直流電機培訓(xùn)資料

直流電機培訓(xùn)資料maxonDCmotor:VariantsA-max-MotorwithAlNiComagnetpreciousmetalbrushessinteredsleevebearingRE-MotorwithNdFeBmagnetgraphitebrushesballbearingCorelessmaxonDCmotor:A-maxel.connectionsflangehousing(magn.return)commutator-plateshaftwindingpreciousmetalbrushespermanentmagnetcommutatorsinteredsleevebearingCorelessmaxonDCmotor(RE30)el.connectionsself-supportedwindingcommutatorbrushespermanentmagnet(inthecenter)housing(magn.return)ConventionalDCmotorel.connectionshousing(magn.return)windingcommutatorbrushsystemironcorepermanentmagnet(attheperiphery)CorelesswindingsystemsmaxonFaulhaberPortescapQuelle:PortescapMautheKodakcorless(DC)–slotless(EC)Advantagecoreless:nocoggingnosoftmagneticteethtointeractwiththepermanentmagnetsmoothrunningevenatsmallspeedslessvibrationandnoiseanyrotorpositioncanbecontrolledinasimplewaynononlinearcontrolbehaviourAdvantagecoreless:noironlossesnoiron–noironlossesconstantmagnetizationhighefficiency,uptoabove90%lownoloadcurrent,typical<50mAdoesnotapplytoECmotorsnosaturationeffectsintheironcoreEvenatthehighestcurrentstheproducedtorqueremainsproportionaltothemotorcurrent.strongermagnets=strongermotorsAdvantagecoreless:smallinductancelessbrushfirecommutation:openandcloseacontactonaninductiveloadhigherliveexpectancylesselectromagneticemissionseasiertosupressinterferences:capacitybetweenconnectionsferritecoreatmotorcablebutfastreactionofthecurrentproblemsincombinationwithpulsedsupply(chokeneeded)Advantagecoreless:compactdesignmoreefficientdesignofthemagneticcircuit(eveniftheairgapislarger)morecompactmagnetinthecenterhigherratioofpowertovolumesmallrotormassinertiahollowcylinderagainstfullcylinderhighdynamicstypicalaccelerationtimes:5–50msSFREARE-maxmaxonDCmotor:Programyear200019951990198519801970A-maxrolledhousingmagnetplasticflangedesignNdFeBAlNiCoFerritedesignandproductionmagnetmaxonDCmotor:Programspermanentmagnet Ferrite AlNiCo NdFeBmotorprogram Fmotor A-max,S,A RE,RE-maxmotorexample 2130GB A-max19GB RE13GBDn/DM[mNm/min-1]

1150 1150 1250assign.power 3W 2.5W 3Wmotorsizediameter 30mm 19mm 13mmlength 33mm 29mm 34.5mmcont.torque 3.3mNm 4.4mNm 3mNm23.3cm34.6cm38.2cm3Stator:themagneticcircuithousing:magneticreturnpathmadeofsteel(iron)guidesmagneticfieldairgap:thelargertheairgap,theweakerthemagneticfieldpermanentmagnet:producesmagneticfieldwithnorthandsouthpolesonoppositesidesDevelopmentofpermanentmagnetsNdFeBSmCoAlNiCoSmFeNsteelFerrityearmax.energyproduct(kJ/m3)max.energyproducttheoreticallimit 960kJ/m3technicallyachievable ca.720kJ/m3PermanentmagnetsB[T]1.21.00.80.60.40.2H[kA/m] 900 800 700 600 500 400 300 200 100magnet Curie operation motordesign temperature Nd2Fe14B 310°C 110-170°C all,ECSm2Co17 825°C 350°CSmCo5 720°C 250°CAlNiCo ~850°C 550°C onlycorelessferrite 450°C 250-350°C conventionalConstructionofrotorscommutatorplatecommutatorwindingconnectionswindingshaftcommut.platewindingcommutatorwireepoxyshaftwithknurlingbondageWinding:enameledwirelacquer:plasticwithsolvantatenhancedtemperature(130-150°C):plasticmeltsandconnectsneighbouringwires.pressingformsthebodyinnarrowtolerances.outgassingofsolvant:plastichardens.bakingofthewinding.copperwirelacquerinsulationcoppercore:goodelectricalconductorinsulation:noshortcircuitsknittedmaxonwindingknittedwindingforbigmotorswithNdFeBmagnetREmotors,ECmotorsthickwalledwindingsstandardmaxonwindingmaxonwinding:standardandknittedCurrentflowinmaxonwinding1 2 3 4 5 6 7 8 9 11 2 3 4 55 6 7 8 9 