Question

A single phase voltage controller has input of 230 V and a load of 15 Ω resistive. For 6 cycles on and 4 cycles off, determine the rms output voltage.

(a) 189 V

(b) 260 V

(c) 156 V

(d) 178 V

The question was asked during a job interview.

My question is taken from AC Voltage Controllers-3 in chapter Voltage Controllers of Power Electronics

Answer 1

Correct choice is (d) 178 V

Explanation: Vrms = Vo x √k

k = (6/6+4) = 6/10 = 0.6

Vrms = √0.6 x 230 =   178.157 V.