Definition
Low-voltageelectricalappliancesusuallyrefertoelectricalappliancesthatworkatACvoltageof1200VorDCvoltageof150
Low-voltageelectricalappliances(2photos)
0V.Commonlow-voltagedevicesincludeswitches,fuses,contactors,leakageprotectorsandrelays.Wheninstallingelectricalcircuits,thepowersupplyandtheload(suchasamotor)areconnectedbylow-voltageelectricalappliancesthroughwires,whichcanrealizecontrolfunctionssuchasloadconnection,cut-off,andprotection.Basicstructure
Low-voltageelectricalappliancesgenerallyhavetwobasicparts:oneisthesensingpart,whichsensesexternalsignalsandmakesregularresponses.Inautomaticcontrolappliances,mostofthesensingpartsComposedofanelectromagneticmechanism,inacontrolledelectricalappliance,thesensingpartisusuallyanoperatinghandle,etc.;theotherisanexecutionpart,suchasacontactthatswitchesonoroffthecircuitaccordingtoinstructions.
Equipmentintroduction
Accordingtoitsworkingvoltage,controlappliancesaredividedintotwocategories:high-voltagecontrolappliancesandlow-voltagecontrolappliances,withAC1200VandDC1500Vastheboundary.AC1200Vandbelow,DC1500Vandbelowarecalledlow-voltageelectricalappliances.
Thedevelopmentoflow-voltageelectricalappliancesdependsonthedevelopmentofthenationaleconomyandtheneedsofthedevelopmentofmodernindustrialautomation,aswellastheresearchandapplicationofnewtechnologies,newprocesses,andnewmaterials.Atpresent,itisdevelopinginthedirectionofhighperformance,highreliability,miniaturization,digitalandanalog,modularization,combinationandcommonparts.
Function
Low-voltageelectricalappliancescanautomaticallyormanuallychangethestateandparametersofthecircuitaccordingtotheoperatingsignalortherequirementsoftheexternalfieldsignaltorealizethecontrolandprotectionofthecircuitorthecontrolledobject,Measurement,indicationandadjustment.
Thefunctionsoflow-voltageelectricalappliancesinclude:
Controlfunctions,suchaselevatorupanddownmovement,automaticspeedswitching,andautomaticfloorstop.
Regulatingfunction,low-voltageelectricalappliancescanadjustsomeelectricityandnon-electricitytomeetuserrequirements,suchasdieselenginethrottleadjustment,roomtemperatureandhumidityadjustment,automaticadjustmentofilluminanceandsoon.
Theprotectionfunctioncanautomaticallyprotecttheequipment,theenvironment,andthepersonaccordingtothecharacteristicsoftheequipment,suchastheoverheatingprotectionofthemotor,theshort-circuitprotectionofthepowergrid,andtheleakageprotection.
Indicatingfunction,usingthecontrolandprotectionfunctionsoflow-voltageelectricalappliancestodetecttheoperationstatusoftheequipmentandtheworkingstatusoftheelectricalcircuit,suchasinsulationmonitoring,protectioncardfailureindication,etc.
Classification
Therearemanytypesoflow-voltageelectricalappliances,andtherearemanyclassificationmethods.
1.Accordingtotheactionmode,itcanbedividedinto:
(1)Manualelectricalappliances-electricalappliancesthatrelyonexternalforcetodirectlyoperatetoswitch,suchasknifeswitches,buttonswitches,etc.
(2)Automaticelectricalappliances-electricalappliancesthatactautomaticallybasedoninstructionsorchangesinphysicalquantities,suchascontactors,relays,etc.
2.Accordingtothepurpose,itcanbedividedinto:
(1)Low-voltagecontrolelectricalappliances--mainlyplayacontrolroleinlow-voltagepowerdistributionsystemsandpowerequipment,suchasknifeswitches,low-voltagecircuitbreakers器等。
(2)Low-voltageprotectiveelectricalappliances-mainlyplayaprotectiveroleinlow-voltagepowerdistributionsystemsandpowerequipment,suchasfuses,thermalrelays,etc.
3.Accordingtothetype,itcanbedividedinto:
Knifeswitch,knifechangeoverswitch,fuse,low-voltagecircuitbreaker,contactor,relay,mainelectricalapplianceandautomaticswitch,etc.
Equipmentselection
Theelectricalappliancesselectedforlow-voltagepowerdistributiondesignshouldmeetthecurrentrelevantnationalstandardsandmeetthefollowingrequirements.
1)Theratedvoltageoftheelectricalapplianceshouldbecompatiblewiththenominalvoltageofthecircuitinwhichitislocated
2)TheratedcurrentoftheelectricalapplianceshouldnotbelessthanthecalculationofthecircuitinwhichitislocatedCurrent
3)Theratedfrequencyoftheelectricalapplianceshouldbecompatiblewiththefrequencyoftheloopwhereitislocated
4)Theelectricalapplianceshouldadapttotheenvironmentalconditionsoftheplacewhereitislocated
5)TheelectricalapplianceshouldMeettherequirementsofdynamicstabilityandthermalstabilityundershort-circuitconditions.Electricalappliancesusedtodisconnectshort-circuitcurrentshouldmeetthemakingandbreakingcapacityundershort-circuitconditions.
2.Checkingthemakingandbreakingcapacityofelectricalappliancesundershort-circuitconditionsshouldusetheeffectivevalueoftheexpectedshort-circuitcurrentperiodiccomponentattheinstallationlocation,whenthesumoftheratedcurrentsofthemotorsconnectedneartheshort-circuitpointexceeds1%oftheshort-circuitcurrentAtthetime,theinfluenceofthemotorfeedbackcurrentshouldbetakenintoaccount.
Applicablestandards
GB14048seriesstandardlow-voltageswitchgearandcontrolequipmenthave16standards
Useattention
Choosedifferenttypesoflow-voltageelectricalappliancesCircuitbreakerswithshort-circuitbreakingcapacitymeettheneedsofdifferentlineexpectedshort-circuitcurrents(whenIisinthesamesituation).Theselectionprincipleofthecircuitbreakeris:theshort-circuitbreakingcapacityofthecircuitbreaker≥theexpectedshort-circuitcurrentoftheline.
1.Differenttypesofcircuitbreakersshouldbeusedforlow-voltageelectricalapplianceswithdifferentloads.
Etc.)Threecategories.MostoftheDW15series,DW17(ME)series,AHseriesandDW40andDW45seriesintheuniversal(alsoknownasframetype)circuitbreakersaretypeB,whileDZ5,DZ15,DZ20,TO,TG,CM1,TM30andSomespecificationsofHSM1andotherseriesanduniversalDW15.DW17onlyhavetwo-stageprotectionwithlongtimedelayforoverloadandinstantaneousshortcircuit.Theyarenon-selectivetypeAcircuitbreakers.Selectiveprotection.
WhenpointFisshort-circuited,onlytheQF2circuitbreakerclosetopointFwilloperate,andtheupperQF1circuitbreakerwillnotoperate.Thisisselectiveprotection(becauseQF1doesnotoperate,nofaulthasoccurredQF3.QF4branchkeepspowersupply).IfQF2andQF1arebothTypeAcircuitbreakers,ashortcircuitoccursatpointF,andwhentheshortcircuitcurrentreachesacertainvalue,QF1.QF2willactatthesametime,andthecircuitofQF1circuitbreakeranditsbrancheswillbepoweredoff,whichisnotselectiveprotection..ThereasonfortheselectiveprotectionisthatQF1isatypeBcircuitbreaker,whichhasshort-circuitandshort-delayperformance.WhenpointFisshort-circuited,theshort-circuitcurrentflowsthroughtheQF2branchandalsothroughtheQF1circuit,QF2'sinstantaneousactionreleaseaction(usuallyitsfullbreakingtimeisnotgreaterthan0.02s),duetotheshortdelayofQF1,QF1willnotactwithin0.02s(itsshortdelayis≥0.1sor0.2.0.3.0.4s).WhentheQF2actioncutsoffthefaultyline,theentiresystemreturnstonormal.Visible,whichmeansthatitcanchooseAtypecircuitbreaker(includingplasticcaseanduniversal)
Thechoiceofconductor
1.Thetypeofconductorshouldbelaidaccordingtothelayingmethodandenvironmentalconditionschoose.Inadditiontosatisfyingtheaboveconditions,theinsulatedconductorshouldstillmeettherequirementsoftheworkingvoltage.
