Experimental Investigation of a New Manufacturing Technology for Hairpin Stators with Litz Wires

Abstract

The increasing demand of electric drives in the mobility sector leads to continuous innovations in the development and production of electric machines. Currently, it can be seen that hairpin technology is well established in the automotive industry for traction drives. In addition to the high level of automation of the process, the reasons therefore are the achievable copper filling factors, which result from the flat conductors used and thus increase the power density of the electrical machine. However, at higher frequencies, as a result of higher driving speeds, large conductor dimensions, especially the height of the conductor, lead to undesirable aspects in the form of eddy current losses. These negative effects can be reduced by replacing the solid rectangular conductor with a stranded conductor. Therefore, the substitution of the conductor material in the field of hairpin technology can be classified as the next innovation stage. The base material is a twisted stranded conductor compacted into a rectangular shape. In this paper, a novel process chain for the manufacturing of a stranded hairpin stator is presented, individual process steps are analyzed and potential improvement measures are explained. Subsequently, an evaluation is made on the basis of an assembled and electrotechnically measured stator with stranded hairpins.