FE-Based Simulation of Hairpin Shaping Processes for Traction Drives

Based on the present change in mobility, there are novel requirements on production technologies of electric drives regarding process reliability, ability for automation, productivity as well as mechanical and electric filling factors. Providing significant advantages compared to conventional winding technologies, the hairpin technology combined with the usage of flat copper wire is a promising opportunity to fulfill the upcoming standards. Hence, the AnStaHa project aims the qualification of the hairpin technology for application in mass production. In spite of numerous advantages, the application of the hairpin technology also shows weaknesses. In particular, the shaping of hairpins is considerably more complex than corresponding process sequences of other winding technologies. The main reasons for this are the rectangular cross section and resulting directional properties of flat copper wires, significant springback effects as well as process-related damage of the wire insulation. Therefore, basic knowledge about the deformation behavior of the wire is required for process dimensioning within the context of system design. This paper handles the numerical simulation of hairpin shaping using the commercial finite element software suite Abaqus FEA. The FE-based approach is validated by experiments for different geometries and includes the complete forming process of hairpins, which is considered to be implemented in two following steps - U-bending and 3-D-shaping. Because the numerical analysis takes wire springback into account, the results can be used for a digital evaluation of hairpin shaping processes during the period of system design.