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 yokeless and segmented armature (YASA) is presented in this paper. Firstly, 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 two machines are 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 materials, thus improve the utilization of magnets and reduce the costs.