Optimization of split ratio to design the PM brushless DC motor

The split ratio of the permanent magnet motor is one of the most important design parameters. It can not only influence the motor electrical torque and efficiency, but also can influence the motor thermal behavior. According to the high torque, short duty permanent magnet brushless motor, the thermal behavior should be investigated carefully. In this paper, the influence of the split ratio on the motor characteristics is investigated by field and circuit coupling finite elements analysis firstly. Then the influence of the split ratio on the motor thermal behavior of is analyzed, emphasis on the high torque short duty operation. The optimal design results are verified experimentally.