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隔离变压器原理及应用
PrincipleandapplicationofisolatingtransformerObjective:
Throughthiscourse,thestudentshaveapreliminaryunderstandingoftheprincipleoftheisolationtransformerandtheroleoftheisolationtransformerinthesafetyandelectricityutilization.
Two.Principleofisolatingtransformer
Itis.Thealternatingcurrentweuseisconnectedtotheearth.
Thereisa220Vdifferencebetweentheotherlineandtheearth.Peopleareexposedtoelectricity.Thesecondaryoftheisolationtransformerisnotconnectedtotheearth,andthereisnodifferencebetweenthetwolinesofitandtheearth.Peopledon'ttouchanyline,soit'ssafer.Theisolationtransformersareusedinelectronicdevicessuchaselectronicpipesandhigh-voltageworkingvoltages,suchaselectronictubeamplifies,oscilloscopes,etc.,andcanalsobeusedforthemaintenanceofpowersupply.InordertomaintainthesafetyofcolorTV,theinsulationtransformerof1to1isused.
Theapplicationoftheisolationtransformer
Applytosafety,isolation,lowleakagecurrent,cleanpowersupply,eliminatethethreeharmonicsandsuppresstheinterferenceofthecommonmode.Applicabletothecircuitof50Hzto400Hz,voltage1000V,widelyusedinlighting,machinetoolelectricalequipment,mechanicalelectronicequipment,
medicalequipment,rectifyingdeviceetc
Theisolationtransformerisdividedintotwotypesbyuse;Atypeofsafetypowertransformerthatpreventstheelectricalpowerfrombeingisolatedbyanelectricalaccident.Theothertypeofisolationtransformerisanisolationof
electromagneticinterferencesignals,whicharewidelyusedinelectroniccircuitstosuppressnoiseandelectromagneticinterference.
Four.Generalelectricprotectionmeasures
1.Thesafetyvoltage
Accordingtoohm'slaw,thehigherthevoltage,thegreaterthecurrent.Therefore,canaddinpersoncanbeplusorminusthevoltagelimitwithinacertainrange,madeunderthisvoltagebycurrentshallnotexceedthepermittedrangeofthebody.Thisvoltageiscalledthesafevoltage,alsoknownasthesafeandlowvoltage.Itshouldbenotedthatinnocaseshouldthesafetyvoltagebeunderstoodasadefinitenodangerousvoltage.Hasthesafetyvoltagedevicesbelongto?class.
Safetyvoltagelimit
Thelimitisthemaximumvoltagethatanytwoconductorcanaskwithoutanyrunningcondition.Thelimitingvalueoftheeffectivevalueofthefrequencyvoltageinourcountryis50V,andthelimitofdcvoltageis120V.
Ingeneral,thebodyallowsthecurrenttobeconsideredfree
ofcurrent.Inthecaseofanelectricshockprotectiondevice,thehumanbodyallowsthecurrenttobeconsideredby30mA.Regulationsin
ourcountryisbasedonthelimitsofthepowerfrequencyvoltage50vinthehumanbodytoallowcurrent30maandhumanbodyresistance1700Ωconditionsdetermined.
Standardinourcountryalsorecommended:whenthecontactareaismorethan1cm2,contactformorethan1s,dryenvironmentzhonggongfrequencyvoltageRMSvalueof33v,dcvoltagelimitis70v.Thelimitvalueoftheeffectivevalueofworkingfrequencyvoltageinwetenvironmentis16Vanddcvoltagelimitis35V
Safetyvoltagerating
ThevaluesoftheeffectivevalueoflaborfrequencyinChinaare42V,36V,24V,12Vand6V.Anelectricvehicleusedinanespeciallyhazardousenvironmentshoulduse42Vsafetyvoltage.Thehand-heldlightingandlocallampsusedinthehazardousenvironmentshouldbe36Vor24Vsafetyvoltage.Thehandheldlampsusedinspecialhazardousenvironments,suchasmetalcontainersandespeciallywetareas,shouldbeequippedwith12Vsafetyvoltage.6Vsafetyvoltageshouldbeusedinplacessuchasunderwateroperation.Whentheelectricalequipmentadopts24Vsafetyvoltage,theprotectivemeasureofdirectcontactwithelectricshockmustbetaken.
Thesecurityisolationtransformer
Thesafetybarrierisusuallyusedasasourceofsafetyvoltage.
