Question

A balanced three-phase star connected load of 100 kW takes a leading current of 80 amp, when connected across a three-phase 1100 V, 50 Hz, supply. Find the circuit constants of the load per phase.

Answer 1

Voltage per phase = 1100/1.732 = 635 V 

Impedance = 635/80 = 7.94 ohms. 

Due to the leading current, a capacitor exists. 

Resistance R can be evaluated from current and power consumed 

3I²R = 100 × 1000, giving R = 5.21 ohms 

X_c = (7.942 – 5.212)^0.5 = 6 ohms 

At 50 Hz, C = 1/(314 × 6) = 531 micro farads.