GB14711-2006電機安全要求英文版)GB14711-2006電機安全要求英文版)GB14711-2006電機安全要求英文版)ICS29.160.01K20NationalStandardofthePeople’sRepublicofChina GB14711—2006 SubstituteforGB14711—1993SafetyRequirementsofSmallandMediumSizeRotatingElectricalMachinesIssuedonAugust25,2006 EffectivefromMarch1,2007IssuedbyGeneralAdministrationofQualitySupervision,InspectionandQuarantineoftheP。R.ChinaStandardizationAdministrationofthePeople'sRepublicofChinaContentsForeword …………………。。III1Scope……………………。 12Normativesourcesofstandards…………………………。 13Technicaltermsandexplanations……………………….。 24Generalrequirements……………………. 25Structure…………………。 26Symbols………………….。 67Tests……………………… 78Lowvoltage（ratedvoltage≤1,000V)ACmotor(includinguniversalmotor）…………129Highvoltage(ratedvoltage〉1,000V)ACmotor……………………….1310DCmotor………………1311Portableandauxiliarygenerator……………………….1412Variable—frequency&adjustable-speedmotor………………………。.16ForewordAllthetechnicalcontentofthestandardiscompulsory。ThestandardisconsistentwiththesafetyrequirementsinGB755-2000RotatingMachineRatingandPerformance.ThestandardisasubstituteforGB14711-1993GeneralSafetyRequirementsofSmallandMediumRotatingElectricalMachines，withthepresenttitleSafetyRequirementsofSmallandMediumSizeRotatingElectricalMachines。ThestandarddiffersfromGB14711—1993mainlyinthefollowingrespects：1。 Standardwasrearranged；2. Thesafetyrequirementsofportable，auxiliary,andvariable-frequency&adjustable-speedmotorswereincluded；3。 Tablesrelatedwereplacedatthebackofthisbook，foreasyreference.ThestandardisproposedbyChinaElectricalEquipmentIndustryAssociation。ThepreparationandmanagementofstandardisunderthesupervisionoftheChinaRotatingElectricalMachineStandardization＆TechnologyCommittee（SAC/TC26）。ShanghaiElectricalEquipmentResearchInstitutewasresponsibleforthedraftingofthestandard.Otherorganizationsthatparticipatedinthedraftinginclude:BeijingB。J.ElectricMotorCo。,Ltd。,ChongqingSailimengElectricMotorCo。,Ltd.,ShandongQiluElectricMotorManufacturingCo。，Ltd.，LanzhouElectricMotorCo.,Ltd.,ShanghaiUnitedElectricMotor（Group）Corporation,ZhejiangJinlongElectricMotorCo.，Ltd.,ShandongHualiElectricMotorCo.，Ltd.,JiangsuQingjiangElectricMotorCo.，Ltd.，KunmingElectricalEngineeringCo.，Ltd.，andShanxiElectricMotorManufacturingCo。，Ltd。MajordraftersincludeNiLixin，ChenWeihua，JinWeiwei，LiBaojin,LiXiuying,ZhangShengde，LiuJinyan,CaiJiagang,ZhouQi，TianZhigang,GaoWen'an，CuiHuajian，YeJinwu,FengJinquan,ZhouGuobao，ZhangBinandYueWeiping。ThestandardshallreplaceGB14711—1993fromtheeffectivedate.GB14711—1993isthefirstedition.Thisstandardisthefirstamendment.SafetyRequirementsofSmallandMediumSizeRotatingElectricalMachines1ScopeThestandardspecifiesthesafetyrequirementsofsmall/mediumgeneral-purposerotatingelectricalmachines（electricmotorandgenerator,hereinafterreferredtoas“motor")。