Multilevel Optimization Design for a Flux-Concentrating Permanent-Magnet Brushless Machine Considering PM Demagnetization Limitation

The flux-concentrating permanent-magnet (FCPM) machine with two V-shape magnet pieces in one stator pole has attracted considerable attention due to its excellent torque density and permanent magnet (PM) usage efficiency, whereas the torque ripple of the FCPM machine is usually high. This article aims to make a multiobjective optimization design for the FCPM machine. The optimization process is divided into three steps for different optimization objectives on two sets of geometric variables at different operation conditions. The simulated results show that the output torque of the optimized FCPM machine is increased significantly while the torque ripple has been decreased greatly. Finally, the open-circuit field distributions, the output torque, the torque-speed characteristics, and PM demagnetization of the optimized FCPM machine are investigated considering different PM shapes and PM temperature rise, which indicates that the optimized FCPM machine has favorable torque characteristics, speed range, and antidemagnetization abilities.