Recently, permanent magnet synchronous motors (PMSMs) have been widely used in the industry owing to their various advantages, such as high-speed operation, high efficiency, and compact design. However, PMSMs have the drawback of noise and vibration, which is caused by local force generated by the interaction between the stator and rotor magnets having high magnetic energy, significantly affecting the machine performance. Moreover, these vibrations and noises cause problems, such as eccentricity, bearing failures, and misalignment of the PMSM. Therefore, it is important to identify which electromagnetic sources actually affect vibration and noise.
Electromagnetic vibration sources can be divided into two types: electromagnetic force and torque pulsations. Previous studies have shown that vibration characteristics are improved by a decrease in each of the electromagnetic vibration sources, and it is related to the noise on PMSM through a interaction. However, it does not clarify the influence of each source.
Thus, to analyze the influence of each source, in this study, we derived the dominant model of the pole/slot combination for each electromagnetic vibration source. The analysis and prototype model used FEM tools for the electromagnetic excitation analysis. The derived pole-slot combination is the 8-pole/9-slot and 8-pole/12-slot. The characteristic analysis results of the electromagnetic excitation are as follows. The torque pulsation, as torque ripple and cogging torque, is lower in the 9-slot model than in the 12-slot model. However, the unbalanced magnetic force in the 9-slot model is higher than that in the 12-slot model. In the 9-slot model, not only is the distribution of force density uneven, but also the magnitude of the unbalanced magnetic force is large. Thus, we analyzed the influence of each vibtation source through experiments and electromagentic-mechanical analysis by comparing the analysis results of two different fractional pole/slot combinations.
The electroamgnetic and mechanical analysis results, and experimenal set, measurements of the PMSM will be presented in more detail in the full paper.