Analytical Study of the Vibration Effects Due to Nonlinear Unbalanced Magnetic Pull in Electrical Machines Under Static Eccentricity

Electrical machines find extensive applications across domestic, commercial, and particularly industrial settings, including their use in Electric Vehicles (EVs). In industrial operations or EVs, these machines often operate under heavy load conditions. During their operation, various factors can lead to an uneven air gap between the rotor and stator assembly, resulting in eccentricity-related faults in induction machines. However, the Unbalanced Magnetic Pull (UMP) induced due to this asymmetric air gap has numerous adverse effects on the rotor. These effects increase vibration and noise levels within the system. Therefore, it is imperative to conduct a thorough analysis of the impact of UMP on the rotor system to comprehend the characteristics of electrical systems under such conditions. This paper focuses on investigating the influence of nonlinear UMP on the rotor in electrical systems with more than three pole pairs with axially constant static eccentricity. The analytical model is then coupled with the mechanical two degrees of freedom equation of motion to formulate and analyze the Multiphysics problem at hand. The paper also highlights the nonlinear effects of UMP by considering various system parameters and different contributing nonlinear terms. Where it is found that the UMP reduces the natural frequency of the system by introducing negative stiffness in the system. if the nonlinearity in UMP is considered it bends the response of the system towards the leftward by showing the softening characteristics which also again reduces the natural frequency of the system. The integration of nonlinear effects and the exploration of diverse system parameters contribute to a comprehensive understanding of this Multiphysics problem.