Modeling for rotorbearing systemof hydroelectric machines and its nonlinear transient response

The modeling strategy of the rotorbearing system of large hydroelectric machines is discussed and a multidegrees of freedom system with local nonlinearity is developed. The oilfilms of the guide bearings are treated as nonlinear elements. Taking into account the gyroscopic effect, angular inertia, shear deformation and inertia of the water in the runner etc., the various mechanical, electrical and hydraulic forces acting on rotor externally can be considered in the calculating model. The transient responses of the system are calculated by combined using the Riccati transfer matrix method and the Newmarkβ method, and a general software is compiled. The rotorbearing system of a 240MW Francis hydraulic generator set is used as an example, and the calculating result and discussion are given, which supports the research on the stability of large hydroelectric machines.