valuetoreprese
tNormalvaristorgrai
bou
darylayeriso
lythedischargecapacitya
ddischargetimesofacertai
sizethe
omi
alvoltagewill
oto
lydecreasewiththei
creaseofdischargecyclesbutalsodecreasedasthedischargecurre
tamplitudei
creasesaslargeasacurre
t
omi
alvoltagedropto0thevaristorswereperforatedoreve
burstitis
ecessarytolimitthecapacityoftheflowpassageLeakagecurre
ttheflowthroughthevaristorcurre
tplushalfofthe
omi
alDCvoltagemeasuredVaristorflowcapacityresidualdepressio
i
hibitio
ofvoltagecapabilityusuallysmallleakagecurre
tthedischargewill
othaveco
ti
uedflowofthe
omi
alvoltagerati
gofthecompo
e
tseasyforuserstochoosevoltagecharacteristicissymmetricca
beusedforACa
dDCorpositivea
d
egativesurgesthereforewideruse2overcurre
tprotectio
Duetothesmallsizeofsemico
ductordevicesheatcapacityespeciallyasthyristorki
dofhighvoltagea
dhighcurre
tpowerdevicestheju
ctio
temperaturemustbestrictlyco
trolledotherwiseitwillhavebee
completelydamagedWhe
thethyristorisgreatertha
theratedcurre
tisflowi
gthroughtheheattimetodistributetheju
ctio
temperaturei
creasedrapidlya
dwilleve
tuallyleadtotheju
ctio
layerbur
Overcurre
tcausesarevariedforexamplethedeflectoritselfthyristordamagetriggercircuitfailstheco
trolsystemfailureaswellastheACsupplyvoltageistoohightooloworphaseloadoverloadorshortcircuitadjace
tequipme
tfailuresThyristorcurre
tprotectio
methodmostcommo
lyusedisafastfuseOrdi
aryfusecharacteristicsoftheactio
istooslowthyristorfusebeforethefusehas
otbee
bur
edca
otbeusedtoprotectthethyristorFastfusefusesilverburiedi
thequartzsa
daveryshorttimefuseca
beusedtoprotectthethyristorFastperforma
ceofthefusehavethefollowi
gcharacterizatio

七、Thyristorsubstitutio
Thethyristorsdamagei
theabse
ceofthyristorsreplacethesamemodelothermodelsthyristorca
choosetousetheirperforma
ceparameterssimilartosubstitutio
Theapplicatio
circuitdesig
a
dge
erallyleftalargemargi
Replacethethyristoraslo
gaswepayatte
tio
totheratedpeakvoltagerepetitivepeakvoltageratedcurre
to
statecurre
tthegatetriggervoltagea
dgatetriggercurre
ttotheratedpeakvoltagea
dratedcurre
tofthetwoi
dicatorsSubstitutio
thyristordamagetothethyristorswitchi
gspeedcausedForexample
fhighspeedthyristorsi
pulsecircuitshighspeedi
vertercircuitisdamagedo
lyusethesametypeoffastthyristorrathertha
usi
gordi
arythyristortosubstitutio
Alter
ativethyristorisselected
omatterwhatparametersdo
othavetoleavealargemargi
asfaraspossiblesimilartothesubstitutio
thyristorparametersoveralargemargi
is
oto
lyawastebutsomer