PPT ON TOPIC PROTECTION DEVICES. POWER ELECTRONIC TOPIC PROTECTION OF DEVICES . PROTECTION OF SEMICONDUCTOR DEVICES. DIFFERENT TYPES OF PROTECTION OF DEVICES IN POWER ELECTRONIC. PROTECTION OF SEMICONDUCTOR DEVICES,POWER ELECTRONIC. DIFFERENT KIND OF PROTECTION FROM VOLTAGE OF SEMICONDUCTOR DEVICES . OVER CURRENT PROTECTION OF DEVICES OF POWER ELECTRONIC DEVICES. OVER VOLTAGE PROTECTION OF POWER DEVICES .

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POWER ELECTRONIC
PROTECTION OF DEVICES

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• WHY PROTECTION OF DEVICES
• TYPES OF PROTECTION
1. Over voltage pr otec tion.
2. Over c ur rent pr otec tion.
3. H igh di/dt pr otec tion.
4. H igh dv/dt pr otec tion
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CONTENT

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WHY PROTECTION OF POWER DEVICES?
• It ver y delic ate s emic onductor devic e. Ther efor e w e
have to us e it in its s pec ified ratings to get des ired
output.
• Pr otec tion of a devic e is an impor tant as pec t for its
r eliable and effic ient oper ation .
• Thes e devic es oper ate fr om the s upply of pow er. And
it may fac e differ ent types of thr eats dur ing its
oper ation due to over voltages , over c ur r ents etc .
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TYPES OF PROTECTION
1. Overvoltage protection.
2. Overcurrent protection.
3. High di/dt protection.
4. High dv/dt protection.
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OVERVOLTAGE PROTECTION
• Over-voltages causes either maloperation of
the circuit by unwanted turn -on of a thyristor
or permanent damage to the device due to
reverse breakdown.
• A thyristor may be subjected to internal or
external over-voltages.
• The effect of over-voltages is usually
minimized by using RC circuits and non -
linear resistors called voltage clamping
device.
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OVERCURRENT PROTECTION
• Over c ur r ent mainly oc c ur s due to differ ent types of
faults in the c ir c uit .
• If a thyris tor is s ubjec ted to over - c urrent due to faults ,
s hort c irc uits or s urge c urrents , it junc tion temperature
may exc eed the r ated value and the devic e may be
damaged.
• Over-current protection is achieved by the use of
circuit breakers (CB) and fast acting fuse.
• A c ir c uit br eak er has long tr ipping time, ther efor e
gener ally it is us ed agains t s ur ge c ur r ents of long
dur ation.
• A fas t ac ting c ur r ent limiting fus e ( FAC LF) is us ed
agains t a large s urge c urrents of very s hort duration.
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HIGH DI/DT PROTECTION
• If the rate of rise of anode current, (i.e. di/dt)
is large as compared to the spread velocity of
carriers, local hot spots will be formed near
the gate connection. This localized heating
may destroy the thyristor.
• The value of di/dt can be maintained below
acceptable limit by using a small inductor,
called di/dt inductor in series with the anode
circuit.
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HIGH DV/DT PROTECTION.
• If the rate of rise of suddenly applied voltage
across thyristor is high, the device may get
turned on. It leads to false operation of the
thyristor circuits.
• False turn-on of a thyristor by large dv/dt can
be prevented by using a snubber circuit in
parallel with the device.
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THANK YOU