Comparison of doubly salient permanent magnet machines with E-shaped and π-shaped stator iron core segments

Recently, double salient permanent magnet (DSPM) machines have been attracting more and more attentions due to the merits of simple and robust rotor and ease of permanent magnet (PM) heat management. In fact, the DSPM machine can be considered to be a combination of a switched-reluctance machine and stator PMs. In the conventional 3-phase DSPM machine, the stator salient teeth wound with 3-phase concentrated windings is composed of E-shaped iron core, between which the PMs are sandwiched in the stator yoke and the magnetization directions of these PMs are adjacent alternant in tangential direction. Since there are no windings and PMs in the rotor, the DSPM machine has the potential for use as a wide-speed motor or generator for lots of industry applications such as electric vehicle, direct-drive ship propulsion system, and direct-drive wind power conversion. In this paper, a novel 12/7 stator/rotor pole DSPM machine with Π-shaped stator iron core is proposed. Due to the symmetrical magnetic circuits, the balanced 3-phase no-load flux linkage and no-load EMF can be performed, thus achieving a smooth torque output. And the electromagnetic performances of the proposed machine in terms of flux-linkage, no-load EMF, cogging torque and torque capability will be compared with conventional 12/8 stator/rotor pole DSPM machine with E-shaped stator iron core.