Split Yoke-Permanent Magnet Biased-Flux Motor

Abstract

In this paper, a split tooth biased-flux slot permanent magnet motor is proposed with the aim of increasing the torque density without affecting the torque ripple. Two sets of magnets are located in the stator; one in the yoke and one in between the stator slots. The shape and location of the magnets is investigated by splitting the sets of magnets into individual blocks. The split-PM structure is able to increase the flux concentration of PMs in the air-gap and it is mathematically proven to increase the flux density. Simulation shows that the cogging torque is reduced due to the flux bridges in the stator yoke and the increase in the flux density occurs only if the armature windings are excited. The split and non-split magnet versions of the biased-flux slot PM motor are comprehensively compared. The comparison shows that while keeping the geometrical, electrical, and magnetic parameters (like PM volume, core volume, armature turns, current density, and PM material) the same for both structures, the split version can react 19% higher torque, with a lower cogging torque, but a higher torque ripple. The manufactured prototype validates the analytical and simulation results.