Question

For the step down chopper shown in the figure below, Vs = 100 V and the duty cycle of the switch is 0.8. The load is sufficiently inductive so that the load current is ripple free. The average current through the diode (D) under steady state is

(a) 2 A

(b) 1.6 A

(c) 8 A

(d) 6.4 A

I have been asked this question in an online quiz.

This question is from Thyristor Chopper Circuits-3 in division Choppers of Power Electronics

Answer 1

Right choice is (b) 1.6 A

To explain I would say: The diode is active only during Toff.

If Ton = 0.8 then Toff = 0.2

Output voltage Vo = 0.8 x 100 = 80 V

When D is active during Toff, consider inductor as a short circuit thus, Id = (VoxToff)/R = 80 x 0.2/10 = 1.6 A.