2.Selecttheconductorcross-section,whichshouldmeetthefollowingrequirements:
1)Thelinevoltagelossshouldmeettherequirementsofthenormaloperationoftheelectricalequipmentandtheterminalvoltagewhenstarting
2)Thecurrentcarryingcapacityoftheconductordeterminedaccordingtothelayingmethodandenvironmentalconditionsshouldnotbelessthanthecalculatedcurrent
3)Theconductorshouldmeettherequirementsofdynamicandthermalstability
4)TheminimumconductorThecrosssectionshouldmeettherequirementsofmechanicalstrength,andtheminimumcorewirecrosssectionofthefixedlylaidconductorshouldmeettherequirementsofTable2.2.2.
3.Whenlayinginsulatedwiresandcablesalongpathswithdifferentcoolingconditions,whenthelengthoftheworstsectionofcoolingconditionsexceeds5m,thesectionofinsulatedwiresandcablesshouldbeselectedaccordingtotheconditionsofthissection,oronlyThesectionuseslargecross-sectioninsulatedwiresandcables.
Typesoflow-voltageelectricalappliances
Developmentdirectionofpowercircuitbreakers
Asoneofthemostimportantproductsinlow-voltageelectricalappliances,powercircuitbreakershavealwaysbeenfavoredbymany.Judgingfromthenewproductslaunched,thecompetitionisfierce.ThenewgenerationofACBaircircuitbreakershavenotonlyimprovedtheiroverallperformanceandmaintechnicalindicatorsbyalargemargin,butalsotheimprovedtechnicalperformanceindicatorshavehighlightedtheirpracticability.Thehigh-currentmonolithicstructurehasbecomeadevelopmentmainstreamofthenewgenerationofaircircuitbreakerswithlarge-scalespecifications.Thenewgenerationofaircircuitbreakersnotonlyfurtherreducethevolumeofeachspecificationproduct,butalsoreducethenumberofspecificationsoftheentireseries.Mostofthecontactarcextinguishingsystemsinthenewgenerationofaircircuitbreakersadoptasingle-breakpointstructure.Theinternalandexternalaccessoriesofmanynewgenerationaircircuitbreakersadoptmodulardesign,whichisnotonlyconvenientforstandardizedassemblyandproduction,butalsoconvenientfordisassembly,replacementandmaintenance.Theelectroniccontrollersinthenewgenerationofaircircuitbreakershavepowerfulfunctions.Allnew-generationproductsareequippedwithcommunicationinterfaces,whichcanuseinternalbuseswiththemainindustrialfieldbussystemsofsomenew-generationframecircuitbreakers.
MoldedCaseCircuitBreaker(MCCB)
Thenewgenerationofmoldedcasecircuitbreakersisintheproductstructure,operatingmechanism,contactarcextinguishingsystem,adjustablethermalmagnetictripandelectronictripTheoldergenerationofplastic-casecircuitbreakershavemadegreaterbreakthroughsintechnologiessuchasbuckles,whichgreatlyimprovesthecomprehensivetechnicalandeconomicindicatorsoftheproduct.Thedevelopmentofthenewgenerationofmoldedcasecircuitbreakerspaysgreatattentiontoimprovingthetechnicalperformanceindicatorswhilereducingthevolume,sothenewdouble-breakpointbreakingtechnologyisgettingmoreandmoreattention.
Withtheimprovementofshort-circuitbreakingcapacity,manyproductshaveachievedIcs=Icu,andsomeseriesofproductshaveIcwindicatorsforlargecurrentratings,whichmakesitpossibletoachieveselectiveprotectionbetweenupperandlowerlevelsofmoldedcasecircuitbreakers.Manynew-generationproductsarenotonlygreatlyreducedinsize,butalsohaveadecreasingtrendinframegrades.Withthereductionofthevolumeandcostofelectronictrips,itisanobvioustrendthatallseriesadoptelectronictrips,andtheprotectionperformanceofplasticcasecircuitbreakersusingelectronictripsismoreperfect.
Thenewgenerationofplasticcasecircuitbreakershavegroundfaultprotectionandresidualcurrentprotection.Thenewgenerationofmoldedcasecircuitbreakersalsohaveresidualcurrentprotectionfunctions.Generally,twomethodsareusedinstructure:twinstructureandassembledstructure.Thetwinstructureissmallinsizeandeasytomaintainandreplace;theassembledstructureisflexibleinderivation.
Inordertomeettheneedsofthesystem,eachattachesmoreandmoreattentiontothedevelopmentofaccessories,andprovidesawealthofinternalandexternalaccessories.Thenewgenerationofmoldedcasecircuitbreakershavecommunicationfunctions.Theycanbeeasilyconnectedtovariousfieldbussystems(suchasProfibus,Devicenet,Modbus,etc.)throughanexternalcommunicationadaptertorealizeremotemonitoring.
Thedevelopmenttrendofcontrolappliances
Withtherapiddevelopmentofelectronictechnology,thedevelopmentofcontrolapplianceshasbecomemoreandmorerapid,especiallyincontrolandprotectionswitchingappliances,electronicmotorprotectionThedevelopmentofinverters,softstartersandfrequencyconvertersisthefastest.Inthepasttenyears,someofthemhavedevelopedtwogenerationsofproducts,whichshowstherapiddevelopmentoftechnology.
ControlandProtectionSwitchingAppliances(CPS)
Inrecentyears,majorcompanieshaveintroducedtheconceptofoverallsolutionstomotorcontrolandprotectiondevices,includingmotorprotectioncircuitbreakers,contactors,andprotectiondevices.Therelayisdirectlyassembledintoacompactmotorstarter(thatis,combinedtypesuchasMOELLER'sXstartseries,etc.),andthemutualconnectioncombinationrequirementsareconsideredintermsofappearance,size,terminalconnectionandperformancecoordinationduringcomponentdesign.Withthedevelopmentoftechnologyandtheincreaseindemand,integratedCPShasalsoappeared(suchasSchneider'sTesysUseries),whichhasamorecompactandreasonablestructureandmorepowerfulfunctions.TheintegratedCPSisrepresentedbySchneider'sTesysUseriesproducts.Thehighintegrationnotonlygreatlyreducesthevolumethanthecombinedtype,butalsohasperfectprotectionperformanceandpowerfulfunctions.Therefore,theintegratedCPSisverylikelytobecomethemainstreamofCPSdevelopmentinthefuture.
Electronicmotorprotector
Electronicmotorprotectorisaprofessionalelectricalapplianceusedfortheprotectionofmotors,whichwasbornwiththedevelopmentofelectronictechnology.Itisdividedaccordingtothelevelofmotorprotectionrequirements.High,mediumandlow-endproductseries.High-endmotorprotectorsareverypowerful,suchasoneofthemainproductsinthemotorprotectorproductseriesunderMM2andGEMultlin,whicharemainlyusedinlow-voltagemotorcontrolcenters.
Electronicmotorprotectorsalsoshowdiversifiedsolutionsintheirfunctionalexpansion.Theprotectionscopeisnotonlymotorprotection,butalsoextendstootherequipmentprotection,suchassubstationprotectionandtransformerprotection.Themechanicalstructureandfunctionoflow-andmid-rangeelectronicmotorprotectorsaresimilartotraditionalthermalprotectionrelays.Theycanbedirectlyassembledwithcontactorsofthesameleveltoformcompactmotorstarters,buttheyaremorepowerfulthanthermalrelaysandwillgraduallyreplacethermalrelays.Relaysoccupyaplaceinthefieldofmotorcontrolandprotection.
Softstarter
Therapiddevelopmentofsoftstartertechnologyhasbasicallyreplacedtheoriginalstep-downstarter,auto-decompressionstarterandotherproducts,becominganimportantMotorstartersgenerallyhavetwoseriesofsoftstarters,economictypeandadvancedtype.Economicalsoftstartersgenerallyhavesimplefunctions,onlyhavesoft-startfunctionsandnootherprotectionfunctions,buttheyarelowincost,compactinstructure,andsmallinsize.Someeconomicalsoftstarterscanalsodoubleassemiconductorcontactors.Advancedsoftstarter,inadditiontosoftstartfunction.Italsohasavarietyofotherprotectionfunctions.
