Design of the large Francis units for Vietnam’s Son La scheme

This article describes the design of the six 400 MW generating units for the Son La hydro scheme in Vietnam, including the technical and economic advantages relating to the arrangement of the thrust bearing support on headcover structure. The thrust bearing pads are supported by the Alstom membrane structure, which ensure self-equalizing of the thrust load on each pad. Good access to the thrust bearing is very convenient for thrust bearing maintenance. The generator is designed with a closed-circuit ventilation system, involving fans attached to the rotor rim, which reduce the air losses to achieve high efficiency.