Hysteresis Loss in Ferrite Permanent Magnets in Rotating Electrical Machinery

In this paper, hysteresis loss in magnetic poles of electrical machines with ferrite permanent magnets is studied. A vibrating sample magnetometer is used to observe the hysteresis behavior of three distinct commercial ferrite magnet grades. The measurement results indicate the presence of additional magnetic phases with reduced coercivity in the samples under study. These phases can act as an additional source of loss in ferrite magnets. A new modeling concept is introduced to simulate the hysteresis behavior of the ferrite magnet grades in the second and first quadrants of the intrinsic BH plane. Finite-element-calculated magnetic field distribution is used as an input for the analytical model to determine the hysteresis loss in the magnets of two distinct permanent magnet machine designs. The results indicate that some hysteresis loss in the ferrite permanent magnet magnetic poles of electrical machines may occur, but it plays a minor role in practice.