Modeling and permanent-magnet shape optimization of an axial-flux machine

This paper proposes a modeling method for axial-flux permanent-magnet machine (AFPMM) based on a finite elements analysis, and achieves a shape optimization of AFPMM poles. To solve the questions regarding the modeling of AFPMM with surface-mounted PMs, an axial 3-D to radial 2-D finite-element transformation is proposed. A special analytical method for back-emf computation is also provided. The results related to 2-D finite-element analysis are presented and compared with the experimental ones, validating the proposed approach. The amount of space-harmonic content in AFPMM is a primary concern to the machine designer due to its impact on the AFPMM performances. These harmonics are directly related to the flux-density and mmf distributions in the airgap, which are mainly determined by the PM excitation. Therefore, the slotless machine is analyzed. The influence of design parameters on the total harmonic distortion (THD) and the methodology to reduce space harmonics by selecting the appropriate PM shape and size are also addressed in this paper. The space-harmonic analysis is carried out according to the variety of design parameters of the finite element models.