Theoretical rotor dynamic analysis of two-pole induction motors regarding excitation due to static rotor eccentricity

Abstract

The paper shows a theoretical rotor dynamic analysis of two-pole induction motors regarding excitation due to static rotor eccentricity, which causes an oscillating magnetic force in the air gap of the machine. The hereby caused rotor vibrations are mathematically described, showing the orbit movements of the rotor centre, the shaft journals and the bearing housings. The influence of the rotor speed as well as influence of the direction of the magnetic force on the vibration behavior is investigated, based on a numerical example. On the one hand the aim of the paper is to derive the mathematical coherences-based on a simplified rotor dynamic model-between rotor dynamics, electromagnetic and the oil film characteristics of the sleeve bearings for two-pole induction machines, considering electromagnetic excitation due to a static rotor eccentricity. On the other hand the aim is to derive a method for calculating the maximum height of the shaft vibrations-as a worst case-caused by a static rotor eccentricity. Therefore the paper shall prepare the basis for implementing this method into more detailed numerical programs, e.g., finite element programs.