Analysis and Reduction of Eddy Current Losses in High-Speed Solid Outer Rotor Induction Machine

This paper studies the influence of the stator winding and rotor design on the parameters of a 1 kW, 30 000 rpm high-speed solid axially slitted outer rotor induction motor. The main focus is set on the modifications of the stator and rotor for the motor to achieve a high torque with low eddy-current losses in the rotor. The eddy-current losses are calculated separately for each harmonic with a modified virtual magnet harmonic model methodology. The presented method removes the virtual magnet and applies a previously determined harmonic of the flux density directly on the boundary in the middle of the air-gap. Resulting data are then used show the main source of eddy-current losses in the machine and the short- pitch winding and radial rotor grooves are used to specifically reduce those losses.