Model-Based Hysteresis Loss Assessment in PMSMs With Ferrite Magnets

Hysteresis losses in ferrite permanent magnets (PMs) of a rotor-surface-magnet (RSM) PM synchronous machine (PMSM) were studied by means of vibrating sample magnetometer (VSM) measurements, updated static history dependent hysteresis model (HDHM) and finite element analysis (FEA). Open magnetic circuit VSM measurement results were applied to determine the magnet intrinsic properties. The HDHM developed originally for electrical steel hysteresis modeling is adopted for ferrite PM material. FEA-based results for magnetic field strength in PMs of a tooth coil winding RSM PMSM under ideal sinusoidal and frequency converter supplies were used as input data for the HDHM and the hysteresis losses were calculated in the machine's magnets. Differently from NdFeB and SmCo PMs ferrite PMs do not seem to demonstrate significant hysteresis behavior. It was found that the hysteresis loss could be neglected in ferrite PMs in most PMSM designs if the magnet is fully polarized.