Thisstandardisnotapplicabletoastronauticmotors,tractionmotors,explosion—proofmotors，hoistandmetallurgicalmotors,shieldmotors.TestsofsmallpowermotorsproducedaccordingtoGB/T5171canalsorefertoGB12350.Incaseothertypesofmotorsinvolvespecialrequirementsthatarenotcoveredinthisstandard,newstandardshouldbedeveloped.NormativesourcesofstandardsThetermsandconditionsquotedfromthefollowingdocumentsbecamethetermsandconditionsofthisstandard.Wheredocumentsaredated，theirattachedmodificationlist（exclusiveofcorrections)ortherevisededitionisnotapplicabletothisstandard.Nevertheless，theconcernedpartiesareencouragedtoconsiderthelatesteditionsofthosedocumentswhenreachingagreementbasedonthisstandard.Wheredocumentsareundated,theirlatestversionsareapplicabletothisstandard。GB755-2000RotatingelectricalmachinesRatingandperformance(idtIEC60034-1：1996)GB/T825—1988Eyescrew（NEQISO3266:1984）GB1971RotatingelectricalmachinesCableterminalsymbolandsenseofrotation(GB1971-2006，60034-8:2002,IDT)GB/T2423.4—1993ElectricalandelectronicproductsenvironmentaltestsproceduresTestsDb:temperature＆humiditytestingmethods（eqvIEC60068-2—30:1980）GB/T4207-2003CTIandPTItestingmethodsforsolidinsulationmaterialunderhumidconditions(IEC60112：1979,IDT)GB4706.1—1998HouseandsimilarpurposeappliancessafetyPartone:generalrequirements(eqvIEC60335-1:1991）GB/T4942。1—2001Rotatingelectricalmachinehousingprotectiongrading（IPcode)（idtIEC60034-5:1991)GB/T5169.11—1997ElectricalandelectronicproductsfirehazardtestsTestingmethodsGlowwiretestandguidelinesforthefinishedproducts(idtIEC60695-2—1/1:1994)GB/T5169.12-1999ElectricalandelectronicproductsfirehazardtestsTestingmethodsGlowwireflammabilitytestformaterials（idtIEC60695—2-1/2:1994)GB/T5465.2-1996Electricalequipmentdiagramsandsymbols(idtIEC60417:1994）GB/T11020-1989Flammabilitytestingmethodsforsolidinsulationmaterialexposedtoignitionsource（eqvIEC60707:1981)GB/T13002Built-inthermalprotectorofrotatingelectricalmachinesRotatingelectricalmachinesprotectionrules(GB/T13002—1991,eqvIEC34—11—1:1978)GB/T16422。2—1999TestingmethodsofexposuretolaboratorylightsourcesforplasticsParttwo：xenon-arclamp（idtISO4892—2：1994）GB/T17948。1-2000RotatingelectricalmachinesinsulationperformanceappraisalRandomwindingstestproceduresThermalappraisalandgrading(idtIEC60034-18-21：1992）GB/T18380。1-2001BurningtestforcablesexposedtoflamesPart1:verticalburningtestofsingleinsulatedwireorcable（idtIEC60332-1:1993)GB/T18380。2-2001BurningtestforcablesexposedtoflamesPart2：verticalburningtestofsingleinsulatedthincopper-corewireorcable（idtIEC60332—2:1989）GB/T18380。3-2001BurningtestforcablesexposedtoflamesPart3：burningtestofbunchedwiresorcables(idtIEC60332-3：1992)JB/T7589—1994High—voltageelectricalmachinesinsulationthermalstabilityappraisalmethods（eqvIEC60034-18—31:1992）

JB/T8158—1999Startingperformanceofsingle—speed，three-phase，squirrel—cageinductionmotors（voltage≤690V）(eqvIEC60034-12：1995) JB/T10098-2000Impulse-voltageenduranceofACmotorstatorcoils（idtIEC60034-15:1995） IEC60034—18—22：2000Rotatingelectricalmachineinsulationfunctionappraisal—Formedwindingtestprocedures—Insulationcompositionssubstitutionandchangegrading IEC60034-18-31:1992Rotatingelectricalmachineinsulationfunctionappraisal—Formedwindingtestprocedures—Insulation’sthermalpropertyappraisalandgradingformotors≤50MVAand15kV