The origin of the electromagnetic vibration of induction motors operating in modern industry: Practical experience — Analysis and diagnostics

Different kinds of anomalies in industrial power lines create a number of problems for normal operation of induction motors. One of them is an excessive amount of motor vibration. The industry today widely uses different kinds of nonlinear systems operating in the power lines, for example, adjustable speed drives (ASD), which cause voltage distortion in the power lines. Single phase load in three phase power systems may cause voltage imbalance. Induction motors operating under voltage distortion or voltage imbalance usually have experienced significant vibration of an electromagnetic nature. Vibration of an electromagnetic nature may also be a result of an internal fault in the motor. Motor vibration data contains substantial analytical information about stator and rotor winding and core condition, air gap eccentricity, current/voltage imbalance, and voltage distortions in the power line, etc. Condition monitoring and fault diagnosis of induction motors based on the vibration analysis technique are widely used in modern industry. Accuracy of the machinery diagnosis made using vibration analysis depends on the ability to correctly analyze vibration data. The aim of this paper is to clarify the origin of the motor vibration of electromagnetic nature at line frequency, twice line frequency, harmonics of line frequency and at twice slip frequency. This opinion is based on the author's many years of experience in the field of vibration diagnostics on electrical machines from different industries.