Question

A 1-\(\phi\) fully controlled bridge rectifier with a highly inductive load is fired at an angle of cos\(^{-1}(0.8)\). Assuming the load current is pure dc, the input power factor is

• A. 0.64
• B. 0.72
• C. 0.80
• D. 0.50

Hint:

In controlled rectifiers with inductive loads, true power factor is less than \(\cos(\alpha)\) due to current waveform distortion.

Answer 1

The Correct Option is B

The firing angle \( \alpha \) is given by \[ \alpha = \cos^{-1}(0.8) = 36.87^\circ \] For a fully controlled rectifier with purely inductive load and constant DC output current, the input power factor is: \[ \text{PF} = \cos(\alpha) = \cos(36.87^\circ) = 0.8 \] However, due to displacement and distortion in the input current, the true input power factor becomes: \[ \text{PF}_{\text{true}} = 0.72 \]