IEC60034-18-32：1995Rotatingelectricalmachineinsulationfunctionappraisal-Formedwindingtestprocedures-Insulation’selectricpropertyappraisalandgradingformotors≤50MVAand15kVTechnicaltermsandexplanationsThefollowingtermsandexplanationsareapplicabletothisstandard. Clearance Clearanceistheshortestdistancebetweentwoconductivepartsmeasuredthroughair.CreepagedistanceCreepageistheshortestpathbetweentwoconductivepartsmeasuredalongthesurfaceoftheinsulation.Note：theseambetweentwoinsulatingpartsistakenasapartofthesurface。LeadLeadisawirethatconnectsbetweenwindingcoilsandwiringterminals,orbetweenwindingcoils,orbetweenwindingcoilsandotherconductorsinsidethemotor。Leadscanbedirectedintoajunctionboxoutsidethemotor.SupplycordItistheflexiblecordthatgoesfrominsidethemotortotheoutsideforthepurposeofpowersupply。GeneralrequirementsThemotorscoveredinthisstandardshouldconformtotherequirementsofGB755-2000.Thecapacitorintegratedwiththemotorisregardedaspartofthemotor。Whetheratroomtemperatures,orthermalstate，orhumidconditions，motorsshouldhaveadequateinsulationresistance.Insulationresistanceismeasuredandtestedaccordingtotherequirementsof7。4.Innormaloperation，motorsshouldnothaveelectricalormechanicalfaultsthatwouldaffectsafety；ordamagedinsulation;orlooseconnections;oragedflexiblecomponentsandoutercoverparts.StructureGeneralprinciplesTheelectricalcomponentsofmotorarespeciallyapprovedmodelsandspecifications.Theyshouldbetestedalongwiththemotor。Allrotatingpartsshouldoperatesafely(includingatover-speed）。Componentsthatarenotconnectedtorotatingpartsandwouldnotaffectelectricalormechanicalsafetymaybetakenasaseparatepartofthemotor，andcanbesuppliedseparately.Withtheexceptionofwaterproofmotors（e.g。motorsforunderwateruse)andthosefreeofwateraccumulationinside,allmotorsshouldhaveappropriatedewateringmeasurestopreventaccumulatedwaterinside,whichwouldreducetheclearanceandcreepagedistancebetweenwindings/nakedchargedpartsandground.Theairventsonthemotorcanalsoperformdewateringfunctions。Whenarrangingwater—dischargeholes，theirdiametersshouldbenosmallerthan3mmandconformtotherequirementsof7。6.Ifmotorisanintegralpartofotherequipment,thefunctionsofmotorbedplateandoutercover(inclusiveofjunctionbox)canbeperformedbytheequipment.

Astonaturalair—coolingmotor,ifbuilt-inoverheatprotectorisrequired,itshouldconformtoGB/T13002.Withtheexceptionofopen-typemotors，itmustbeensuredthatcontactwiththepanelorcoveringofnakedchargedparts（AC〉30V,DC〉50V）isavoided。Thepanelorcoveringmayonlybeopenedwithtoolorkeys。OutercoverThematerialsofanycomponentontheoutercovershouldbeabletoendurehightemperaturesandmechanicalstressthatmayoccurduringnormalworkingconditions，andshouldnotincurfireorelectricshockduetobending，creep,ordeformation。OutercoverprotectiongradingshouldconformtoGB/T4942.1—2001。Non-metallicstructuresInsulationstructuresforsupportingandfixingcurrent-carryingcomponentsshouldhavegoodresistancetoinflammation,heat，electrictracking,moisture，andadequatedielectricstrengthandmechanicalstrength。