Question

In case of a single-phase half-wave circuit with RL load, with firing angle α and extinction angle β,  the thyristor is reversed biased from

(a) β to α

(b) β to 2π+α

(c) β to 2π

(d) β to 2β

This question was addressed to me during an interview.

The origin of the question is Single-Phase HW AC-DC-2 topic in portion Converters of Power Electronics

Answer 1

Right answer is (c) β to 2π

Explanation: As the load current goes to zero from β, the SCR is reversed biased or in the OFF state till it is turned on at 2π again by the positive AC cycle.