A three-phase load takes a line current of 18 A from a 525V supply. Calculate the following:
a) The phase current and phase voltage if the load is star connected
b) the phase current and phase voltage if the load is delta connected
c) the power drawn by the load if the load operates at a power factor of 0,8 lagging
d) does the method of connecting the load influence the magnitude of the power drawn?
a) If the load is star connected, the phase current (Iph) is equal to the line current (Iline). Also, the phase voltage (Vph) is equal to the line voltage (Vline) divided by square root of 3.
Iph = Iline = 18 A
Vph = Vline / √3 = 525 V / √3 ≈ 302.1 V
b) If the load is delta connected, the phase current (Iph) is equal to the line current (Iline) divided by square root of 3. The phase voltage (Vph) remains the same as the line voltage (Vline).
Iph = Iline / √3 = 18 A / √3 ≈ 10.4 A
Vph = Vline = 525 V
c) The power drawn by the load can be calculated as follows:
Power = (√3) × Vline × Iline × power factor
= (√3) × 525 V × 18 A × 0.8
≈ 16963.68 Watts or 16.96 kW
d) No, the method of connecting the load (star or delta) does not influence the magnitude of the power drawn. The power drawn is determined by the line current and line voltage, as well as the power factor, which remains the same regardless of the connection method.