hazards是什么意思ards在线翻译读音例句

SafetyTestingofMedicalElectricalEquipment

1HazardsofMedicalElectricalEquipment

Medicalelectricalequipmentcanpresentarangeofhazardstothe

patient,theuser,chhazardsare

commontomanyoralltypesofmedicalelectricalequipment,whilst

below

arevarioustypesofcommonhazards.

1.1MechanicalHazards

Alltypesofmedicalelectricalequipmentcanpresentmechanical

anrangefrominsecurefittingsofcontrolstoloose

mermaypreventa

pieceoflifesupportingequipmentfrombeingoperatedproperly,

whilstthelattercouldcauseseriousaccidentsintheclinical

environment.

Suchhazardsmayseemtooobvioustowarrantmentioning,butitis

unfortunatelyalltoocommonforsuchmundaneproblemstobe

overlookedwhilemoreexoticproblemsareaddressed.

1.2Riskoffireorexplosion

Allmainspoweredelectricalequipmentcanpresenttheriskoffirein

theeventofcertainfaultsoccurringsuchasinternalorexternalshort

ainenvironmentssuchfiresmaycauseexplosions.

Althoughtheuseofexplosiveanaestheticgasesisnotcommontoday,

itshouldberecognisedthatmanyofthemedicalgasesinuse

vigorouslysupportcombustion.

1.3AbsenceofFunction

Sincemanypiecesofmedicalelectricalequipmentarelifesupporting

ormonitorvitalfunctions,theabsenceoffunctionofsuchapieceof

equipmentwouldnotbemerelyinconvenient,butcouldthreatenlife.

1.4Excessiveorinsufficientoutput

Inordertoperformitsdesiredfunctionequipmentmustdeliverits

hanoutput,forexample,inthecaseof

surgicaldiathermyunits,y,toolow

anoutputwouldresultininadequatetherapy,whichinturnmaydelay

patientrecovery,ghlights

theimportanceofcorrectcalibrationprocedures.

1.5Infection

Medicalequipmentthathasbeeninadequatelydecontaminatedaft我的祖国诗歌朗诵 er

usemaycauseinfectionthroughthetransmissionofmicroorganisms

y,

patients,nursingstaffandservicepersonnelarepotentiallyatrisk

here.

1.6Misuse

Misuseofequipmentisoneofthemostcommoncausesofadverse

susemaybearesultof

inadequateusertrainingorofpooruserinstructions.

1.7Riskofexposuretospuriouselectriccurrents

Allelectricalequipmenthasthepotentialtoexposepeopletotherisk

aseofmedicalelectrical

equipment,theriskispotentiallygreatersincepatientsare

intentionallyconnectedtosuchequipmentandmaynotbenefitfrom

thesamenaturalprotectionfactorsthatapplytopeopleinother

allofthehazardslistedareimportant,the

preventionofmanyofthemrequiremethodspeculiartotheparticular

mple,inordertoavoid

theriskofexcessiveoutputofsurgicaldiathermyunits,knowledgeof

r,

theelectricalhazards楚成王 arecommontoalltypesofmedicalelectrical

equipmentandcanminimisedbytheuseofsafetytestingregimes

thesereasons,itistheelectricalhazardsthatarethemaintopicof

thissession.

2Physiologicaleffectsofelectricity

2.1Electrolysis

Themovementofionsofoppositepolaritiesinoppositedirections

throughamediumiscalledelectrolysisandcanbemadetooccurby

urrentis

passedthroughbodytissuesforaperiodofminutes,ulcerationbegins

cers,whilenotnormallyfatal,canbepainfulandtake

longperiodstoheal.

2.2Burns

Whenanelectriccurrentpassesthroughanysubstancehaving

electricalresistance,untofheatdepends

onthepowerdissipated(I2R).Whetherornottheheatproducesa

burndependsonthecurrentdensity.

Humantissueiscapableofcarryingelectriccurrentquitesuccessfully.

Skinnormallyhasafairlyhighelectricalresistancewhilethemoist

ical

burnsoftenproducetheirmostmarkedeffectsneartotheskin,

althoughitisfairlycommonforinternalelectricalburnstobe

produced,which,ifnotfatal,cancauselonglastingandpainfulinjury.

2.3Musclecramps

Whenanelectricalstimulusisappliedtoamotornerveoramuscle,

themuscledoesexactlywhatitisdesignedtodointhepresenceof

longedinvoluntary

contractionofmuscles(tetanus)causedbyanexternalelectrical

stimulusisresponsibleforthephenomenonwhereapersonwhois

holdinganelectricallyliveobjectcanbeunabletoletgo.

2.4Respiratoryarrest

Themusclesbetweentheribs(intercostalmuscles)needto

repeatedlycontractandrelaxinordertofacilitatebreathing.

