Comparison of Various Manufacturing Processes for Hairpin-Stators with Different Conductor Material

The increasing demand for alternative drives in the mobility sector is continuously generating innovations in the development and production of electrical machines. The automotive industry relies more and more on traction machines with hairpin stators, as the process chain can be automated more easily and the copper filling factor can be increased. Enhancing the electrical copper filling factor in particular allows an improvement of the power density of the electrical machine. However, large conductor diameters lead to additional losses at high frequencies, as they occur in high-speed applications, due to eddy current effects. These operational disadvantages can be avoided by substituting the solid rectangular conductor by a litz-wire. Nevertheless, this semi-finished product requires a more complex manufacturing process. Within this paper the process chain for the production of a litz-wire hairpin-stator is illustrated and the challenges in the process chain of a stranded conductor compared to a solid conductor are presented. In this context, the manufacturing aspects for the production of the litz-wire hairpins are considered in detail.