Load Commutation Technique of Thyristor
Commutation is defined as the process of turning-OFF a thyristor. Several commutation techniques have been developed with the sole objectives of reducing their turn-OFF time. Use resonant LC or under-damped RLC circuits to force the current and/or voltage of a thyristor to zero to turn-OFF the device.
- Load commutation
- Resonant pulse commutation
- Complementary commutation
- Impulse commutation
- External pulse commutation
- Line commutation
Load commutation used in series inverter and also called as resonant commutation, self commutation or Class-A commutation.
- For low value of load R, L and C are connected in series with R.
- For high value of load R, C is connected across load R.
- The essential requirement for both the circuits is that the overall circuit must be under-damped.
- Current i first rises to maximum value and then begins to fall.
- When current decays to zero and tends to reverse, thyristor T is turned-OFF on its own at instant a.
- Possible in dc circuits and not in ac circuits.
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