The power factor is related to the load nature of the circuit. For example, the power factor of pure resistive loads such as incandescent bulbs and resistance furnaces is 1, and the power factor of general circuits with inductive loads is less than 1. Power factor is an important technical data of power system. Power factor is a coefficient to measure the efficiency of electrical equipment. The low power factor shows that the reactive power of the circuit used for alternating magnetic field conversion is large, which reduces the utilization rate of equipment and increases the power supply loss of the line. Therefore, the power supply department has certain standard requirements for the power factor of power users.
The electric loads such as motors, transformers, fluorescent lamps and arc furnaces in the power grid are mostly inductive loads. During operation, these inductive devices need to absorb not only active power from the power system, but also reactive power. Therefore, after installing the shunt capacitor reactive power compensation equipment in the power grid, it can provide reactive power to compensate the inductive load and reduce the reactive power provided by the inductive load on the power supply side of the power grid and transmitted by the line. Because the flow of reactive power in the power grid is reduced, the power loss caused by the transmission of reactive power by transformers and buses in transmission and distribution lines can be reduced, which is the benefit of reactive power compensation. The main purpose of reactive power compensation is to improve the power factor of compensation system. Because the electricity generated by the power supply bureau is calculated according to KVA or MVA, but the electricity fee is charged according to kilowatts, that is, the actual work is useful. There is a difference between the reactive power of the two, which is generally reactive power in KVAR. Most useless work is perceptual, that is, the so-called motors, transformers, fluorescent lamps ... almost all useless work is inductive, and capacitive work is very little. For example, the inverter is capacitive, and adding a reactor at the power supply end of the inverter can improve the power factor.
In DC circuit, voltage multiplied by current is active power. But in AC circuit, voltage multiplied by current is apparent power, and the part of power that can do work (that is, active power) will be less than apparent power. The ratio of active power to apparent power is called power factor, which is expressed by cosφφ. In fact, the simplest measurement method is to measure the phase difference between voltage and current, and the result is the power factor.