Large low-speed hydro-generators ¿ unbalanced magnetic pulls and additional damper losses in eccentricity conditions

A combined analytical and numerical method for computation of unbalanced magnetic pulls (UMPs), damper bar currents and losses of laminated low-speed hydro-generators in eccentricity conditions under no-load is presented. The described method takes into account saturation effects and the damping effects of the damper winding in the calculation of the UMPs and the damper bar currents. The combination of magnetostatic two-dimensional (2D) finite element field calculations and an analytical resolution of electrical circuit equations results in a precise prediction of the damper bar currents and of the UMPs. At the same time, simulation time is drastically reduced compared to transient magnetic 2D finite element simulations.The presented method was verified on several examples, comparing the obtained results (damper bar currents and UMP) to the results obtained from transient magnetic finite element simulations.