Abstract：A fractional slot 32 poles /30 slots low speed and high torque permanent magnetic synchronous motor( FS-PMSM) is designed,and the fractional slot windings are wound down about four layers,breaking the conventional single and double winding methods. Analyzing the electromagnetic torque by finite element method,it is found that choosing appropriate slot potential offset angle can not only increase the electromagnetic torque to a certain degree and can effectively reduce the torque ripple. Considering the motor torque performance and sinusoidal flux density of air gap,the structure of rotor poles was optimized with the method that combining Nd Fe B and ferrite permanent magnet to reduce the consumption of Nd Fe B. With two permanent magnet materials combined in the rotor,can decrease harmonic components in electromotive force. In the two-dimensional dynamic simulation of motor,the results show that the design is reasonable. It can exhibit good performance,and has a good reference value to the design and optimization of this kind of motor.

Keyword：fractional slot;low speed and high torque permanent magnetic motor;four layers winding;optimization of magnetic pole;finite element;