# Why Generator & Alternator rated in kVA. Not in kW?

DWQA QuestionsCategory: Alternator & Synchronous MotorWhy Generator & Alternator rated in kVA. Not in kW?

The power √3 VL IL Cos φ delivered by the alternator for the same value of current, depends upon p.f. (Power Factor=Cos φ) of the load. But the alternator conductors are calculated for a definite current and the insulation at magnetic system are designed for a definite voltage independent of p.f. (Cos φ) of the load. For this reason apparent power measured in kVA is regarded as the rated power of the alternator.

Generator and transformer are rated in KVA becoz at that time we dont know the consumer power factor as we know that the (KW= KVA X Cos Phi) as we know the power factor we have ratings in KW and on the other hand motor has defined power factor and the rating has been mentioned in KW for example if we have transformer of rating 50KVA this rating of transformer is its apparent power that is KVA if we multiply the same withh the power factor 0.85 we will get the real power that is KW.
KW= KVA X Cos phi
KW = 50 X 0.85
KW= 42.5KW