Question

Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 120° and supply frequency is 60 Hz.

(a) 1.8 msec

(b) 3.2 msec

(c) 6.3 msec

(d) 2.7 msec

This question was posed to me in class test.

The query is from Solid State Controlled Drives in chapter Introduction to Solid State Controlled Drives of Electric Drives

Answer 1

Correct choice is (d) 2.7 msec

To elaborate: The circuit turn-off time for 3-Φ Fully controlled rectifier is (180°-α)÷ω. The value of circuit turn-off time for ∝ ≥ 60° is (180°-120°)÷6.28×60=2.7 msec.