COMMUTATION

• The process of turning OFF SCR is termed as commutation.
• By turning OFF thyristor we bring it from forward conducting to the forward blocking mode.

Conditions to turn OFF an SCR

The condition to be satisfied in order to turn off an SCR are :-

• $I_A \lt I_H$ (Anode current must be less than holding current)

• A reverse voltage is applied to SCR for sufficient time enabling it to recover it's blocking state.

Forced Commutation

• Used in DC circuits
  • the forward current should be forced to zero by means of some external circuit.
  • to turn OFF thyristor,the forward anode current should be brought to zero for sufficient time to allow the removal of charged carriers.