Defect types and mechanisms of hairpin coils in manufacturing of electric traction motors

Abstract:
As a consequence of the increasing relevance of electrified drive trains for mobility solutions, manufacturing technologies for electric traction motors need to be continuously improved in order to meet the automotive demands for productivity, quality and costs. With focus on the manufacturing of efficient and powerful distributed stator windings, the hairpin technology already provides advantages regarding the level of automation and productivity in comparison to conventional winding technologies, but still shows technological weaknesses concerning the process reliability. Against this back-ground, both geometric and functional defect types of hairpin coils are introduced, clustered and discussed based on a conceptual analysis in this paper. In addition, possible defect mechanisms are evaluated and the influence of the defect types on the insulation system of the stator winding, the process reliability of the subsequent process steps as well as the quality of the hairpin winding is analyzed by experimental test series in this paper.