Analysis of 3D thermal field and deformation in the stator of large hydro-generators

In order to reduce the vibration of the stator core in the large hydro-generators, the recent tendency is to stack the stator core at site for the hydro-generators with the diameter larger than ten meters. Owing to the temperature difference between the core and frame of the stator, the frame will restrain the expansion of the core, which will lead to buckling of the stator core in case of high-stiffened frame. But in order to prevent from the electromagnetic vibration the stator frame will be required to have an appropriate supporting stiffness for the stator core. The investigation of the thermal deformation in the generator must be based on comprehensive analysis of the temperature distribution within the generator under different operation conditions. In this paper a method by FEM for calculation of the 3D thermal field within the generator is applied. Based on the results of the thermal field calculation, the thermal deformation of the stator core and the frame can be calculated. As an example, the thermal field and deformation of a 400 MW evaporating cooled generator have been calculated. The comparison of the calculated results with those measured at site proves that the applied method in this paper has appropriate precision.