Torque ripple minimization technique in fractional-slot PM brushless machines

This paper presents a technique to reduce torque ripple in a fractional-slot PM brushless machine. A 12-slot/10-pole machine equipped with various stators design is the subject of investigation. A better torque performance at rated condition is desirable when additional permanent magnets are inserted on the stator part. The design optimization process on motor topology is performed in order to obtain the best torque performance. It is shown that significant reduction of torque ripple is achieved without losing the desired average torque. The influences of the proposed stator design on the back-EMF, output torque and cogging torque are analysed and compared with the initial machine design.