Analysis of rotor eddy current losses in slotless high-speed permanent magnet machines

Rotor eddy current losses are one of the main reasons of permanent magnet demagnetization in high-speed permanent magnet machines. In this paper the rotor eddy current losses of high-speed permanent magnet machines with different slotless windings have been analysed. The analysis of the losses was performed using 2D and 3D analytical models. In the study, test machines with different windings and the same torque production capability have been analysed. Presented paper shows the dependency of rotor eddy current losses on sine- and square-wave PWM supply voltages and rotor sleeve properties. Several recommendations for reduction of rotor eddy current losses in high-speed permanent magnet machines are given.