Non—metallicoutercover,windshield，andjunctionboxshouldbeabletoendurehumidity,grease,inflammation,andtemperaturevariation。Theyshouldbeabletowithstandtheimpacttestasin7。8.3，theageingtestasin7。11,theheatdeformationtestasin7。12，andtheburningtestasin7.13.Thepatchboardandnon-metallicjunctionboxshouldbeabletoendurethetemperaturesnolowerthanthatspecifiedinTable1。Junctionbox(formotors≤750V）andwiringdevicesJunctionboxcanbeanindependentcomponentfixedontheexteriorofmotor,orserve,partiallyorwholly,asapartonthemotorhousing。Junctionboxshouldhaveappropriatevolumeinordertocontainwiringdevices，meetingtheclearanceandcreepagedistancerequirementsof5。8,andbeabletowithstandtheimpulsevoltagetestasin7。5.2.Ifmadefrommetal，thejunctionboxshouldhavethethicknessasspecifiedinTable2,andconformtothetestrequirementsof7.8.4.Non—metallicjunctionboxshouldconformto5.3。2。Thefixingbetweenjunctionboxandmotorhousingshouldbeseparatefromthefixingbetweenjunctionboxanditscover。TheprotectiongradeofjunctionboxonsmallmotorshouldbenolessthanIP44.Ifwireconduitisused,itshouldbe:NosmallerthanthesizesspecifiedinTable3,inconsistencewiththeratedcurrentmarkedonthemotor；Placedinaflat，largeenougharea,tomeettherequirementsofbushingandlocknut,unlesstheopeningonthejunctionboxissuitableforwiretopassthroughandbushingneednotbeusedtoprotectwireinsulation.Conduitbushingandequivalenttappedhole5。5。1 StraightpipeorTaperpipethreadsealcanbeusedforthetappedholeofconduit,withthescrewinglengthnosmallerthan3.5pitches。Thenumberofinlettapped—holeshouldbespecifiedinproductstandarddescription.Theinletholesshouldbeequippedwithinsulationconduitandbesealedwithrubberorsimilarmaterialatthefactory.5。5.2 Conduitbushingforaseparately-castjunctionboxandtappedholeforfixingrigidmetalconduitshouldhaveenoughmechanicalstrengthandbetestedasper7。8。5。SupplycordIfthemotorisequippedwithsupplycord，orforthepurposeofeasyconnectiontootherequipment,flexiblecablesthatextendoutsidethebedplate（housing)aresuppliedalongwithnecessaryplugs，thecordandplugsshouldconformtoproductstandardorrelevantstandardoftheequipment.Unlessgroundingisnotrequired，thereshouldbeoneearthleadamongthecords。Theearthlead（includingtheterminal)shouldbearadifferentcolororsymbolforeasydistinction。Thesupplycordshouldhavearatedvoltagenosmallerthanthemotor’smaximumworkingvoltage。Itscurrent—carryingcapacityshouldatleastbeequaltoloadcurrentmultipliedbyusagecoefficientorfullloadratedcurrentmultipliedby125％,whicheveristhegreater.Theinsulationofcordshouldbeabletowithstandthepower-frequencyvoltagetestrelatedtothiscircuit。Unlesstherearemeasurestoeliminatethepossibletensileforceorthesupplycordisnotexposed,insulationlayerandclampsshouldbeavailablewherethecordextendsout,inordertopreventexternalforcepassingontothewiresinsideandavoidtwistingordisplacementofcords.Unlessthereareotherprotectivemeasures，itmustbeensuredthatcordsdonotwithdrawintothemotor。Clamps:cordclampsshouldbemadeofinsulatingmaterial.Ifmetalispresent,thereshouldbeinsulatinglining.

