comsol电磁场——线圈载荷激励施加方式

Single-turnandmulti-turncoildomainsin3D©2012COMSOL.Allrightsreserved.Introduction•ThistutorialshowshowtousetheSingle-TurnCoilDomainandMulti-TurnCoilDomainfeaturesinCOMSOL’sMagneticFieldsinterfaceformodelingcoilsin3D•ThesefeaturesareavailableonlywiththeAC/DCModule•Theyaresuitableforcomputationallyefficientmodelingofcurrent-carryingconductorscreatingmagneticfield•AdditionalinformationrelatedtosuitabilityofusingthesecoilmodelingfeaturesinDCandACareprovidedWeshouldhaveaclosedcurrentloop•Useaclosedgeometry•SpecifyaclosedcurrentpathusingappropriatemodelingtechniquesWhenmodelingmagneticfield,weneedtohaveaclosedcurrentloopUseappropriateboundaryconditionsforopengeometriesOverview•Thistutorialdescribeshowtousethefollowingfeatures•Single-turncoildomain–Gapfeed–Boundaryfeed•Multi-turncoildomain–Linearcoil–Circularcoil–Numericcoil–Usingsymmetry–User-definedcoilSingle-turncoildomain•Modeltheactualconductortocomputemagnitudeanddirectionofcurrentflow•Usethisinformationtofindthemagneticfieldinandaroundtheconductor•Usefulwhenyouhaveafewturns•Alsowhenyouwanttoresolvethecurrentdistributioninindividualwiresandturns•Note:YouneedtomodelanairdomainaroundtheconductorSingle-turntoroidalcoilModelinginfrequencydomain-AC•Alwaysusethiswhenthesignalisperiodic(e.g.sinusoidal,squarewave)•Canbeusedforsingle-turncoildomainaslongastheskindepthisnottoosmallcomparedtotheconductorthickness–Whentheskindepthissmallerthantheconductorthickness,useaboundarylayermesh–Whentheskindepthissignificantlysmaller(1/20th)thantheconductorthicknessthenwecannotusesingle-turncoildomainanymoreModelingintimedomain-Transient•Cannotbeusedforsingle-turncoildomain–COMSOLusesanA-Vformulationlocallywithinthesingle-turncoil–Solvesforbothmagneticvectorpotential(A)andelectricpotential(V)–TransientsimulationisnotsupportedforsuchcasesbecauseVisnotuniquelydefinedateachpointinspace–Intimedomainanalysis,thevoltage(V)isdefinedasapathintegralbetweentwopointsinspace•FordetailsontheA-Vformulation,refertotheAC/DCModuleUser’sGuideSingle-turncoil–Gapfeed•Single-turncoil•Leadsarenotmodeled•Geometrymustformaclosedloop•CrosssectionandshapecanbearbitraryCoilexcitationmethod•Excitationsourceismodeledasaninternalcrosssectionboundarycalledgapfeed•WeneedtobecarefulwhiledrawingthegeometrysothatwecreatethisinternalboundaryGapfeed1.Specifythevoltageacrossthisboundary2.Specifythecurrentthroughthisboundary3.OptionstoconnecttolumpedelectricalcircuitModelinginCOMSOL•Fordetailedmodelingsteps,seethefollowingfile:–single_coil_gap_feed.mph•ThismodelshowsbothDCandACcasesUsingsingle-turncoildomainwithgapfeedResults–Magneticfluxdensity(DC)Inductance=1.17e-8HResults–CurrentdensityDCsolutionResistance=1.65e-4ΩHighercurrentdensityalongtheinnerradiusindicatesthatmorecurrentisconcentratedalongashorterconductionpathAC(20kHz)solutionImpedance=2.3e-4+0.001iΩCurrentdistributionclearlyshowstheskineffectUsinggapfeedinACsingle-turncoil•GapfeedinACindicatesaconnectiontoatransmissionline•Inrealitythereisacapacitivecouplingbetweenthetwoendsofthis“gap”feed–Capacitivecouplingismoresignificantathigherfrequencies–Wecannotmodelitsinceweassumethegapfeedtobeazerothicknesssurface–Gapimpedancewilldependontheactualgapthicknessandmaterialpropertyofthe“gap”•GapfeedisperfectlyaccurateforDCmodelsbutagoodapproximationonlyforlowfrequencyACmodelsSingle-turncoil–Boundaryfeed•Single-turncoil•Leadsaremodeled•Geometrydoesnotformaclosedloop•Crosssectionandshapecanbearbitrary•YoucanusethistomodelmorethanasingleturnCoilexcitationmethod•Directionofcurrentflowismodeledbyspecifyingagroundsurfaceandaboundaryfeed•ThesesurfacesshouldtouchtheexternalwallsoftheairdomainsurroundingtheconductorBoundaryfeed1.Specifythevoltageatthisboundary2.Specifythecurrentthroughthisboundary3.OptionstoconnecttolumpedelectricalcircuitGroundUsingsingle-turncoildomainwithgroundandboundaryfeedResults–Magneticfluxdensity(DC)Inductance=3.16e-8HModelinginCOMSOL•Fordetailedmodelingsteps,seethefollowingfile:–single_coil_boundary_feed.mph•ThismodelshowsbothDCandACcasesResults–CurrentdensityDCsolutionResistance=3.25e-4ΩHighercurrentdensityalongtheinneredgesindicatesthatmorecurrentisconcentratedalongashorterconductionpathAC(10kHz)solutionImpedance=3.83e-4+0.002iΩCurrentdistributionclearlyshowstheskineffectMeshingconsiderationsDefaultfreetetrahedralmeshissuitablefortheDCproblemBoundarylayermeshisbettertoresolvetheskineffectforACproblemswheretheskindepthissmallerthantheconductorcrosssectionResolvingtheskineffectinconductorsusingboundarylayermesh•Computeskindepth:•Iftheskindepthislessthan½thethicknessoftheconductor,considerusingaboundarylayermesh–Twolayersofmesharoundtheconductorwallisgoodenough–Eachlayerhasthesamethicknessastheskindepth2Multi-turncoildomain•Modelahomogenizedcurrentcarryingregiontocomputemagnitudeanddirectionofcurrentflow•Usethisinformationtofindthemagneticfieldinandaroundtheconductor•Usefulwhenyouhavealotofturns•Eachindividualwireisinsulated–hencenoshortingbetweenconductors•Individualwireandmultiplelayersarenotresolved•Note:Youstillneedtomodelanairdomainaroundthe