What is the rating used to rate a Transformer?

Question

Question

This question was previously asked in

RRB ALP Electronics Mechanic 23 Jan 2019 Official Paper (Shift 3)

Answer 1

Explanation:

Transformer voltage comes into play in iron losses and the current is used to calculate copper losses.
Thus the transformer ratings consist of both voltage and current and thus the ratings are expressed in kVA.

kW is Working Power also known as Actual Power or Active Power or Real Power. It is the power that powers the equipment and performs useful work.
Active power is measured by kW or MW meter.
KVAR is Reactive Power also known as watt less power. It is the power that magnetic equipment (transformer, motor, relay e.t.c.) needs to produce the magnetizing flux.
Reactive power is measured by kVAR or MVAR meter.
kVA is Apparent Power. It is the vectorial summation of kVAR and KW.
Apparent power is measured by kVA or MVA meter.