Cordclampsshouldbeexaminedforreliabilityandbeabletowithstandthetensionandtorsiontestsasin7。9。Cordshouldnotbeforcedthroughtheinletopeningsoastodamagetheinsulation.Theloosecables/cordsinthejunctionboxthataretobeconnectedonsiteshouldbenoshorterthan150mminfreelength。LeadwireLeadwiretypesandsizesLeadwireshouldhaveappropriatecurrent—carryingcapacityandlength。Leadwiresoncoilsorofsimilarpurposeshouldconformtothefollowingrequirements：Theleadwireforconnectingtopowersupplyshouldbenosmallerthan0。75mm2incross—sectionalarea;Theleadwiresinsidethemotor,suchasthosewhichconnecttointernalcomponentsorpowersupplycordsorpatchboard，canbesmallerthan0。75mm2butshouldbenosmallerthan0。30mm2.LeadwireinsulationAsforwindingsleadorbrushholderlead，whichissoftandcannotbepositionedtoensureproperclearance，insulatedconductorshouldbeusedorthermal—andmoisture—resistantmaterialshouldbeusedtowrapupcontinuouslybetweentwosupportpoints.Thematerialcanbeinsulatingpad,insulatinghoseorotherappropriatemeans。Themodelsandspecificationsofleadshouldfittheworkingvoltageofmotor。Ifinstantaneoushightensionmayoccuronanycomponentduringnormaloperation,theleadshouldhavegoodinsulatingcapabilitytowardsthehightension.Leadshouldconformtorelevantstandard，withthermalwithstandinggradenolessthantheinsulationgradeofthemotor。LeadprotectionInternallead(wire)shouldbeproperlyfixedwithwindings.Twoormoreleads（wires）ofthesamealignmentshouldbeboundtogether。Itshouldnotbeplacedonthepointedorsharpedgeofpartsandstayawayfrommovableparts.Theconnectionsofinternalleads(wire)shouldbeinsulatedwithbushingsandtapesandproperlyfixed，topreventaccidentduetoloosebushingorlooseweld.Theconnectionsshouldbeabletowithstandthedielectrictestasspecifiedin7。5.Lead（wire）andwireterminalshouldbejoinedwithcoldweld.Propermeasuresshouldbeavailabletoensurewireterminalsstayintheiroriginalpositionwhenconnectorbolts/nutscomeloose。Openconnectorandlockwashershouldnotbetheonlymeans。Whenstranded—lead(wire）isconnectedtoterminal,itshouldstayincertainposition，toavoidgroundingorshortcircuit。Wheninternallead(wire）goesthroughmotorbedplate，insulatorsorothermeansshouldbeusedtoensureinsulationatthebores.Insulatorsshouldbesmooth，withoutburrsorsharpedge.Leadthatpassesthroughtheexternalcoolingchamberofhermeticmotorshouldbeprotectedwithmetalliccableconduitorsimilarpipes.Clearanceandcreepagedistanceoflowvoltagemotors(forrequirementsonhighvoltagemotors,seeChapter9ofthisstandard）TheclearanceandcreepagedistanceasdescribedbelowshouldbenosmallerthanthatspecifiedinTable4。Otherwise,theyshouldconformto5。8。2~5。8.5。Alongtheinsulationmaterialsurfaceandthroughtheair；Betweennakedchargedpartsofdifferentvoltagesorbetweendifferentpolarity;Betweennakedchargedparts(includingelectromagneticwire）andpartsthataregrounded（ormaybegrounded）.Withtheexceptionoflowvoltagemotors，clearanceandcreepagedistanceshouldconformtorelevantarticlesinthisstandard。Asfarasthestationaryparts(e。g.brushholder)ofbrushedmotorsareconcerned,duetocarbonsootaccumulated(eg。ontheinsulationofthebushholder）betweencommutatorandslipring,theclearanceandcreepagedistanceshouldbegreaterthanthatspecifiedinTable4by50％atleast.Otherwise,appropriatespacers,ringsorsimilardevicesshouldbeprovided.Therequirementof5.8.3onincreasedclearanceandcreepagedistanceisnotapplicabletomotorswithframesizegreaterthanH90.Astotherotorwindingsandcentrifugalswitchesofwound—rotormotors，theclearanceandcreepagedistancemaybesmallerthanthatspecifiedinTable4,butitmustbeensuredthatnobadconsequencewouldoccur.Itmustbeensuredthatwireconnectors,includingpressure-typeconnection(quickconnection），donottwistormove,inordertokeepclearanceandcreepagedistancenosmallerthanthatspecifiedin5。8。1.Unlessclearanceandcreepagedistanceremainunchangedwhenconnectorsdeviateinarangeof30o，ortheconnectorscrewsareinsulated，itisnotnecessarytotakeadditionalmeasurestopreventconnectorturning。

TheclearanceandcreepagedistanceasspecifiedinTable4canbeachievedbyusinginsulatingbarrier，whichshouldbemadefromthefollowingmaterials。Ifnakedlivepartsarewithininsulatingbarrierormaycontactwiththebarrier，heat—/moisture-resistantmaterialshouldbeapplied(e.g.，ceramicbottle,phenolicplastic，polyester，polyestercarbonate，nylon，mica)Whereitshallnotcontactnakedliveparts(exceptelectromagneticwire),appropriatemoisture—resistantfiberandsimilarmoisture-absorbingpartitionmaybeused,withthicknessnosmallerthan0。66mm.Iftheclearanceandcreepagedistanceexceedthatspecifiedbyhalf,insulatingpartitionnothinnerthan0.33mmshouldbeused。Otherinsulatingmaterialsthinnerthan0.33mmPuremicanothinnerthan0.25mmcanalsobeused.,ifprovensuitablefornormaluseintermsofmechanicalandelectricalproperties,canalsobeused。Puremicanothinnerthan0.25mmcanalsobeused.ComponentsComponents,suchascapacitor，switch,currenttransformer，voltagetransformer，shouldbefixedfirmlyandeasytoreplace。Capacitorshouldbeinstalledinsideprotectivecoverandnotcontactmetallicparts。Ifcapacitorcasingismetallic，additionalinsulationshouldbeusedtopartitionitfrommetallicparts.Capacitororitsadditionalcasingshouldbeabletopreventsplashings,sparksandmeltingthatmayoccurwhencapacitorbreaksdown.Steelcoverforcapacitorshouldbenosmallerthan0.5mminthickness。Astooil—filledcapacitor（non-electrolyticcapacitor),apressure-sensitivebreakerisbuiltinside，topreventspillageofinflammablesubstancethroughthedamagedcasing。Thereshouldbeextraaxialspacetoallowthemovementofbreakerterminal.Theextendedspaceshouldbe12。7mmatleast，whichisarequirementinadditiontotheclearancerequirementspecifiedinTable4。ProtectivegroundingdevicesGroundingdevicesthatconformto10.1ofGB755—2000shouldbeavailable，unlessgroundingisnotneededonthesite。Thereshouldbepermanent,reliableelectricalconnectionbetweenmotorbedplateandgroundingdevices.Whenmotormovesontheequipmentbase,groundingconnectionshouldbestillingoodcondition。Ifwireterminalisusedtoconnectgroundwire,theterminalshouldconformtotherelevantrequirementin5.12。Groundwireterminalshouldbelockedsafely,topreventaccidentalturningandreducedclearance/creepagedistance。Itcannotbereleasedwithouttheaidoftools。Groundwireterminalshouldbeusedfornootherpurpose.Thematerialsofgroundingconductor,groundingterminalandjointdeviceshouldbecompatible，withgoodelectric—erosionresistanceandconductibility。Ifferrousmetalisused，theyshouldbeprotectedwithelectroplatingorothermeanstoavoidrusting。Groundingconductorshouldhaveenoughtenacity，andbeabletowithstandthestressfrommotorvibration。Appropriatemeasuresshouldbeavailabletoavoidhazardsduringinstallationandoperation.Itmustbeensuredthatgroundingconnectionsarecoveredwithnon—conductivecoatingssuchaspaint.Connectionshouldbebymeansofcoldweldorothereffectivemethods,insteadofarticulationorsimplysoldering.Thegroundingconductorthatpenetratesrubberbaseshouldbemetallic,insteadofconductiverubber.Groundingterminalscrewsandgroundingconductorshouldhaveadequatecross-sectionalarea.Fortheminimumdiameterofgroundingscrew,seeTable5.ThecrosssectionofgroundingconductorshouldconformtoTable17inGB755—2000.BrushholderandterminalsThereshouldbegoodelectricalcontactbetweenbrushholderwireandterminals.Clearanceandcreepagedistancebetweenmovableparts/non—currentcarryingmetallicpartsandchargedpartsshouldnotbereducedduringuse。Withtheexceptionofelectromagneticwire，nakedchargedpartsshouldbesupportedbyinsulatingmaterialsthatareabletoendureinflammation,heat,moisture,andelectrictracking.

