Calculation and Analysis of AC Loss in Variable-section Hairpin Windings for Traction Motors of Electric Vehicles

In electric vehicles, hairpin windings are used to increase the torque and power density of motors. The main disadvantage of hairpin windings is the high AC loss incurred during high-frequency operation. Hairpin windings with variable section conductors can overcome this problem, but there is a lack of analytical models for AC losses in such unconventional windings and an analysis of the manufacturing complexity of unconventional windings. In this paper, the mechanisms of AC loss generation in hairpin windings are firstly analyzed and its expression is derived. Then, based on the field-circuit coupled finite element method, the AC loss analysis model of four kinds of variable-section hairpin winding topologies is established, aiming at summarizing the variation rule of AC loss with motor parameters in such windings. Finally, to verify the feasibility of additive manufacturing of windings, the most suitable material for the current application is selected based on the loss properties.