Torsional Vibration Analysis of Interior Permanent Magnet Synchronous Motors With Rotor Step-Skewing for Electric Vehicles

This article presents a thorough study on the torsional vibration of interior permanent magnet synchronous motors (IPMSMs) with rotor step-skewing for electric vehicles (EVs). First, the effects of different rotor skewing types on the spatial distribution characteristic along axial direction for the tangential electromagnetic force are investigated and compared, and an excitation index is proposed to describe the interaction between the tangential force and torsional modal, which represents contributions of the torsional modal to the vibration response. Then, a multidegree of freedom (MDOF) dynamics model of the multisegmented rotor is built, and the stiffness matrix and torsional modal frequency considering the contact layer condition between rotor segments are calculated based on the Hertz contact theory. In addition, modal experiments of the rotor are implemented to validate the accuracy of the MDOF dynamics model. Based on the proposed model, the torsional vibration response of the rotor with three-segmented linear skewing exciting by tangential electromagnetic force is calculated. It reveals that the rotor step-skewing has a significant influence on the tangential force, torsional modal, and vibration. Finally, a motor with linear skewing rotor has been manufactured and the noise is tested to validate the analysis results.