Interior permanent magnet synchronous motors (IPMSMs) are widely utilized due to their high power density. However, noise and vibration issues are often encountered in these motors. While researchers have extensively investigated individual aspects such as noise, vibration, and heat generation in PMSMs, there has been a lack of comprehensive studies examining the interrelationships among these factors. In this paper, a novel approach is proposed for predicting vibration by considering the radial force in the air gap as the exciting force, while also accounting for the changes in the permanent magnet (PM) characteristics caused by heat generation during motor operation. The method involves decomposing and identifying vibration components associated with each vibration mode and predicting noise based on the sound radiation efficiency of each mode. By constructing a vibration map based on current and temperature at a specific frequency, the components most affected by current variations and PM characteristics can be identified. This allows for the proposal of design improvements aimed at reducing vibration. Furthermore, by comparing the vibration map with the noise map, it is confirmed that vibration serves as a source of noise and influences its generation. However, it is found that vibration and noise are not strictly proportional. Overall, a comprehensive analysis of the correlations between vibration, noise, and other factors in IPMSMs is presented in this study. The proposed method and findings contribute to the understanding of the complex dynamics involved and provide valuable insights for the design of quieter and more efficient motor systems.

Permanent magnet synchronous motors (PMSMs) having high power density and high efficiency are rigorously researched in various premium applications. Among PMSMs, many studies have been conducted on interior permanent magnet synchronous motors (IPMSMs) to improve torque ripple, but its accurate estimation is not straightforward. Therefore, a six-pole nine-slot (6p/9s) IPMSM is adopted as a base model due to its popularity in academia and industries, and other two pole/slot combinations (8p/12s and 10p/15s) are additionally selected to investigate the influence of a pole/slot combination on torque ripple. Torque performance is easily identified by analyzing tangential force due to their direct proportional relation. In this paper, magnetic flux densities in radial and tangential direction are systematically analyzed since tangential force is determined by the product of the two magnetic flux densities. The modification of a stator pole regarding its tip thickness is chosen as a key parameter in 6p/9s IPMSM. The thickness of a stator pole tip opposite to the direction of spin is more critical in torque ripple improvement. It is verified that the proposed method is sufficient for accurate torque prediction.

A sixteen-pole eighteen-slot (16p/18s) permanent magnet synchronous motor (PMSM) developed in Korea Electrotechnology Research Institute (KERI) for a vertical articulated robot is chosen as a reference model, and other two pole/slot combinations (20p/18s, 20p/24s) are together compared in terms of electrical and mechanical performance. Radial force density varying in time and space is decomposed through Fast Fourier Transform (FFT), and vibration is calculated from the harmonics of radial force. The vibration of 20p/24s is best due to its mode of 4 among the three pole/slot combinations. Additionally, the variation of radial force density with respect to torque is compared between 16p/18s and 20p/18s. Despite the same number of slots in both motors, the slope of 20p/18s is greater than that of 16p/18s in radial force density due to the different number of poles. As a result, the vibration of 20p/18s is worse than that of 16p/18s.