GATE 2021 IN – Question 22
A single-phase transformer has magnetizing inductance 250 mH and core-loss resistance 300 $\Omega$, referred to its primary. With a 230 V, 50 Hz sinusoidal primary supply and open secondary, its input power factor is ______ (two decimal places).
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Show answer and explanation
Correct answer: 0.24 to 0.26
Explanation
The core-loss current V/Rc is in phase and magnetizing current V/Xm is in quadrature. Xm=2π·50·0.25=78.54 Ω.
Thus PF=(1/300)/√[(1/300)²+(1/78.54)²]=0.2533, or **0.25**. Voltage cancels in the ratio.