“Dynamic Analysis and Field Balancing of 70 MW Gas Turbine-Generators,”
This paper summarizes the multi-plane balancing procedure and dynamic characteristics experienced with several 70 MW gas turbine-generator sets. The gas turbine is a W501 class and weighs approximately 72,000 lb., and the generator weighs approximately 51,000 lb. There are two bearings supporting the gas turbine and three bearings sup porting the generator. The generator and gas turbine are connected by a rigid coupling.
The W501 gas turbine has had a previous history of high vibrations during cold and hot starts. Thermal bowing of the rotor under load normally occurs with this class of rotor. The bowing effect may be attributed to two sources; the expansion of the copper conductors in the generator and the thermal expansion of the gas turbine. In the later case, re-machining of the torque tube has been reported in the literature to have some benefit.