Rotordyamic analysis of a 2-pole induction motor considering magnetic excitation due to dynamic rotor eccentricity during startup

Abstract

This paper considers the accelerated passing through the critical speed of an overcritical induction motor in the case of an excitation by electromagnetic forces due to a dynamic rotor eccentricity. The dynamic rotor eccentricity is caused by a magnetic eccentricity of the rotor core related to the rotor shaft. An analytical rotor model as well as a finite element rotor dynamic model are presented for rotordynamic analysis related to startup with magnetic eccentricity. Based on a finite element model, the vibrations of a 2-pole induction motor (2 MW) are analyzed during the startup with a magnetic eccentricity of 1% of the air gap. The FE-calculation shows the influence of the start-up time on the vibration amplitudes and on the critical speed for this special kind ofexcitation.