Power factor is a measure of the efficiency of an AC power system. It is defined as the ratio of the real power absorbed by the load to the apparent power flowing in the circuit. Real power is the average of the instantaneous product of voltage and current and represents the capacity of the electricity for performing work. Apparent power is the product of RMS current and voltage. Due to energy stored in the load and returned to the source, or due to a non-linear load that distorts the wave shape of the current drawn from the source, the apparent power may be greater than the real power, so more current flows in the circuit than would be required to transfer real power alone.
Power factor is usually expressed as a percentage, and the lower the percentage, the less efficient power usage is. A high power factor indicates effective utilization of electrical power, whereas low power factor signifies inefficient use of electrical power. A power factor magnitude of less than one indicates the voltage and current are not in phase, reducing the average product of the two. A negative power factor occurs when the device (which is normally the load) generates real power, which then flows back towards the source.
To calculate power factor, divide working power (kW) by apparent power (kVA) . A 96% power factor demonstrates more efficiency than a 75% power factor. Power factor below 95% is considered inefficient in many regions.
