Transformer

Transforemer is a static electrical device which transfers electrical power from one circuit to another without having any connection. It works on the principle of Faraday's law of electromagnetic induction. Transfer of energy took place due to mutual inductance between the two circuits(windungs).

The figure shown here depicts the opeartion.

There are a few things related to the transforemer, most of the engineers don't know.

Ques: Why transforemer is rated in kVA whereas all other electrical equipments like motors, mixers, drill machines etc are rated in KW.

Ans: Tansformer is an energy(or power) transferring device, its not a load. Whereas all others are load (i.e. suppose to consume electrical power and convert it into useful work). The transformer is supposed to transfer electrical power from primary winding to secondary winding without consuming any power. Therfore the power factor during the load condition can not be defined. Actually the power factor on load of a transformer is considered to be same as that of its load. So in absence of self power factor, the rating of transformer is defined in kVA and not kW (= KVA*power factor)