Methodology for the Mechanical Characterization of Rectangular Winding Wire in the Context of Electric Mobility

The increasing market share of electrified powertrains results in a high demand for efficient and powerful electric traction motors. Against this background, bar winding technologies have become established in automotive production systems for manufacturing of distributed stator windings due to its high level of automation and the resulting productivity, in particular the so-called hairpin-technology. However, despite iterative optimizations, the robustness of the industrial process chains is still limited due to fluctuating mechanical and geometric properties. For example, the enameled rectangular copper wire leads to different springback effects in hairpin bending and twisting. To increase the process reliability, both the mechanical forming properties of the copper conductor and the insulation coating of the rectangular winding wire need to be specified and analyzed in a universal but application-oriented manner. In this paper, a methodology for characterizing the mechanical forming properties of insulated rectangular copper wire is presented. This methodology goes beyond the basic requirements of IEC 60317 and the testing methods of IEC 60851. Based on the proposed methodology, Young’s modulus, yield strength and flow curve as well as the adhesion of the insulation coating can be analyzed for both statistical delivery control and numerical process simulations.