隔離變壓器原理及應用

隔離變壓器原理及應用

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