Analysis of the Electromagnetic Performance of Homopolar Inductor Machine Through Nonlinear Magnetic Equivalent Circuit and Air-Gap Permeance Function

Homopolar inductor machine (HIM) has a wide range of applications in the field of flywheel energy storage system and ship propulsion due to its merits of simple structure, brushless exciting, and low idling losses. However, the three-dimensional finite element method (3-D FEM) is mainly used to investigate the electromagnetic performance indexes of HIM due to its intrinsic 3-D flux density distribution, which is time-consuming. To facilitate the analysis of HIM, an analytical method (AM) is necessary, especially in the initial design stage. Hence, this article presents an AM for analyzing the electromagnetic performance of HIM. First, the structure and operation principle of HIM are illustrated. Second, the magnetic equivalent circuit of HIM is built considering the saturation of stator and rotor core. Third, the air-gap permeance function is obtained considering the affection of stator and rotor slots. Finally, the magnetomotive force, air-gap flux density, back electromotive force, inductances and electromagnetic torque of HIM are calculated, then validated by 3-D FEM and corresponding experiments. The results indicate that the proposed AM can provide reasonable results to estimate the electromagnetic performance of HIM, which would be helpful for the analysis of HIM.