Study of the impact of eccentricity in large synchronous generator with finite elements

This paper presents a numerical model for computing electromagnetic forces in an existing large hydro generator at Hydro-Québec. Due to the high mass and low rotational speed, hydro generators present static, dynamic or combined eccentricities resulting in unbalanced magnetic pull in the air gap and unbalanced stator currents caused by the variation of the magnetic flux density distribution. The model uses advanced 2-D numerical finite-element analysis to compute the electromagnetic forces based on Maxwell stress tensor and the obtained results were used later as inputs to study the dynamic behavior of hydro power turbine shaft. The results obtained for electromagnetic forces, damper bar currents and circuit currents due to any magnetic unbalance are presented and discussed in detail.