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Introductiontosparkdischarge

Whenthepowerofthehigh-voltagepowersupplyisnottoohigh,thegasbetweenthehigh-voltageelectrodesisbrokendown,andgasdischargephenomenasuchasflashingandpoppingsoundoccur.Undernormalairpressure,whenahighvoltageisappliedbetweencoldelectrodeswithanottoolargecurvature,ifthepowersuppliedbythepowersupplyisnottoolarge,sparkdischargewilloccur.Duringsparkdischarge,impactionizationdoesnotoccurintheentireareabetweentheelectrodes.Inside,itjustfollowsthenarrowandtortuousluminouschannel,accompaniedbypoppingsound.Afterthegasisbrokendown,theinsulatorsuddenlychangesfromaninsulatortoagoodconductor,thecurrentsoars,andthepowerofthepowersupplyisnotenough,sothevoltagedrops,thedischargeistemporarilyextinguished,andthedischargeisagainafterthevoltageisrestored.Therefore,thesparkdischargeisintermittent.Lightningisalarge-scalesparkdischargeinnature.Sparkdischargecanbeusedformetalprocessinganddrillingfineholes.Thesparkgapcanbeusedtoprotectelectricalequipmentsothatitwillnotbedamagedwhenstruckbylightning.

Thephenomenonofgasdischargegeneratedbetweenpositiveandnegativechargedareaswithahighpotentialdifference.Usedforthetreatmentofthebondingsurfacetoimprovethebondingstrength.Itismostlyusedforsurfacetreatmentofdifficult-to-stickplasticsandmetals.Aformofgasdischargeunderatmosphericpressureorhighpressure,sonamedbecausethepowergenerationchannelresemblesaspark.

PrincipleofSparkDischarge

Aflashandsoundinstantaneousgasdischargeoccursbetweenpositiveandnegativechargedareaswithahighpotentialdifference.Inthedischargespace,gasmoleculesareionized,thegasrapidlyandviolentlyheatsup,flashesandsounds.Thepaththatthedischargechanneltraversesanditsluminescenceandconductivitydependontheshapeandsizeofthepositiveandnegativechargedregions,thepotentialdifferencebetweenthem,andthenatureandpressureofthegas.Sincethevoltagebetweenthetwopolesisveryhighduringsparkdischarge,butthepowerofthepowersupplyisnotlarge,oncethedischargeoccurs,thecurrentintensityincreasessharply,andthevoltagedropsinstead,causingthedischargetobetemporarilyextinguished.Thedischargewillnotbeperformeduntilthevoltageisrestored.Therefore,thesparkdischargeisintermittent.Lightningisalarge-scalesparkdischargephenomenoninnature.Inhigh-voltageinstallations,electricalsparksmayoccurbetweenpartswithpoorcontact.Thisphenomenonconsumesenergy,damagesthedevice,andeasilycausesdanger.

Influencingfactors

Whenotherconditionsremainunchanged,thebreakdownvoltagethatcausessparkdischargedependsontheshapeoftheelectrodeandthedistancebetweenit.Inhigh-voltageengineering,itoftenpassesthroughacertainshapeThedistancebetweentheelectrodeswhenasparkdischargeoccurs(calledthesparkgap)isusedtomeasuretheunknownhighvoltagevalue.Thefollowingtableshowstherelationshipbetweenthesparkgap(mm)andvoltageofseveralelectrodeshapes.

SparkDischargeHazard

Anexplosionoccursduetostaticsparksignitingsomeflammableobjects.Inthedarknight,whenpeopletakeoffnylonandwoolenclothes,theywillmakesparksand"beating"noises,whicharebasicallyharmlesstothehumanbody.Butontheoperatingtable,electricsparkscancauseananestheticexplosion,hurtingdoctorsandpatients;incoalmines,itcancauseagasexplosion,whichcancausedeathsandinjuriestoworkers,andtheminewillbescrapped.Inshort,electrostatichazardsarecausedbytheuseofelectricityandelectrostaticsparks.Themostseriouselectrostaticdischargeinelectrostatichazardscausesfiresandexplosionsofcombustibles.Itisoftensaidthatthemeasurestopreventtheoccurrenceofstaticelectricityaregenerallytoreducetheflowrateandflow,transformtheprocesswithstrongelectrification,anduseequipmentandmaterialswithlesselectrification.Theeasiestandmostreliablewayistogroundtheequipmentwithawire,sothatchargescanbeintroducedintothegroundandavoidstaticelectricityaccumulation.Carefulpassengerswillprobablyfindthatdischargebrushesareinstalledonbothsidesofthewingtipsoftheaircraftandthetailoftheaircraft.Whentheaircraftislanding,inordertopreventpassengersfromgettingelectricshockswhentheydisembark,mostoftheaircraftlandinggearsusespecialgroundingtiresorgroundingwires.,Inordertoventthestaticchargegeneratedbytheaircraftintheair.Weoftenseeanironchainattherearofatankertruck.Thisisthegroundingwireofthetruck.Properlyincreasethehumidityoftheworkingenvironmenttoallowthechargetobedischargedatanytime,anditcanalsoeffectivelyeliminatestaticelectricity.Thisisthereasonwhyitisnoteasytodoanelectrostatictestinhumidweather.Theantistaticagentstudiedbytheresearcherscaneliminatethestaticelectricityinsidetheinsulatorwell.

Utilizationofsparkdischarge

Mainapplications:①Spectralanalysis.②Theigniteroftheinternalcombustionengine.③Metalelectricdischargemachining:usesparkdischargetocorrodemetalworkpiecesinelectrolytesolutiontoformasurfacecorrespondingtotheshapeofthetoolelectrode(thismachiningmethodcanperforate,engraveandmakevariousprofilesonveryhardmetalsCavity).④Measurementofhighvoltagevalue:Thelowestvoltagethatcausessparkdischarge(iebreakdownvoltage,see"gasdischarge")isrelatedtotheshapeoftheelectrodeandthedistancebetweentheelectrodes.Inhighvoltageengineering,itisoftenmeasuredbetweenelectrodesofacertainshape.Theintervalofsparkdischargeisusedtodeterminetheunknownhighvoltagevalue.

Thestarteroffluorescentlampalsousestheprincipleofsparkdischarge.Whentheelectrickeyofthefluorescentlampisclosed,thevoltagecausestheneongasintheglasstubeofthestartertobedischarged,andtheheatgeneratedbythedischargecausesthemovingpieceintheglasstubetoexpandandconnectwiththestaticpiece.Flashingandclickingsoundswereemittedduringthisprocess.Whenthemovingfilmisdisconnectedfromthestaticfilm,thehighvoltagedischargesthemercuryvaporinthelamptube,andthefluorescentlampemitslight.