Definition of Power Factor

From Electrical Installation Guide

The Power Factor is an indicator of the quality of design and management of an electrical installation. It relies on two very basic notions: active and apparent power.

The active power P (kW) is the real power transmitted to loads such as motors, lamps, heaters, and computers. The electrical active power is transformed into mechanical power, heat or light.

In a circuit where the applied r.m.s. voltage is Vrms and the circulating r.m.s. current is Irms, the apparent power S (kVA) is the product: Vrms x Irms.

The apparent power is the basis for electrical equipment rating.

The Power Factor λ is the ratio of the active power P (kW) to the apparent power S (kVA):

[math]\displaystyle{ \lambda = \frac {P(kW)}{S(kVA)} }[/math]

The load may be a single power-consuming item, or a number of items (for example an entire installation).

The value of power factor will range from 0 to 1.