The Effects of the Damper Winding and the Eddy Currents in the Solid-Rotor of an Inverter-Fed Turbo Generator

Variable speed technology has become available at all power levels. Large generators in pumped storage power plants are combined with full-size converters for motor and generator operation, when using a combined pump turbine. Medium sized machines in wind power plants use a full size converter for decoupling the generator from the fixed grid frequency. And small generators one used in the so called micro power plants. The improved operation behavior by the use of an inverter comes at the price of increased losses and a higher voltage stress to the insulation of the machine. This paper focuses on the effects of the damper winding and the eddy currents in the solid rotor of a turbo generator. Shielding effect, pole-face losses and the dynamic behavior are analyzed by measurements on a specially adapted turbo generator in the laboratory. The analyses are complemented by results from a 2D-FEM model.