Question

In the circuit shown below, find the expression of average output voltage if due to some faults the SCR T3 gets permanently open circuited.

(a) 2Vm/π cosα

(b) Vm/π cosα

(c) Vm/√π

(d) Zero

The question was asked during an interview for a job.

This interesting question is from Single Phase FW AC-DC-5 topic in division Converters of Power Electronics

Answer 1

Correct option is (b) Vm/π cosα

Explanation: If one of the device gets O.C the circuit would behave just like a half-wave rectifier. Only Two SCRs T1 & T2 will operate, even T4 is useless in this case.

Vo = 1/2π x [ ∫ Vm sinωt d(ωt) ] where the integration would run from α to π+α.