1ForceandtorqueproductionrhombiccurrentareasmagneticfieldinairgapforcemagneticreturnforceTorqueandcurrent:torqueconstantforces:forceoncurrentleadingconductorinamagneticfieldtorque:sumofallforcesatthedistancetotherotatingaxisinfluencingparameters:geometryfielddensitywindingnumbercurrentIdesignapplicationcurrentdirectiontowardsflangeforceforcecurrentdirectiontowardsbrushmagneticfieldSpeedandvoltage:speedconstantwindingrotatesinairgapwithinhomogeniousmagneticfieldinducedvoltageUind(backEMF)dependingongeometrymagneticfielddensitywindingnumberspeednspeedconstantkninverselyproportionaltokMinverselyproportionaltogeneratorconstant(V/1000rpm)designapplicationBrushcoveradjustingatno-loadadjustingthebrushsystemrotatinguntiloptimumcommutation:commutationpictureformaximummotorlifeno-loadcurrent:measureoffrictionthehighertheload(friction),thehigherthe(no-load)currentfrictioninbearingandcommutationfaults:e.g.touchingwinding,misalignedbearingsno-loadspeed:measureofmagnetandwindingbadmagnet(impropermagnetization)=higherno-loadspeedtoostrongamagnet=lowerno-loadspeeddependsonvoltageandmagneticfieldintheairgaphigherappliedvoltage=higherspeedCommutationpicture1:ripple2:modulationbecauseofasymmetricalwinding3:currentsignalofarevolutionCommutationprocess_++_12345671 41 52 52 63 63 74 74 15 15 26 26 37 37 41 4Torqueripplecommutator commut. torquesegments points ripple5 10 5%6 6 14%7 14 2.5%9 18 1.5%11 22 1%13 26 0.75%5%14%DCcommutationsystemspreciousmetalbronzebrushbodywithplatedsilver(withpalladium)contactareasilvercoppercommutatorsmallcontactandbrushresistance(50mW)CLLforextendedservicelifegraphitegraphitebrushwith50%coppercopperreducescontactandbrushresistancegraphiteactsaslubricantspringDCcommutation:rotorsglasfibrebondagecoppercommutatorscotchbondageCLLdiscsilvercommutator2shaftendspreciousmetalgraphiteDCcommutation:contactresistanceterminalresistanceRwindIA currentRmotIA currentterminalresistanceRmotRwindRmot(I)preciousmetalgraphite~50mWtheproblemsolutioncapacitancebetweenneighbouringcommutatorsegmentsenergyisdeviatedintocapacitance:noarcsproducedPreciousmetalcommutation:CLL+_short-circuitaftershortcircuitarcproductioncommutatorwearsoffRSCcommutatorCLLdiscCCPreciousmetalcommutation:CLLtimeshort-circuitaftershort-circuitwithoutCLL:energyisgivenawayveryrapidly,highvoltages,sparkswithCLL:energyisgivenawayslowlydampedoscillationlowvoltages10V200Vvoltagebetweenthecommutator-segmentsLifetestingofCLL2'500 5'000 7'500 10'000hMotor2017.941I=50mA n=13'000rpm U=24V108642CLLtestterminated5 10 15 20 x1000h108642CLLMotor2140.935I=250mA n=1'500rpm U=10VDCcommutation:prosandconsgraphitewellsuitedforhighcurrentsandcurrentpeakswellsuitedforstart-stopandreversedoperationbiggermotorshigherfriction,higherno-loadcurrentsnotwellsuitedforsmallcurrentsmoreaudiblenoiseandelectromagneticemissionmoreexpensivepreciousmetalwellsuitedforsmallestcurrentsandvoltageswellsuitedforcontinuousoperationsmallermotorsverylowfrictionandnoiselowelectromagneticemissionfavourablepricenotwellsuitedforhighcurrentsandcurrentpeaksnotwellsuitedforstart-stopoperationmaxonDCmotor:servicelifelifeinfluencingfactorstheelectricload:highercurrents=higherelectricwear(arcing)speed:higherspeed=highermechanicalweartypeofoperation:reversedoperation=reducedservicelifetemperaturehumiditywithgraphitebrushesCLL(withpreciousmetalbrushes)enhancesservicelifeloadonshaft(bearings)servicelifenogeneralstatementpossibleaverageconditions:1'000-3'000hoursunderextremeconditions:lessthan100hoursunderfavourableconditions:morethan20'000hoursusegraphitebrushesandballbearingsforextremeoperatingconditionsballbearingsmallfriction,rollingballsenhancedbyaxialpreloadordisbalancewithlubricantsuitableforheavyloadsforcesactonballsforlargermotorshighernoiselevelthansleevebearingsmoreexpensiveloadontoshaftsinteredsleevebearingmateriallubricantbetweengrains,upto30%ofvolumelubricantreservoirdependsonbearingsizeviscosityandporesizemustbetunedfunctionathighspeeds:hydrodynamical lubricationatlowspeed:directcontactof shaftandbearingmechanicallowerloadsthanballbearingforsmallermotorslowernoiselevelthanballbearinglowercostsshaftsintere