Influence of Rotor Damping Structure on Speed Fluctuation and Asynchronous Operating Ability of Turbogenerators With Loss of Excitation

The asynchronous operation of turbogenerators with the loss of excitation can avoid equipment damage and improve the reliability of power systems. The rotor damping that provides asynchronous torque plays an important role in asynchronous operation. In order to study the influence of rotor damping structures—comprised of damping bars, slot wedges, and core—on asynchronous operating ability of turbogenerators, a time-stepping finite-element model is established and verified by the experiment on a model machine. By using this model, the relationship between the rotor damping structures and speed fluctuation during asynchronous operating process is studied. The asynchronous operating ability is compared in terms of the separate and combined effects of the rotor damping structures. Considering the material options for rotor slot wedges, the influence of aluminum, beryllium bronze, and stainless steel slot wedges on the speed fluctuation and the asynchronous operating ability is also studied. The study shows that the speed fluctuation of turbogenerators with the loss of excitation depends on the asymmetry of the rotor winding structure and the asynchronous operating ability depends on the average damping torques. The results provide theoretical basis for an approach to the enhancement of power system stability by improving rotor damping structures of turbogenerators.