Evaluation of Laser-welded Electrical Steel Laminations for Electric Motors

The soft magnetic core is a basic component in electric motors, along with the winding and insulation systems. Soft magnetic cores are continuously magnetized and demagnetized to guide and amplify the magnetic flux. To reduce iron losses during operation, stator and rotor cores are usually made of thin laminated iron-silicon sheets insulated electrically from each other. These materials are easy to process (cutting, joining etc.), the costs are low, and the magnetic as well as the mechanical properties are adjustable during production. Due to the increasing requirements for electric motors for automotive sector, the material grades and corresponding manufacturing processes have been even optimized. For the production of Fe-Si laminations, the single sheets are stacked and joined. For this purpose, laser beam welding is increasingly used, especially in the series production of larger stators. However, the welding process affects the microstructure in the heat-affected zone and creates an electrically conductive connection between the single sheets. This increases the production-related iron losses, which have to be considered already in the design of the electric machine. As part of this research paper, the impact of laser welding of Fe-Si electrical steel sheets on the electromagnetic properties is analyzed and relationships are derived. This makes it possible to consider the production-related impact factors at an early stage.