Study on the Influence of a Combined-Halbach Array for the Axial Flux Permanent Magnet Electrical Machine With Yokeless and Segmented Armature

To increase torque density, a combined-Halbach array for the axial flux permanent magnet machine (AFPMM) with a yokeless and segmented armature (YASA) is presented in this article. First, the YASA machine models with conventional axial magnets and combined-Halbach array magnets are established by using 3-D finite-element method (FEM). Then, the torque, torque per magnet-volume, and no-load back electromotive force (back EMF) are calculated, and the performance of the two machines is analyzed and compared. It is demonstrated that the combined-Halbach array can improve the torque density of the machine and the utilization rate of the magnets. Finally, the combined-Halbach array rotor is optimized, where the rotor with unequal-thickness magnets is established, and its torque density is calculated under different thickness. The results show that the combined-Halbach array with unequal-thickness magnets can decrease the amount of permanent magnet (PM) materials, thus improving the utilization of magnets and reducing the costs.