Analytical determination of optimal split ratio for high-speed permanent magnet brushless motors

Split ratio is an important parameter for permanent magnet brushless motors (PMBLM) since it have significant influence on torque and loss. The split ratio of low-speed PMBLM has been optimized analytically in existing papers, while the iron loss is neglected. However, the iron loss in high-speed PMBLM can not be neglected. The split ratio and the maximum flux density in the stator iron is relate to both the copper loss and the iron loss closely. The split ratio, togerther with the maximum flux density in the stator iron, is optimized for maximum torque. An analytical model to determine the optimal combination of the split ratio and the maximum flux density in the stator iron for high-speed PMBLM is proposed in this paper. The analytical results are verified by finite element analysis.