High precision calorimetry for the measurement of the efficiency of induction motors

Calorimeters are used to measure directly the loss in electrical machines operating under various load conditions. This paper examines experimental errors resulting from calorimeter design and from operating procedures. The techniques of minimising these errors used by previous researchers are reviewed. An improved technique for obtaining high accuracy in the measurement of power loss is discussed based on two generations of a calorimeter. The performance of these designs is presented with the first providing an accuracy of 0.5% and the second better than 0.2% in measurement of total loss at the 30 kW level.