Power losses generally take the form of hysteresis loss, eddy current loss, coil electrical resistance loss, and mechanical friction. The losses that are discussed here are the losses in the magnetic material, called core loss Pc, which includes the hysteresis loss PH and the eddy current loss PE. Data from U.S. Steel for the typical 60-Hz core loss in steel motor-lamination materials (M19 through M45) indicates that approximately 67 percent of the core loss is due to hysteresis effects and 33 percent of the core loss is due to eddy current effects. The published core loss properties of magnetic materials show only the total core loss. Therefore, the hysteresis loss and the eddy current loss can be approximated as follows. The units of core loss are in power per unit mass, for example, watt per kilogram.
Total core loss PC, W/kg
FIGURE 1.29 Permanent magnet reluctance model for the system in Fig. 1.26.