Improvements to precision measurement of stray load loss by calorimeter

Induction machine stray load losses have always been difficult to determine with precision, so it has been difficult to refine methods of their prediction. This paper provides further description of and results from an improved form of air-cooled calorimeter used to measure the stray load losses of induction machines. Losses may be determined for either loaded or unloaded operation. By adjusting the set mass flow rate of coolant, the calorimeter is capable of measuring losses ranging from 1.5 kW to 6 kW full scale. Absolute errors are 5W in measurement and resolution is to 0.1W with averaging. However, it is the total machine loss that is measured accurately. Stray load loss is then evaluated by loss segregation. This again imposes a particular "loss model" which may not be correct but is directly comparable to international standards.