Thewiringdiagramisshowninfigure3-8.Inadditiontotheisolationtransformer,thegenerator,battery,electronicdevice,
etc.,canbeusedasasafetyvoltagesource.Butregardlessofthe
powersupply,thesafetyvoltagesideshouldbestrengthenedbythehighvoltageside.
Figure3-8safetyisolationtransformerwiringdiagram
Whenusingthesafetyvoltagepowersourceofthesafetyisolationtransformer,thetransformerhasagoodinsulationbetweenoneandtwotimes.Thereisalsoagroundingbarrier.Theinsulationresistanceshallnotbelowerthanthefollowingvalues:
Livepartandshell2mΩinsulationbetweenwork
ThereinforcedinsulationbetweenthelivepartandshellΩ
7m
5mΩbetweeninputcircuitandoutputcircuit2mΩbetweeninputcircuitinputcircuit
2mΩbetweenoutputcircuitandoutputcircuit
?classtransformerchargedpartofthe2mΩwithmetalobjects
?classtransformerbetween5mΩmetalobjectsandshellInsulationshellin2mΩbetweeninternalandexternalmetal
objects
Single-phasetransformersecurityisolationtransformerratedcapacity,shallnotexceed10kva,shallnotexceed16kvathree-phasetransformer,electricbelltransformerratedcapacityshouldnotbemorethan100va,toytransformerratedcapacityshouldnotbemorethan200va.Ratedvoltageofthesecurityisolationtransformer,acvoltageRMSmustnotexceed50v,pulsatingdcvoltagemustnotexceed50v,the
electricbelltransformerdifferenceshouldnotexceed24vand24v,toytransformershallnotbemorethan33vand33vrespectively.
Chargedpartofthesafetyvoltageloopmustmaintainelectricalisolationwithhighvoltagecircuit,andnotwiththeearth,toprotecttheelectriccircuitsoftheconductororotherconnection,butthetransformerbetweentheprimaryandsecondaryisolationlayershouldbeproperlygroundedorzero.Ifthetransformerdoesnothavethestructureofreinforcedinsulation,thesecondarysideshouldbegroundorzerotoreducethedangerofasecondaryshortconnection.Forordinaryinsulatedpowertransformers,nolinelengthshallexceed3mandshallnotbeusedinmetalcontainers.
Thewiringofthesafetyvoltageisbestseparatedfromtheothervoltagelevelwiring.Otherwise,theinsulationlevelshouldbethesameastheinsulationleveloftheotherhighvoltagelevel.
3.Electricalisolation
ElectricalisolationisUSESthevoltageratioof1:1,thatis
asideandsecondarysidevoltageisolationtransformertoachieveequalworkingcircuitandotherelectriccircuitsoftheelectricalisolation.
Applyelectricalisolationtomeetthefollowingsafetyconditions:
1.Theisolationtransformermusthavereinforcedinsulationstructure,itstemperatureisthesameastheinsulationresistanceandsafetyisolationtransformer,thiskindofisolationtransformershouldalsomeetthefollowingrequirements:
Themaximumcapacitysinglephasetransformermustnotexceed25kVA,thethree-phasetransformermustnotexceed40kVA.
nomorethan1000Vshallnotexceed1000V,andthevoltagedropshallnotexceed5~15%oftheratedvoltage.
theisolationtransformerhasaheat-resisting,moisture-proof,water-resistantandanti-vibrationstructure;Nostructuralmaterialsshallbemadeofsuchinflammablematerialsascelluloid.Handle,lever,button,etc.Shouldnotbecharged;Theshellshouldbemechanicallystrongenoughnottobeopened,andshouldpreventaccidentaltouchingofthechargedpart.Thepanelsshouldbefixedatleasttwoways,andatleastoneofthemmustbeimplementedusingatool.
unlessotherwisespecified,theoutputwindingshallnotbeconnectedtotheshell;Theinputwindingshouldnotbeconnectedtotheoutputwinding;Thewindingstructureshould
preventthepossibilityofsuchconnection.
thepowerswitchshouldbefullpoleswitch,andthecontactshouldbegreaterthan3mm.Theoutletshouldbeabletopreventinterpolationofdifferentvoltage.Fixedtransformerinputcircuitshallnotbepluggedin.Theportabletransformercanhavea2-4mpowerline.
whenthedistancebetweentheinputterminalandtheoutputterminalislessthan25mm,itmustbeseparatedbyaninsulatingpartitionthatisconnectedtothetransformer.