Motorfrequencyconversionspeedregulationdevice(frequencyconverter)Themotorfrequencyconversionspeedregulationdevicecanadjustthemotorspeedarbitrarilybychangingtheoutputfrequencyofthepowersupplytoachievesmoothsteplessspeedregulation,whichiswidelyusedinindustrialcontrolthatrequiresspeedregulationTherefore,eachattachesgreatimportancetothedevelopmentoffrequencyconversionspeedcontroldevices.Thegeneralcharacteristicsofthenewgenerationofmotorvariablefrequencyspeedregulationdeviceare:highperformance;easytouse,installationandinitializationsettingsarefurthersimplified;haveawidepowerrange,excellentspeedcontrolandtorquecontrolcharacteristics;powerstructureandcontrolunitModular,thecontrolunitcansupportplugandplayfunction;intelligent,supportmulti-buscommunication,provideopenfieldprogrammablestructure;highpowerdensity,compactsize;lessaffectedbyEMI/RFIharmonics.Withthedevelopmentofinvertercontroltechnology,itsadvancedproductshavehighcontrolperformance,whichcannotonlycontrolACasynchronousmotors,butalsoACpermanentmagnetsynchronousmotors,anditscontrolperformancelevelhasreachedthelevelofgeneralservocontrollers.Motor-integratedinvertersandcomponentinvertershavedevelopedrapidly.Thistypeoffrequencyconverterwillbecomethemainstreamofthedevelopmentofsmallfrequencyconverters.
Thedevelopmenttrendofterminalelectricalappliances
Thedevelopmentofterminalelectricalapplianceshasexperiencedrapiddevelopmentinthe1990s,andhasshownasteadydevelopmenttrendinrecentyears.Theproductserieshavecompletespecificationsandtechnicalperformance.Theindexishigh,thesizeismodularized,andtheinstallationistrack-based.
Thedevelopmentofminiaturecircuitbreakers(MCB)
Asthemainproductinterminalappliances,thedevelopmentofminiaturecircuitbreakershasalwaysdominatedthedevelopmentofterminalappliances.Theselectiveprotectionoftheterminalpowerdistributionsystemhasnotbeenpossibleinthepast.Thebirthofminiaturecircuitbreakerswithselectiveprotection,suchasABB'sS700,completelysolvedtheproblemofselectiveprotectionbetweentheupperandlowerlevelsoftheterminalpowerdistributionsystem.Thereliabilityisgreatlyimproved.TheminiaturecircuitbreakerofP+Nstructurehasbeendevelopedrapidlyinrecentyears.Atpresent,theminiaturecircuitbreakerofP+Nstructureisdevelopinginthedirectionoflargecapacityandhighbreakingcapacity.WiththebreakthroughofP+Nstructureandminiaturecircuitbreakertechnology,thevolumeissmaller.Theminiaturecircuitbreaker(expectedtobesingle-pole12mmwide)willalsobeavailableinthenearfuture,whichwillusherinanotherpeakinthedevelopmentofminiaturecircuitbreakers.Thesameminiaturecircuitbreakerhasvarioustrippingcharacteristics,canmeetavarietyofstandards,meettherequirementsofdifferentpowerdistributionsystems,andmeettheneedsofglobaltrade.Inadditiontoitsowntechnologicaldevelopment,miniaturecircuitbreakershavemorecompleteaccessories.Thereisanewbreakthroughintheinstallationmethodofminiaturecircuitbreakers,fromscrewinstallationtotrackinstallation,whichmakestheinstallationofminiaturecircuitbreakersmoreconvenient.Atpresent,theintegratedtechnologyofbusbarconnectionandinstallationisadoptedbymoreandmoreminiaturecircuitbreakerstoimproveproductionefficiency..
DevelopmentofresidualcurrentcircuitbreakersRCCBandRCBO
Inrecentyears,thedevelopmentofresidualcurrentcircuitbreakersRCCBandRCBOhasmainlyfocusedontypeBresidualcurrentcircuitbreakersandself-checkingfunctionResidualcurrentcircuitbreakers,theintroductionofnewtechnologiesandcontinuousbreakthroughs,notonlymaketheprotectionperformanceofresidualcurrentcircuitbreakersmorecomplete,morecompletefunctions,butalsocontinuetoshrinkinsize.Theappearanceofthesmall-sizedB-typeRCCBmakestheresidualcurrentprotectionperformancemoreperfectontheonehand,andlaysthefoundationforwiderapplicationinthefutureontheotherhand.Thebirthoftheresidualcurrentcircuitbreakerwithself-checkingfunctionisanotherbrightspotinthedevelopmentoftheresidualcurrentcircuitbreakerfamily.Theapplicationofthistechnologywillgreatlyimprovethesafetyandreliabilityoftheterminaluseofresidualcurrentcircuitbreakers.
Developmentofterminalcombinedelectricalappliances
Afternearlytwodecadesofdevelopment,theprotectiveshellsofterminalcombinedelectricalappliancesmostlyusehigh-strengthengineeringplastics,withnovelstructure,beautifulappearance,brightcolors,andshells.Theprotectionlevelhasbeencontinuouslyimproved,fromIP30andIP40toIP55andIP65.Themodulardimensionsenablethemtobeusedaloneorincombination.Terminalcombinedelectricalinstallationandbusbarconnectionareincreasinglyadoptingintegratedbusbarconnectionandinstallationtechnology,whichwillbecomethemainstreamstructureoftheprotectiveenclosure.
Thedevelopmenttrendoflow-voltagesurgeprotectors(SPD)
Withthedevelopmentofelectronictechnology,lightningprotectiontechnologyandlightningprotectionproductsarereceivingmoreandmoreattentionfromvariouscountries.Launchedacompleteseriesofproducts.Inadditiontogradedproducts,inordertofacilitatetheuseofsupport,alotofSPDswithacombinedstructureofⅠ+Ⅱhavebeenintroduced,whichcanbedirectlyusedfortheprotectionofLPZ0toLPZ2,simplifyinginstallationandwiring,andreducingcosts.
Developmentdirection
Marketpattern
Domesticcompaniespushthethirdgenerationofproducts
Butforeigncountrieshavelaunchedthefourthgenerationofproductsp>
China'slow-voltageelectricalindustryhasdevelopedfromsimpleassembly,imitatingmanufacturingtoself-developeddesign,andnowithasgrowntonearly1,000series,withabout1,500manufacturingcompanies,andanannualoutputvalueofabout20billionyuan.
Itisexpectedthatin2010,thefirst-generationproductswillbeeliminated,thesecond-generationproductswillbereducedtolow-endproducts,andthethird-generationproductswillgraduallybecomemid-rangeproducts.
Whileweareacceleratingthedevelopmentofthird-generationproductsandlaunchingthemonthemarket,anumberofwell-knownforeignlow-voltageelectricalappliancemanufacturershavelaunchedanewgenerationofproductsfromthelate1990stotheearly21stcentury.ThereareSchneider’sMTseries,Siemens’3WLseries,ABB’sEseries,GE’sM-PACTseries,Kama’sMagnumseries,etc.;moldedcasecircuitbreakersincludeSchneider’sNSseries,Siemens’3VLseries,andABB’sTmaxseries,GE'sRecordplusseries,Moeller'sNZMseries,Kama'sGseries,Mitsubishi'sWSseries,etc.Inadditiontohighperformance,electronic,intelligent,modular,modular,andminiaturizedfeatures,thenewgenerationofproductsalsoaddsfeaturessuchascommunication,highreliability,goodmaintenanceperformance,andcompliancewithenvironmentalprotectionrequirements.Inparticular,thenewgenerationofproductscanbeconnectedwiththefieldbussystemtorealizesystemnetworking,whichmakesaqualitativeleapinthefunctionoflow-voltageelectricalproducts.
Newtechnicalfeatures
Highperformance,highreliability,intelligence,modularityandgreenenvironmentalprotection
Highperformance.Theratedshort-circuitbreakingcapacityandtheratedshort-timewithstandcurrentarefurtherimproved,andIcu=Icsisrealized.Forexample,Schneider’sMTseriesproductshaveoperatingshort-circuitbreakingandultimateshort-circuitbreakingcapacityupto150kA.
Highreliability.Inadditiontorequiringhigherperformanceindicators,theproductcanbeusedwithoutderating,andcanbeusedforalongtimeatfullcapacitywithoutoverheating,therebyachievingsafeoperation.
Intelligent.Withtheadventofapplication-specificintegratedcircuitsandhigh-performancemicroprocessors,circuitbreakershaverealizedtheintelligenceofthetripunit,whichgreatlystrengthenstheprotectionfunctionofthecircuitbreaker,whichcanrealizelongoverloaddelay,shortcircuitshortdelay,shortcircuittransient,Grounding,undervoltageprotectionandotherfunctionscanalsodisplaysystemoperatingparameterssuchasvoltage,current,frequency,activepower,reactivepower,andpowerfactoronthecircuitbreaker,andcanavoidmalfunctionsundertheinfluenceofhigherharmonics.
