Dynamics of a Hydropower Rotor Supported by an Elastic Generator-Bearing Bracket

This paper studies the dynamics of a 150 MW hydropower rotor system, in which an elastic structure supports the generator guide bearing. A quasi-static large-displacement force-deflection relationship for the bearing support is derived within the elastic range, which is incorporated into the equations of motion for a rotor dynamic model. The proposed model includes two tilting pad journal bearings, along with nonlinear magnetic interaction and unbalance forcing acting on the generator. The equation of motion is solved by time-integrating procedures to study the system’s dynamics. A drastic softening effect is observed for the bracket within the elastic range, in which the nominal value represents merely \(10\%\) of the bearing stiffness. It is concluded that the excessive support flexibility significantly reduces the lowest pair of frequencies, diminishes the damping ratios and alters the orbit characteristics during operation. Furthermore, the amplified eccentricity increases the risk of instability due to the radial magnetic pull.