Non-Conventional Concentric Winding Layout Design of Hairpin Windings for Enhanced Traction Performance of Induction Machines

Future electric vehicle (EV) traction motors require high power density, high efficiency, wider speed range, lower torque ripple, and lower weight and volume. Hairpin (HP) windings are a favored option for traction motor windings; however, their efficiency tends to degrade due to AC losses at high operating speeds. Therefore, HP winding designs that offer higher EM performances, including higher efficiencies in the full operational region, and lower winding weight are necessary for future EVs. In this regard, this paper investigated the arrangement of the HP windings within the stator slot, considering different phases, and utilized an improved winding function-based model and analytical AC loss estimation to propose an optimal concentric winding (CW) configuration for a commercially available 140 kW, 15000 rpm induction machine (IM). According to the results, except for the similar torque capacity in the maximum torque per ampere (MTPA) region, the proposed optimal CW IM configuration demonstrated superior overall performance and characteristics, including output power, torque, and efficiency, across a wide speed range; both MTPA and field weakening regions compared to the IM with distributed windings (DW). Additionally, the proposed CW configuration reduces winding weight by 12.96% compared to the IM with conventional DW, which is a significant advantage in terms of weight and volume reduction.