ABSTRACT
In the paper an iterative calculation procedure is presented for deriving 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 and arbitrary controller structures. The mathematical model considers the electromagnetic influence, stiffness and internal damping of the rotor, stiffness and damping of the bearing housings with end shields, of the foundation and of the oil film of the sleeve bearings, as well as the stiffness and damping of the motor foot mounts and the controlled forces, which are applied by the motor foot mounts.
