An Improved Magnetic Equivalent Circuit Method for Segmented-Halbach Axial-Flux Permanent Magnet Machines

Much attention is paid to axial-flux permanent magnet (AFPM) machines due to the compactness and high torque density. However, the finite-element method (FEM) for AFPM machines will cause a large computational burden during simulation. Thus, this article proposes an improved magnetic equivalent circuit method (MECM) to predict the performances of segmented-Halbach AFPM machines, which can consider the different magnetization directions of Halbach PMs. A magnetic circuit is built in the whole machine. Besides, the air gap is treated as a slide layer to avoid the additional models for position-dependent permeances. Then, the predicted performances are compared with those calculated by FEM and measured in an experiment. As a quasi-3-D analytical method, it predicts the same air-gap flux density as the FEM. The only errors are due to the serious flux leakage caused by opening slots. The predicted back electromotive force (EMF) is consistent with the measurement in the experiment. The electromagnetic torque is affected by the errors of air-gap flux density, which results in large ripples. However, the trend of torque with current coincides with the measurement. It means that the proposed MECM is effective for the segmented-Halbach AFPM machine.