Question

In the below given circuit, __ and __ conduct along with T2.

(a) T1, T3

(b) D1, D2

(c) D1, D3

(d) T1, T2

The question was asked during an interview.

I'd like to ask this question from Three Phase Converters-3 topic in chapter Converters of Power Electronics

Answer 1

The correct option is (c) D1, D3

To explain: When one SCR conducts, a diode conducts along with it at a time to provide the path of current flow. . For example, if T2 starts conducting at 90° it will conduct till 90+120 = 210°. But while T2 is conducting, half of the time i.e. from 90 to 150 D1 is conducting and another half of the time D3 is conducting. T2 and D2 cannot conduct together as it will cause a short circuit. Hence, T2-D1 conduct for 60° and then T2-D3 conduct for another 60°.