GATE 2019 EE – Question 65
A single-phase fully-controlled thyristor converter is used to obtain an average voltage of 180 V with 10 A constant current to feed a DC load. It is fed from single-phase AC supply of 230 V, 50 Hz. Neglect the source impedance. The power factor (round off to two decimal places) of AC mains is ________.
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Show answer and explanation
Correct answer: 0.77 to 0.79
Explanation
The real power is $P=180\times10=1800$ W. With a constant DC current of 10 A the AC line current is a square wave with an rms value of 10 A, so $S=230\times10=2300$ VA. The power factor is $\frac{1800}{2300}=0.78$.