Fieldbustechnology.Thenewgenerationoflow-voltageelectricalproductscanbecommunicatedandnetworked,andcanbeconnectedwithavarietyofopenfieldbusestocarryouttwo-waycommunicationtorealizethefunctionsofremotecontrol,remotesignaling,remotemeasurement,andremoteadjustmentofelectricalproducts.Theapplicationoffieldbustechnologycannotonlymonitorthequalityofpowerdistributionandreducelosses.Moreover,thefieldbustechnologycanrealizeregionalinterlockingofmultiplecircuitbreakersinthesameregionalpowergrid,realizetheautomationofpowerdistributionprotection,andfurtherimprovethereliabilityofthepowerdistributionsystem.ThebusesusedinthefieldofindustrialfieldbusesincludeProfibus,Modbus,DeviceNet,etc.,amongwhichModbusandProfibushaveagreaterimpact.
Modularizationandcombination.Combiningmoduleswithdifferentfunctionsintomodularproductsaccordingtodifferentneedsisthedevelopmentdirectionofanewgenerationofproducts.Forexample,theTmaxserieslaunchedbyABB,thermalmagnetic,electronic,andelectronicallycommunicabletripunitscanallbeinterchanged.Allaccessoriesadoptmodularstructureandcanbeinstalledwithoutopeningthecover.
Usegreenmaterials.Theselectionofproductmaterials,manufacturingprocessanduseprocessdonotpollutetheenvironmentandcomplywithEUenvironmentalprotectiondirectives.
Manufacturingtechnology
Aimstoimprovethelevelofavarietyofprofessionalprocesses
Themanufacturingoflow-voltageelectricalproductsinvolvesavarietyofprofessionalprocesses,suchascoldstamping,plasticmolding,coilsWinding,contactwelding,moldprocessing,SMTpatchtechnology,etc.,sotheimprovementoflow-voltageelectricalproductmanufacturingtechnologyisinseparablefromtheimprovementoftheseprofessionalcraftsmanship.
High-speed,automation,andspecializationofpartsprocessing
Stampingpartsaccountforalargeproportionoflow-voltageelectricalparts,about70%,sostampingpartsareprocessedatlowpressureOccupiesanimportantpositionintheproductionofelectricalappliances.Toimprovetheproductionefficiencyandqualityofstampingparts,itisimperativetoadopthigh-speedautomaticpunchingmachinesandmulti-stationprogressivepunchingdies.
Plasticpartsareimportantpartsoflow-voltageelectricalappliances.Theyadoptfullyautomaticorsemi-automaticthermoplasticorthermosettinginjectionmoldingmachines,andadoptacentralizedfeedingmethod.
Automaticweldingmachineryiswidelyused,andtheweldingcurrent,pressure,andpulseperiodareadjustable,keepingthetemperaturecontrollable,andensuringtheweldingstrength.
Automaticassembly
Automaticassemblytechnologyisusedforkeycomponentswithlargeproductionbatchesandstricttechnicalrequirements,suchasthermomagneticreleasesandcontrolelectricironcores.
On-lineinspection
OnlineinspectionequipmentintheproductionprocessisthemaingapbetweenChina'slow-voltageelectricalThedirectionoffuturetechnologydevelopment.
Wiringprinciple
Openwirewiring
Whenwiringmanually(non-model,moldwiring),itshouldbestraight,neat,andclosetothelayingsurface.Thewiringisreasonableandthecontactsmustnotbelooseforeasymaintenanceandotherrequirements.
1.Thewiringchannelsshouldbeasfewaspossible.Thesinkingwiresinthesamechannelshouldbeconcentratedaccordingtothemainandcontrolcircuitclassifications,single-layerparalleldenselyarrangedorbundled,andshouldbeclosetothelayingsurface.
2.Thelengthofthewireshouldbeasshortaspossible,anditcanbecrossedhorizontally,suchastheconnectionbetweentwoelementcoilsandthemaincontactoftheconnection.Itisnotnecessaryifthereisacertainmargin.Closetothelayingsurface.
3.Thewiresofthesameplaneshouldbeconsistentinheightorinthesamedirection,andcannotbecrossed*.Whenitmustbehandedover,itcanbecrossedhorizontally,butthewiringmustbereasonable.
4.Thewiringshouldbehorizontalandvertical,andthetransformationdirectionshouldbevertical90°.
5.Iftheupperandlowercontactsarenotunderthesameverticalline,theyshouldnotbeconnectedbydiagonallines.
6.Whenthewireisconnectedtotheterminalorthewirepost,theinsulationlayer,theloopandtheexposedcoppershouldnotbegreaterthan1mm.Andkeepthedistancebetweenthewiresofthesamecomponentanddifferentcontactsofthesamecircuitconsistent.
7.Thereshouldbenomorethantwoconnectingwiresonanelectricalcomponentterminal.Generally,onlyoneconnectingwireoneachterminalboardisallowedtobeconnected.
8.Whenwiring,itisstrictlyforbiddentodamagethecoreandwireinsulation.
9.Whenthecross-sectionalareaofthewireisdifferent,thelargercross-sectionalareaisplacedonthelowerlayer,andthesmallercross-sectionalareaisplacedontheupperlayer.
10.Whenmultiplewiresarewired(maincircuit)Thewholeshouldbeonthesamehorizontalplaneor
thesameverticalplane.11.Ifthecircuitissimple,nocodingsleeveisneeded.
Colorsigns
1.Theprotectiveconductor(PE)mustuseyellowandgreentwo-colorwires:
2.Theneutralline(N)andthemiddleline(M)Mustbelightblue:
3.TheACorDCpowercircuitshouldbeblack:
4.TheACcontrolcircuitshouldbered:
5.TheDCcontrolcircuitusesblue:
6.Thewireusedasthecontrolcircuitinterlock,ifitisconnectedtotheexternalcontrolcircuit,andwhenthepowerswitch:disconnectedandstilllive,itshouldbeorangeoryellow:
7.Thecircuitconnectedtotheprotectiveconductoriswhite:
Selectionprinciple
Themainlow-voltageelectricalcomponentsusedintheelectricdriveandtransmissionsystem,Accordingtoincompletestatistics,Chinaproducesmorethan120series,nearly600varieties,andtensofthousandsofspecifications.Theseswitchingapplianceshavedifferentusesanddifferentconditionsofuse,sotherearedifferentmethodsofselection,butthegeneralrequirementsshouldfollowthefollowingtwobasicprinciples:
SafetyPrinciples
UseSafetyandreliabilityarethebasicrequirementsforanyswitchingequipment,andensuringthereliableoperationofcircuitsandelectricalequipmentisanimportantguaranteefornormalproductionandlife.
Economicprinciples
Economicconsiderationscanbedividedintotheeconomicvalueoftheswitchgearitselfandthevaluegeneratedbytheuseoftheswitchgear.Theformerrequiresthattheselectionbereasonableandapplicable;thelatterconsidersthatitmustbereliableinoperation,soasnottocauseeconomiclossessuchasshutdownordamagetoequipmentduetofailures,andendangeringpersonalsafety.
Precautions
Theclassificationanduseenvironmentofthecontrolledobject(suchasmotorsorotherelectricalequipment);confirmtherelevanttechnicaldata,suchastheratedvoltage,ratedpower,andstartofthecontrolledobjectCurrentmultiples,loadproperties,operatingfrequency,workingsystem,etc.;understandthenormalworkingconditionsofelectricalappliances,suchasambientairhumidity,relativehumidity,altitude,allowableinstallationazimuthandresistancetoshockandvibration,harmfulgases,conductivedust,rainandsnowTheability;understandthemaintechnicalperformance(ortechnicalconditions)ofelectricalappliances,suchasuse,classification,ratedvoltage,ratedcontrolpower,makingcapacity,breakingcapacity,allowableoperatingfrequency,workingsystemandservicelife,etc.
Faultrepair
Variouselectricalcomponentswillbedamagedafterlong-termuseorimproperuse.Atthistime,theymustberepairedintime.Therearemanyelectricalappliancesusedinelectricalcircuits,withvaryingdegreesofcomplexityandsimplicity.Here,wefirstanalyzethecommonfaultsandrepairmethodsofvariouscomponentssharedbyelectricalappliances,andthenanalyzethecommonfaultsandrepairmethodsofsomecommonelectricalappliances.
