Noise in Electric Motors: A Comprehensive Review

Abstract

Electric machines are important devices that convert electrical energy into mechanical energy and are extensively used in a wide range of applications. Recent years have seen an increase in applications where electric motors are used. The frequent use of electric motors in noise-sensitive environments increases the requirements placed on electric motors intended for these applications, especially when compared to electric motors commonly used in industrial applications. This paper provides a comprehensive review of electric motor noise. Firstly, a brief introduction to noise is given. Then, the sources of electromagnetic noise and vibration in electric machines, including mechanical, aerodynamic and electromagnetic factors, are presented. Different methods such as analytical, numerical and semi-analytical for calculating electromagnetic force, natural frequencies and noise are also analyzed. Various methods for noise reduction are presented, including skewing, stator and rotor notching and slot opening width. Finally, noise measurement standards and procedures are described.

Noise and vibration modelling of Permanent Magnet Synchronous Motors - a review

“…Mechanical vibration and noise in electric motors have three main sources [5], [8], [10], [14] • Mechanical noise: originated by the mechanical components of the motor such as fasteners, rotating parts like bearings and shaft. Noise associated to rotor dynamics includes both lateral and torsional dynamics [15].…”

“…This is the main source of vibration that is deeply analysed in the paper. Concerning electromagnetic excitation, Remus [5] identifies different forces or moments that generate noise and vibration iron magnetic saturation: it causes a distortion of the magnetic flux distribution [20] -Harmonics in motor voltage supply: harmonic contribution introduced by PWM (Pulse Width Modulation) have influence on electromagnetic forces rotor-stator eccentricity: a small variation in airgap cylindricity can lead to large differences in the resulting harmonics [8] The noise sources highlighted by Remus [5] summarize all the major contributions of motor-related vibrations. Along the paper, the noise generated by electromagnetic forces will be studied in detail.…”

“…Especially in industrial applications, a weighting function is often applied to acoustic data to better simulate human-perceived loudness. Such an approach is adopted for the analysis of acoustic emission in electric machines as well [8], [21]- [24], [28], [130]. The common filter is the "A-weighting" function, for which the resulting data is defined as dB(A).…”

“…Several authors have published review papers concerning NVH of electric motors. A general review on the noise in electric machines is proposed by Gonzalez et al [8]. Various methods for the noise reduction, which will not be the subject of the current paper, are presented.…”