A study of the natural vibratory response of stator structures to improve condition monitoring strategies for induction motors

On-line condition monitoring is widely used to detect failure mechanisms in large highvoltage three-phase induction motors. The high-voltage winding is installed in a complex, stator core structure which vibrates due to electromagnetic forces. Insulation degradation can be diagnosed via on-line monitoring of partial discharges but the fundamental cause is often mechanical damage due to stator vibration. This paper presents results of an investigation into the natural vibratory response of the complete stator assembly. Results from finite element models of complex stator assemblies, including the frames, are supported by experimental measurements. These include freely suspended stator cores as in previous studies, and also now introduce the much more realistic condition of the complete stator assembly securely bolted on to a solid baseplate. The knowledge gathered in this study will aid the application of a vibration monitoring strategy to detect stator core vibration which can lead to winding insulation damage.