In a three-phase circuit, the complex power in case of a capaciti
| In a three-phase circuit, the complex power in case of a capacitive load is given by:
A. S = |S|∠ϕ kVA
B. S = |V| |I| kVA
C. S = Q + jP kVA
D. S = P – jQ kVA
Please scroll down to see the correct answer and solution guide.
Right Answer is: D
SOLUTION
Concept:
Complex Power of an AC circuit is given as:
\(P = V \times {I^*}\)
P = complex power
V = Voltage
I* = Conjugate of current
Application:
For lagging loads, the current lags the voltage by an angle ϕ.
Voltage = V∠0°
Current = I∠-ϕ°
Complex power = VI* = (V∠0°) (I∠ϕ°)
= VI cos ϕ + VI sin ϕ = P + jQ
For leading loads, current leads the voltage by an angle ϕ.
Voltage = V∠0°
Current = I∠ϕ°
Complex power = VI* = (V∠0°) (I∠-ϕ°)
= VI cos ϕ – VI sin ϕ = P – jQ