Prolongedtetanusofthesemusclescanthereforepreventbreathing.

2.5Cardiacarrest

Theheartisamuscularorgan,whichneedstobeabletocontractand

relaxrepetitivelyinordertoperformitsfunctionasapumpforthe

softheheartmusculaturewillpreventthepumping

process.

2.6Ventricularfibrillation

Theventriclesoftheheartarethechambersresponsibleforpumping

eheartisinventricularfibrillation,the

musculatureoftheventriclesundergoesirregular,uncoordinated

ditionprovesfatalif

notcorrectedinaveryshortspaceoftime.

Ventricularfibrillationcanbetriggeredbyverysmallelectricalstimuli.

Acurrentaslowas70mAflowingfromhandtohandacrossthechest,

or20rthis

reasonthatmostdeathsfromelectricshockareattributabletothe

occurrenceofventricularfibrillation.

2.7Effectoffrequencyonneuro-muscularstimulation

Theamountofcu春光懒困倚微风上一句 rrentrequiredtostimulatemusclesisdependentto

ingtofigure1,itcanbeseenthat

thesmallestcurrentrequiredtopreventthereleaseofanelectrically

10kHzthe

neuro-muscularresponsetocurrentdecreasesalmostexponentially.

trequiredtopreventreleaseofaliveobject.

2.8Naturalprotectionfactors

Manypeoplehavereceivedelectricshocksfrommainspotentialsand

thereasonforthisisthe

existenceofcertainnaturalprotectionfactors.

Ordinarily,apersonsubjecttoanunexpectedelectricalstimulusis

protectedtosomeextentbyautomaticandintentionalreflexactions.

Theautomaticcontractionofmusclesonreceivinganelectrical

stimulusoftenactstodisconnectthepersonfromthesourceofthe

ionalreactionsofthepersonreceivingtheshock

portanttorealisethata

patientintheclinicalenvironmentwhomayhaveelectricalequipment

intentionallyconnectedtothemandmayalsobeanaesthetisedare

relativelyunprotectedbythesemechanisms.

Normally,apersonwhoissubjecttoanelectricshockreceivesthe

shockthroughtheskin,whichhasahighelectricalresistance

comparedtothemoistbodytissuesbelow,andhenceservesto

,a

resistanceoftheskinmayintentionallyhavebeenloweredinorderto

allowgoodconnectionsofmonitoringelectrodestobemadeor,inthe

caseofapatientundergoingsurgery,theremaybenoskinpresentin

thecurrentpath.

Theabsenceofnaturalprotectionfactorsasdescribedabove

highlightstheneedforstringentelectricalsafetyspecificationsfor

medicalelectricalequipmentandforroutinetestandinspection

regimesaimedatverifyingelectricalsafety.

3Leakagecurrents

3.1Causesofleakagecurrents

Ifanyconductorisraisedtoapotentialabovethatofearth,some

trueeven

ofconductorsthatarewellinsulatedfromearth,sincethereisnosuch

untof

currentthatflowsdependson:

tageontheconductor.

acitivereactancebetweentheconductorandearth.

istancebetweentheconductorandearth.

Thecurrentsthatflowfromorbetweenconductorsthatareinsulated

fromearthandfromeachotherarecalledleakagecurrents,andare

r,sincetheamountofcurrentrequiredto

produceadversephysiologicaleffectsisalsosmall,suchcurrents

mustbelimitedbythedesignofequipmenttosafevalues.

Formedicalelectricalequipment,severaldifferentleakagecurrents

aredefinedaccordingtothepathsthatthecurrentstake.

3.2Earthleakagecurrent

Earthleakagecurrentisthecurrentthatnormallyflowsintheearth

cal

electricalequipment,veryoften,themainsisconnectedtoa

theearthleakage

currentfindsitswaytoearthviatheimpedanceoftheinsulation

betweenthetransformerprimaryandtheinter-windingscreen,since

thisisthepointatwhichtheinsulationimpedanceisatitslowest(see

figure2).

eakagecurrentpath.

Undernormalconditions,apersonwhoisincontactwiththeearthed

metalenclosureoftheequipmentandwithanotherearthedobject

wouldsuffernoadverseeffectsevenifafairlylargeearthleakage

becausetheimpedancetoearthfromthe

enclosureismuchlowerthroughtheprotectiveearthconductorthan

r,iftheprotectiveearthconductor

becomesopencircuited,,ifthe

impedancebetweenthetransformerprimaryandtheenclosureisof

thesameorderofmagnitudeastheimpedancebetweenthe

enclosureandearththroughtheperson,thenashockhazardexists.

