Question

single-phase thyristor-bridge rectifier is fed from a \(230\;V,\;50\;Hz\), single-phase AC mains. If it is delivering a constant DC current of \(10\;A\), at firing angle of \({30^o}\), then value of the power factor at AC mains is
1. 0.87
2. 0.9
3. 0.78
4. 0.45

Answer 1

Correct Answer - Option 3 : 0.78

Concept:

In a single phase thyristor-bridge rectifier,

Displacement factor or displacement power factor, \(DF=\cos \alpha\)

Current distortion factor, \(CDF=\frac{{{I}_{s1}}}{{{I}_{s}}}=\frac{2\sqrt{2}}{\pi }\) = 0.9 

Input power factor = CDF × DF \(=\frac{2\sqrt{2}}{\pi }\cos \alpha\)

Calculation:

input power factor = CDF × DF \(=\frac{2\sqrt{2}}{\pi }\cos \alpha\)

\(= \frac{{2\sqrt 2 }}{\pi }cos\alpha = \frac{{2\sqrt 2 }}{\pi }cos30^\circ = 0.78\)