Optimum Design of Hollow Conductor in Stator Winding for Large Evaporative Hydro-generator

A new type of evaporative inner-cooling system used in large hydro-generator has exceeded over other traditional cooling methods that is characterized by two-phase flow and boiling heat transfer. For this reason, in the case of the optimum design of generator, some design variables different from an water-cooling or air-cooling machine should be considered, which will lead to substantial improvement on the temperature rise of stator winding and core. The major design variables that are considered by using 3D electromagnetic finite element method (FEM) coupled with evaporative-cooling heat transfer analysis in this paper are dimension of hollow conductor used in the stator bar, efficiency of machine and ultimate capacity of machine. The analysis results show that, based on the existing design of water-cooling system of Three Gorges' hydro-generator installed on the left bank, increase the dimension of hollow conductor will result in a whole better temperature distribution and thermal load capability in the stator of evaporative cooling hydro-generator than in water-cooling hydro-generator. This study presents an effective dimension of hollow conductor for the Three Gorges' hydro-generators that satisfy the request of operating efficiency. Conclusion of this paper can be provided as academic foundation for improving design and manufacture high-capacity hydro-generator with evaporative inner-cooling system