Design Guideline of an AC Hairpin Winding

Abstract

This work aims to investigate the design rules and the additional losses in an AC hairpin winding. Such a winding type is more and more used in traction motor of electric and hybrid-electric vehicles. The actual trend is to require higher operating frequency. In fact, the motor power and speed are continuously increasing even though keeping a high number of poles to reduce the end winding length. Hairpin winding allows a higher slot fill factor in comparison with traditional round wire windings. However, the larger cross-area section of such solid wires cause a strong non-uniform current density distribution, which can delete the higher copper area benefit. Hereafter, the main rules design of an AC hairpin winding are described, to satisfy voltage and current constraints. Furthermore, different analysis has been carried out to determine the additional losses amount considering different coil connections. Finite Element analysis has been compared with analytical models.