Reduction of Vibration and Acoustic Noise in Fractional-Slot Concentrated-Windings Permanent-Magnet Machine.

摘要

Due to the advantages of high efficiency, high power density, and high fault-tolerant capability, the fractional-slot concentrated-windings permanent-magnet (FSCW-PM) machines have received increased attention. [1]. However, the abundant harmonics in FSCW-PM machines will produce low-order radial electromagnetic force, thus aggravating the vibration and acoustic noise performances [2]. Therefore, many magnetomotive force (MMF) harmonic reduction techniques were proposed [3], but their abilities to reduce the low-order radial electromagnetic force were relatively poor. The purpose of this paper is to analyze the generation mechanism of low-order radial electromagnetic force from different magnetic field components, and a new design will be proposed to reduce the vibration and acoustic noise of FSCW-PM machines. New design Due to the interaction of tooth harmonics and fundamental magnetic field, the lowest order radial electromagnetic force will be generated in FSCW-PM machine, thus resulting in vibration and acoustic noise. Fig. 1 compares the stator structure of two existing and proposed machines. In the proposed unequal tooth stator, the angle of two adjacent opening-slots has been designed to control the MMF amplitude of each harmonic component. It should be noted that the fundamental wave keeps constant with the existing one, so the output performance is unchanged. However, the tooth harmonic is weakened effectively. Results In order to verify the proposed machine, the finite-element method and acoustic boundary-element method are employed to evaluate vibration and noise performances. The MMF and radial electromagnetic force between the existing and proposed machines are compared in Fig. 2 and 3, respectively. The proposed machine can effectively weaken the tooth harmonics and the radial electromagnetic force which plays a significant role in the vibration and acoustic noise of FSCW-PM machines. Fig. 4 compares the vibration spectrum between the existing and proposed machines. It can be seen that the proposed one has 12% lower vibration than the existing one. Finally, the sound power level spectrum of the proposed FSCW-PM machine is given in Fig. 5. Resonance does not occur because of the large difference between the electromagnetic force frequency and the modal frequency.