comsol_涡流模块

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1、------------------------------------------作者xxxx------------------------------------------日期xxxxcomsol_涡流模块【精品文档】InductionCurrentsfromCircularCoilsIntroductionAtime-varyingcurrentinducesavaryingmagneticfield.Thisfieldinducescurrentsinneighboringconductors.Theinducedc

2、urrentsarecallededdycurrents.Thefollowingmodelillustratesthisphenomenonbyatime-harmonicfieldsimulationaswellasatransientanalysis,whichprovidesastudyoftheeddycurrentsresultingfromswitchingonthesource.Twocurrent-carryingcoilsareplacedaboveacopperplate.Theyaresurrounded

3、byair,andthereisasmallairgapbetweenthecoilsandthemetalplate.Apotentialdifferenceprovidestheexternalsource.Toobtainthetotalcurrentdensityinthecoilsyoumusttaketheinducedcurrentsintoaccount.Thetime-harmoniccaseshowstheskineffect,thatis,thatthecurrentdensityishighcloseto

4、thesurfaceanddecreasesrapidlyinsidetheconductor.ModelDefinitionEQUATIONTosolvetheproblem,useaquasi-staticequationforthemagneticpotentialA:----------σ-∂--A----+∇×(μ–1μ–1∇×A)=σVcoi-l【精品文档】【精品文档】∂t0r2πr【精品文档】【精品文档】Hereμ0isthepermeabilityofvacuum,μrtherelativepermeabili

5、ty,σtheelectricconductivity,andVcoilthevoltageoveroneturninthecoil.Inthetime-harmoniccasetheequationreducesto【精品文档】【精品文档】–1–1Vcoil=-----------【精品文档】【精品文档】jωσA+∇×(μ0μr∇×A)σ2πr【精品文档】【精品文档】FORCESThetotalelectromagneticforceactingonregionofspaceΩcanbeobtainedbyintegra

6、tingMaxwell’sstresstensoronthedelimitingboundary∂Ω:F=òTndS∂ΩTheForceCalculationfeatureautomaticallyperformstheintegralalongtheboundariesofthedesiredregion,consideringalsotheaxisymmetricgeometryoftheproblem.Thecomputedforcewillbeavailableinresultsprocessingasaglobalva

7、riable.ResultsandDiscussionInthetime-harmonicregime,thevaryingmagneticfieldinduceselectricalcurrentsinthemetallicplate.Thecurrents,inturn,actassourcesofanopposingmagneticfield“shielding”theplatefromthemagneticfield.Asaresultofthisphenomenon,theregioninwhichelectrical

8、currentsaregeneratedisconfinedinproximityofthesurfaceandreducesinsizewithincreasingfrequency.Figure1andFigure2showtheinducedcurrent