A Novel Structure of Doubly Salient Permanent Magnet Machine in Square Envelope

Abstract

In conventional 12/8-pole doubly salient permanent magnet machines (DSPMMs) with outer type flux focusing method, the relatively thicker stator back iron next to magnets results in smaller slot area. This paper proposes a novel structure of DSPMMs in square envelope. In such structure, the thickness of stator back iron is roughly uniform and the magnets are inserted from the corners of square envelope to the slots. In addition, the tooth tips of all stator teeth are kept uniformly distributed on the stator bore while the tooth bodies of side stator teeth next to magnets are bended by an angle from the corresponding tooth tips. Meanwhile, the side stator teeth size should be optimized to achieve the balanced slot areas. The main parameters of the proposed and conventional structures with outer type flux focusing method are scanned for higher torque under the fixed copper loss and square envelope. The comparison between two structures shows that the proposed structure can achieve larger slot area, lower torque ripple, and 11.5% higher average torque with the same magnet usage.