Experimental analysis on noise characteristics of surface-mounted permanent magnet synchronous motors

Abstract

Starting with the analysis on sound pressure level (SPL) spectrum of surface-mounted permanent magnet synchronous motors (SMPMSMs), the reasons for producing main peaks are investigated. According to different causes, different methods for reducing noise are proposed. Firstly, the SPL spectrum of SMPMSMs is obtained by experiment under the conditions of 2000 rpm rated speed, full load and 4 kHz switching frequency. Meanwhile, the frequencies corresponding to main peaks are found out. Secondly, the reasons for generating peaks in the SPL spectrum are researched from three aspects, namely, force sources, natural frequencies, coefficient of relative sound intensity. Then, on the basis of different causes for generating noise, different measures for decreasing noise are presented, namely, single cutting of two end rabbets of motor case in single clamping, waveform reconstruction of radial electromagnetic force density, enhancing of switching frequency, changing of natural frequency and decreasing of the lengthdiameter ratio of stator. Furthermore, the effectiveness for these methods is studied. Finally, a comprehensive method is proposed to decrease noise. The noise value of SMPMSMs is reduced by 4.7 dB(A) at the rated speed of 2000 rpm, full load and switching frequency of 4 kHz. In addition, the sharpness and loudness are respectively decreased by 0.522 acum and 6.97 sone at no load. The study provides references for the design of SMPMSMs with low noise.