Novel Selection of the Slot/Pole Ratio of the PMSM for Auxiliary Automobile

For environment protection, auxiliary machines of automobiles are changing to electric machines. Especially, electric power steering (EPS) has higher efficiency than hydraulic power steering. An EPS motor needs smooth rotation without torque ripple and cogging torque. The surface permanent magnet synchronous motor (SPMSM) is used for the EPS motor because it has high efficiency and low loss torque. It is known that changing the slot and pole combination of the SPMSM can reduce the cogging torque. In this paper, the cogging torque and torque ripple were examined for different slot and pole combinations of SPMSM. The result showed a minimum cogging torque existed for a specific slot and pole combination