Validation of the Analytical Prediction of the Damper Winding Pole-to-Pole Impedance in Hydro Generators

The indirect pole-to-pole connection is a common damper winding design in salient pole synchronous hydro generators. The inter-pole damper current passes radially through the pole end and tangentially through the rotor rim to reach the neighbouring pole. There are two types of indirect pole-to-pole connections investigated in this paper where the damper bars are connected to A) the steel pole end plate or B) an extra copper plate between the pole end plate and the pole lamination. The aim of this paper is to provide an analytical prediction method of the indirect pole-to-pole impedance. Therefore, the methodological assumptions are compared with 3D FE simulations and the analytical calculation results are compared with measurements. The findings of this investigation are important parameters required for analytical and 2D FE calculations to predict the currents in the damper winding, which compensate unbalanced loads, torque oscillations and unbalanced magnetic pull.