A Hybrid Analytical Model of Open-Circuit Air Gap Magnetic Field of Interior Permanent Magnet Synchronous Motor With Non-Uniform Air Gap Structure Considering Saturation Effect

The air gap magnetic field of the interior permanent magnet synchronous motor (IPMSM) with the non-uniform air gap structure is affected by both local non-linear magnetic saturation and the non-uniform air gap, while the non-uniform air gap structure further affects the degree of magnetic saturation. However, the existing methods cannot consider the effect of the non-uniform air gap on magnetic saturation and cannot calculate the tangential air gap magnetic field. In this paper, a hybrid analytical model is proposed. Firstly the non-uniform air gap is converted to the uniform air gap through the air gap segmentation. The open-circuit air gap magnetic field with the equivalent uniform air gap is calculated by the hybrid analytical method. Then the permeance correction factor that can account for magnetic saturation is obtained, and the air gap magnetic field is calculated. Moreover, the influence of non-uniform air gap on tangential air gap magnetic field and the slotting effect are considered. Finally, the correctness of the proposed model is verified by a back electromotive force experiment and a magnetic field measurement. The proposed model has high accuracy and calculation efficiency and can provide a reference for the non-uniform air gap design.