电气外文文献

电气与自动化工程系2014届毕业生英文文献专业：班级：学号：姓名：时间：年月日CircuitbreakerCompressedaircircuitbreakerisamechanicalswitchequipment,canbeinnormalandspecialconditionsbreakingcurrent(suchasshortcircuitcurrent).Forexample,aircircuitbreaker,oilcircuitbreaker,interferencecircuitconductorfortheapplicationofthesafetyandreliabilityofthecircuitbreaker,currentinarcfromisusuallydividedintothefollowinggrades:airswitchcircuitbreaker,oilcircuitbreaker,lessoilcircuitbreaker,compressedaircircuitbreaker,adegaussingofisolatingswitch,sixsulfurhexafluoridecircuitbreakerandvacuumbreaker.Theirparametersofvoltage,current,insulationlevelofbreakingcapacity,instantaneousvoltageofftimeofrecoveryandabombing.Breakerplateusuallyinclude:1themaximumtolerablecurrent;2ofthemaximumcurrentisinterrupted;3largestlinevoltage;4interruptthecyclenumber.Inthe60hHZsystem,interruptmaylastfrom3-to8cycle,inordertoquicklybreakuptotheloadcurrent,wehavetoensurecontinuedtocoolit,high-speed,breakingcanlimitontransmissionlinedamage,itisequallyimportanttohelpsystemtomaintainstableoperationatanytimeoftheaccident,themaincircuitbreakerbyoperatingmechanism,actuatorandarcquenchingchamber.Whenatriggercurrentorvoltage,springoperationmechanismofairisolationswitchmovesquicklytoreducethecontactloss,specialshapeandusethematerialofmaincontactcompletelyfitforthearcofcontact,airisolationswitchfurtherimprovementisduetothearcquenchingperformance,insulatingbaffleplatesarcshield,witharcthefunctionofthesespecialproperties,itisusedinlowvoltageandDCcircuitbreaker.Oilcircuitbreakerinaround1900,mainlytomeetthenew,breakingcapacityrequirements,ACswitchisimmersedinanoilcylinder,theoilinthearcquenchingandzerosetofffunctionisveryeffectiveinthecurrent,arcgate,nozzle,pear,anewoperationmechanismandavarietyofthenewcircuitfunctioninrecentdecadestointroducetheuseofoilcircuitbreakercanadaptto362kV.TypesandConstructionofTransformerAtransformerisadevicethatalternatingcurrentelectricenergyatonevoltagelevelintoalternatingcurrentelectricenergyatanothervoltagelevelthroughtheactionofamagneticfield.Itconsistsoftwoormorecoilswirewrappedaroundacommonferromagneticcore.Thesecoilsare(usually)notdirectlyconnected.Theonlyconnectionbetweenthecoilsisthecommonmagnecticfluxpresenwithinthecore.Oneofthetransformerwindingsisconnectedtoasourceofacelectricpower,andthesecond(andperhapsthird)transformerwindingsupplieselectricpowertoloads.thetransformerwindingconnectedtothepowersouceiscalledtheprimarywindingorinputwinding.andthewindingconnectedtotheloadsiscalledthesecondarywindingorinputwinding.Ifthereisathirdwindingonthetransformer,itiscalledthetertiarywinding.Powertransformerareconstructedononeoftwotypesofcores.onetypeofconstructionconsistsofasimplerectangularlaminatedpieceofsteelwiththetransformerwindingswrappedaroundtwosidesoftherectangle.Thistypeofconstructionisknowascoreform.Theothertypeconsistsofthree-leggedlaminatedcorewiththewindingswrappedaroundthecenterleg.Thistypeofconstructionisknowasshellform.Ineithercase,thecoreisconstructedofthinlaminationselectricallyisolatedformeachotherinorderinordertoreduceeddycurrentstoaminimum.Theprimaryandsecondarywindingsinaphysicaltransformerarewrappedoneontopoftheotherwiththelow-voltagewindinginnermost.Suchanarrangementseverstwopurposes:1.Itsimplifiestheproblemofinsulatingthehigh-voltagewindingfromthecore.2.Itresultsinmuchlessleakagefluxthanwouldbethetwowindingswereseparatedbyadistanceonthecore.Powertransformeraregivenavarietyofdifferentnames,dependingontheiruseinpowersystems.Atransformerconnectedtotheoutputofageneratorandusedtostepitsvoltageuptotransformerlevelsissometimescalledunittransformer.Thetransformeraitheotherendofthetransformerline,whichstepsthevoltagedownfromtransmissionlevlstodistributionlevels,iscalledasubstationtransformer.Finally,thetransformerthattakesthedistributionvoltageandstepsisdowntothefinalvoltageaiwhichthepowerisactuallyusediscalledadistributiontransformer.Allthesedevicesareessentiallythesame-theonlydifferenceamongthemistheirintendeduse.Inadditiontothevariouspowertransformer,twospecial-purposetransformersareusedwithelectricmachineryandpowersystems.Thefirstofthesespecialtransformersisadevicespeciallydesignedtosampleahighvoltageandproducealowsecondaryvoltagedirectlyproportionaltoit.Suchatransformeriscalledapotentialtransformer.Apowertransformeralsoproducesasecondaryvoltagedirectlyproportionaltoitsprimaryvoltage;thedifferencebetweenapotentialtransformerandapowertransformeristhatthepotentialtransformerisdesignedtohandleonlyaverysmallcurrent.Thesecondtypeofspecialtransformerisadevicedesignedtoprovideasecondarycurrent.muchsmallerthanbutdirectlyproportionaltoitsprimarycurrent.Thisdeviceiscalledacurrenttransformer.LingtingprotectionThethunderandlightningprotectstoconnecttheground;Connectthegroundtoavoidthethunderthemostimportantlinkofthetechnique,ignoreisashotthunder,respondthethunderofthethunderorotherform,andavoidthethunderworkmostallofsendintotheearththethunderelectriccurrent.Storethethunderenergytobehavethetypetobuildthe,currenttechnologytostillreachtonotarrive,andthereforehavenoth