Question

In a three-phase, three-pulse, M-3 type controlled converter T1 starts to conduct at 30 + n°. At what angles do T2 and T3 start to conduct? Assume that the conduction sequence is T1-T2-T3.

(a) 2n° and 3n°

(b) 150 + n° and 270 + n°

(c) n° each

(d) 30 + n° and 60 + n°

The question was asked during an interview.

The above asked question is from Three Phase Converters-1 topic in portion Converters of Power Electronics

Answer 1

The correct choice is (b) 150 + n° and 270 + n°

Explanation: In three-phase three pulse converter the conduction can start only after 30°. As each SCR conducts from 120°, T2 would conduct on 30+120+n° = 150+n° and so on.