Itisafundamentalsafetyrequirementthatintheeventofasingle

faultoccurring,suchastheearthbecomingopencircuit,nohazard

earthatinorderforthistobethecaseintheabove

example,theimpedancebetweenthetransformerprimaryandthe

uldbeevidencedwhenthe

equipmentisinthenormalconditionbyalowearthleakagecurrent.

Inotherwords,iftheearthleakagecurrentislowthentheriskof

electricshockintheeventofafaultisreduced.

3.3Enclosureleakagecurrent

Enclosureleakagecurrentisdefinedasthecurrentthatflowsfroman

exposedconductivepartoftheenclosuretoearththrougha

r,ifa

protectiveearthconductorisconnectedtotheenclosure,thereislittle

pointinattemptingtomeasuretheenclosureleakagecurrentfrom

anotherprotectivelyearthedpointontheenclosuresinceany

measuringdeviceusediseffectivelyshortedoutbythelowresistance

y,thereislittlepointinmeasuringthe

enclosureleakagecurrentfromaprotectivelyearthedpointonthe

enclosurewiththeprotectiveearthopencircuit,sincethiswouldgive

thesamereadingasmeasurementofearthleakagecurrentas

sereasons,itisusualwhentestingmedical

electricalequipmenttomeasureenclosureleakagecurrentfrom

pointsontheenclosurethatarenotintendedtobeprotectively

earthed(seefigure3).Onmanypiecesofequipment,nosuchpoints

tisincludedintestregimesto

covertheeventualitywheresuchpointsdoexistandtoensurethatno

hazardousleakagecurrentswillflowfromthem.

ureleakagecurrentpath.

3.4Patientleakagecurrent

Patientleakagecurrentistheleakagecurrentthatflowsthrougha

itherflowfrom

theappliedpartsviathepatienttoearthorfromanexternalsourceof

s

4aand4billustratethetwoscenarios.

tleakagecurrentpathfromequipment.

tleakagecurrentpathtoequipment.

3.5Patientauxiliarycurrent

Thepatientauxiliarycurrentisdefinedasthecurrentthatnormally

flowsbetweenpartsoftheappliedpartthroughthepatient,whichis

notintendedtoproduceaphysiologicaleffect(seefigure5).

tauxiliarycurrentpath.

6ElectricalSafetyTests

6.1Normalconditionandsinglefaultconditions

Abasicprinciplebehindthephilosophyofelectricalsafetyisthatin

theeventofasingleabnormalexternalconditionarisingorofthe

failureofasinglemeansofprotectionagainstahazard,nosafety

nditionsarecalled\"singlefault

conditions\"(SFC\'s)andincludesuchsituationsastheinterruptionof

theprotectiveearthconductororofonesupplyconductor,the

appearanceofanexternalvoltageonanappliedpart,thefailureof

basicinsulationoroftemperaturelimitingdevices.

Whereasinglefaultconditionisnotapplied,theequipmentissaidto

bein\"normalcondition\"(NC).However,itisimportanttounderstand

thatinthiscondition,theperformanceofcertaintestsmay

example,ifearthleakagecurrentismeasuredinnormalcondition,

th月夜古诗原文 eimpedanceofthemeasuringdeviceinserieswiththeprotective

earthconductormeansthatthereisnoeffectivesupplementary

protectionagainstelectricshock.

Manyelectricalsafetytestsarecarriedoutundersinglefault

conditionssincetheserepresenttheworstcaseandwillgivethemost

ythesafetyoftheequipmentundertestmay

nelcarrying

outelectricalsafetytestsshouldbeawarethatthenormalmeansfor

protectionagainstelectricshockarenotnecessarilyoperativeduring

testingandshouldthereforeexercisedueprecautionsfortheirown

safetyandthatofothers.

6.2ProtectiveEarthContinuity

Theresistanceoftheprotectiveearthconductorismeasuredbetween

theearthpinonthemainsplugandaprotectivelyearthedpointon

theequipmentenclosure(seefigure6).Thereadingshouldnot

tisobviouslyonly

applicabletoclassIequipment.

InIEC60601,thetestisconductedusinga50Hzcurrentbetween10A

ghthisisatypetest,

toequipmentcanoccurifhighcurrentsarepassedtopointsthatare

notprotectivelyearthed,forexample,are

shouldbetakenwhenhighcurrenttestersareusedtoensurethatthe

probeisconnectedtoapointthatisintendedtobeprotectively

earthed.

HEI95andDB9801Supplement1recommendthatthetestbecarried

theinstrumentuseddoesnotdosoautomatically,theresistanceof

thetestleadsusedshouldbedeductedfromthereading.

Ifprotectiveearthcontinuityissatisfactorytheninsulationtestscan

beperformed.

ApplicabletoClassI,alltypes

Limit:0.2

DB9801

recommended?:

Yes,at1Aorless.

HEI95recommended?:Yes,at1Aorless.

