Transformers are rated in apparent power (kVA or MVA) because their thermal limits depend on current and voltage together, regardless of load power factor. Copper losses are proportional to current and iron losses mainly to voltage. The transformer cannot “know” whether the load is inductive or resistive, it only experiences current and flux. Rating in kVA lets the same transformer serve loads with different power factors within its thermal capability. Real power in kW or MW depends on both the transformer kVA rating and the actual power factor of the connected load.