Why electrical equipment rated in KVA not in KW

The ratings of all electrical equipment are all rated in KVA or Kilo Volt Amp. However, the practical use is in KW. We can say it also that electrical equipment are rated in apparent power (KVA or VA) other than active power (KW or W).

Electrical equipment rated in KVA - the main reason

Electrical equipment rated in KVA – is due to the variety of power factor rating in consumer side. KVA is independent of power factor. The KW depends on Power factor of the consumer utility. 

The trend of electrical rating in terms of VA (volt amp), KVA (kilo volt amp), MVA (mega volt amp) is due to the variation in the consumer side. In consumer or user side, the electrical parameters are so varieties that a manufacturer cannot cope of to all these variation. So the safe side is to rate the equipment in KVA.

The main criteria of the consumer side is variation in power factor that is not predictable. Moreover, KVA rating has no terms or influence of power factor as it is the direct multiplication of voltage and current. On the other hand, the kW is calculated by power factor that a manufacturer cannot predict.

KW = V x I x (PF)

KVA = V x I

With KVA rating, we can get the rated value of voltage and current. Say a small motor rated as 2KVA, we can get that its maximum current is 5amp with 400volt.

Say a high capacity power plant alternator is rated by 12MVA, 0.80 power factor. We can get the MW value with simple calculation (12 x 0.80 = 9.6) that is 9MW. Therefore, we can get it that the KVA rating is not sufficient, we need the power factor also if it is applicable.