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

Abstract

Electromagnetic analysis of hydropower generators is common practice but there is little emphasis on studying the effect ofrotor whirling in the analysis. This paper demonstrates the use ofthe unbalanced magnetic pull (UMP) curves based on purely dynamiceccentricity motion for a wide range of whirling frequencies in theprediction of the steady state UMP in the case of mixed eccentricitiesmotion. The latter motion type is more realistic in practice. Actualelectromagnetic (EM) simulations are also carried out for these mixedeccentricities motion cases in order to verify the proposed method. Goodagreement between the UMP from the actual EM simulations and theUMP predictions are made when low eccentricities exist. The proposedmethod is thus very useful since firstly, very few EM software packagescan handle mixed eccentricities motion and secondly, since actual EMsimulations of intricate rotor centre motion are time-consuming, theproposed method is a big time saver. A modified feature selective validation(FSV) method, the FSV-UPC, is also applied to assess the similarities andthe differences in the force computations.