Optimisation of Hairpin Winding in Electric Traction Motor Applications

Abstract

This paper investigates the influence of number of layers and conductor size of hairpin windings of electric motors for electric vehicle applications. Firstly, the hairpin winding technology for electric motors is reviewed and key design rules are introduced. Based on these design rules, a traction motor with hairpin winding technology is modelled in a finite element analysis (FEA) software. The influence of the hairpin winding layers on the DC and the AC copper losses is investigated, based on the results obtained considering different operating points and drive cycles. The results indicate that using a higher number of winding layers does not always lead to higher efficiency. The trade-off between DC and AC losses under different operating points and drive cycles must be considered when designing for the optimal number of winding layers. Furthermore, using a larger conductor and higher fill factor for hairpin winding not necessarily lead to higher efficiency. In this study, the optimal conductor size for electric motors with hairpin windings is identified by carrying out optimizations considering drive cycle efficiency.