1;Commonfaultsandrepairsofelectricalparts
1.1Faultsandrepairsofcontacts
⑴Thecontactsareoverheated.Whenthecontactisturnedon,itwillgenerateheatwhencurrentpassesthroughit,andthecontactwillnotoverheatundernormalcircumstances.Whenthecontactresistanceofthemovingandstaticcontactsistoolargeorthepassingcurrentistoolarge,itwillcausethecontactstooverheat.Whenthetemperatureofthecontactsexceedstheallowablevalue,thecharacteristicsofthecontactswilldeteriorate,andevenweldingwilloccur.Thespecificreasonsfortheoverheatingofthecontactsareanalyzedasfollows:①Thecurrentpassingthroughthemovingandstaticcontactsistoolarge.Thecontactsofanyelectricalappliancemustoperateunderitsratedcurrentvalue,otherwisethecontactswilloverheat.Therearefourpossiblereasonsfortheexcessivecontactcurrent:thesystemvoltageistoohighortoolow;theelectricalequipmentisoverloaded;theelectricalcontactcapacityisnotproperlyselectedandthefaultoperationisfourpossible.②Thecontactresistancebetweenthemovingandstaticcontactsbecomeslarger.Thecontactresistanceisrelatedtothedegreeofheatingofthecontact.Thereasonsforitsincreaseareasfollows:First,thecontactpressurespringlosesitselasticityandthepressureisinsufficientorthecontactwearsthin.Thespringorcontactshouldbereplacedaccordingtothesituation;Poorcontactonthecontactsurface.Forexample,duringoperation,dustandoilstainscoverthesurfaceofthecontact,whichincreasesthecontactresistance;anotherexample,whenthecontactisclosedandbroken,thesurfaceofthecontactwillbesingedandburnedduetothearc,resultinginincompleteunevennessandareductioninthecontactarea.,Resultinginpoorcontact.Therefore,attentionshouldbepaidtothemaintenanceofthecontactsinoperation.
Thesurfaceoxidelayerandburnsofcoppercontactscanbecorrectedwithscrapersorfinefiles;forlargeandmediumcurrentcontactsurfaces,smoothnessisnotrequired,butsmoothnessisimportant;forsmallcapacitycontacts,surfacequalityisrequiredGood;thesilverandsilver-basedcontactsonlyneedtobecleanedwithcottonsoakedingasolineorcarbontetrachloride,andtheoxidelayerdoesnotaffectthecontactperformance.Whenrepairingthecontacts,themaintenancepersonnelmustremembernottoscrapethepinstoomuch,soasnottoaffecttheservicelife.Atthesametime,donotuseemeryclothorgrindingwheelsforgrinding,soastoavoidthequartzsandparticlesembeddedinthecontactsurface,whichwillaffectthecontactperformance.
Thetestofthecontactpressurecanbedeterminedempiricallywithapaperstrip.Clampapaperstripslightlywiderthanthecontact(thickness0.01mm)betweenthemovingandstaticcontacts,andkeeptheswitchintheclosedposition,thenusethehandtopullthepaperstrip.Generally,small-capacityelectricalappliancesusealittleforce.Itcanbepulledout;forlarger-capacityelectricalappliances,thepaperstripmaytearafterbeingpulledout.Theabovephenomenonindicatesthatthecontactpressureisappropriate.Ifthepaperstripiseasilypulledout,itmeansthatthepressureisnotenough;ifthepaperstripispulledoff,itmeansthatthecontactpressureistoohigh.
Adjustingthecontactpressurecanbesolvedbyadjustingthecontactspring.Ifthecontactspringisdamaged,youcanreplaceitwithanewspringormakeityourselfaccordingtotheoriginalsize.Contactpressurespringsareusuallymadeofcarbonsteelspringwire.Newlywoundspringsshouldbetemperedat250oC~300oC,andtheholdingtimeisabout20~40min.Thelargerthediameterofthewire,thelongertherequiredtime..Galvanizedspringsshouldbedeoxidizedandkeptatatemperatureofabout200oCfor2hourstoremovebrittleness.
⑵Thecontactiswornout.Therearetwotypesofcontactwear:oneiselectricalwear,whichiscausedbythevaporizationofthecontactmetalduetothehightemperatureoftheelectricsparkorarcbetweenthecontacts;theotherismechanicalwear,whichiscausedbytheimpactofthecontactwhenthecontactisclosed.Causessuchassurfaceslidingfriction.
Duringuse,thecontactwillbecomethinnerandthinnerduetowear.Whenthereisabout1/2oftheoriginalthickness,youshouldreplacethenewcontact;ifthecontactwearstoofast,youshouldcheckExplainthereasonandeliminatethefault.
⑶Contactwelding.Thephenomenoninwhichthesurfacesofthemovingandstaticcontactsaremeltedandweldedtogetherbutcannotbebrokeniscalledtheweldingofthecontacts.Whenthecontactisclosed,duetoimpactandvibration,ashortcurrentisgeneratedinthesmallgapbetweenthemovingandstaticcontacts,andthearctemperatureisashighas3000oCto6000oC;thesurfaceofthecontactcanbeburnedormelted,causingthemovingandstaticcontactsSoldertogether.Thecommonreasonsforcontactweldingareimproperselection,whichmakesthecontactcapacitytoosmallandtheloadcurrentistoolarge;theoperatingfrequencyistoohigh;theinitialpressureofthecontactspringisreducedwhenthecontactspringisdamaged.Afterthecontactsarewelded,onlynewcontactscanbereplaced.Ifweldingoccursduetoinsufficientcontactcapacity,electricalapplianceswithlargercapacityshouldbeused.
1_2Failureandmaintenanceoftheelectromagneticsystem
⑴Theironcoreisnoisy.Aslight"buzzing"soundoccurswhentheelectromagneticsystemisworking,whichisnormal;ifthesoundistooloudorabnormal,itcanbejudgedthattheelectromagneticmechanismismalfunctioning.①Thecontactsurfaceofthearmatureandtheironcoreisnotingoodcontactorthearmatureisskewed.Theironcoreandthearmaturewilldeformandwearafterrepeatedmagneticcollisions,ortheaccumulationofdust,oil,rust,etc.onthecontactsurfacewillcausevibrationandnoiseduetopoorcontactbetweeneachother.Thevibrationoftheironcorewillcausethecoiltooverheatandburnthecoilinseverecases.FortheE-shapedironcore,thereisanairgapof0.1-0.2mmbetweentheironcorecolumnandthearmature.Itwillalsoincreasethecorenoise.Ifthereisgreasestainontheendfaceoftheironcore,itshouldbefoldedandcleaned;iftheendfaceisdeformedorworn,itcanbespreadontheflatplatewithfineemeryclothtorepairtheendface.②Theshort-circuitringisdamaged.Afterthecorehasbeencollidedmanytimes,theshort-circuitringinstalledinthecoregroovemaybreakorfalloff.Theshort-circuitringfractureoftenoccursinthecornersandnotchesoutsidethegroove.Whenrepairing,thefracturecanbeweldedfirmly,andthetwoendscanbefixedwithepoxyresin;ifweldingisnotpossible,theshort-circuitringorironcorecanbereplaced.Presstheshort-circuitringintothegroove.③Mechanicalreasons.Ifthecontactpressureistoolargeorthemovementofthemovablepartisblocked,sothattheironcorecannotbesuckedincompletely,strongvibrationandnoisewillbegenerated.
⑵Thefailureandmaintenanceofthecoil.①Malfunctionofthecoil.Whenthevoltageacrossthecoilisconstant,thegreateritsimpedance,thesmallerthecurrentpassingthroughit.Whenthearmatureisintheseparatedposition,thecoilimpedanceisthesmallestandthecurrentpassingthroughisthelargest;duringthecorepull-inprocess,thegapbetweenthearmatureandthecoregraduallydecreases,andtheimpedanceofthecoilgraduallyincreases.Whenthearmatureiscompletelypulledin,thecoilcurrentisthesmallest,Ifthearmatureandtheironcorearenotcompletelyattractedforwhateverreason,thecoilcurrentwillincrease,thecoilwilloverheat,orevenbeburned.Ifthecoilinsulationisdamagedormechanicallydamagedtoformashortcircuitbetweenturns,orashortcircuittotheground,alargeshort-circuitcurrentwillbegeneratedinthecoilpart,whichwillincreasethetemperaturesharplyuntiltheentirecoilisburned.Inaddition,ifthecoilpowersupplyvoltageistoolowortheoperatingfrequencyistoohigh,itwillcausethecoiltooverheatandburn.②Repairofthecoil.Ifthecoilisburnt,itshouldbere-wound.Ifthenumberofshort-circuitturnsisnotmany,theshort-circuitisneartheendofthecoil,andtheotherpartsarestillintact,youcanremovethedamagedturns,andtherestcancontinuetobeused.Atthistime,theworkoftheelectricalappliances
Theperformanceimpactwillnotbegreat.
