Which of the following statement is correct for two wattmeters method of power measurement in 3 phase circuit?

[A].	Power can be measured by this method only for star connected loads
[B].	When two wattmeters have equal readings power factor is 0.5.
[C].	When power factor is 1, one of the wattmeters readings is zero
[D].	When the two wattmeter read equal and opposite, p.f. is zero.

Answer: Option D

Explanation:

When p.f. is zero, active power is zero and the two redaings are equal and opposite.