PF = P / S
P = Real Power (W), S = Apparent Power (VA)
PF = cos(φ)
φ = Phase angle between V and I
Q = √(S² − P²)
Q = Reactive Power (VAR)
Lagging (Inductive): Current lags voltage. Common in motors, transformers, and inductive loads.
Leading (Capacitive): Current leads voltage. Common in capacitor banks and some electronic equipment.
Power factor is a measure of how efficiently electrical power is being used in an AC circuit. It is the ratio of real power (the power actually consumed by equipment) to apparent power (the total power supplied to the circuit). A power factor of 1 (unity) means all the power supplied is being used effectively, while a lower power factor indicates that some power is being wasted as reactive power.
In practical terms, power factor represents the efficiency of power utilization. Industrial facilities with large motors, transformers, and other inductive loads often have power factors below 1, which can result in higher electricity bills and require power factor correction using capacitor banks.
The relationship between real power (P), reactive power (Q), and apparent power (S) can be visualized as a right triangle known as the power triangle. Real power forms the adjacent side, reactive power forms the opposite side, and apparent power is the hypotenuse. The angle between real and apparent power is the phase angle (φ), and cos(φ) equals the power factor.
S² = P² + Q²
PF = P/S = cos(φ)
tan(φ) = Q/P
Power factor calculations are estimates based on ideal conditions. Actual system power factor may vary due to harmonics, non-linear loads, or measurement inaccuracies. Consult an electrical engineer for precise analysis and power factor correction recommendations.