Modelling of Magnetic Forces and Vibrations in the Stator of Hydro Generators

This dissertation aims to enhance the accuracy of the mechanical and electromagnetic models used to predict vibrations in the stator of large hydro generators. For the mechanical model, this includes determining the equivalent mechanical parameters to represent the laminated stator core and the winding at different temperatures and clamping pressures. The electromagnetic model, in turn, is developed with a focus on the damper winding's effect on the magnetic forces considering the typical construction of large hydro salient-pole machines, which may not possess a direct electrical connection between the damper bars of adjacent poles.
As an outcome, a semi-analytical calculation method based on beam and shell elements is developed for a fast calculation of the mechanical eigenmodes and eigenfrequencies including the stator frame. The results are applied to a 366 kVA research machine and a real 55 MVA hydro generator in normal operation and evaluated using a new graphical method developed for root cause analysis of possible vibration problems.