Notes:

Ensureprobeisonaprotectivelyearthed

point

ementofprotectiveearthcontinuity.

6.3InsulationTests

IEC60601-1,clause17,laysdownspecificationsforelectrical

separationofpartsofmedicalelectricalequipmentcomplianceto

whichisessentiallyverifiedbyinspectionandmeasurementof

rtestsoninsulationaredetailedunderclause

20,\"dielectricstrength\".ThesetestsuseACsourcestotest

equipmentthathasbeenpre-conditionedtospecifi春深似海的意思 edlevelsof

tsdescribedinthestandardaretypetestsandare

notsuitableforuseasroutinetests.

HEI95andDB9801recommendthatforclassIequipmentthe

insulationresistanceismeasuredatthemainsplugbetweenthelive

sHEI

95recommendsusinga500VDCinsulationtester,DB9801

ticethis

lastrequirementcouldprovedifficultanditisacknowledgedina

footnotethata500VDCtestvoltageisunlikelytocauseanyharm.

Thevalueobtainedshouldnormallybeinexcessof50Mbutmaybe

mple,equipmentcontaining

mineralinsulatedheatersmayhaveaninsulationresistanceaslowas

1Mtshouldbeconductedwithallfuses

intactandequipmentswitchedon(seefigure9).

ApplicabletoClassI,alltypes

Limits:Notlessthan50M

DB9801

recommended?:

Yes

HEI95

recommended?:

Yes

Notes:

Equipmentcontainingmineralinsulatedheaters

maygivevaluesdownto1M.Checkequipment

isswitchedon.

ementofinsulationresistanceforclassIequipment

HEI95furtherrecommendsforclassIIequipmentthattheinsulation

resistancebemeasuredbetweenallappliedpartsconnectedtogether

ue

shouldnotnormallybelessthan50M(seefigure10).DB9801

Supplement1doesnotrecommendanyformofinsulationtestbe

appliedtoclassIIequipment.

ApplicabletoClassII,alltypeshavingappliedparts

Limits:notlessthan50M.

DB9801recommended?:No

HEI95recommended?:Yes

Notes:Moveprobetofindworstcase.

ementofinsulationresistanceforclassIIequipment.

Satisfactoryearthcontinuityandinsulationtestresultsindicatethatit

issafetoproceedtoleakagecurrenttests.

6.4Leakagecurrentmeasuringdevice

TheleakagecurrentmeasuringdevicerecommendedbyIEC60601-1

loadstheleakagecurrentsourcewitharesistiveimpedanceofabout

ommended

measuringdevicewaschangedslightlyindetailbetweenthe1979

11

livolt

meterusedshouldbetrueRMSreadingandshouldhavean小学生端午节作文 input

impedancegreaterthan1M.Inpracticethisiseasilyachievable

erinthe

arrangementsshownmeasures1mVforeachAofleakagecurrent.

learrangementsformeasurementofleakagecurrents.

6.5EarthLeakageCurrent

ForclassIequipment,earthleakagecurrentismeasuredasshownin

rentshouldbemeasuredwiththemainspolarity

95andDB9801Supplement1recommend

thattheearthleakagecurrentbemeasuredinnormalcondition(NC)

fetytestersoffertheopportunitytoperformthetest

underasinglefaultconditionsuchasliveorneutralconductoropen

circuit.

ApplicabletoClassIequipment,alltypes

Limits:

0.5mAinNC,1mAinSFCor5mAand10mA

respectivelyforpermanentlyinstalled

equipment.

DB9801

recommended?:

Yes,innormalconditiononly.

HEI95

recommended?:

Yes,innormalconditiononly.

Notes:Measurewithmainsnormalandreversed.

Ensureequipmentisswitchedon.

ementofEarthLeakageCurrent.

6.6Enclosureleakagecurrent

Enclosureleakagecurrentismeasuredbetweenanexposedpartof

theequipmentwhichisnotintendedtobeprotectivelyearthedand

tisapplicabletobothclassI

andclassIIequipmentandshouldbeperformedwithmainspolarity

95recommendsthatthetestbe

performedundertheSFCprotectiveearthopencircuitforclassI

equipmentandundernormalconditionforclassIIequipment.

DB9801Supplement1recommendsthatthetestbecarriedoutunder

safetytestersalsoallowtheSFC\'sofinterruptionofliveorneutral

onclassIequipmentwhicharelikely

nottobeprotectivelyearthedmayincludefrontpanelfascias,handle

assembliesetc.

ApplicabletoClassIandclassIIequipment,alltypes.

Limits:0.1mAinNC,0.5mAinSFC

DB9801

recommended?:

Yes,NConly

HEI95

recommended?:

Yes,classISFCearthopencircuit,classIINC.

