reactive power
reactive power:
see power, electricpower, electric,energy dissipated in an electrical or electronic circuit or device per unit of time. The electrical energy supplied by a current to an appliance enables it to do work or provide some other form of energy such as light or heat.
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Reactive Power
the quantity that describes the load created in electric equipment by the energy oscillations of an electromagnetic field in an AC network. The reactive power Q is equal to the product of the operating value of the voltage U and the current I multiplied by the sine of the angle of the phase shift Φ between them: Q = UI sin Φ. It is measured in vars. Reactive power is related to the apparent power S and the active power P by the expression 
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The reactive power consumed in electric circuits creates additional resistance losses, which are met by the expenditure of energy at power stations, and voltage losses, which degrade the voltage regulation conditions. In some electric installations, the reactive power may be substantially greater than the active power. This causes high reactive currents to develop and overloads the current sources. In order to avoid overloads and to improve the power factor of electric installations, the reactive power is compensated.