELECTRICMOTORSAREMANUFACTUREDWITHMORETHANTWOCOILSMORECOILSMEANSHIGHEROVERALLTORQUEASMORECOILSAREADDED，MORECOMMUTATORSEGMENTSARENECESSARYTHISREDUCESTHEAVAILABLESEGMENT（ANDBRUSH）SIZESEEFIGURE4DYNAMOTHEMOTORANDGENERATORARELIKETHECHICKENANDTHEEGGBECAUSETHEREWASNOPOWERDISTRIBUTIONSYSTEM，WHILETHEELECTRICMOTORMIGHTHAVEBEENUSEFUL，ELECTRICMOTORSWERENTPRACTICALWITHOUTAPOWERSOURCETHEFACTTHATANELECTRICMOTORCOULDALSOPRODUCEPOWERMEANTTHATCONVERTINGMECHANICALTOELECTRICALENERGYWASPOSSIBLEUPTOTHISPOINT，IVEDISCUSSEDHOWAMAGNETICFIELDPRODUCEDBYACURRENTTHROUGHAWIREISUSEDTOCREATEANELECTROMAGNET（ANDROTARYMOTION）。THEREVERSEISALSOTRUEAWIRE（ORCOIL）PASSEDTHROUGHAMAGNETICFIELDWILLHAVEACURRENTINDUCEDINITTHISISSIMILARTOTHETRANSFEROFPOWERINATRANSFORMER（CURRENTFLOWTOMAGNETICFIELDTOCURRENTFLOW）IFYOUTAKEADCMOTORANDSPINTHESHAFT，THEMAGNETICFIELDOFTHEPERMANENTMAGNETSWILLCUTTHROUGHTHEELECTROMAGNETICCOILS，INDUCINGACURRENTFLOWINTHECOILSCURRENTFLOWSONLYWHILETHEMAGNETICFIELDISCHANGINGMAXIMUMCURRENTFLOWSASTHEPERMANENTANDELECTROMAGNETSCORESBECOMEPERPENDICULARTOONEANOTHER，WHILETHECOILISCUTTINGTHROUGHTHEMAXIMUMNUMBEROFFLUXLINESMINIMUMCURRENTFLOWSWHENPERMANENTANDELECTROMAGNETSCORESAREPARALLELWITHEACHOTHER，ANDWHILETHECOILCUTSTHROUGHTHEFEWESTLINESOFFLUXUSINGMULTIPLEELECTROMAGNETICCOILSANDCOMMUTATORSEGMENTS（ASWASSHOWNTOIMPROVETORQUEINANELECTRICMOTOR）WILLSMOOTHOUTCURRENTRIPPLE（SEEFIGURE5）WHILETHECOMMUTATORISNECESSARYFORDCCURRENTANDDCMOTORS，ATTHETIMENOONEKNEWWHATTODOWITHTHEACTHATWASPRODUCEDBYADYNAMOUSINGSLIPRINGS（SEEFIGURE6）。SLIPRINGSENABLETHECONNECTIONOFTHEROTORCOILSTOTHEOUTSIDEWORLDWITHOUTREVERSINGTHECURRENTFLOW（THEWAYACOMMUTATORDOES）。SLIPRINGSHAVELESSARCINGANDWEARASSOCIATEDWITHTHEMBECAUSETHECURRENTISNTINTERRUPTEDFINALLY，ACFOUNDITSNICHEINTHEWORLDANDTHEACDYNAMOBECAMEKNOWNASTHEALTERNATORBYUSINGPERMANENTMAGNETSWITHINTHEROTORANDELECTROMAGNETSINTHESTATOR，THEALTERNATORCANPRODUCEACCURRENTWITHOUTTHENEEDOFACOMMUTATORORSLIPRINGSTHISSIMPLICITYMAKESITTHEMOSTCOSTEFFECTIVESOURCEOFEXCHANGINGMECHANICALENERGYFORELECTRICALENERGYWHENTHEROTORSMAGNETSAREREPLACEDWITHCOILS，THEALTERNATORMUSTPOWERTHEFIELDWINDINGSTOPRODUCEROTORCURRENT，ASITSUSEDTORECHARGETODAYSAUTOMOTIVEBATTERYFROMOURAUTOMOBILESINTERNALCOMBUSTIONENGINEACMOTORSWWITHTHEFIGHTOVERPOWERTRANSMISSIONANDDISTRIBUTIONTECHNIQUESALLBUTOVER，AMERICANSINTHELATE1880SCOULDNOTHAVEPOSSIBLYUNDERSTOODHOWTHEIRFUTUREWASABOUTTOCHANGELABORSAVINGDEVICESBEGANTOINVADEEVERYHOUSEHOLDSYNCHRONOUSACMOTORSBECAMEIMPORTANTBECAUSETHEYREQUIRENOSLIPRINGSORCOMMUTATORSANDARELESSEXPENSIVETOMANUFACTUREBECAUSETHEIRSPINWASAFUNCTIONOFLINEFREQUENCY（60HZ），THEYCOULDBEUSEDTOKEEPTIMEANDSTAYINSYNCWITHTHERESTOFTHEGRIDASPREVIOUSLYDISCOVERED，ADYNAMOUSINGPERMANENTMAGNETSINTHESTATORANDELECTROMAGNETSWITHSLIPRINGSINTHEROTORPRODUCED（ATTHETIME）ANUNUSABLEACVOLTAGEONCETESLASHOWEDHOWACCOULDBESTEPPEDUPFORMOREEFFICIENTTRANSMISSIONOFPOWEROVERLONGDISTANCES，THEUSEFULNESSANDSIMPLICITYOFACMOTORSANDGENERATORS（ALTERNATORS）GRABBEDHOLDBYEXCHANGINGTHEROTORANDSTATORPOSITIONSOFTHEPERMANENTANDELECTROMAGNETS，THESLIPRINGSBECOMEUNNECESSARY，ENABLINGLESSEXPENSIVEMANUFACTURINGTHESTATORCANBEWOUNDWITHASERIESOFCOILS，EACHSTAYINGINSTEPWITHTHEAC，ALTERNATELYMAGNETIZINGEACHPOLEINONEDIRECTIONANDTHENTHEOPPOSITE，60TIMESASECOND（60HZ）。THEPERMANENTMAGNETROTORISPULLEDTOWARDAPOLEANDTHENPUSHEDAWAYONCEEACHCYCLETHEROTORSTEPS（IFYOUWILL）BETWEENPOLESATTHE60HZRATE，MAKINGACOMPLETEREVOLUTIONONCEEACH60HZPERTHENUMBEROFPOLESSINGLEPHASESYNCHRONOUSACMOTORSHAVEASTARTINGPROBLEMBECAUSETHESINGLEPHASEDOESNTOFFERANYOFFCENTERTORQUETOENSUREINITIALROTATIONSELFSTARTINGCANBEACCOMPLISHEDBYADDINGALEADINGORLAGGINGCOMPONENTTOMAINWINDINGSYOUCANSEETHATASECONDPHASECANPROVIDETHENECESSARYSTARTINGTORQUEWITHASINGLEPHASEACSOURCE，THISISNTPOSSIBLEASECONDPOLE（WINDING）AT90WOULDSIMPLYBEINPHASEWITHTHEORIGINALPOLEBYSLIGHTLYALTERINGTHESECONDPOLE，CHANGINGTHENUMBEROFTURNSINTHESTATORFIELD，ORBYADDINGACAPACITOR，THEPHASECHARACTERISTICSAREALTEREDSUFFICIENTLYSOTHATITWILLBESLIGHTLYOUTOFPHASEWITHTHEMAINWINDINGTHISWILLGIVETHEROTORABITOFTORQUETOINITIATEROTATIONCOREISSUESCOREISSUESTHECHANGING（ALTERNATING）FIELDOFACMOTORSBROUGHTSOMEUNIQUELOSSESTOTHEFOREFRONTINADDITIONTOTHEI2RLOSSESINALLMOTORWINDINGS，HYSTERESIS，ANDEDDYCURRENTSSOLIDCOREDESIGNSWERESHOWNTOCREATEEDDYCURRENTSWITHINTHECOREASITEXPERIENCEDACHANGINGMAGNETICFIELDANYCHANGINGCURRENTWILLCREATEAMAGNETICFIELDTHEREFORE，EDDYCURRENTSPRODUCEANOPPOSINGFIELDTOTHEFIELDRESPONSIBLEFORITSFORMATIONEDDYCURRENTSCANBEREDUCEDBYMANUFACTURINGTHINNERCORESANYNEWENERGYTRYINGTOMAGNETIZETHECOREMUSTNULLRESIDUALMAGNETISMBEFOREITCANPERFORMITSDESIGNEDFUNCTIONEFFICIENTLYATTENTIONTOCOREMATERIALANDMANUFACTURINGREDUCECOREHYSTERESISELECTRONICCONTROLPPRIORTOTHEADVENTOFTHESEMICONDUCTOR，CONTROLOFTHEELECTRICMOTORWASPRACTICALLYNONEXISTENTANDLIMITEDTOAPHYSICALSWITCHTHATCOULDTURNCOILCURRENTONANDOFFINITIALLY，ASTACKOFBATTERYCELLSWASTAPPEDTOAPPLYVARYINGDCPOTENTIALTOABRUSHEDDCMOTORTHENTHEPOWERRHEOSTATWASUSEDTOREDUCETHEPOTENTIALTOMOTORS，WITHGREATLOSSESINEFFICIENCYANDHEATASSEMICONDUCTORSWEREDEVELOPED，THEIRFUNCTIONSWEREEXPLOITEDBYTHEELECTRICMOTORINDUSTRYDIODESENABLEDCHOPPINGALTERNATINGACINTOPULSATINGDCTORUNDCMOTORSSCRS（ANDTRIACS）PROVIDEDALARGELEAPINCONTROLBYPROVIDINGAVARIABLEDELAYEDONCONTROLDURINGEACHHALFCYCLEOFTHEACWAVEFORMTHEDEVICESTURNEDOFFAUTOMATICALLYATEACHZEROCROSSINGOFTHEINPUTBECAUSETHEDELAYEDONTIMINGWASBASEDONEACHZEROCROSSING，EACHHALFCYCLEWASTREATEDTOTHESAMEDELAYATRANSISTORSLINEARCHARACTERISTICSENABLEDITTOBEUSEDASANELECTRONICRHEOSTATFORDCMOTORCONTROLITSUFFEREDFROMTHESAMEINEFFICIENCIESANDHEATISSUESASTHEMECHANICALRHEOSTATTHEQUESTIONBECAMEHOWCOULDTHEELECTRONICDEVICEBEUSEDMOSTEFFICIENTLY（OUTSIDEOFITSINEFFICIENTLINEARREGION）YETSTILLPROVIDEMORECONTROLTHANSIMPLYANON/OFFSWITCHTHEANSWERLEDTOTHEBEGINNINGOFANEWAGEINMOTORCONTROLPHASECONTROL（PWM）。UPTOTHATPOINT，MOTOROPERATIONWASBASEDONTHEPOWERDELIVEREDFROMTHEPUBLICUTILITIESTHISNEWELECTRONICCOMMANDOFPOWERTOAMOTOREVENTUALLYLEDTOOUROWNMULTIPHASEDPOWERSOURCENEWSEMICONDUCTORDEVICESWERESPECIFICALLYDEVELOPEDTOHANDLETHEHIGHERCURRENT/VOLTAGESOFELECTRICMOTORSTHEFETFAMILYHASEXTREMELYLOWONSTATERESISTANCES，WHICHMEANSTHATLESSOFTHEINPUTVOLTAGEISLOSTACROSSTHEDEVICEWHENITISCONDUCTINGCURRENTLESSCURRENTEQUALSLESSHEATANDHIGHEREFFICIENCIESASINGLEFETWILLEFFICIENTLYTURNONANDOFFTHEBASICDCBRUSHEDMOTOR，EFFECTIVELYCONTROLLINGITSSPEEDBYBEINGDRIVENBYAVARYINGONVERSUSOFFCONTROLSIGNAL（PWM）。FORINSTANCE，IFTHEONVERSUSOFFTIMINGIS50，THENTHEAVERAGEVOLTAGE（OVERTIME）ONTHEMOTORWILLBEONEHALFOFTHEINPUTVOLTAGELESSONTIME（EG，30）WILLLOOKLIKEANAVERAGEOF30OFTHEINPUTVOLTAGEANDTHEMOTORWILLSLOWDOWNMOREONTIME（EG，70）WILLLOOKLIKEANAVERAGEOF70OFTHEINPUTVOLTAGEANDTHEMOTORWILLSPEEDUPTHEFREQUENCYOFTHISPWMCONTROLSIGNALHASPRACTICALLIMITSATA50DUTYCYCLE，ASLOWFREQUENCYOF，SAY，ONCEPERSECOND，WILLCAUSETHEMOTORTORUNATFULLSPEEDFOR05SANDSTOPFOR05SALTHOUGHTHEOVERALLWORKOFTHEMOTORIS50，THESPEEDISNTCONSTANTATTHEINPUTOFMANYACTODCPOWERSUPPLIES，AFULLBRIDGENETWORKOFDIODESISUSEDTOGETTHEALTERNATINGPOLARITIESOFANACVOLTAGETOPASSTHROUGHALOADINONEDIRECTIONONLY（TOCHARGEUPTHEINPUTCAPACITOR）。