Notes:

and

obetofindworstcase.

ementofEnclosureLeakageCurrent.

6.7Patientleakagecurrent

UnderIEC60601-1andHEI95,forclassIandclassIItypeBandBF

equipment,thepatientleakagecurrentismeasuredfromallapplied

partshavingthesamefunctionconnectedtogetherandtrueearth

(figure14).FortypeCFequipmentthecurrentismeasuredfromeach

appliedpartinturnandtheleakagecurrentleakagemustnotbe

exceededatanyoneappliedpart(figure15).

DB9801Supplement1recommendsthatpatientleakagecurrentbe

measuredfromeachappliedpartinturnforalltypesofequipment,

althoughtherecommendedleakagecurrentlimitshavenotbeen

revisedtotakeintoaccountthechangedtestmethodforBandBF

equipment.

Greatcaremustbetakenwhenperformingpatientleakagecurrent

icular,

outputsofdiathermyequipmentandstimulatorscanbefatalandcan

damagetestequipment.

Applicableto

Allclasses,typeB&BFequipmenthaving

appliedparts.

Limits:0.1mAinNC,0.5mAinSFC.

DB9801

recommended?:

No

HEI95

recommended?:

Yes,classISFCearthopencircuit,classII

normalcondition.

Notes:

andreversemains.

ementofPatientLeakageCurrentwithappliedpartsconnected

together.

Applicableto

ClassIandclassII,typeCF(B&BFforDB9801

only)equipmenthavingappliedparts.

Limits:0.01mAinNC,0.05mAinSFC.

DB9801

recommended?:

Yes,alltypes,normalconditiononly.

HEI95

recommended?:

Yes,typeCFonly,classISFCearthopencircuit,

classIInormalcondition.

Notes:

and

areperelectrode.

ementofpatientleakagecurrentforeachappliedpartinturn

6.8Patientauxiliarycurrent

Patientauxiliarycurrentasdefinedinsection3.5ismeasured

betweenanysinglepatientconnectionandallotherpatient

tusualto

testallpossiblecombinationssincetogetherwithallpossiblesingle

faultconditionsthiswouldgiveanexceedinglylargeamountofdataof

questionablevalue.

Applicableto

Allclassesandtypesofequipmenthaving

appliedparts.

Limits:

TypeB&BF-0.1mAinNC,0.5mAinSFC.

TypeCF-0.01mAinNC,0.05mAinSFC.

DB9801

recommended?:

No.

HEI95

recommended?:

No.

Notes:

and

reversemains.

ementofpatientauxiliarycurrent.

6.9Mainsonappliedparts

Byapplyingmainsvoltagetotheappliedparts,theleakagecurrent

thatwouldflowfromanexternalsourceintothepatientcircuitscan

suringarrangementisillustratedinfigure18.

Althoughthesafetytesternormallyplacesacurrentlimitingresistor

inserieswiththemeasuringdevicefortheperformanceofthistest,a

ore,greatcareshouldbetakenifthe

testiscarriedoutinordertoavoidthehazardpresentedbyapplying

mainsvoltagetotheappliedparts.

Carefulconsiderationshouldbegivenastothenecessityor

usefulnessofperformingthistestonaroutinebasiswhenweighed

againsttheassociatedhazardandthepossibilityofcausingproblems

poseofthetestunderIEC60601-1isto

ensurethatthereisnodangerofelectricshocktoapatientwhofor

someunspecifiedreasonisraisedtoapotentialaboveearthdueto

standardrequiresthattheleakagecurrentlimitsspecifiedarenot

snoguaranteethatequipmentperformancewillnot

icular,

cautionshouldbeexercisedinthecaseofsensitivephysiological

t,thetestisa\"typetest\".

Applicableto

ClassI&classII,typesBF&CFhavingapplied

parts.

Limit:TypeBF-5mA;typeCF-0.05mAperelectrode.

DB9801

recommended?:

No.

HEI95

recommended?:

No

Notes:

andreverse

nrequired,especiallyon

physiologicalmeasurementequipment.

nappliedpartsmeasurementarrangement.

6.10Leakagecurrentsummary

Thefollowingtablesummarisestheleakagecurrentlimits(inmA)

specifiedbyIEC60601-1forthetestsmostcommonlyperformedas

forDB9801recommendedtestsareunderlined.

LimitsforHEI95recommendedtestsaregiveninboldtype.

Leakagecurrent

TypeB

N云霄的意思 CSFC

TypeBF

NCSFC

TypeCF

NCSFC

Earth0.510.510.51

Earthforfixed510510510

equipment

Enclosure0.10.50.10.50.10.5

Patient0.10.50.10.50.010.05

Mainsonapplied

part

---5-0.05

Patientauxiliary0.10.50.10.50.010.05

*ForclassIItypeCFequipmentHEI95recommendsalimitfor

enclosureleakagecurrentof0.01mAasperthe1979editionofBS

5724.

ecurrentlimitssummary.

