Why are transformers rated in kva but motor in Kw ?

Answer:

Transformers are rated in kilovolt-amperes (kVA) because their primary function is to transform voltage levels while maintaining the apparent power (volt-amperes). Apparent power is the combination of real power (measured in kilowatts, kW) and reactive power.

Motors, on the other hand, are rated in kilowatts (kW) because their primary function is to convert electrical power into mechanical power. The rating reflects the actual power consumed by the motor to perform work, which is the real power.

In summary, transformers deal with the transformation of voltage and maintain apparent power, while motors convert electrical power into mechanical power, and their rating reflects the real power consumed.