Question

Give an example why the power rating of transformer is expressed in kva but not in kw?

Answer 1

That's why the Transformer Rating may be expressed in kVA,Not in kW. Copper losses ( I²R)depends on Current which passing through transformer winding while Iron Losses or Core Losses or Insulation Losses depends on Voltage. That's why the Transformer Rating may be expressed in kVA,Not in kW.