An Efficient Semi-Analytical Method for Noise Improvement in PM Machines Based on Main Vibration Mode and Dominant Excitation Force

The 3-D finite-element-analysis (FEA) is regarded as the most accurate method to calculate the vibration and noise in machines; however, not only is it time-consuming, but also its accuracy depends heavily on the setting of material and boundary properties. This article, thus, presents an efficient semi-analytical method for improving the electromagnetic noise in permanent-magnet (PM) machines. First, based on the analysis of noise spectrum, the major harmonics of electromagnetic noise are determined. Second, the main vibration mode of the stator is identified by combining the noise harmonics with the structure characteristic of the machine. Then, through the derivation and analysis of radial force, the specific spatial and temporal harmonic of radial force is considered to be the dominant excitation source of noise. Finally, the noise is improved by weakening the dominant excitation force and modifying the resonance speed of the machine. This proposed method does not need to directly calculate the noise using the 3-D model. It can save a considerable amount of computing resources and shorten the project period. The example validates that it is feasible and has reliable accuracy.