Just a note about power factor.
In a reactive circuit (one that has elements of inductive or capacitive reactance),the reactive power (kVAr) still has to be allowed for, even though it does no real work.
True power(kW), is the only component that does real work, this is dissipated in the resistive elements of the circuit.
Apparent power(kVA) is the product of RMS voltage and RMS Current, this is made up of both True and Reactive power.
Reduction of the reactive and Apparent power components, improves over-all power factor.
Just a note on the kVA rating of transformers, they are rated this way because the load that they supply, may have a variable power factor, depending up on what is connected to them.