The 3D negative sequence currents arising from unbalance system operations in large turbogenerators are studied by using the finite element method. The mathematical models of the three dimensional negative sequence eddy current fields of large turbogenerators considering the flexible slots are firstly proposed. To emulate the distributed exciting sources of the negative sequence current fields with enough precisions, the geometrical complication of the stator are accurately modeled in the proposed solid models, making it be readily to take into account of practical distributions of the negative sequence exciting currents. And finally, the negative sequence eddy current fields of a 1055 MVA turbogenerator are studied extensively by using numerical simulation results.
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