The input power of 3 phase motor bias measured by two watt meters method. The reading of two watt meters are 5.2kW and -1.7 kW and the line voltage is 415 V. Calculate the active power, power factor and line current -

$W1 = 5.2 kW \\ W2 = -1.7 kW \\ VL = 415 V \\ P= W1 + W2 = 5.2 – 1.5 = 3.5 kW \\ \tan ф = \sqrt3 W1 – W2/ W1 + W2 \\ = \sqrt3 (5.2 + 1.7/ 5.2 – 1.7) = 3.41 \\ Ф= \tan-1 (3.41) \\ Ф= 73.68o \\ Pf = \cos ф = \cos (73.68) \\ = 0.28 (lagging) \\ P= \sqrt3 VLIL \cos ф \\ 3.5 * 103 = \sqrt3 * 415 * IL * 0.28 \\ IL = 17.39A$