ABRIDGEARRANGEMENTOFFETDEVICESCANBEUSEDTOSTEERASINGLEPOLARITYINPUTVOLTAGETHROUGHALOADINEITHERDIRECTIONTHISARRANGEMENTOFFETSASSOCIATESDIAGONALDEVICESASPAIRSONEDIAGONALPAIROFFETS，WHENTURNEDON，ALLOWSCURRENTTOFLOWINONEDIRECTIONTHROUGHTHELOAD（MOTOR），WHILETHEOPPOSITEDIAGONALPAIROFFETSALLOWSCURRENTTOFLOWTHROUGHTHELOADINTHEOPPOSITEDIRECTIONTHISADDSTHEFLEXIBILITYOFDIRECTIONTOTHESPEEDCONTROLOFABRUSHEDDCMOTORALTHOUGHTHEDIRECTIONANDPWMCONTROLTOTHESEMICONDUCTORPOWERDEVICESWASORIGINALLYPROVIDEDBYDISCRETETIMINGCIRCUITS，THEINTRODUCTIONOFTHEMICROCONTROLLERHANDEDCONTROLOFTHESEFUNCTIONSTOTHEPROGRAMMERWITHADDEDINTERNALHARDWARETOSUPPORTTHESECONTROLSIGNALS，INTERFACINGTOTHEPOWERDEVICESBECAMESIMPLERINTHEPREVIOUSEXAMPLE，PAIRSOFFETSWEREUSEDTOCONTROLTHESPEEDANDDIRECTIONOFCURRENTTHROUGHAWINDING（POLE）OFAMOTOR，EFFECTIVELYCONTROLLINGTHESTRENGTHOFAMAGNETICFIELDASWELLASITSPOLARITYYOUCANBEGINTOSEEHOWTHESEDEVICESCANSIMULATEACANDDCINPUTSTOANYELECTRICMOTORINFACT，THISFLEXIBILITYLEADSTOADDITIONALMOTORCONFIGURATIONSTHEADVANTAGEOFTHEACMOTORWASMOVINGTHEELECTROMAGNETSTOTHESTATOR，ELIMINATINGTHENEEDFORSLIPRINGSMULTIPHASEACCREATEDAROTATINGMAGNETICFIELDTHESAMECONCEPTCOULDBEUSEDONDCMOTORSTHECOMMUTATORWOULDNOTBENECESSARY，BECAUSEALLOFTHEAPPROPRIATELYPHASEDINPUTSWOULDBEPRODUCEDBYTHEMICROCONTROLLERTHEDISTINCTIONBETWEENACANDDCMOTORSNOWBECOMESBLURRYTHISNEWABILITYTOCONTROL（ORCREATE）INPUTTOELECTRICALMOTORSALSOPROVIDESANEWCONTROLFUNCTIONTHATWASPREVIOUSLYNONEXISTENT（UNLESSYOUCONSIDERTHECENTRIFUGALGOVERNOR）。FEEDBACKOFTHEROTATION（POSITIONORSPEED）ISHELPFUL（INSOMECASESMANDATORY）INMAINTAININGPROPERCONTROLSIGNALSREFERENCEDTOAMOTORSPHYSICALMOVEMENTSTHEREARENONSENSORMETHODSOFOBTAININGFEEDBACKBASEDONMONITORINGTHEBACKEMF（OUTPUTPRODUCEDBYTHEMOTORACTINGASAGENERATOR）。THEMORECONVENTIONALAPPROACHISTOUSEASENSORMOUNTEDTOTHEMOTORONEOFTHELEASTEXPENSIVEAPPROACHESUSESHALLEFFECTSENSORSTOSENSEROTORPOSITIONWHENINCREASEDACCURACYISNEEDED，ANOPTICALENCODERCANBEUSEDTHEMETHODYOUCHOOSEWILLDEPENDONTHETYPEOFFEEDBACKINFORMATIONYOUREQUIRETHESTEPPERMOTORWASONEOFTHEFIRSTSPECIALIZEDBRUSHLESSDCMOTORSTHEDESIGNCALLSFORAROTORWITHMANYPOLESSOATWOPHASEINPUTWILLCOGORSTEPTHEROTORBETWEENSTATORWINDINGSINEITHERDIRECTION，DEPENDINGONTHEORDEROFTHEAPPLIEDPHASES，ONESMALLSTEPATATIMETHISISAMICROMOVEMENTOFFOURSTEPSPEREACHTOOTH（PMPOLE）THATMAKEUPTHEROTORASTEPPERMOTORMOVESAPRECISEDISTANCEANDHOLDSPOSITIONWITHOUTUSINGFEEDBACKTWOTYPESOFSTEPPERMOTORSAREMANUFACTUREDUNIPOLARANDBIPOLARAUNIPOLARSTEPPERUSESACENTERTAPPEDCOILONEACHPOLEWITHTHECENTERTAPASCOMMON，THEPOLECANBEENERGIZEDINEITHERPOLARITYBYTURNINGONTHEASSOCIATEDPOWERDEVICECONNECTEDTOEACHFREEENDABIPOLARSTEPPERUSESASINGLECOILPERPOLE，PROVIDINGTWICETHETURNSPERPOLEBUTREQUIRINGFOURFETS（HBRIDGEARRANGEMENT）TOCONTROLTHEPOLARITYMOTORCHOICESAREEXPANDINGALTHOUGHMOTORCONTROLLERSINCREASETHECOSTOFMOTORAPPLICATIONS，THEYHAVEENCOURAGEDTHEINTRODUCTIONOFSPECIALIZEDMOTORSDESIGNEDTOTAKEADVANTAGEOFTHEIRFLEXIBILITY。CONTROLLERSINCORPORATETHENECESSARYINTERFACESTOCONTROLEXTERNALHIGHPOWERDEVICESBASEDONTHECOMMUTATORLESSACSYNCHRONOUSMOTOR，THEBRUSHLESSDCMOTORHASNOMAINTENANCEISSUESASSOCIATEDWITH“BRUSHES“ANDITISQUICKLYBECOMINGTHEMOTOROFCHOICEINMANYAPPLICATIONSWHILEMOSTMOTORCONTROLAPPLICATIONSCANBEHANDLEDWITHMICROCONTROLLERSANDANAPPROPRIATEAMOUNTOFSOFTWARE，WHENITCOMESTOHIGHPRECISIONANDCOMPLEXMOVEMENT，THEREAREALTERNATIVESTOROLLINGYOUROWNDESIGNPERFORMANCEMOTIONDEVICES（PMD）HASSINGLEANDMULTIAXISCONTROLLERSTHATCANHANDLEABOUTANYMOTORCONFIGURATIONGIVINGCLOSEDLOOPCONTROLHERE，YOUREDEALINGWITHMOTIONPROFILING，INCLUDINGSCURVE，TRAPEZOIDAL，ANDVELOCITYCONTOURINGIAMWANDERINGABITFROMMYINTENDEDPATHHEREITISDIFFICULTTOKEEPALLOFTHISSTRUCTUREDBECAUSETHEDEVELOPMENTOFTHEMOTORHASBEENINFLUENCEDSOMUCHBYELECTRONICSTHEBLOODLINESOFTHEMOTORFAMILYTREEARENOLONGERPUREWHEREWILLTHISLEADUSITSBECOMINGOBVIOUSTHATTHEREISABIGFUTUREFORSMALLDEVICESTHEVENTRICULARASSISTDEVICEPUMP（VAD）INFIGURE7WASCREATEDTOASSISTPATIENTSWITHCONGESTIVEHEARTFAILURE“TOOBIG，“YOUSAYTAKEALOOKATTHEULTRASONICPIEZOELECTRICMOTORDEVELOPEDBYRESEARCHERSATPENNSYLVANIASTATEUNIVERSITYSMATERIALSRESEARCHINSTITUTE（SEEPHOTO1）。STILLTOOBIGTHENANOMOTORWASCONSTRUCTEDATTHEUNIVERSITYOFCALIFORNIA，BERKELEY（SEEPHOTO2）。THIS“MOTOR“（IFYOUWANTTOTHINKABOUTITTHATWAY）ISABOUT500NMACROSSTHATS300TIMESSMALLERTHANTHEDIAMETEROFAHUMANHAIR“BUTTHISISJUSTRESEARCHSTUFF，“YOUSAYYES，HOWEVER，THEFUTUREISSTARTINGOUTTHERETODAYONSOMEONESLABTABLETHISISNTACASEOFREINVENTINGTHEWHEELITSAMATTEROFUSINGTHENEWESTTECHNOLOGYTOIMPROVEEXISTINGIMPLEMENTATIONSORCREATEENTIRELYNEWONESMEANWHILE，OURWASHINGMACHINES，POWEREDBYACINDUCTIONMOTORS，STILLGETOURCLO