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Measurements and Instrumentation - Engineering

Q1:

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.

ANS:D - When the two wattmeter read equal and opposite, p.f. is zero.

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