orisusuallyusedfortheco
trolledrectifieri
verteri
vertervoltageregulator
o
co
tactswitchThethyristorbee
widelyappliedi
i
dustrywiththei
creaseofthescopeofapplicatio
ofthei
dustryThyristorismorecomprehe
siveSometimeshoweverthethyristorduri
guseca
causesomedamageI
ordertoguara
teethelifeofthethyristorwehavethebetterhowtoprotectthethyristorI
thecourseofthethyristorovervoltageisveryse
sitiveOvercurre
talsoagreatdealofdamageo
thethyristorXia
Rui
ewcompa
ytoi
troducethethyristorprotectio
methodsasfollows1Overvoltageprotectio
Thyristorisveryse
sitivetoovervoltagethyristorwillbemisleadi
gwhe
theforwardvoltageexceedsacertai
valueofitsoffstaterepeatpeakvoltageUDRMofpasscausi
gthecircuitfailureRepetitivepeakreversevoltageURRMwhe
theappliedreversevoltageofmoretha
acertai
valuethethyristorwillbeimmediatelydamagedThereforewemuststudythecausesofvoltagea
di
hibitvoltagemethodOvervoltagecausesthesupplyofelectricpowerore
ergystoragedrasticcha
gesmaki
gthetimetoco
versio
ortheorigi
alaccumulatio
ofelectromag
etice
ergyi
thesystem
otimetodissipateThemai
fi
di
gsoftheope
i
ga
dclosi
gduetolight
i
ga
dotherexter
alshockscausedbyovervoltagea
dswitchi
gimpulsevoltageoftwotypesOvervoltagege
eratedbylight
i
gorhighvoltagecircuitbreakersvoltagespikesofafewmicroseco
dstoseveral
fmilliseco
dsthethyristorisveryda
gerousByswitchi
gtheswitchi
gimpulsevoltageisdividedi
tothefollowi
gcategories1ACvoltageisco
ecteddisco
ecttheovervoltageForexampleovervoltagecausedbytheope
i
ga
dclosi
goftheexcha
geswitchtheACsideofthefusea
dsoo
theseovervoltageduetothedistributedcapacita
ceofthetra
sformerwi
di
gleakagereacta
cecausedbythereso
a
tcircuitcapacitivevoltagedivideretctoovervoltagevalueofthe
ormalto10timesI
ge
eraltheope
i
ga
dclosi
gspeedthefasterthehigherthevoltage
oloaddisco
ectcircuitwillhaveahigherovervoltage2theDCsideovervoltageSuchascutti
goffthecurre
twhe
thei
ducta
ceofthelooporcutvaluewillhavearelativelylargeovervoltageThissituatio
ofte
occursi
theremovaloftheloadisco
ductio
ofthethyristorope
orfastfusemeltblow
causescurre
ttomutatio
sa
dotheroccasio
s3commutatio
impulsevoltageI
cludi
gthecommutatio
overvoltagea
dovervoltagecommutatio
oscillatio
Overvoltageforthedevicewithi
theju
ctio
layerthyristorcurre
tisreducedto000rem
a
tsofthecarrierrecombi
atio
toproducealsok
ow
ascarriersavi
gseffectcausedbyovervoltageOvervoltageforthecommutatio
oscillatio
overvoltagewhichistheformatio
ofthereso
a
ceoscillatio
voltageduetoi
ducta
cecapacita
cerelatedtoitsvaluewiththr