Electromagnetic evaluation and quantification of welding processes for the packaging of electrical steel

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The power density and efficiency of electrical machines is determined by the magnetic properties of the core material. Magnetic cores of rotating electrical machines are manufactured from isolated electrical steel laminations that are packaged and fixated. Thus, not only the properties of the initial strip material are crucial for their application, but also their processing, because it affects the magnetization and magnetic losses.Currently, gluing, interlocking and welding are used as packaging technology. Gluing leads to smaller stacking factors, due to the excess non-magnetic material. Interlocking leads to electric short circuits, which increases eddy currents. This leads to a deterioration of magnetic properties. Welding leads to a change in microstructure, residual stress and local destruction of electric isolation.The effect of welding on the magnetic properties of electrical steel is not comprehensively described in literature. The aim of the project is an electromagnetic evaluation and quantification of welding processes for the packaging of electrical steel. Focus of this study is put to laser welding, as a welding process is with a small energy impact. Process modifications include laser spot welding and welding in vacuum. Besides conventional welding lines, a statistical and geometrical distribution of welding spots is studied and discussed as packaging pro-cess. For the quantification of the effects, the phenomenological impacts are comprised in model that includes the manufacturing as well as the magnetic property change. A simulation chain from the welding to the magnetic properties is used for quantification and evaluation of welding joints of electrical steel with consideration of the required torsion strength.