Question

The wattmeter method is used to measure power in a three-phase load. The wattmeter readings are 400W and -35W. Find the reactive power.

(a) 751.44

(b) 752.44

(c) 753.44

(d) 754.44

This question was addressed to me by my college professor while I was bunking the class.

This intriguing question originated from Power Measurement in Three-Phase Circuits topic in portion Polyphase Circuits of Network Theory

Answer 1

Correct option is (c) 753.44

For explanation I would say: Reactive power = √3VLILsinØ. We know that WR – WY = 400-(-35)) = 435 = VLILsinØ. Reactive power = √3 x 435 = 753.44 VAR.