Design optimization of Outer-Rotor Surface-Mounted Permanent Magnet Synchronous Machines Using Trapezoid Permanent Magnet Shape

This paper investigates the performance of an outer-rotor surface-mounted permanent magnet (OR-SPM) synchronous machine designed for integrated starter-generator (ISG) systems. The electromagnetic characteristics of OR-SPM machines using different PM shapes are analyzed and compared, including no-load behaviors, output torque, and torque ripple. This paper introduces a novel trapezoid-shaped PM for OR-SPM, distinct from the conventional ring-shaped PM. The optimization process employs a multi-objective genetic algorithm (MOGA) to optimize the geometrical parameters of the trapezoidal-shaped PM. The goal is to maximize the output torque while simultaneously minimizing the volume of PM, thereby enhancing the overall utilization of PM. Finite element analysis (FEA) is conducted on the two machines with the same rotor size and stator operating at the same rated current to validate the feasibility of the trapezoidal PM machine. The results demonstrate that the trapezoidal shape design effectively increases the output torque compared to the ring-shaped PM machine.