Sleeve design of permanent-magnet machine for low rotor losses

In this study, a novel rotor sleeve for permanent-magnet (PM) machines equipped with fractional-slot concentrated-windings (FSCW) is proposed. With the newly designed rotor sleeve, the rotor eddy-current (EC) losses are significantly reduced, and the torque density of the machine is improved. First, the rotor EC losses of a surface-mounted PM machine with the sleeve are analyzed. Meanwhile, the sleeve EC barriers and PM segmentation technologies for the suppression of the rotor EC losses are evaluated. Subsequently, an FSCW PM machine with the newly designed sleeve is proposed and optimized for a given set of specifications. Its electromagnetic and mechanical performances are evaluated by the finite element method (FEM). Finally, three assembling methods are presented and assessed comprehensively in terms of their merits and drawbacks.