Investigations of eddy current losses in laminated cores due to the impact of various stacking processes

This paper presents investigations into the eddy current losses of laminated electrical steel cores as implemented in electric motors, that were manufactured by applying various stacking processes. The application of interlocking and welding stacking processes create an electrical connection of the initially insulated laminations and therefore lead to additional eddy current losses. This paper considers the impact of the stacking processes on the eddy current losses of a ring core test sample. For identification of the eddy current characteristics within the laminated stack and for determination of the losses, a finite element method simulation, an analytical calculation and a measurement for verification were carried out. The analysis results confirm, that the eddy current losses increase for the interlocked and welded test sample in comparison to a perfect insulated reference sample. The results confirm further, that the eddy current characteristics are being well matched by an introduced equivalent electric circuit model. Finally, the investigation is also addressing the combination of the stacking impact and an additional electrical connection of the laminations as it may occur when the stator cores are pressed into an electrically conductive housing.