Increasing the threshold of vibration stability of soft mounted induction motors with elastic rotors and sleeve bearings using active motor foot mounts

摘要

In the paper, the threshold of vibration stability of induction motors with flexible shafts and sleeve bearings, mounted on soft steel frame foundations with active motor foot mounts, is analyzed. The developed model is based on a multibody model, considering electromagnetic influence, stiffness and internal damping of the rotor, stiffness and damping of the bearing housings and end shields, stiffness and damping of the foundation and stiffness and damping of the oil film of the sleeve bearings. Additionally the stiffness and damping of the motor foot mounts - which are positioned between the motor feet the soft steel frame foundation - are considered, as well as the controlled forces which are applied in the vibration system by the motor foot mounts, using PD-controllers. The aim of the paper is to unite all these influences in a mathematical model and to derive a procedure for calculating the threshold of vibration stability. Based on a numerical example it can be shown, that the threshold of stability can be pushed to very high rotor speeds, using active motor foot mounts.