Why a transformer is rated in kVA and not in kW??

Answer Posted / ashok bhatnagar

The current drawn by a transformer depends on the load
connected in the secondary. If the load cneected is a
resistive load the majority of current drawn is in pahse
with the supply voltage and transformer operates at near
unity power factor. In this case transformer supplies kw
nearly equal to its kva input. However if a inductive load
like motor is connected it draws lagging current and
operates at lower power factor. In this case trasformer
supplies lower kw as compared the kva drawn. Thus
powerfactor of a trasnformer depends on type of load
connected and hence it can not have defined kw rating. That
is why transformers are rated in KVA and not KW

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