Analysis of 3D thermal field in the stator of large hydro-generator with evaporation-cooling system

In recent years the advantages and broad application prospect of the new cooling system have been proved by engineering practice, with which the generator will be cooled by the two-phase flow formed by the evaporation of the coolant with low boiling point. But most of past works were concentrated on experimental researches for its applicability. The theme of this paper is aimed at its influence on the thermal field within the electric machine. A method to calculate 3D thermal field in the stator of large hydro-generators with evaporation-cooling system is presented in this paper. The full length with half of tooth and slot, including conductors, end windings and ventilation ducts, is taken as the calculation area. As an example the 3D temperature distributions of the 400MW evaporation-cooled hydro-generator at Lijiaxia Power Station have been calculated. After comparison of the calculated results with those measured at site, some useful conclusions can be made and it has been proved that the evaporation cooling system is an effective, easy maintained and safe cooling system.