3Faultsandmaintenanceofarcextinguishingsystem0Faultsofarcextinguishingsystem
referstoarcextinguishingcoverdamage,moisture,carbonization,shortcircuitbetweenturnsofthemagneticblowingcoil,arcangleandgridPiecesfalloffandsoon.Thesefaultscancausethearcnottobeextinguished
orthearcextinguishingtimeisprolonged.Ifthearcextinguishinghoodgetsdamp,itcanbeusedafterdrying;itcanbeusedtoscrapeoffthefoulingduringcarbonization;whenthemagneticblowingcoilisshort-circuited,asinglewordcanbeused
toopentheshort-circuitwithascrewdriver;whenthearcanglefallsoff,itshouldbereinstalled;Whenthegridsheetfallsoffandburns,itcanbemadewithironsheetaccordingtotheoriginalsize.
2Commonelectricalfaultsandrepairs
2.1;Contactorfaultsandrepairs
RemovethefaultanalysisandfaultanalysisofthecontactandelectromagneticsystemthathavebeenintroducedaboveOutofmaintenance.Othercommonfaultsaredescribedbelow.
⑴Thecontactisbroken.Duetothepoorcontactofacertainphaseorthelooseconnectionscrews,themotorwillrunwithoutphaseduetophasefailure.Atthistime,themotorcanalsorotate,butthespeedislowanditmakesastrong"humming"sound.Ifyoufindthissituation,youmuststopformaintenanceimmediately.
⑵Contactwelding.Excessiveoperatingfrequencyofthecontactor,overloadoperation,short-circuitontheloadside,conductiveparticlesonthecontactsurface,ortoosmallcontactspringpressurewillcausecontactwelding.Ifthisfaultoccurs,evenifthestopbuttonispressed,themotorwillnotstop,andthepreviousswitchshouldbedisconnectedimmediately
andthenoverhaul.
⑶Shortcircuitbetweenphases.Duetothefailureofthecontactor'sforwardandreverseinterlocking,orthetwocontactorsareputintooperationatthesametimeduetomisoperation,causingashortcircuitbetweenphases;orbecausethecontactormovestoofastandtheconversiontimeisshort,anarcshortcircuitoccursduringtheconversionprocess.Forsuchfailures,contactorsandbuttoncompoundinterlockscanbeusedinthecontrolcircuittocontroltheelectricmotor;themachine'sforwardandreverserotation.
2.2Faultsandmaintenanceofthermalrelays
Thefaultsofthermalrelaysgenerallyincludethermalelementburnout,malfunctionandnon-operation.
⑴Thethermalelementisblownout.Whentheoperatingfrequencyofthethermalrelayistoohigh,ashortcircuitoccursontheloadsideorthecurrentistoolarge,causingthethermalelementtoburnout.Ifyouwanttoeliminatethisfault,youshouldfirstcutoffthepowersupply,checkthecircuittoeliminatetheshort-circuitfault,thenre-selectasuitablethermalrelay,andre-adjustthesetting.
⑵Thethermalrelaymalfunctions.Thereasonforthiskindoffailureis:thesettingvalueistoosmall,sothatitwilloperatewithoutoverload;themotorstartingtimeistoolong,sothatthethermalrelaymaytripduringthestartingprocess;theoperatingfrequencyistoohigh,sothatthethermalrelayisoftenimpactedbythestartingcurrent;Strongimpactandvibrationintheplaceofusewillcausethethermalrelaytoloosenandtrip;inaddition,iftheconnectingwireistoothin,itwillcausethethermalrelaytomalfunction.Inviewoftheabove-mentionedfailurephenomenon,thethermalrelaysuitablefortheabove-mentionedworkingcharacteristicsshouldbereplaced,andthesettingvalueshouldbeadjustedreasonablyorthesuitableconnectingwireshouldbereplaced.
⑶Thethermalrelaydoesnotoperate.Becausethethermalelementburnsorfallsoff,thecurrentsettingvalueistoolarge,sothatthelong-termoverloadstilldoesnotoperate;theguideplatetrips;theconnectionlineistoothick,etc.,sothatthethermalrelaydoesnotoperate,soitdoesnotprotectthemotor.Accordingtotheabovereasons,targetedrepairscanbemade.Inaddition,afterthethermalrelayistripped,itcannotberesetmanually.After2minutes,thecontactshouldberesetafterthebimetalhascooleddown.
2.3Faultmaintenanceofthetimerelay
Theairbagoftheair-typetimerelayisdamagedorisnottightlysealedandleaks,sothatthedelayactiontimeisshortened,andthereisnodelay;theairchamberExtremelycleanisrequired.Ifdustenterstheairwayduringdisassemblyandassembly,theairwaywillbeblocked,andthedelaytimeofthetimerelaywillbecomeverylong.Inviewoftheabovesituation,theairchambercanbedisassembled,andtherubberfilmcanbereplacedorthedustcanberemovedtosolvetheproblem.Air-typetimerelaysareaffectedbyenvironmentaltemperaturechangesandlong-termstoragewillcausedelaytimechanges,whichcanbeadjustedappropriatelyforspecificconditions.
2.4Failureandmaintenanceofthespeedrelay
Afterthespeedrelayfails,itgenerallyshowsthatwhenthemotorstops,itcannotbebrakedtostop.Ifthisfaultisnotduetopoorcontact,itmaybecausedbyimproperadjustmentoftheadjustingscreworthefractureofthebakelitependulumrod.Justdisassemblethebackcoverofthespeedrelayformaintenance.
Instructions
Low-voltageelectricalapplianceschoosedifferenttypesofcircuitbreakerswithshort-circuitbreakingcapacitytomeettheneedsofdifferentlineexpectedshort-circuitcurrents(whenIisinthesamesituation).Theprincipleis:theshort-circuitbreakingcapacityofthecircuitbreaker≥theexpectedshort-circuitcurrentoftheline.
1.Differenttypesofcircuitbreakersshouldbeusedforlow-voltageelectricalapplianceswithdifferentloads.
Etc.)Threecategories.Correspondingtothis,therearepowerdistributionprotectiontype,motorprotectiontypeandhouseholdandsimilarhouseholdprotectiontypecircuitbreakers.Theprotectionpropertiesandprotectioncharacteristicsofthesethreetypesofcircuitbreakersaredifferent.Forthedistributiontypecircuitbreaker,itisdividedintotypeAandtypeB:typeAisnon-selectivetype,andtypeBisselectivetype.Theso-calledselectivetypemeansthatthecircuitbreakerhasthethree-stageprotectioncharacteristicsofoverloadlongdelay,shortcircuitshortdelayandshortcircuitinstantaneous.MostoftheDW15series,DW17(ME)series,AHseriesandDW40andDW45seriesintheuniversal(alsoknownasframetype)circuitbreakersaretypeB,whileDZ5,DZ15,DZ20,TO,TG,CM1,TM30andSomespecificationsofHSM1seriesanduniversalDW15andDW17onlyhavetwo-stageprotectionwithlongtimedelayforoverloadandinstantaneousshortcircuit.Theyarenon-selectivetypeAcircuitbreakers.Selectiveprotection.
2.WhenpointFisshort-circuited,onlytheQF2circuitbreakerclosetopointFwilloperate,andtheupperQF1circuitbreakerwillnotoperate.Thisisselectiveprotection(becauseQF1doesnotoperate,itwillnothappenThefailedQF3andQF4brancheskeeppowersupply).IfQF2andQF1arebothTypeAcircuitbreakers,ashortcircuitoccursatpointF,andwhentheshortcircuitcurrentreachesacertainvalue,QF1andQF2actatthesametime,andthecircuitoftheQF1circuitbreakeranditsbranchesareallpoweredoff,whichisnotselectiveprotection..ThereasonfortheselectiveprotectionisthatQF1isatypeBcircuitbreaker,whichhasshort-circuitshort-delayperformance.WhenpointFisshort-circuited,theshort-circuitcurrentflowsthroughtheQF2branchandalsothroughtheQF1circuit,andtheinstantaneousactionofQF2tripsTheactionofthedevice(usuallyitsfullbreakingtimeisnotmorethan0.02s),duetotheshortdelayofQF1,QF1willnotoperatewithin0.02s(itsshortdelayis≥0.1sor0.2,0.3,0.4s).WhentheQF2actioncutsoffthefaultyline,theentiresystemreturnstonormal.
3.Itcanbeseenthatifyouwanttomeettherequirementsofselectiveprotection,theupper-levelcircuitbreakershouldchooseatypeBcircuitbreakerwiththree-stageprotection.Forthemotorprotectioncircuitbreakerthatdirectlyprotectsthemotor,thelow-voltageelectricalapplianceonlyneedstohavethetwo-stageprotectionperformanceofoverloadlongdelayandshortcircuitinstantaneous.),DZ5,DZ15,TO,TG,GM1,TM30,HSM1andDW15series,inadditiontothepowerdistributionprotectionperformance,their630Aandbelowspecificationshavethefunctionofprotectingthemotor.
