Analysis of mechanical vibrations caused by eccentricity in a slow-speed slotless permanent magnet generator

This paper focuses on the analysis of mechanical vibrations caused by different eccentricities in the rotor of a slow-speed slotless permanent magnet generator. The analysis of different eccentricities and their influences was carried out on a full scale laboratory test machine. Three most common mass center dislocation faults of a generator rotor that can occur in the production phase of the machine were investigated: asymmetrical rotor weight distribution, none coaxiality of rotor and stator, dislocated rotor. The analysis was conducted to obtain information on how different eccentricities influence vibrations and how to take this into account in production. Mentioned cases were chosen as they represent most common eccentricity faults caused by mistakes in production and assembly. Vibration measurements were carried out by non-contact optical measurement system. The measurement procedure and process are described in the paper as they are a crucial part of the analysis. The obtained results show that additional mechanical vibrations depend on the relation between eccentricity types. In addition, it was identified that rotor rotational speed affects the vibration amplitudes only slightly and the rate of influence is also dependent on the eccentricity type. Dynamic eccentricity was found to be the most dangerous case compared to the others.