Split Ratio Optimization for High-Speed Permanent Magnet Brushless Motors

The split ratio is an important design parameter for permanent magnet (PM) brushless motors. It has been optimized for low speed PM brushless motors whose iron loss can be neglected in existing papers. However, the iron loss of high-speed PM brushless motors can't be ignored, thus a new analytical model should be built to solve this problem. Split ratio is optimized with the goal of generating maximum torque for a given motor volume and loss constraint, and an analytical model to determine the optimal split ratio for high-speed PM brushless motor is proposed in this paper. The variation of the optimal split ratio with the loss constraint, flux density in the stator iron and speed is investigated. Finally, the theoretical analyses are verified by finite element analysis.