Hairpin Winding Topology and the Influence on Traction Motor Performance for EV Applications

This paper investigates the effect of hairpin winding topology on the electromagnetic and thermal performance in order to improve the torque, power density and efficiency of traction motors. First, traction motors' importance in developing electric vehicle (EV) and the advantages of hairpin windings compared to round windings are introduced. The winding losses of the traction motor operating at 3000 rpm and 10000 rpm, and the efficiency during the whole speed process are then analyzed. The results show that eight layers of hairpin winding will cause more losses and lower efficiency. Moreover, the effect of hairpin winding topology on spray cooling performance is evaluated. Finally, the optimal number of hairpin winding layers and dimensions for the proposed motor are determined by weighing the effects of AC and DC losses and considering the efficiency of the traction motor under the drive cycle.