Study on Electromagnetic Vibration Analysis Process for PM Motors

Conventional electromagnetic vibration analysis methods mainly focus on the spatial harmonic components of the radial force density. Because they do not consider time harmonics, they cannot consider the frequency component of electromagnetic vibrations. Therefore, they are not suitable for optimally designing motors by considering electromagnetic vibrations. In this paper, we propose a process to analyze electromagnetic vibrations considering time harmonics as well as spatial harmonics. For the calculation of the magnitude of electromagnetic vibrations with respect to the frequency, the natural frequency of the circumferential mode was calculated by simplifying the shape of the stator core. The natural frequency increases as the order of the stator circumferential mode increases. Using the vibration equation, it was confirmed that electromagnetic vibrations decrease as the natural frequency increases. For analyzing the correlation between the vibration source and the electromagnetic vibrations, the radial force was separated into time and spatial harmonics, and the contribution of each harmonic component to the vibration was calculated. The results revealed the harmonic components that have the most significant influence on the vibrations. Then, using the proposed process, the vibration performance, as well as the electromagnetic performance, can be used as an objective function to design motors. To verify the validity of the proposed process, the vibrations of conventional and proposed motors were analyzed. Finally, a prototype was manufactured, and its vibrations were tested using the proposed process.