Why transformer rating in KVA instead of KW?


Any device is rated depending on losses of the machine. In a transformer the losses are iron losses which depends on voltage and copper losses which depends on current so there are no losses which depend on power factor hence transformer is rated in KVA.

There are 2 losses in transformer. One is copper loss which depends on current and the other is iron loss which depends on voltage. These two factors are not affected by the power factor. This is why transformers are rated in KVA and not KW. Single phase KVA = Amps x Volts/1000. Single phase KW = Amps x Volts x pf/1000. 3 phase KVA = Amps x Volts x 1.73/1000. 3 phase KW = Amps x Volts x 1.73 x pf/1000

yes, there are two type of losses in transformer is that ohmic losses and core losses . ohmic losses due to transformer current and core losses due to transformer voltage. these losses are due to transformer voltage and current. and these losses not depends on load ie kw that’s the way its rating in kva…