Analytical Calculation for Magnetic Field in Spoke-Type Permanent Magnet Machines Based on a Rotor Magnetic Potential Model

In this article, the rotor magnetic potential (RMP) model of spoke-type machines is proposed, which can accurately describe rotor surface magnetic potential distribution. No-load and load magnetic fields are calculated by using the proposed RMP model. In order to accurately establish and solve the RMP model, the magnetic field in the machine is divided into the d-axis magnetic field and the q- axis magnetic field. Then, corresponding d- and q-axis RMP models are proposed, which can consider the saturation of the bridge region and the dq-axis cross-coupling. The unknown parameters in d- and q-axis RMP models are then obtained using simple lumped magnetic circuit (LMC) models. Furthermore, the total RMP model can be obtained by superimposing the above d- and q-axis RMP models. The modeling process proposed in this article is intuitive and straightforward, and it has fewer variables to be solved. Moreover, the proposed method does not need to consider the change of the relative position between the stator and rotor caused by rotor rotation. Finally, the FEA is used to validate the validity of the proposed method.