On the Modal Characteristics of Motor Stators under Different Interlaminate Fastening Conditions

<div>The increasing demand for quiet and efficient electric vehicles has highlighted the importance of understanding vibration and noise characteristics of motor stators. Previous studies have extensively modeled electromagnetic excitation and laminated structures, but there has been little experimental evidence clarifying how different interlaminate fastening methods affect vibration modes under comparable conditions. This knowledge gap limits the ability to optimize fastening strategies for noise and vibration control in practical motor design. In this study, laminated stator cores were fabricated with different fastening conditions—bolting, clinching, and welding—and subjected to vibration testing and experimental modal analysis. Natural frequencies, damping ratios, and mode shapes were identified for torsional, circumferential, and breathing modes. The results revealed that the in-plane torsional natural frequencies increase with bolt axial force, while clinching provides additional resistance to interlaminate movement but shows only a minor dependence on the number of clinching points. In contrast, the circumferential modes and the breathing-type (0,0) mode remain largely unaffected by these fastening variations. Welding points did not exhibit a consistent trend across the tested conditions, indicating that their influence on the modal properties is less systematic compared with bolting and clinching. The findings contribute not only to fundamental understanding of laminated stack vibration behavior but also to practical guidelines for designing fastening strategies that enhance vibration robustness and acoustic performance in automotive electric motors.</div>