Question

If R and X are equivalent resistance and equivalent reactance of a transformer respectively, then at maximum voltage regulation, the power factor is

• A. R/\( \sqrt{X^2 - R^2} \) leading
• B. R/\( \sqrt{X^2 - R^2} \) lagging
• C. R/\( \sqrt{X^2 + R^2} \) lagging
• D. R/\( \sqrt{X^2 + R^2} \) leading

Hint:

Maximum regulation occurs at lagging PF: use \( \cos\phi = \frac{R}{\sqrt{R^2 + X^2}} \)

Answer 1

The Correct Option is C

At maximum voltage regulation: \[ \cos \phi = \frac{R}{\sqrt{R^2 + X^2}}, \text{ and the current lags voltage} \]