Rotor Design for Reducing the Switching Magnetic Noise of AC Electrical Machine Variable-Speed Drives

This paper is focused on the analysis of the acoustic noise of the magnetic origin emitted by ac electrical machine variable-speed drives. First, the principle of noise generation is presented as well as the method for taking into account the effects of the current harmonics on noise generated by the pulsewidth modulation supply. The experimental results for noise and vibrations are then presented. Afterward, the elements of the per-phase equivalent circuit for higher harmonic orders are identified. They show that usual assumptions to characterize that circuit are not applicable for high-frequency harmonics. The originality of this paper concerns the rotor design: A practical procedure to diminish the acoustic noise due to the switching is defined from the per-phase equivalent circuit. It is also shown that this design makes it possible to increase the machine efficiency.