Analytical Calculation and Optimization of the Segmented-Stator Dual-Rotor Axial Flux Permanent Magnet Motors

The segmented-stator dual-rotor axial flux permanent magnet motor (AFPMM) in this article adopts two-segment Halbach permanent magnets (PMs) in the rotor and soft magnetic composite materials in the stator core, so it has the advantages of high torque density and high efficiency. This article proposes an optimization method for AFPMMs combining analytical optimization and nonlinear optimization, based on the analytical calculation of the magnetic field and electromagnetic performance. To realize analytical calculations, the AFPMM is regarded as the superposition of equivalent linear PM motor slices at different radii. The magnetic field is calculated using the slotless 2-D equivalent model and the slotted air gap relative permeability. Compared with finite-element analysis (FEA), the analytical calculation of the electromagnetic characteristics has acceptable accuracy and faster speed. The multiobjective optimization program for the AFPMM aims at lighter motor mass and lower loss. In analytical optimization, the expression of the optimal axial magnetization coefficient of the two-segment Halbach array and the expression of the minimum rotor core thickness is deduced to improve the optimization speed and results. Then, the nonlinear optimization algorithm is used to solve the multiobjective optimization problem.