Quasi-3-D Analytical Method of Open-Circuit Magnetic Field for Yokeless and Segmented Armature Machine

This article presents an accurate and efficient quasi-3-D analytical method for the yokeless and segmented armature (YASA) axial flux permanent magnet (AFPM) machine. The proposed method takes into account the 3-D magnetic flux distribution, slotted effect, and end effect simultaneously. To facilitate the modeling of the YASA machine, the quasi-3-D method is utilized to transform it into a multislice linear machine. The linear machine is then modeled by the exact subdomain method considering the slotted effect, which eases the numerical computation using the elimination method compared with the conventional subdomain method. The scalar magnetic potential of the above subdomains is solved by applying boundary conditions, and the flux density distribution in the air gap is derived accordingly. To compensate for the flux density variation at the inner and outer radii owing to the end effect, the virtual equivalent linear model is adopted to construct an end-effect compensation function considering the slotted effect. Besides, the electromagnetic characteristics, in terms of flux linkage, back electromotive force, and cogging force, are derived based on the compensated flux density distribution in the air gap. Finite element analysis validates the accuracy and efficiency of the proposed analytical method. The proposed analytical method is generic and can be applied to other AFPM machines.