Reactive power, many electrical equipment is based on the principle of electromagnetic induction, such as distribution transformers, motors, etc., they all rely on the establishment of alternating magnetic field in order to carry out energy conversion and transmission. The electrical power required to establish an alternating magnetic field and induce magnetic flux is called reactive power. Therefore, the so-called "reactive power" is not "useless" electrical power, but its power does not translate into mechanical energy and thermal energy; therefore, In addition to the need for active power in the power supply system, reactive power is also required. Both are indispensable. The reactive power unit is Var.