Kvar is equal to what?

Answer 1

kVA is the unit for apparent power. Apparent power consists of active and reactive power. Active power is the share of the apparent power which transmits energy from the source (generator) to the user. Reactive power is the share of the apparent power which represents a useless oscillation of energy from the source to the user and back again. It occurs when on account of some »inertia« in the system there is a phase shift between voltage and current. This means that the current does not change polarity synchronous with the voltage. But the heat generated in a winding as well as the eddy current losses generated in a transformer core depend on the current only, regardless of whether it aligns with the voltage or not. Therefore the heat is always proportional to the square of the current amplitude, irrespective of the phase angle (the shift between voltage and current). So a transformer has to be rated (and selected) by apparent power. We define "complex power" as voltage times current (V*I), and thus the unit for power is the Volt-Amp (VA). When a circuit contains non-resistive elements (such as Transformers), there is a component of power called "reactive power", which is power that is transmitted as a result of energy stored in inductors and capacitors. Reactive power does no useful work. Complex power is the sum of reactive power and real power (power which does work). When only real power is considered, the unit of power is the Watt. Transformers are rated in VA and not W because heat generated by electricity flowing through a conductor is proportional to the current flowing through the conductor. Although reactive power does no work, the current exists nonetheless and must be accounted for when selecting the proper sized wiring.