?transformershouldbeprotecttheterminal,thepowercordshouldhaveaspecialprotection;TheRclasstransformerhasnoprotectionterminal.
Thesecondsideremainsindependent,whichmeansnottotaketheearth,nottoprotecttheconductor,nottotakeotherelectricalcircuits.Asshowninfigure3,9,ifthegroundingtransformersecondaryside,iswhensomeoneinthesecondarysideofsingle-phaseelectricshocks,currentflowsthroughthehumanbodyandeasilythesecondaryloopedgelocation.Asaresult,theuseofelectricalisolationasasafetymeasure,
Theremustalsobemeasurestopreventthegroundingofthesecondarycircuitandtheothercircuits.Becauseonceagroundfailureoccursonthesecondside,thiswillcompletelyloseitssecurity.Fortheelderofthesecondarycircuitcircuit,theinsulationmonitoringdeviceshouldbeinstalled.
FIG.3-thedangerofasecondarygroundingofthetransformer
3.Thesecondedgelinevoltageistoohighorvicelinepassinglong,willreducethecircuittogroundinsulationlevel,increasetheriskofgroundingfault,andincreasethegroundingfaultcurrent.Therefore,thelengthofthepowervoltageandthesecondarylinemustberestricted.Inaccordancewiththeregulations,thevoltageUisnotequalto500V,thelinelengthLislessthantheproductof200m,thevoltageandthelengthoftheproductULislessthanorequalto100000V?m.
Equipotentialconnections
Thedottedlinesinfigure3-10areisoelectricconnections.Ifthereisnoequipotentialconnectionline,whentheisolationcircuitisclosetothedistancebetweentwodevicesindifferentphaselineofshellfaultoccurs,thetwodevicesshellwithdifferentgroundvoltage.Ifsomeonetouchesbothdevicesatthesametime,thecontactvoltageislinevoltageandtheshockisextremelydangerous.Asaresult,iftheisolationcircuithasanumberofelectricalequipment(orappliances),themetalcaseofeachequipment(orappliance)shouldbeusedforequipotentialbonding.Atthispoint,thesocketshouldbeusedforthespecialsocketthatisconnectedtothepotentialconnection.
Figure3-10electricalisolation,equipotentialconnections
Five.Cleanpowersupply,eliminatethreeharmonicsandsuppressthecommonmodeinterference
Isolationtransformerintheacpowerinputfeatures:vvv1threetimes,ifthepowergridharmonicandseriousinterferencesignal,usingisolationtransformer,harmonicandreducethedisturbancesignalcanberemovedthreetimes.Vvv2andtheisolationtransformercanproducenewneutrallinestoavoidtheimproperoperationoftheequipmentduetothebadlineofthegrid.Vvv3,thewaveformdistortioncausedbynonlinearloads(suchasthreeharmonics)canbeisolatedwithoutpollutingthegrid.
Visolationtransformerfeaturesinacpoweroutput:
Preventthecurrentdistortionofnon-linearloadtoaffectthenormalworkofacpowersupplyandthepollutionofthepowergrid,whichcanbeusedtocleanupthepowergrid.Thedistortionofthenonlinearloadcurrentisnotaffectedbythesamplingoftheinputendoftheisolationtransformer,andthecontrolsignalcanbeobtained.Iftheloadisnotbalanced,itdoesnotaffectthenormaloperationofthestabilizedpowersupply.
Somepeoplewholistentothestereooftenaddalargeamountofinsulationtothepowersource,theSKVAofHP,orthedomesticmanufactureroftheIKVA.Someusea220vcoolingoutletfor110V,others110V110V,anditseffectistoreducethenoiseinthepowersupplytoincreasetheS/Nratio.InChina,especiallyordinary110Vand220V,becauseeveryhouseholdhaselectricapplianceinuse,likemicrowaveoven,electromagnetoven.Onpowerswitch,themotorrunning,etc.,intheformoffrequencydoublingorsurgetothepowersupplyplug,sothepollutionofpowersupplysituationisquiteserious.
Unless
youcaninavarietyofwaysatallcostgeneratingtheirownpower,otherwisewillbetofind
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