Enhanced harmonic injection for determination of harmonic loss in induction machines

This paper compares direct, by calorimeter, and indirect, by harmonic injection, methods for measurement of inverter induced, harmonic power loss across a range of induction motors from 1.1 to 30 kW. Techniques to obtain the necessary experimental precision are described. Comparisons between segregated losses for the machines operating on sinusoidal supplies show a link between iron loss and high frequency PWM induced loss. Iron loss is not a constant proportion of total loss for all machines so that neither is harmonic loss independent of machine design.