Userneeds
Analysisofuserneeds1.Basiccharacteristicsofuserneeds.⑴Thequantityislargeandwide.Itcanbesaidthatallsectorsofthenationaleconomycannotdowithoutlow-voltageelectricalappliances,andpeople’sdailylifecannotdowithoutlow-voltageelectricalappliances.⑵Variousvarietiesandspecifications(voltage,current,protection,numberofpoles),andcomplexenvironmentalconditions(altitude,temperature,humidity,pollution,etc.).⑶Userspaymoreandmoreattentiontothequalityoflow-voltageelectricalappliances(appearance,reliability,life,volume,etc.).Productswithlowqualityandprice,andproductsthatareenergy-savinganddonotpollutetheenvironmentarepopular.
2.Demandstructure.Thestructureofthedemandforlow-voltageelectricalproductsinvariousindustriesisdifferent,butgenerallytherearethefollowingrules:
First,theratiooftheconsumptionofframetypecircuitbreakerstomoldedcasecircuitbreakersisabout1:9.
Secondly,theconsumptionofproductswithhighcurrentlevelsissmall(forexample,theconsumptionofcircuitbreakersabove1600Aisless,andtheconsumptionofproductsabove3000Aisless),whiletheconsumptionofproductsof100Aandbelowisverylarge,andthesmallplasticcaseMorecircuitbreakersareused.
Thirdly,low-voltageelectricalproductssuchasstarters,fuses,contactors,thermalrelays,signallights,etc.,usedtoprotectmotorsareusedinverylargequantities.
Fourth,theautomaticcontrolindustryandtheelectricdriveindustryhavealargeamountofcontactors,fuses,limitswitches,travelswitches,buttons,andsignallights.
Fifth,therearealargenumberofvacuumcircuitbreakersusedinminingandcoalchemicalindustries.
Industrydevelopment
Basicintroduction
Low-voltageelectricalAcomponentordevicethatrealizestheswitching,control,protection,detection,transformationandadjustmentofcircuitsornon-electricobjects.Accordingtotheworkingvoltageofthecontrolappliances,withAC1200VandDC1500Vastheboundary,theycanbedividedintotwocategories:high-voltagecontrolappliancesandlow-voltagecontrolappliances.Ingeneral,low-voltageelectricalappliancescanbedividedintotwocategories:powerdistributionappliancesandcontrolappliances,whicharethebasiccomponentsofcompletesetsofelectricalequipment.Inindustry,agriculture,transportation,nationaldefense,andpeople'selectricitysectors,mostofthemuselow-voltagepowersupply,sothequalityofelectricalcomponentswilldirectlyaffectthereliabilityofthelow-voltagepowersupplysystem.
Thedevelopmentoflow-voltageelectricalappliancesdependsonthedevelopmentofthenationaleconomyandtheneedsofthedevelopmentofmodernindustrialautomation,aswellastheresearchandapplicationofnewtechnologies,newprocesses,andnewmaterials.Itismovingtowardshighperformance,highreliability,andsmallsize.Developmentinthedirectionofmodularization,digitalmodeling,modularization,combinationandgeneralizationofpartsandcomponents.
EnterpriseIndustryDevelopment
China'slow-voltageelectricalapplianceindustryhasgrownfromsimpleassembly,imitatingmanufacturingtoself-developeddesign,andhasnowgrowntonearly1,000series,about1,500manufacturers,andanannualoutputvalueofabout200Billionyuan.However,domesticlow-voltageelectricalappliancemanufacturersaresmallinscaleandexcessiveinnumber.Morethan90%ofthemareintherepeatedproductionofmediumandlow-gradeproducts.Thethreegenerationsofproductscoexist.Accordingtotheoutputvalue,themarketshareofthefirstgenerationproductis15%,thesecondgenerationproductmarketshareis45%,andthethirdgenerationproductmarketshareis40%.Accordingtothenationalpolicytrend,thestructureoflow-voltageelectricalproductsneedsfurtheradjustmentinthefuture.Productswithoutdatedtechnology,largevolume,highenergyconsumptionandenvironmentalpollutionwillbeeliminated.
The"threepillars"situationofChina'sstate-owned,private,andforeign-fundedenterprisesinthelow-voltageelectricalapplianceindustryhasbeengoingonformanyyears.ABB,Siemens,SchneiderElectricandotherinternationalelectricalcompanieshaveallenteredtheChinesemarket,andwhileoccupyingthehigh-endproductmarket,theyareactivelyexpandingintothedomesticmediumandlow-endmarkets.Withtheglobalizationofthemarket,themutualpenetrationofforeign-fundedenterprisesanddomesticenterprisesisanotherinevitabletrendinthedevelopmentofthelow-voltageelectricalapplianceindustry.Thiskindofpenetrationincludesthepenetrationofhigh-endproductsofdomesticenterprisesintoforeignmarkets;theproductsofforeign-fundedenterpriseswillpenetrateintothedomesticmediumandlow-endmarkets.However,asfarasthedomesticmarketisconcerned,foreign-fundedenterpriseshavestrongR&D,design,andmanagementcapabilities,whiledomesticenterprises,especiallyprivateenterprises,althoughtheyhaveflexiblebusinessideasandstrongsaleschannels,havemixedgoodandbadintermsofenterprisescaleandproductquality,andtheirdesignandR&DcapabilitiesStillneedstobestrengthened.Thestateandlocalgovernmentsshouldactivelyencourageenterprisesandindustrialclusterstoextendtheindustrialvaluechain,supportlow-voltageelectricalappliancesenterprisestodevelopinthedirectionof"specialization,refinement,andspeciality",andformanumberofindustrialchainswiththeirowncharacteristicsandkeypoints,soastopromoteindustrialupgrading.
Prospectforecast
Thedomesticwireandcableandlow-voltageelectricalappliancesarenowofficiallyincludedinthecompulsorycertificationsystem.mycountry'scompulsorycertificationproductscurrentlyhave22categoriesand157categories.Compulsoryproductsinvolvemanycategories,includingwiresandcables,low-voltageelectricalappliances,motorvehicles,etc.;theyinvolvemanyindustries,includingelectronicappliances,chemicaltechnology,agriculturalmachinery,andfiresafetyEtc.;involvingawiderangeofknowledge,includingelectricalappliances,machinery,wirelesstechnology,medicalcare,etc.
Inaddition,wires,cablesandlow-voltageelectricalapplianceswilldeveloptogetherunderthepromotionofnationalpoliciesandmarketenvironmentinthefuture.First,withthecontinuousandrapidgrowthofChina’seconomy,hugemarketspacehasbeenprovidedforcableproducts.ThestrongtemptationoftheChinesemarkethasmadetheworldfocusontheChinesemarket.Injustafewdecadesofreformandopeningup,ThehugeproductioncapacityformedbyChina'swireandcablemanufacturingindustryhasmadetheworldlookatitwithadmiration.WiththecontinuousexpansionofChina'spowerindustry,datacommunicationsindustry,urbanrailtransitindustry,automobileindustry,shipbuildingandotherindustries,thedemandforwiresandcableswillalsogrowrapidly,andthewireandcableindustrystillhashugedevelopmentpotentialinthefuture;second,AgainstthebackdropofthegranddevelopmentgoalssetforthintheTwelfthFive-YearPlanandthecontinuedmacroeconomicgrowth,fixedassetinvestment,industrialproductionandoverallconsumption,especiallytherapidgrowthofurbanpopulation,willinevitablydrivethegrowthofpowergenerationandelectricityconsumption.Therefore,thefuturemarketdevelopmentspaceforlow-voltageelectricalapplianceswillcontinuetoexpand.2011-2020willbethemainperiodforChina’ssmartgridconstruction.Thetotalinvestmentinsmartgridsisexpectedtobecloseto4trillionyuan.Smartgridshaveenteredanimportantstageofcomprehensiveconstruction.Theintelligentconstructionofthepowergridwillbefullydeveloped,andthesmartgridandsmartcompletesetsofequipment,smartpowerdistributionandcontrolsystemswillusherinagoldendevelopmentperiod.Atthesametime,itwillacceleratetheupgradingofChina'slow-voltageelectricalproductsandthere-segmentationofthelow-voltageelectricalmarket.ThispairManufacturingcompanieswiththird-generationimprovementsandfourth-generationlow-voltageelectricalR&Dcapabilitiesareboundtobea"goodnews."
