简介:Thispaperintroducestheconfigurationandtheoperationprinciplesofahighpowerdirectcurrentcircuitbreaker(DCCB).Thecommutatingcurrentprincipleofthebreakerisde-scribedindetailswithitstheoryandsimulationanalysis.ThetestresultspresentedshowthattheDCCBmeetstherequirementsforquenchingprotection.ItwillbeusedasthemainbreakerforquenchprotectioninEAST.
简介:Hugoniotrelationsofatwo-dimensionalaxialshockwithcurrentandmagneticfieldinacylindricalshocktubewereinvestigatedbyanumericalmethod.Theradialprofilesofthemagneticfield,electriccurrent,pressures,flowvelocitiesandtemperaturesbetweentheupanddown-streamradialforce-balancedplasmaoftheshockwererevealedbynumericalanalysis.Itisclearlyfoundthattheaxialshockcanleadtotwoeffects:oneisaninverseskineffect(i.e.,thecurrentdensityrisestowardsthecenteroftheconductor),theanotherisareversedcurrenteffectwhichoccursneartheedgeandaboutahalfradius.Itisalsofoundthattheradialgradientofpressure,densityandtemperatureallbecomeverylargenearthecenterduetotheaxialshock.
简介:Radiationsimulationutilizingplasmaradiationsources(PRS)generatesalargenumberofundesirabledebris,whichmaydamagetheexpensivediagnosingdetectors.Anultrafastshutter(UFS)drivenbypulsedhighcurrentcanerectaphysicalbarriertotheslowlymovingdebrisafterallowingthepassageofX-rayphotons.TheUFSconsistsofapairofthinmetalfoilstwistingtheparallelaxesinaNyloncassette,compressedwithanoutermagneticfield,generatedfromafastcapacitorbank,dischargingintoasingleturnloop.Atypicalcapacitorbankisof7.5μFchargingvoltagesvaryingfrom30kVto45kV,withcorrespondingcurrentsofapproximately90kAto140kAanddischargingcurrentperiodsofapproximately13.1μs.Ashutterclosingtimeasfastas38microsecondshasbeenobtainedwithanaluminiumfoilthicknessof100micrometersandacross-sectionalareaof15mmby20mm.Thedesign,constructionandtheexpressionsofthevalve-closingtimeoftheUFSarepresentedalongwiththemeasuredresultsofvalve-closingvelocities.
简介:Neutralbeaminjectionisoneofthemainplasmaheatingmethodsinnuclearfusiondevices.InordertosupportthescientificstudyoftheExperimentalAdvancedSuperconductingTokamak(EAST),amegawatt-levelhighcurrentionsourceisdesignedandmanufacturedintheASIPP,andtheprogressandpreliminarytestresultswillbepresentedinthispaper.
简介:AbridgearmprototypeofITERpoloidalfield(PF)convertermoduleshasbeendesignedandfabricated.Non-cophasecounterparallelconnectionischosenasthearmstructureoftheprototype.Amongallfactorsaffectingcurrentsharing,armstructureisthemainone.Duringthedesignofthearmprototype,anovelmethodbasedoninductancematrixesisemployedtoimprovethecurrentsharingofthebridgearm.Thetestresultsontheprototypeshowthatthecurrentsharingperformanceofthearmprototypeismuchbetterthanrelevantdesignrequirement,andthatthematrixmethodisveryeffectivetoanalyzeandsolvethecurrentsharingproblemsofthyristorconverters.
简介:ARogowskicoilisdevelopedtodetectthenanosecondpulsesignalsofthedischargecurrentwithawidebandwidthof800kHzto106MHzandhighsensitivityof2.22V/A.Perfor-mancetestsshowthattheRogowskicoilhasbothexcellentdynamicandstaticcharacteristics.CalibratingresultsandthecomparisonbetweenthestandardcurrentshuntandthedevelopedRo-gowskicoilforthemeasurementofnanoseconddischargepulsesdemonstratethatthedevelopedRogowskicoilcanreproducetheactualwaveformofthedischargecurrentaccurately.
