Revision of the hysteresis and excess loss computation method as a means of improving the rotational loss estimate in induction motors

The paper evaluates the impact that the relationship between purely rotational and alternating losses has on the computation of core losses in induction motors. At frequencies other than 50 Hz, the analysis is simplified if statistical loss theory is considered, as discussed in the paper. The paper outlines a practical method of computation of hysteresis and excess losses when the rotation of flux is considered and loss data for these terms at 50 Hz are available. An imposed constraint is that the quantity of experimental loss data available for the motor designer is, in general, reduced. To deal with the problem, Kochmann general relationships for 36 NO grades, covering the main spectrum of electrical steel grades at 50 Hz, have been found to be helpful. An approach is proposed to convert these relationships, so that they can be fitted into the statistical loss theory. The results are validated using FEA and bench tests. As a conclusion, the loss estimate is improved in all cases, not incurring an overestimation with respect to bench results.