Why to use kva?

Answer 1

The kVA (kilovolt ampere) is the vector sum of real + reactive power in an AC circuit. The kW (kilowatt) is a measure of the real power in that circuit. Inherently, a circuit will not require only real power, but also reactive power. Thus kVA is a more meaningful value when considering sizing equipment (such as Transformers, bus work, breakers, etc.) because this equipment must be sized for the total current drawn, not just the real power usage.

Answer 2

kva is the term which is used without power factor kva = Voltage x Current(Amp.) and Kw= Voltage x current x power factor.when we use kva means power factor is not taken in to the account.and the effect or variation of power factor will not considard.

Answer

The volt ampere is used to measure the apparent power of a load, and is the product of the load current and the supply voltage. The watt is used to measure the true power of a load, and is the product of the load current, supply voltage, and the power factor of the load. Power factor can be any value from 0 to 1. So, the only time true power, in watts, can equal the apparent power, in volt amperes, is when the load's power factor is 1 -that is, when the load current is in phase with the supply voltage. For all other values of power factor, the true power will always be less than the apparent power. So, for the purpose of determining the current demand of any given load, it is the load's apparent power that represents the 'worse case' in terms of a load's current demand.