1- A balanced, wye-connected, resistive and capacitive, three-phase circuit has

Question

1- A balanced, wye-connected, resistive and capacitive, three-phase circuit has a phase voltage of 80V and a phase current of 2.5A. Calculate the total apparent power ST in the circuit.
2- A balanced, three-wire, resistive and capacitive, three-phase circuit is conneted to two power meters set up to measure power using the two-wattmeter method of power measurment. The two power meterd indicate active power readings of 175W and -35W. Calculate the total active power dissipated in the circuit.
3- in which type of three-phase circuits does the two-wattmeter method of power measurment not work to measure the total power in the circuit?

Explanation / Answer

1. given Voltage V =80 V

Current I = 2.5 A

So apparent power S = V*I = 80*2.5 =200 VA

2.Given power measurements in two watt meter menthod

W1 =175 W

W2 =-35W

So total active power of circuit P = W1+W2

= 175-35

= 140 Watts

So P = 140 Watts

3. In unbalaced load condition the two watt meter method has a more error wen comparate to three watt meters mesaured power. So it is not used in unbalced load conditions.

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