Question

The turn on time of an SCR with inductive load is 20 µs. The pulse train frequency is 2.5 KHz with a mark/space ratio of 1/10, and then SCR will ______

(a) Turn On

(b) Not turn on

(c) Turn on if inductance is removed.

(d) Turn on if pulse frequency is increased to two times

I got this question in a job interview.

This intriguing question originated from Power BJTs topic in division Differential and Multistage Amplifiers of Electronic Devices & Circuits

Answer 1

The correct answer is (a) Turn On

To elaborate: Pulse repetition rate (PRR) = 1/(2.5 – 10^3) = 0.4 ms = 400 µs.

                         Mark/space ratio = 1/10.

Pulse width = 400/11 = 36.4 µs.

The SCR will ‘turn on’ as the pulse width is greater than SCR turn on time.