机电传动控制-DC Motor

Referencewebsite(althoughthisisgenerallyafunctionofthephysicalsizeofthemotor),areeasytominiaturize,andcanbethrottledviaadjustingtheirsupplyvoltage.DCmotorsarealsonotonlythesimplest,buttheoldestelectricmotors.DCmotorThebasicprinciplesofelectromagneticinductionwerediscoveredintheearly1800'sbyOersted,Gauss,andFaraday.By1820,HansChristianOerstedandAndreMarieAmperehaddiscoveredthatanelectriccurrentproducesamagneticfield.Thenext15yearssawaflurryofcross-Atlanticexperimentationandinnovation,leadingfinallytoasimpleDCrotarymotor.DCmotorAnumberofmenwereinvolvedinthework,sopropercreditforthefirstDCmotorisreallyafunctionofjusthowbroadlyyouchoosetodefinethewordmotor.“DCmotorMichaelFaraday(U.K.),Oct.1821WilliamSturgeon(U.K.),oneyearlaterDCmotorJosephHenry(U.S.),summer,1831DCmotorElectronicallycommutatedPermanent-Magnet(PM)Brushless(position-triggered)StepperDCMotorWound-RotorConventionalPMDiscRotorCupRotorshuntseriesCompoundPMRotorVariableReluctanceWound-RotorDCMotorStructureandOperatingPrinciplesRunningCharacteristicsofGeneratorTorque-speedCharacteristicsofMotorStarting,braking,andspeed-regulationofDCmotorBasicPrincipleLorentz’sRelationship–TtorqueproductionLefthandformula–effectofmagneticfieldtothestraightleadFaradayLaw–EelectromagneticinductionLenzLaw(Righthandformula)–generationofelectromotiveforceLeft-handRuleshowsthedirectionofthethrustonaconductorcarryingacurrentinamagneticfield.Thelefthandisheldwiththethumb,indexfingerandmiddlefingermutuallyatrightanglesLeft-handRuleTheFirstfingerrepresentsthedirectionoftheField.TheSecondfingerrepresentsthedirectionoftheCurrent(intheclassicaldirection,frompositivetonegative).TheThumbrepresentsthedirectionoftheThrustorresultantMotion.BIFLorentz’sRelationshipThemechanicalforceonacurrent-carryingwirewithinamagneticfieldisF＝BILInwhichListhewirelength,Iisitscurrent,andBisthemagneticfieldstrength(fluxdensity).MotionalEMFandFaraday'sLawmotionalemf(electromotiveforce)expressionisanapplicationofFaraday'sLaw,ascanbeseenfrom:InducedEMFThusforthearrangementshownbelowtΦNVddcosdsindddNBAtNBAtΦNVLenzLawIfoutsideforcescauseawindingcoiltoexperienceachangeinthrough-the-coilflux,thewindingattemptstocirculatecurrentinitsconductorsinthedirectionthatcausesitsown“internal”fluxtoopposethechangebeingforceduponitbyoutsideeventsTheInducedcurrentissuchastoOPPOSEtheCHANGEinappliedfield.NSIvThislawwasdeducedin1834bytheRussianphysicistHeinrichFriedrichEmilLenzFleming’sRight-handRuleInventedbyBritishengineerJohnAmbroseFleming,showsthedirectionofinducedcurrentflowwhenaconductormovesinamagneticfieldTherighthandisheldwiththethumb,firstfingerandsecondfingermutuallyatrightanglesFleming’sRight-handRuleBIvTheThumbrepresentsthedirectionofMotionoftheconductor.TheFirstfingerrepresentsthedirectionoftheField.TheSecondfingerrepresentsthedirectionoftheinducedorgeneratedCurrent(intheclassicaldirection,frompositivetonegative).Right-handGripRuleaphysicsprincipleappliedtoelectriccurrentpassingthroughasolenoid,resultinginamagneticfield.Wrapyourrighthandaroundthesolenoidwithyourfingersinthedirectionoftheconventionalcurrent,yourthumbpointsinthedirectionofthemagneticnorthpole.Canalsobeappliedtoelectricitypassingthroughastraightwire,thethumbpointsinthedirectionofthecurrent,andthefingersinthedirectionofthemagneticfield.StructureCommutatorBrushAssemblyArmatureWindinginRotorSlotsFieldPole(1of4)FieldWindingCoil(1of4)RotorAssemblyRotorShaftVentilationOpeningTerminalJucntionBoxFrameBearingBearingEnd-bellEnd-bellAxle/shaftRotor(Armature)StatorFieldmagnetsCommutators(slip-rings)BrushesMainPartsGenerator--VoltageProductionNSISlip-Rings(insulatedfromShaft)StationaryCarbonBlock(Brush)Bybrush-to-slip-ringarrangement,movingarmaturewindingcanbeconnectedtoastationaryexternalloadonecompleterotationofthecoilproducesonecompletesine-wavecycleofvoltageforper-turn.Iftheoverallwindinghasmanyturns,N,theoverallvoltagethatitproducesisNmultipliedbytheper-turnvoltageVoltageProductioncosdsindddNBAtNBAtΦNVSingleslip-ringcutintotwopieces/segments,stillsolderedtocoilends,butinsulatedfromeachotherandshaftAtthe180°instant,brushesswitchsegments,exactlyatthesameinstant,thewindingterminalschangeelectricalpolarityMechanicalswitchingofsegmentswithbrushesexactlycoincideswiththeelectricalchangingofsegmentploarityMechanicallyRectifyingACtoDC-CommutationSplitSlip-Ring(Commutator)CarbonBurshRotation90°(TheInstantShown)(TheInstantwhenthewindingplaneisverticalandbrusheschangecommutatorsegments)NS90°180°0°load－＋Vload180°270°0°Commutator,asplit-ringdeviceBrushes,theelectricalcontactstotherotatingring,sincecopperbr