GATE 2014 EE (EE2) – Question 63
The fully controlled bridge shown supplies a highly inductive load with ripple-free current from sinusoidal AC. Trigger angle is α = 30°. Find input power factor.
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Correct answer: 0.74 to 0.82
Explanation
With ripple-free dc current,the ac input current is a square wave of magnitudeId. Its fundamental rms is(2√2/π)Id,while total rms isId,so distortion factor is2√2/π. The fundamental lags voltage byα=30°,giving displacement factorcos30°. True power factor is(2√2/π)cos30°=**0.779697**. Using onlycosαwould omit harmonic distortion.