Opportunities of Model-Based Production-Oriented Design of Stators with Hairpin Winding

摘要

The hairpin technology is a promising and widely used production method that meets the growing demand for high productivity and quality in the manufacturing of electric drives caused by increasing sales of electric vehicles. In comparison to conventional winding technologies, the technology provides significant advantages regarding the ability for automation, the productivity as well as the attainable filling factors, but also exhibits weaknesses concerning the process reliability and manufacturing constraints, which limit important degrees of freedom in electric design.Within the process chain of stator manufacturing by hairpin technology, especially the manufacturing constraints of the multi-step shaping processes of hairpin coils as well as the twisting and subsequent welding processes of the open coil endings show a high interdependency with important design parameters such as wire dimensions, coil pitch, stator diameter and number of slots. However, the complex interactions can only be captured by experimental tests on machine prototypes, which often leads to numerous time- and resource-intensive adaptations of tool and machine.To enable a production-oriented, cost-efficient design of stators with hairpin winding, several process models are introduced within the scope of this paper that allow a consideration of manufacturing influences within early periods of electric drives development. For this purpose, numerical approaches of process modeling carried out in Abaqus FEA are presented for different types of tool-bound bending processes as well as the twisting process. Furthermore, a study on the influence of different wire dimensions is carried out using the examples of rotary draw bending and twisting processes. In addition, simplified mathematical models for minimizing the winding head size under consideration of manufacturing aspects are described. The proposed methodology of virtual process assessment by FE-based as well as simplified process models offers particular advantages in the early phase of product design.