Individual and global optimization of switched flux permanent magnet motors

With the aid of genetic algorithm (GA), global optimization with multiple geometry parameters are feasible in the design of switched flux permanent magnet (SFPM) machine. To investigate the advantages of global optimization over individual one, which has been used extensively for the design of SFPM machines, the comparisons between two approaches are carried out at the fixed copper loss and volume. Little difference may be achieved in the produced torque although the sequence is important in the individual parameter optimization. According to the obtained global optimization the performance in machines having two types of stator and rotor pole combinations, i.e. 12/10 and 12/14, are compared, and higher torque is exhibited in 12/14 SFPM machine. Finally, this paper also demonstrates that global optimization with the restriction of same pole width, magnet thickness and slot opening can maximize the torque density without significantly sacrificing other performance, such as cogging torque and overload capability.