A six-pulse thyristor bridge rectifier is connected to a balanced three-phase, 50 Hz AC source. Assuming that the DC output current of the rectifier is

Q. A six-pulse thyristor bridge rectifier is connected to a balanced three-phase, 50 Hz AC source. Assuming that the DC output current of the rectifier is constant, the lowest harmonic component in the AC input current is

(A) 100 Hz

(B) 150 Hz

(C) 250 Hz

(D) 300 Hz

Ans: 250 Hz

Solution:

In a six-pulse thyristor bridge rectifier, the harmonics present are = 6 k ± 1

So, the harmonics are = 5, 7, 11, 13, …

lowest harmonic component = 5th harmonic supply frequency = 50 Hz

5th harmonic frequency = 5f = 250 Hz