Question

In the below given figure, the converter 1 (to the right side) has firing angle = α1, converter 2 has firing angle = α2. For the dual converter to operate in the fourth quadrant.

(a) α1 > 90°

(b) α2 > 90°

(c) α1 < 90°

(d) α2 < 90°

I got this question in homework.

This intriguing question originated from Dual Converters-3 in section Converters of Power Electronics

Answer 1

The correct choice is (a) α1 > 90°

Easiest explanation: Converter 1 would control the first and the forth quadrant and converter 2 would operate in the second and the third quadrant. In the fourth quadrant, voltage should be negative and current should be positive, hence C1 as an inverter is operated with α1 > 90°.