Prospectanalysis
Afteryearsofdevelopment,China’slow-voltageelectricalArelativelycompletesystemisformed.Nearly1,000seriesoflow-voltageelectricalproductscanbeproduced,withanoutputvalueofabout30billionyuan.Duetothelargenumberofenterprises,especiallytheriseofalargenumberofprivateenterprisesinWenzhou,anabsolutebuyer'smarkethasbeenformed,resultinginaseriousovercapacityof50%Ormore.
China'slow-voltageelectricalappliancemanufacturingcompaniesaremainlyconcentratedinBeijing,Tianjin,Liaoning,Shanghai,Jiangsu,Zhejiang,andGuangdong.Thedistributionofcompaniesisgenerallyreasonable.CompaniesexistintermsofeconomicscaleSeveralproblems:
(1)Theenterpriseorganizationissmallandscattered,lackingcompetitivestrengthandadvantages.Atpresent,thereareonlyafewlow-voltageelectricalappliancecompaniesinChinawhohaveenteredthecountry'slarge-scaleenterprises,andsmallandmedium-sizedenterprisesaccountformorethan90%(Thosewithannualsalesrevenueandtotalassetsof500millionyuanandabovearelarge-scaleenterprises;thosewith50millionyuanandabovearemedium-sizedenterprises,andtherestaresmallenterprises);
(2)TheregionalstructureisconvergentandcannotReflectingcomparativeadvantagesandcollaborativebenefits.Inthe20yearssincethe1980s,thenumberoflow-voltageelectricalappliancesfactorieshasincreasedfrommorethan600tomorethan1,000.Duetoblindprojectsandpaving,thephenomenonofregionalindustryconvergenceisserious,economicbenefitsarelow,andeconomicbenefitsarelow.Levelrepeatedconstruction,resultinginproductbacklogs,wasteofenergyandmaterials,andloweconomicbenefits;
(3)Thetechnicalstructureisunreasonable,andtheleveloftechnologyandequipmentinmajorindustriesislow.Accordingtostatistics,thecompany’smaintechnologyAmongtheequipment,only1/3haveadvancedtechnicalandeconomicperformanceratios.Onlyabout18%oftheleadingproductsofkeyenterpriseshavereachedtheinternationaltechnologicallevelinthe1990s.
In2011,China’selectricpowerinfrastructurewillcontinuetoberelativelylarge.Thescaleofinvestmentisabout90millionkilowattsofnewinstalledcapacityinnationalinfrastructureconstruction,andthecountry’sinstalledcapacityexceeded1.04billionkilowattsattheendoftheyear.Theproductionofsomanypowergenerationequipmentwillinevitablyrequirecorrespondinglow-voltageelectricalcomponents.Inaddition,anewroundofruralpowergridsTherenovationandupgradingprojectandthenewmeasuresof300billionyuaninvestmentinthetransformationofruralpowergridsinthenextthreeyearsareagreatopportunityforthefutureexpansionofthelow-voltageelectricalindustry.Thekeyisstilltoseewhetherthecompanycancatertotheurgentlyneededproductsinthemarketintermsofindependentinnovationproducts,aswellasproductqualitystabilityandoperationalreliability.Fromthesurveyofmajorenterprisesintheindustry,thesalesoutputvaluesituationinthesecondhalfoftheyearisoptimistic.Itisestimatedthattheoverallsalesoflow-voltageelectricalappliancesin2011willcontinuetogrowcomparedwith2010,about45billionyuan.Corporateprofitswillalsogrowsteadilyandmoderately.
In2011,thesmartgridwillenterthefullimplementationstage,withatotalinvestmentscaleofnearly4trillionyuan.AllthesehaveonceagaindemonstratedthedeterminationandwilloftheChinesegovernmenttorationallyuseresources,vigorouslypromoteenergyconservationandemissionreduction,andactivelydevelopalow-carboneconomy.Atthesametime,thepowergridconstructioninvestmentwillalsoenteraperiodofrapidgrowth,andthelong-termdevelopmentpotentialoftheprimaryequipmentsub-industryandthesecondaryequipmentsub-industryishuge.Therefore,industryenterprisesmustfirmlygraspthedevelopmentopportunitiesofsmartgrids,andwiththedevelopmentofsmartgrids,enterprisesmustclearlyrealizethatthedevelopmentoflow-voltageelectricalappliancesinthefuturemustfirstbeconsideredfromtheperspectiveofsystemdevelopment.Andwemustworkhardoneverythingfromthesystemtoallpowerdistribution,protection,andcontrolcomponents,fromstrongtoweakcurrentsolutions.
Inthefuture,thedevelopmentoflow-voltageelectricalproductswillshowthefollowingdevelopmenttrends:
Intelligentlow-voltageelectricalproducts.Inmodernpowerstationsandindustrialandminingenterprises,electroniccomputermonitoringsystemshavebeenwidelyadopted,andhigh-performanceandintelligentrequirementsareputforwardforthelow-voltagecircuitbreakersthatarematchedwiththem,andproductsarerequiredtohaveprotection,monitoring,testing,self-diagnosis,display,etc.Function.
Productsareelectronic.Inmodernenterprises,theuseofPCcontrolsystemstoreplacesystemscomposedofelectricalandmechanicalcomponentshasbecomethemainstreamofmechanicalelectricalcontrolsystems.Thesystemrequireselectricalproductswithhighreliabilityandhighanti-interference,andalsorequiresthecontactstobeabletoreliablyconnecttolowvoltageandweakcurrent,andthearcwhenthecontactsaredisconnectedcannotinterferewiththenormaloperationoftheelectroniccircuit.
Productcombinationandmodularization.Combiningmoduleswithdifferentfunctionsintomodularcombinedelectricalappliancesaccordingtodifferentneedsisthedevelopmentdirectionoftoday'slow-voltageelectricalappliancesindustry.Addingauxiliarycontactcomponents,delaycomponents,self-lockingcomponents,interfacecomponents,mechanicalinterlockingcomponentsandsurgevoltagecomponentstothebodyofthecontactorcanadapttotherequirementsofdifferentoccasions,therebyexpandingthescopeofproductapplicationandsimplifyingtheproductionprocess,Itisconvenientforuserstoinstall,useandmaintain.Atthesametime,itwillfurtherimproveproductreliabilityandproductquality.
Installationanduseprinciples
1.Low-voltageelectricalappliancesshouldbeinstalledvertically.Especiallyforoil-immerseddecompressionstarters.Inordertopreventtheinsulatingoilfromoverflowing,thefueltankshouldnotbetiltedmorethan5.Boltsshouldbeusedtofixthesupportinsteadofwelding:theinstallationpositionshouldbeeasytooperate,andacertaindistancebetweenthehandleandthesurroundingbuildingsshouldbemaintained.Noteasytobebroken.
2.Low-voltageelectricalappliancesshouldbeinstalledinaplacewithoutseverevibrationandhaveanappropriateheightfromtheground.Powercordssuchasknifeswitchesandloadswitchesmustbeconnectedtothefixedcontacts.Itisstrictlyforbiddentoconnectthepowercordtotheknifeswitch.
3.Themetalshellormetalbracketoflow-voltageelectricalappliancesmustbegrounded(orconnectedtozero).Theexposedpartoftheelectricalapplianceshouldbeprotectedwithaprotectivecover.Theopeningpositionofthedouble-throwknifeswitchshouldhaveadevicetopreventself-closing.
4.Inworkshopswithflammable,explosivegasordust,electricalappliancesshouldbesealedandinstalledoutdoors,withrain-proofmeasures,explosion-proofelectricalappliancesmustbeusedinplaceswithexplosionhazards.
5.Whenusing,keeptheelectricalcontactsurfaceclean,smooth,andingoodcontact.Thecontactshouldhavesufficientpressure,theactionofeachphasecontactshouldbeconsistent,andthearcextinguishingdeviceshouldbekeptintact.
6.Theprotectiveoillayeroneachcontactsurfaceshouldberemovedbeforeuse,anditshouldbeoperatedseveraltimesbeforeputtingitintooperationtochecktheaction.Thestaticcontactofthelow-voltageelectricalapplianceshouldbeconnectedtothepowersupply,andthemovingcontactshouldbeconnectedtotheload.
7.Thesingle-poleswitchmustbeconnectedtothephaseline.Low-voltageelectricalappliancesinstalledontheground.Itsbottomshouldbe100mmhigherthantheground.Onthepanelwherelow-voltageelectricalappliancesareinstalled,indicatethenameoftheinstallationequipmentandthecircuitnumberorroadtype.