6.11ComparisonofHEI95andDB9801Supplement1

recommendations

TestHEI95

DB9801

Supplement1

Earthcontinuity

Usetestcurrentof1A

orless

Limit0.2ohm

Usetestcurrentof1A

orless

Limit0.2ohm

InsulationforClass1

equipment

MeasurebetweenL

andNconnected

togetherandEusing

500vDCtester.

Limit>50M.

Investigatelower

values

MeasurebetweenL

andNconnected

togetherandEusing

350vDCtester.

Limit>20M.

Investigatelower

values

InsulationforClassII

equipment

Measurebetween

appliedpartsand

accessibleconductive

partsofthe

equipment.

Limit>50M.

Investigatelower

values

Norecommendation.

Earthleakagecurrent

Measureinnormal

condition

Limit<0.5mA

Measureinnormal

condition

Limit<0.5mA

Enclosureleakage

current

MeasureinSFC,earth

opencircuitfor

Class-1,NCfor

Class-II

Limit<0.5mAfor

Class1

<0.1mAforclassII

MeasureinNConly

Limit<0.1mA

Patientleakage

current

Measurefromall

appliedparts

connectedtogetherfor

B&BFequipmentand

fromeachappliedpart

inturnfortypeCF.

MeasureunderSFC,

eartopencircuitfor

Class1,NCforclassII.

Limits:

ClassI,B&BF<

0.5mA

ClassII,B&BF

<0.1mA

ClassI,CF<

0.05mAper

electrode

ClassII,CF<

0.01mAper

electrode

Measurefromeach

appliedpartinturn,

foralltypesof

equipment

MeasureunderNC

only

Limits

TypeB&BF

<0.1mAper

electrode

TypeCF<0.01

perelectrode

也介绍下\"接触电流\"6Q>{

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IEC60990《接触电流和保护导体电流的测量方法》中提到接触电流是“当人体或动物接触

一个或多个装置的或设备的可触及零部件时，流过他们身体的电流。”接触电流也称之为

泄漏电流，然而经常会与耐压测试中的漏电流混为一谈，因此近些年的标准中或是相关的刊

物中都把泄漏电流称作为”接触电流”。7QiBy%

对于I类设备的电子产品可触及的金属部件或是外壳还应具备良好的接地线路，以作为基

本绝缘以外的一种防电击保护措施。但是我们也经常遇到一些使用者随意将I类设备当成

II类设备使用，或是说其I类设备电源输入端直接将接地端(GND)拔除，这样就存在一

定的安全隐患。即便如此，作为生产厂商有义务去避免这种情况对使用者造成的危险。这就

是我们为什么要做接触电流测试的目的所在。kQPxwm$

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接触电流的分类X<[64:$h

对于不同结构的电子产品，接触电流的量测也是有不同的要求，但总括来说接触电流可分为

对地接触电流、表面对地接触电流以及表面间接触电流测试三种。v>j>wi+R~

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对地接触电流(GroundLeakageCurrent)L;

“由电源网络产生的漏电流穿过或跨过绝缘层并流入保护接地导线(Protective

Conductor)的电流。”I类设备在保护接地导线断开的单一故障条件下，如果接地的人体

接触到与该保护接地导线相连的可触及导体（如外壳），则这个对地接触电流将通过人体流

到地(GND)，当这个电流大于一定值时，就有电击的危险。这种情况正如上述的事例，即

使接地线出现了故障或最极端的情况下断开，这时外壳的漏电流亦不能对人体造成伤害。此

时人就是充当了接地线路，流经人体电流也应在标准规定的限值之内。T\':fz7xI

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表面对地接触电流(SurfacetoLineLeakageCurrent)e9>\'3Q+bj

根据IEC60601-1《医用电气设备第一部分：安全通用要求》标准，外壳接触电流还包括

患者漏电流以及F型的患者漏电流。这里是指由于应用部分要接触到患者，而患者又接地，

如果应用部分对地存在一个电位差，则必然有一个电流从应用部件经患者流到地（这要排除

设备治疗上需要的功能电流），这便是患者漏电流。F8@A1-BH

K5,oRH

由于在患者身上意外地出现一个来自外部电源的电压而从患者经F型应用部分流入地的电

流。vTt[&78a

表面间接触电流(SurfacetoSurfaceLeakageCurrent)

在正常或是单一故障条件下，设备与地无关联任意两点之间的漏电流，电流从设备的一部分

流经人体后流入设备的另一部分；

结论

接触电流测试已作为产品安全性能的主要指针之一，是对产品是否存在触电危险的判断依

据。而且接触电流测试较其它安规测试复杂，因此必须掌握接触电流的概念及测量方式，

对于不同产品、不同标准的要求采取不同测量方式。

泄漏电流在不同情况不同标准下有不同的表示.这时要注意其内在的相同之处和做检测时

的不同意义.

