Calorimetric measurement of variable-speed induction motor

Accurate measurement of power losses of high efficiency motors is difficult with the input-output method. In the calorimetric method, the power losses are measured directly rather than using the power difference between the electrical input power and mechanical shaft power. This paper describes a practical calorimetric system suitable for measuring motor losses. A 37 kW induction motor losses with sinusoidal and pulse-width-modulation supplies is presented.