Question

Calculate the circuit turn-off time for 3-Φ Fully controlled rectifier if the firing angle is 20° and supply frequency is 60 Hz.

(a) 8.8 msec

(b) 7.4 msec

(c) 10.1 msec

(d) 6.5 msec

This question was posed to me in exam.

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

Answer 1

Right option is (c) 10.1 msec

To explain I would say: The circuit turn-off time for 3-Φ Fully controlled rectifier is (240°-α)÷ω. The value of circuit turn-off time for ∝ < 60° is (240°-20°)÷6.28×60=10.1 msec.