Thyristor Commutation Techniques

Commutation

Commutation is defined as the process of turning off a thyristor. A thyristor can be turned on by applying a gate pulse but the gate has no control over turning off a thyristor. The turning-off of a thyristor requires the below two conditions;

1. The cathode should be at higher potential than that of anode for sufficient time, so that the thyristor attains its reverse blocking state.
2. The anode current fall below the holding current.

As the gate cannot be used to turn off a thyristor, it necessitates the use of external commutation circuits to turn off a thyristor. The following are the various types of commutation techniques which uses resonant LC circuits, under-damped RLC circuits etc.

Types Commutation Techniques

• Class A Commutation – Load Commutation (go to Class A Commutation for full article)

• Class B Commutation – Resonant Pulse Commutation

• Class C Commutation – Complementary Commutation

• Class D Commutation – Impulse Commutation

• Class E Commutation – External Pulse Commutation

• Class F Commutation – Line Commutation