Electromagnetic force calculations on a 3-phase autotransformer under time-varying fault by a 3D non-linear finite element code

An application of a magnetostatic 3-D nonlinear finite-element code to the computation of the axial forces on the windings of a large-power autotransformer due to short-circuit currents is described. The analyzed five-limb core autotransformer has an internal tertiary delta-connected winding. A comparison between the axial forces due to the peak currents of both a time-varying configuration fault and two conventional faults-two-phase earth fault and three-phase earth fault-has been made. The results obtained show that the time-varying fault yields greater axial forces than the conventional faults, particularly on the internal tertiary delta-connected winding.>