Question

A step down chopper has input dc voltage of 220 V and R  = 10 Ω in series with L = 65 mH. If the load current varies linearly between 11 A and 17 A, then find the duty cycle α.

(a) 1

(b) 0.4

(c) 0.6

(d) 0.7

The question was posed to me during an online interview.

My doubt stems from Choppers-4 topic in portion Choppers of Power Electronics

Answer 1

Correct option is (d) 0.7

To explain I would say: Average load current = 11+17 / 2 = 14A

Average load voltage = IxR = 14×10 = 140V

But, Vo = α x Vs

Therefore, α x 220 = 140, α = 0.7.