Electromagnetic and mechanical analysis of high speed SPM rotor with copper shield

Abstract

For high-speed applications, the surface-mounted permanent magnet (SPM) machine is preferred due to its high torque density and efficiency. However, induced eddy currents in the rotor conductive parts result in a loss of efficiency and rotor heating. Therefore, several methods to reduce such losses have been proposed in the literature including copper shielding. In this paper, a high-speed SPM machine rotor with a copper shield is designed and investigated both electromagnetically and mechanically. Several quantitative investigations including placing the copper sheet around the retaining sleeve or magnets, different copper sheet and airgap thicknesses, different retaining sleeve materials, different harmonic contents in the current waveform, i.e. pulse amplitude modulation (PAM) and pulse width modulation (PWM) generated waveforms, and different frequencies and current levels are reported. Additionally, a mechanical analysis investigating possible failure modes of the rotor with the copper sheet is reported.

Electrical Machine Rotor Shielding for Low Cost Electrical Drive

“…The torque production of the SPM machine with copper shield was investigated in [11] emphasizing on the torque produced by the copper shield. Finally, a preliminary mechanical analysis as well as feasibility study of the copper shield taking in consideration the copper shield location, current harmonic, sleeve material and rotor speed was reported in [12].…”