Influence of rotor configuration on iron and magnet losses of fractional-slot IPM machines

Abstract

This paper investigates the influence of different permanent magnet (PM) rotor configurations, viz. the I-shape and V-shape interior PM (IPM) and surface-mounted PM (SPM), on the iron and magnet losses of the fractional-slot PM machines under both constant torque and flux weakening operation. The investigation shows that generally fractional-slot IPM machines have greater iron loss than SPM machines. However, the magnet loss of such topology is smaller, since their magnets are shielded by the rotor iron. The V-shape IPM machine exhibits the lowest magnet loss, because each magnet pole is formed by two pieces. Also, the magnet segmentation in both IPM and SPM machines can significantly reduce the magnet loss. Relatively this reduction is more significant in the IPM machine.