简介:Ahigh-currentvacuumarc(HCVA)withtheconsiderationofanodevaporismod-eledandsimulated.First,fromtheHCVAcolumnmodel,theheatfluxdensitytotheanodeisobtained,whichisputintotheanodeactivitymodel,andtheparameterdistributions(suchasthevaportemperatureandvelocity)ofanodevaporareobtainedfromthesimulationresultsoftheanodeactivitymodel.Then,byiteratingandcalculatingtheHCVAcolumnmodelandanodeactivitymodel,theinteractionbetweentheHCVAcolumnandtheanodevaporissimulatedandanalyzed.Inthesimulation,thedistributionoftheaxialmagneticfield(AMF)generatedbytheelectrodesystemiscalculatedbysoftwareANSYS.Thesimulationresultsshowthattheinfluenceofanodevaporontheparameterdistributionsinthearccolumnissignificant.Thesimulationresultsarealsocomparedwiththevacuumarcphotograph.
简介:Becausethelargermetallicsurroundsareheatedbytheeddycurrent,whichisgeneratedbytheACcurrentflowingthroughtheACbusbarintheInternationalThermonuclearExperimentalReactor(ITER)poloidalfield(PF)convertersystem,shieldingoftheACbusbarisrequiredtodecreasethetemperatureriseofthesurroundstosatisfythedesignrequirement.ThreespecialtypesofACbusbarwithnaturalcooling,aircoolingandwatercoolingbusbarstructurehavebeenproposedandinvestigatedinthispaper.Foreachcoolingscheme,a3Dfinitemodelbasedontheproposedstructurehasbeendevelopedtoperformtheelectromagneticandthermalanalysistopredicttheiroperationbehavior.Comparingtheanalysisresultsofthethreedifferentcoolingpatterns,watercoolinghasmoreadvantagesthantheotherpatternsanditisselectedtobethethermaldissipationpatternfortheACbusbarofITERPFconverterunit.TheapproachtoqualifythesuitablecoolingschemeinthispapercanbeprovidedasareferenceonthethermaldissipationdesignofACbusbarintheconvertersystem.
简介:Hybridcircuitbreaker(HCB)technologybasedonavacuuminterrupterandaSF6interrupterinserieshasbecomeanewresearchdirectionbecauseofthelow-carbonrequirementsforhighvoltageswitches.Thevacuuminterrupterhasanexcellentabilitytodealwiththesteeprisingpartofthetransientrecoveryvoltage(TRV),whiletheSF6interruptercanwithstandthepeakpartofthevoltageeasily.AnHCBcantakeadvantageoftheinterruptersinthecurrentinterruptionprocess.Inthisstudy,anHCBmodelbasedonthevacuumiondiffusionequations,iondensityequation,andmodifiedCassie-Mayrarcequationisexplored.Asimulationplatformisconstructedbyusingasetofsoftwarecalledthealternativetransientprogram(ATP).AnHCBprototypeisalsodesigned,andtheshortcircuitcurrentisinterruptedbytheHCBunderdifferentactionsequencesofcontacts.ThevoltagedistributionoftheHCBisanalyzedthroughsimulationsandtests.TheresultsdemonstratethatifthevacuuminterrupterwithstandstheinitialTRVandinterruptsthepost-arccurrentfirst,thentherecoveryspeedofthedielectricstrengthoftheSF6interrupterwillbefast.Thevoltagedistributionbetweentwointerruptersisdeterminedbytheirpost-arcresistance,whichhappensaftercurrent-zero,andsubsequently,itisdeterminedbythecapacitiveimpedanceafterthepost-arccurrentdecaystozero.
简介:TheHTScurrentleadsofsuperconductingmagnetsforlargescalefusiondevicesandhighenergyparticlecolliderscanreducethepowerconsumptionforcoolingby2/3comparedwithconventionalleads.Theresistivesectionsofhigh-ratedcurrentleadsareusuallymadeofaheatexchangercooledbygasflow.Thesupplyofthecoolingmassflowincursmorethan90%ofthecoolingcostfortheHTSleads.Themassflowraterequirementdependsnotonlyonthelengthandmaterialoftheresistiveheatexchanger,butalsoontheheattransfercoefficientandHEXsurface,thejointresistanceatthecoldendanditscoolingapproach.Thedesignandoperationofasheet-stackHEXwithalargerspecificsurfaceandamuchsmallerhydraulicdiameterarepresentedinthepaper.ThetestresultsofanHTSleadoptimizedfor8kAshowthata98.4%efficiencycanbeachieved.
