Manufacturing Influences on the Motor Performance of Traction Drives with Hairpin Winding

Abstract

To face the challenges posed by the electrification of the automotive drivetrain, rotating electrical machines are getting an impetus to innovation. Thus, machines of high power density are required to be manufactured cost-effectively in a large-scale production. To meet these requirements, the application of stators with hairpin windings is focused in industry and research institutions, as they show potentials to realize improved copper fill ratios in the armature slots. In addition, this technology also is seen as one possibility to substitute the elaborate winding technologies that often feature a lack of reproducibility, by bending, assembling and joining processes. During the design of electric drives, the influences of deviations of manufacturing processes on its performance usually are not taken into account. This particularly applies to the technology of hairpin windings, whose manufacturing requires a large number of bending and contacting operations. These process steps may influence the electrical properties of the winding, changing the behavior of the electrical machine. For this reason, the objective of this paper is to identify deviations in the manufacturing processes of hairpin windings and to validate their influence on the performance of the drive. For this purpose, measuring systems are set up which make it possible to quantify the influence of bending and contacting processes on the electrical properties of the winding by means of highly accurate resistance measurements. As next step, a simulation is set up to map the production influences on the hairpin winding to the machine's efficiency. Based on simulation studies, the influences of the manufacturing imperfections on the engine performance become visible.