Simple non-linear magnetic analysis for three-phase hybrid stepping motors

Hybrid Stepping Motors(HBM) are one of candidate for direct drive motors and will be more attractive from the standpoints of higher torque capacity and efficiency by combining the rare-earth magnets. However, in general, since HEM have a grate number of small-teeth on the stator and rotor surface, the magnetic saturation in the teeth becomes severe with increasing flux-density in the air gap. In addition, the magnetic non-linearity makes the design of the motor more difficult. Although 3D-FEM is one of solutions for the magnetic non-linear analysis of HEM, a large amount of computation time is necessary. This paper presents a simple non-linear magnetic analysis of HBM for an assistant design tool of 3D-FEM. The equivalent magnetic circuit of the motor used in the proposed magnetic analysis is composed of the air gap permeance model between the stator and the rotor teeth which includes the saturable permeance tips in the teeth for considering the local saturation. The validity of the proposed analysis has been verified through the comparisons between the measured and the calculated electric parameters of 400W test motor which uses Nd-Fe-B magnet having a BH-product of 255kJ/m(3).