Modeling the Lateral Vibration of Hydraulic Turbine-Generator Rotors

An extensive hydro-generator rotordynamic model is presented along with a technique for determining imbalances and shaft misalignments using the model and mechanical run vibration measurements. The hydro-generator model combines a finite element rotor model with a finite difference guide bearing model, generator magnetic forces and turbine hydraulic forces to calculate natural frequencies, stability and steady-state response. The complete model allows a great number of inputs including imbalances, rotation speed, guide bearing misalignments, coupling misalignments, bearing clearances, bearing temperatures, generator stator and rotor center misalignments, generator average air gap, generator power output and turbine blade tip clearance, all of which are described in this paper. Finally, the numerical results are compared with vibration data from the mechanical run and load test of an actual hydro generator unit.