简介:Inresponsetothecurrentimbalancephenomenonanditsharmfulness,acurrentsharingcircuitmodelisbuiltup,whichrevealstheunderlyingcausesforthecurrentimbalancethroughaquantitativeanalysis.Then,afeasibleapproachofimprovement,namelyenlargementofthelengthofconnectionbusbars,isproposed.Aftertheamendment,itcanbeseenthatthecurrentsharingcoefficientisalmostunityunderratedorfaultcurrentconditions.
简介:ThesolutionofGrad-Shafranovequationdeterminesthestationarybehavioroffusionplasmainsideatokamak.Tosolvetheequationitisnecessarytoknowthetoroidalcurrentdensityprofile.Recentworksshowthatitispossibletodetermineamagnetohydrodynamic(MHD)equilibriumwithreversedcurrentdensity(RCD)profilesthatpresentsmagneticislands.InthisworkweshowanalyticalMHDequilibriumwithaRCDprofileandanalyzethestructureofthevacuumvectorpotentialassociatedwiththeseequilibriausingthevirtualcasingprinciple.
简介:Theeffectofarcplasmaonelectrodeerosioninaliquidmetalcurrentlimiter(LMCL)isstudied.Basedonasimplifiedtwo-dimensionalmagnetohydrodynamicmodel,theelongatedGaInSnmetalvaporarcanditscontractionprocessinaliquidmetalcurrentlimiteraresimulated.Thedistributionsoftemperature,pressureandvelocityofthearcplasmaarecalculated.Thesimulationresultsindicatethattheelectrodeerosionismainlycausedbytwohightemperaturegasjetflowsarisingfromthepressuregradient,whichisaresultofthenon-uniformarctemperaturedistribution.Thegasflows,whichactasjetsontotheelectrodesurface,leadtotheevaporationoftheelectrodematerialformthesurface.Aredesignstructureoftheelectrodeisproposedandimplementedaccordingtotheanalysis,whichgreatlyincreasedtheservicelifeoftheelectrode.
简介:Adirect-currentairplasmajetoperatedunderwaterpresentsthreestablemodesincludinganintermittently-pulseddischarge,aperiodically-pulseddischargeandacontinuousdischargewithincreasingthepowervoltage.Thethreedischargemodeshavedifferentappearancesfortheplasmaplumes.Moreover,gapvoltage-currentcharacteristicsindicatethatthecontinuousdischargeisinanormalglowregime.Spectrallinesfromreactivespecies(OH,N_2,N_2~+,H_α,andO)havebeenrevealedintheemissionspectrumoftheplasmajetoperatedunderwater.SpectralintensitiesemittedfromOHradicalandoxygenatomincreasewithincreasingthepowervoltageorthegasflowrate,indicatingthatreactivespeciesareabundant.Thesereactivespeciescausethedegradationofthemethylenebluedyeinsolution.Effectsoftheexperimentalparameterssuchasthepowervoltage,thegasflowrateandthetreatmenttimeareinvestigatedonthedegradationefficiency.Resultsindicatethatthedegradationefficiencyincreaseswithincreasingthepowervoltage,thegasflowrateorthetreatmenttime.Comparedwithdegradationintheintermittently-pulsedmodeortheperiodically-pulsedone,itismoreefficientinthecontinuousmode,reaching98%after21mintreatment.
