Design of Hairpin Winding and Random Winding Stators for High Speed Heavy-Duty Traction Motor

Hairpin winding with rectangularly shaped conductors are gradually replacing random winding wound with stranded wires in electric vehicle (EV) industry. As the newgeneration winding technology, hairpin winding features high electromagnetic and thermal performance to meet the stepchange requirements on power density and efficiency levels of EV traction motors. To quantitatively analyze the advantages of hairpin winding compared to random winding, in this paper, two interior permanent magnet (IPM) traction motors, with random winding and hairpin winding, respectively, are designed and compared for the same output torque-speed requirement with 350kW peak power, 550Nm peak torque and 15000 rpm peak speed. The overall design process takes into consideration of performance boundaries in multi-physics domain based on global optimization against typical operating points. A detailed comparison of the optimized motors is carried out in terms of geometry dimensions, material usage, power losses, and thermal performance. The comparison results show improvements of 21.6% decrease in overall volume, 17.4% decrease in active mass, 27.1% increase in peak power density and 28.1% increase in continuous current density for the 96-slot IPM design with hairpin winding. Two prototype machines are manufactured, and experimental validation will be conducted in future research work.