A Novel Structure of Doubly Salient Permanent Magnet Machine

Because permanent magnet (PM) penetrates into the slot, three phases of doubly salient PM machine (DSPMM) employing inner type flux focusing method have imbalanced slot areas in the conventional design. To enhance its torque performance, this paper proposes a novel structure, of which the side tooth next to the PM has two parts. Its tooth body is parallel to the middle tooth between two PMs, while the tooth-tips of all teeth are still kept uniformly distributed on the stator bore. The position of the tooth body of side tooth is optimized to have the balanced slot areas. The main parameters of the novel structure together with two conventional structures are globally optimized under the fixed copper loss and stator outer radius. Their performance comparison shows that by using the proposed structure, the average torque is increased by 25%-31%, while the ratio of torque to cross-section area is increased by 17%-25%.