简介:Thecurrentsheathvelocityin0.25TorrgaspressureofFilippovtypeplasmafocusisstudiedexperimentally.Byusingtwotridimensionalmagneticprobesontopoftheanodesurface,thecurrentsheathvelocityismeasuredforargon,oxygenandnitrogen.Additionally,theeffectofchargingvoltageonthecurrentsheathvelocityisstudiedinbothaxialandradialphases.Wefoundthat,themaximumcurrentsheathvelocitiesatbothradialandaxialphasesarerespectively4.33±0.28(cm/μs)and3.92±0.75(cm/μs)withargonastheworkinggasat17kV.Also,theminimumvaluesofcurrentsheathvelocityare1.48±0.15(cm/μs)attheradialphaseand1.14±0.09(cm/μs)attheaxialphasewithoxygenat12kV.Thecurrentsheathvelocityattheradialphaseishigherthanthatattheaxialphaseforallgasesandvoltages.Inthisstudy,variationofthefullwidthhalfmaximum(FWHM)ofmagneticprobesignalswithvoltageisinvestigatedfordifferentgasesatradialandaxialphases.
简介:Atwo-dimensionalhybridcodeisdevelopedtomodelthetransportofahigh-currentelectronbeaminadenseplasmatarget.Thebeamelectronsaretreatedasparticlesanddescribedbyparticle-in-cellsimulationincludingcollisionswiththetargetplasmaparticles.Thebackgroundtargetplasmaisassumedtobeastationaryfluidwithtemperaturevariations.Thereturncurrentandtheself-generatedelectricandmagneticfieldsareobtainedbycombiningAmpere’slawwithoutthedisplacementcurrent,theresistiveOhm’slawandFaraday’slaw.Theequationsaresolvedintwo-dimensionalcylindricalgeometrywithrotationalsymmetryonaregulargrid,withcenteredspatialdifferencingandfirst-orderimplicittimedifferencing.Thealgorithmsimplementedinthecodearedescribed,andanumericalexperimentisperformedforanelectronbeamwithMaxwelliandistributionejectedintoauniformdeuterium-tritiumplasmatarget.
简介:Sinteredsiliconcarbide(SiC)wasetchedbyadielectricbarrierdischargesource.Ahighvoltagebipolarpulsewasusedwithheliumgasfortheplasmageneration.OnestablefilamentplasmawasgeneratedandcouldbeusedforSiCetching.Astheprocessinggas(NF3)mixingrateincreased,thewidthanddepthoftheetchingprofilebecamenarroweranddeeper.ThedifferentiatedV-QLissajousmethodwasusedformeasuringthecapacitances(Ceq)oftheelectrodeaftertheplasmaturnedon.ThewidthoftheetchingprofilewasproportionaltoCeq.Asthecurrentpeakvalue/smxofthesubstratecurrentincreased,thevolumeremovalrateofSiCincreased.Theetchdepthwasproportionaltotheratioof/smxtoCeq.Additionally,becauseofthedifferentcharacteristicsoftheplasmadisksonSiCsubstratebythevoltagepolarity,theetchingprofilewasunstable.However,inhighNF3mixingprocess,theetchingprofilebecamestableanddeeper.
简介:WehavedevelopedaplasmaetchingsimulatortoinvestigatetheevolutionofpatternprofilesinSiO2materialunderdifferentplasmaconditions.Thismodelfocusesonenergyandangulardependentetchingyield(physicalsputteringinthispaper),neutralandionangulardistributions,andreflectionofionsorneutralsonthesurfaceofaphotoresistorSiO2.TheeffectofpositivechargeaccumulationonthesurfaceofinsulatedmaskorSiO2isstudiedandthechargeaccumulationcontributestoadeflectionofiontrajectory.Thewaferprofileevolutionhasbeensimulatedusingacellular-automata-likemethodunderradio-frequency(RF)biasanddirect-current(DC)bias,respectively.Onthebasisofthecriticalroleofangulardistributionofionsorneutrals,thewaferprofileevolutionhasbeensimulatedfordifferentvariancesofangles.Observedmicrotrenchinghasbeenwellreproducedinthesimulator.Theratioofneutralstoionshasbeenconsideredandtheresultshowsthatbecausetheneutralsarenotacceleratedbyanelectricfield,theirenergyismuchlowercomparedwithions,sotheyareeasilyreflectedonthesurfaceofSiO2,whichmakesthetrenchshallower.