The modelling of segmented laminations in three dimensional eddy current calculations

A formulation is presented for the inclusion of segmentation effects in a three-dimensional eddy current model of large laminated iron cores. The model has been developed for the study of eddy currents induced in the end laminations of turbogenerator stator cores. It includes magnetic nonlinearity and represents the overlapping pattern which occurs between successive lamination layers by introducing multiple electric vector potentials directed normal to the laminations. Such a formulation has permitted study of the segmentation effect without explicitly modeling each lamination layer, an impractical proposition in terms of the discretization required. Results have demonstrated that the overlapping of successive segment layers has a very substantial influence upon the eddy current distribution in the stator core back. For the open-circuit condition a reduction in total core loss of over 30% is calculated to occur due to the presence of segmentation and third lapping.>