Vibration measurements for validation of electromechanical rotor model for cage induction motor

Eccentric rotor motion of an electric motor induces an unbalanced magnetic pull. This eccentricity force may couple the electromagnetic system with the flexural vibration modes of the shaft. Recently, a simple parametric model was presented for this electromechanical interaction. The aim of this study was to produce experimental data for the validation of this electromechanical rotor model. A standard six-pole 18 kW induction motor was equipped with a long flexible shaft for the experiments. The frequency and damping of the first flexural rotor mode was identified in unloaded steady-state operation. The limit-cycle vibrations and sub-critical unstability was observed in measurements.