why designer use kva rating instead of kw in transformer
rating???????????????
Answer Posted / rudra
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 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.
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, Therefore the heat is always proportional to the square of the current amplitude, irrespective of the phase angle. So a transformer has to be rated by apparent power.
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