Torsional Vibration Diagnosis of Induction Machines Based on High-Frequency Electromagnetic Vibration

Pumps used for irrigation and drainage are usually connected with induction machines (IMs), which are widely employed in industry and daily life. Relatively severe working conditions force pumps to meet the requirement of high-level reliability. Aiming at the general problem of torsional vibration on shafts, a diagnosing method based on radial electromagnetic vibration is studied, which distinguishes torsional vibration from lateral vibration by characteristic frequencies. The lumped-mass model is utilized to analyze the torsional angle of the rotor. The air-gap magnetic field of the IM is analyzed to obtain the characteristic components induced by torsional vibration. High-frequency harmonics, which are ignored in previous studies, are considered in the analysis of electromagnetic forces to eliminate the influence of mechanical vibration on torsional vibration diagnosis. Characteristic frequencies of radial electromagnetic vibration are analyzed under healthy, torsional vibration, and lateral vibration conditions. Finally, the proposed method is validated by finite element analysis and experiments.