安全距离包括电气间隙（空间距离），爬电距离（沿面距离）和绝缘穿透距离

1、电气间隙：两相邻导体或一个导体与相邻电机壳表面的沿空气测量的最短距离。

2、爬电距离：两相邻导体或一个导体与相邻电机壳表面的沿绝绝缘表面测量的最短距离。

电气间隙的决定：

根据测量的工作电压及绝缘等级，即可决定距离

一次侧线路之电气间隙尺寸要求，见表3及表4

二次侧线路之电气间隙尺寸要求见表5

但通常：一次侧交流部分：保险丝前L—N≥2.5mm，（大地）≥2.5mm，保险丝装

置之后可不做要求，但尽可能保持一定距离以避免发生短路损坏电源。

一次侧交流对直流部分≥2.0mm

一次侧直流地对大地≥2.5mm（一次侧浮接地对大地）

一次侧部分对二次侧部分≥4.0mm，跨接于一二次侧之间之元器件

二次侧部分之电隙间隙≥0.5mm即可

二次侧地对大地≥1.0mm即可

附注：决定是否符合要求前，内部零件应先施于10N力，外壳施以30N力，以减少其距离，

使确认为最糟情况下，空间距离仍符合规定。

爬电距离的决定：

根据工作电压及绝缘等级，查表6可决定其爬电距离

但通常：（1）、一次侧交流部分：保险丝前L—N≥2.5mm，L.N大地≥2.5mm，保险丝之后

可不做要求，但尽量保持一定距离以避免短路损坏电源。

（2）、一次侧交流对直流部分≥2.0mm

（3）、一次侧直流地对地≥4.0mm如一次侧地对大地

（4）、一次侧对二次侧≥6.4mm，如光耦、Y电容等元器零件脚间距≤6.4mm要开槽。

（5）、二次侧部分之间≥0.5mm即可

（6）、二次侧地对大地≥2.0mm以上

（7）、变压器两级间≥8.0mm以上

3、绝缘穿透距离：

应根据工作电压和绝缘应用场合符合下列规定：

——对工作电压不超过50V（71V交流峰值或直流值），无厚度要求；

——附加绝缘最小厚度应为0.4mm；

——当加强绝缘不承受在正常温度下可能会导致该绝缘材料变形或性能降低的任何机械应

力时的，则该加强绝缘的最小厚度应为0.4mm。

如果所提供的绝缘是用在设备保护外壳内，而且在操作人员维护时不会受到磕碰或擦伤，并

且属于如下任一种情况，则上述要求不适用于不论其厚度如何的薄层绝缘材料；

——对附加绝缘，至少使用两层材料，其中的每一层材料能通过对附加绝缘的抗电强度试验；

或者：

——由三层材料构成的附加绝缘，其中任意两层材料的组合都能通过附加绝缘的抗电强度试

验；或者：

——对加强绝缘，至少使用两层材料，其中的每一层材料能通过对加强绝缘的抗电强度试验；

或者：

——由三层绝缘材料构成的加强绝缘，其中任意两层材料的组合都能通过加强绝缘的抗电强

度试验。

4、有关于布线工艺注意点：

如电容等平贴元件，必须平贴，不用点胶

如两导体在施以10N力可使距离缩短，小于安规距离要求时，可点胶固定此零件，保证其

电气间隙。

有的外壳设备内铺PVC胶片时，应注意保证安规距离（注意加工工艺）

零件点胶固定注意不可使PCB板上有胶丝等异物。

在加工零件时，应不引起绝缘破坏。

5、有关于防燃材料要求：

热缩套管V—1或VTM—2以上；PVC套管V—1或VTM—2以上

铁氟龙套管V—1或VTM—2以上；塑胶材质如硅胶片，绝缘胶带V—1或VTM—2

以上

PCB板94V—1以上

6、有关于绝缘等级

（1）、工作绝缘：设备正常工作所需的绝缘

（2）、基本绝缘：对防电击提供基本保护的绝缘

（3）、附加绝缘：除基本绝缘以外另施加的独立绝缘，用以保护在基本绝缘一旦失效时

仍能防止电击

（4）、双重绝缘：由基本绝缘加上附加绝缘构成的绝缘

（5）、加强绝缘：一种单一的绝缘结构，在本标准规定的条件下，其所提供的防电击的

保护等级相当于双重绝缘

各种绝缘的适用情形如下：

A、操作绝缘oprationalinsulation

a、介于两不同电压之零件间

b、介于ELV电路（或SELV电路）及接地的导电零件间。

B、基本绝缘ba满船清梦压星河的寓意 sicinsulation

a、介于具危险电压零件及接地的导电零件之间；

b、介于具危险电压及依赖接地的SELV电路之间；

c、介于一次侧的电源导体及接地屏蔽物或主电源变压器的铁心之间；