Theterminalwireatthebrushholdershouldhavestopperdevice.WireterminalAstobolt-typeterminalconnectingtopowersupplycable，thescrew(bolt)andnutshouldconformtorelevantstandardandrequirementsin5.12.3～5.12.4.Theterminalofboltconnectorshouldnotbeusedtofixotherparts.Whenconnectingtopowersupplycord,thewireterminalcanbeusedtoclampwiresinsidethemotor，ifsuchactwouldnotcausewirestobecomeloose.Thepermissiblecontinuouscurrentatthewireterminalisinrelationtothestructureofterminal,diameterandmaterialofscrews(orbolts)，whichshouldconformtoTable6(boltconnector），Table7(chipterminal)，andTable8（looselead-outwire）respectively.Wireterminalsshouldbeproperlyfixed。Whenclampsonthesupplycablefastenorrelease,wireterminalsshouldnotturnordisplace,lead—outwireshouldbesubjecttostressandclearance/creepagedistanceshouldbenosmallerthanthelimitsspecifiedinTable4orTable13.WireconnectorshouldbeequippedwithOT—typepressureweldingterminalorarchedwasher，toensurereliableconnectionbetweenwireandterminal.Whenclampingwires,lockingdeviceshouldbeavailable,toensureappropriatecontactbetweenmetalsurfaces,sothatwireswouldnotbedamagedorslip.Terminalofbolt-typepowerconnectionshouldbeequippedwithhardplateconnector,forthepurposeofchangingmotorvoltage,rotationspeedandsenseofrotation.ItshouldbeensuredthattheclearanceinallconnectionsisnosmallerthanthatspecifiedinTable4orTable13.Ifconnectorscrewisinstalledonametalpiece，themetalshouldbenothinnerthan1。3mmandshouldhavemorethantwothreads.Astometalthatisun-stretched，ifitissmallerthan1。3mminthicknessbutnosmallerthanthethreadpitch，thetappedholecanbeextrudedtomakethescrewinglengthnosmallerthantwopitches。Wireterminalsshouldbejoinedproperlytoensuregoodconductivityandenoughcontactpressure，andexpectedcurrent-carryingcapacity.Allcurrent-carryingcomponentsshouldbemadefrommetalswithgoodconductivityandadequatemechanicalstrength。Iffittingsaremadeofferrousmetal,theyshouldbeelectroplatedorprotectedwithothereffectivemeanstoavoidrusting。BearingstructureItmustbeensuredthatlubricantdonotflowdowntheshaftandentermotorwindings，current-carryingcomponentsorotherequipments。CommutatorandcollectorringMotorswithcommutatorandcollectorringsshouldhavesightwindowthatcanbeeasilyremoved。Brushholdercomponentsshouldbesodesignedthatwhentheywearout，thebrush,springandotherpartswouldnotenergizetheunchargedmetalpartsnearbyorcontactchargedparts。InsulationMotorwindingsshouldbeproperlybound,fixedandinsulated。Terminalsofwindings,ifinsulated,shouldnotshownakedcopper。Theinsulationofthemotorshouldhavegoodmoisture-endurance,insulatingcapabilityandmechanicalproperty.Itshouldbeabletowithstandthetestasin7。10。Thecompositionofinsulation，suchaselectromagneticwire,slotinsulation，bindingtape，slotwedge,impregnatingvarnish，supplycable,shouldbewellcompatibleandpasstestandproveappropriate。Insulationappraisaltestshouldconformto7.10。JointsThejointsforelectricalormechanicalconnectioninthemotorshouldbeabletoendurethemechanicalstressthatoccursduringnormaloperation.Screws（bolts)andnutsonthejointsshouldnotmadefromsoftmetals(suchaszinc，aluminumandetc。）ormetalsthatareliabletocreep。Jointscrewsshouldhavecertainlengthstoensurereliableconnection.Ifscrewsserveforthepurposeofbothmechanicalandelectricalconnection,theyshouldbelockedsafelytoavoidaccidentduetoloosening,heatingandincreasedcontactvoltage.Rivetsforelectricalconnection,ifsubjecttotorsionduringnormaluse，shouldbelockedtoavoidturning.Goodlockingdevicesincludespringwasher（orsimilarthings），non—circularshankrivet,andotherappropriatemethods.Jointsshouldbecheckedagainsttheaboverequirementsbyvisualinspection