Question

A single-phase ac switch is used in between a 230 V source and load of 2 kW and 0.8 lagging power factor. Determine the rms current rating required by the SCR. Use the factor of safety = 2.

(a) 10.87 A

(b) 87 A

(c) 21.74 A

(d) 32 A

This question was posed to me in an online interview.

This is a very interesting question from Applications of Power Electronics-2 topic in section Applications, Cycloconverters and  Miscellaneous of Power Electronics

Answer 1

Right answer is (c) 21.74 A

The best explanation: I = (200√2)/(230 x 0.8) = 15.37 A.

I(rms) = 15.37/1.414 = 10.87

Required rating = 10.87 x factor of safety = 15.37 x 2 = 21.74 A.