d、做为双重绝缘的一部分。

C、补充绝缘supplementaryinsulation

a、一般而言，介于可触及的导体零件及在基本绝缘损坏后有可能带有危险电压的零件之间，

如：

Ⅰ、介于把手、旋钮，提柄或类似物的外表及其未接地的轴心之间。

Ⅱ、介于第二类设备的金属外壳与穿过此外壳的电源线外皮之间。

Ⅲ、介于ELV电路及未接地的金属外壳之间。

b、做为双重绝缘的一部分

D、双重绝缘

DoubleinsulationReinforcedinsulation

一般而言，介于一次侧电路及

a、可触及的未接地导电零件之间，或

b、浮接（floating）的SELV的电路之间或

c、TNV电路之间

双重绝缘=基本绝缘+补充绝缘

注：ELV线路：特低电压电路

在正常工作条件下，在导体之间或任一导体之间的交流峰值不超过42.4V或直流值不超过

60V的二次电路。

SELV电路：安全特低电压电路。

作了适当的设计和保护的二次电路，使得在正常条件下或单一故障条件下，任意两个可触及

的零部件之间，以及任意的可触及零部件和设备的保护接地端子（仅对I类设备）之间的电

压，均不会超过安全值。

TNV：通讯网络电压电路

在正常工作条件下，携带通信信号的电路。

1.何谓漏电流?

当电流经过绝缘阻抗後溢出，称之为漏电流(Leakagecurrent)，当漏电流经由人体接触，使

电流经过人体後流向Earth，即造成电气伤害。漏电流测试与耐压测试丶接地保护测试的不

同处，在於设备是在运作状态下做测试。漏电流测试中会加上一个人体模拟阻抗电路，可模

拟在真实情况下漏电流经过人体的大小。

2.何谓患者附属电流?

当产品运作时，电流从一个appliedpart测试点经过MD後至另一个appliedpart测试点再流

向地端。

3.何谓对地漏电流?

产品运作时，电流从电源端经过待测物流向电源E端，人体接触到产品E端时会导致感电，

称之为对地漏电流。

4.为何医疗设备安规标准这麽重视漏电流测试?

医疗设备的定义为与病患(大多法规指为人类，欧规则指人类及动物)有物理或电气上的接

触，用於诊断丶治疗丶监控之设备。医疗设备的漏电流测试注重在Appliedpart－在一般使

用情况下，以物理方式接触病患或病患须碰触的配件或设施，如探针丶心电图丶血压棒丶手

术台等。漏电流皆会对病患及相关人员产生危害。

5.何谓接触漏电流?

产品运作时，电流从二种电源端经过待测物流向外壳丶接点丶镙丝等产品可接触部位

(Accessiblepart)，人体接触时产生感电，称之为接触漏电流。

6.漏电流共分为哪几种?

漏电流依不同安规而有不同的测试模式，也依不同的测试点而有不同的漏电流标准。最常见

的为电流从经过待测物流向电源E端，人体接触到产品E端时会导致感电，醉落魄咏鹰思想感情 称之为对地漏

电流(EarthLeakageCurrent)。对地漏电流测试时电源端输入110%额定电压，加上人体模拟

电路，并判断经过人体模拟电路之电流值是否超过漏电流限制值。另外还有病患漏电流丶病

患从属漏电流等不同漏电流测试。

7.产品的绝缘类型有哪些?

不论是国家标准法规或地区标准法规，漏电流的标准依产品之绝缘类型而有所不同。

“CLASSI,II,III”主要是考虑产品的绝缘系统，源自IEC体系，简单解释如下：

CLASSI是指产品的防触电保护不仅依靠基本绝缘，而且还包括接地方式。

CLASSII是指产品的防触电保护不仅依靠基本绝缘，而且还包括附加的安全措施，例如双

重绝缘或加强绝缘，但没有接地或依赖安装条件的保护措施。

CLASSIII是指产品的防触电保护依靠电源电压为安全特低电压（SELV），并且其中不会产

生危险电压。

8.何谓患者漏电流?

患者漏电流共有三种测试。第一种是当产品运作时，电流从电源端经过appliedpart後流向

地端；另一种测试为将电力来源以110%最高使用电压施加於MD上，让电流经过appliedpart

丶accessiblepart後流向地端；第三种测试，将电力来源以110%最高使用电压施加於

SOP/SIP上，当产品运作时，电流从二个电源端经过appliedpart丶MD後流向地端。