Estimating forces in mixed eccentricities motion from purely dynamic eccentric rotor centre motion in a hydropower generator and their validation against EM simulations

Abstract

Abstract-Electromagnetic analysis of hydropower generators is common practice but there is little emphasis on studying the effect of rotor whirling in the analysis. This paper demonstrates the use of the unbalanced magnetic pull (UMP) curves based on purely dynamic eccentricity motion for a wide range of whirling frequencies in the prediction of the steady state UMP in the case of mixed eccentricities motion. The latter motion type is more realistic in practice. Actual electromagnetic (EM) simulations are also carried out for these mixed eccentricities motion cases in order to verify the proposed method. Good agreement between the UMP from the actual EM simulations and the UMP predictions are made when low eccentricities exist. The proposed method is thus very useful since firstly, very few EM software packages can handle mixed eccentricities motion and secondly, since actual EM simulations of intricate rotor centre motion are time-consuming, the proposed method is a big time saver. A modified feature selective validation (FSV) method, the FSV-UPC, is also applied to assess the similarities and the differences in the force computations.Index Terms-eccentricity, electromagnetic simulations, hydropower, rotor, whirl