A source V s = 200 cos ωt delivers power to a load at power facto
| A source Vs = 200 cos ωt delivers power to a load at power factor 0.8 lag. The reactive power is 300 VAR. The Active Power is given by?
A. 200 Watts
B. 225 Watts
C. 400 watts
D. 300 Watts
Please scroll down to see the correct answer and solution guide.
Right Answer is: C
SOLUTION
Concept:
The power triangle is as shown below.
P = Active power (or) Real power in W = Vrms Irms cos ϕ
Q = Reactive power in VAR = Vrms Irms sin ϕ
S = Apparent power in VA = Vrms Irms
S = P + jQ
\(S = \sqrt {{P^2} + {Q^2}} \)
ϕ is the phase difference between the voltage and current
Power factor \(\cos \phi = \frac{P}{S}\)
Calculation:
Given that, power factor (cos ϕ) = 0.8
⇒ sin ϕ = 0.6
Reactive power (Q) = VI sin ϕ = 300 VAR
⇒ VI = 500 VA
⇒ Active power (P) = VI cos ϕ = 500 × 0.8 = 400 W
