A Comprehensive Design Guideline of Hairpin Windings for High Power Density Electric Vehicle Traction Motors

Abstract

The rapidly increasing demand on power density levels of electric vehicle (EV) drive systems is pushing the boundaries of traction motor performance. Hairpin windings are becoming a popular option for EV motors due to their reduced DC losses and improved heat dissipation capability when compared to traditional random windings. In this paper, a comprehensive design approach of hairpin winding layouts is firstly presented. The flexibility and limitation of end-winding patterns is thoroughly investigated in terms of basic pin connections, special jumpers, transposition, parallel branches, terminal positions, phase shift, winding pitches as well as slot-pole combinations. To address the challenge of much reduced practical layout options with increased slot number per pole per phase, two novel hairpin winding designs are proposed. A 160kW, 18000rpm PM traction motor featuring the new winding layout with 54-slot, 6-pole is developed using a multidomain design platform which puts special focus on the conductor size optimization. The advantages of the designed motor are clearly revealed by comparison with the more traditional 48-slot, 8-pole counterpart. Finally, a corresponding stator prototype with the proposed hairpin winding is built to validate its manufacturability.

On the AC Losses in the End Conductors of Hairpin Windings

“…An important aspect regards the estimation of the end winding AC/DC loss ratio Kac. Nearly all the connections are between the following layers: layers 1 and 2, layers 3 and 4, and layers 5 and 6 as underlined in [16]- [18]. There are a few exceptions, provided by the jumpers, which can connect layers 2 and 3 or layers 4 and 5, but their number is much lower and is kept usually as low as possible.…”

“…These aspects have On the AC Losses in the End Conductors of Hairpin Windings Marco Pastura, Riccardo Notari, Stefano Nuzzo, Davide Barater, Giovanni Franceschini led, up to now, to consider only integer slot distributed windings, mainly with a full pitch being implemented. Some guidelines for appropriate conductor connections are available in [10], [16]- [18].…”