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A 3D FEM approach to evaluate the flux leakage and the magnetic induction in proximity to the end region of turbogenerators

Roberto Biondi, Michele Raciti

Ansaldo Energia

The magnetic flux leakage in the air is an undesired phenomenon which occurs in proximity of the turbogenerators end region, caused mainly by the inevitable axial extension of the stator bars. This phenomenon causes several effects on the operation and safety of the turbogenerators. Regarding this last topic, one of the well-known problems is the generation of hot spots on the stator frame due to the eddy current circulation created by the potential difference induced between points of the stator frame by the flux leakage lines passing through it.

The 3D FEM model of the turbogenerator end region presented in this paper aims to investigate how the dislocation in the space of the stator windings (including the connections to the electric machine terminals) and their distance to the stator frame affect this current circulation.

The FEM model implemented, can also be used to support the designer in the research of design solutions able to reduce the eddy currents circulation on the stator frame and thus the temperature reached in the hot spots.