Effects of Rotated Stacking, Bolts, and Bonded Regions on Modal Parameters of Bonded Stator Cores of Electric Machines

This paper discusses the vibration characteristics of the electric machine stators used for the traction of electric vehicles. Of particular interest is the effects of rotated stacking, bolts, and bonded regions on the modal characteristics of the bonded laminated stator cores. Test specimens for vibration testing have been fabricated, and experimental modal analyses have been conducted. Modal parameters, i.e., natural frequencies, mode shapes, and modal damping ratios have been extracted by a curve fit methodology. It is revealed that natural frequencies of modes involving shear deformations along axial direction are affected by rotated stacking, and bolts. Furthermore, the effect of partial bonding on the teeth region on the natural frequencies is small for low frequency modes but relatively large for high frequency modes. Moreover, it was found that bonding on the teeth region tends to increase the modal damping ratios.