Power Factor (Electrical Power Toolkit)

In an AC circuit, the power factor (PF) is the ratio of active power to apparent power, given by the following equation:

where θ is the angle difference between voltage and current. The power factor is a measure of the efficiency of an electrical power distribution system. A system with a higher power factor is more efficient because reactive loads cause lower energy losses. If voltage and current are in phase, PF has a value of one. If voltage and current are 90 degrees out of phase, PF has a value of zero.

Power factors less than one increase the overall cost of an electrical power distribution system. A poor power factor in a circuit describes a power factor that is less than 0.85. A poor power factor can result in heat damage to insulation and other circuit components, reduce the amount of useful power available, and require increased conductor and equipment sizes.