Direct Cooled Hairpin Winding via Expandable Slot Liner – The Wedge-Pin

Zürrlein T, Walch D, Gehring J, Preitschaft A, Stauber S, Hahn R, Franke J, Risch F (2026)

Publication Type: Conference contribution

Publication year: 2026

Original Authors: Tobias Zürrlein, Daniel Walch, Jonas Gehring, Anja Preitschaft, Simon Stauber, Roman Hahn, Jörg Franke, Florian Risch

Pages Range: 1-8

Event location: Funchal (Madeira) PT

DOI: 10.1109/ICEM68283.2026.11757068

Abstract

Efficient cooling is essential for achieving higher power densities in traction motors, while there is a growing emphasis on the cost-effective mass production of electrical machines. This paper presents a novel approach to direct slot cooling of hairpin machines using profiled conductors to form cooling channels within the slot. In addition to U- and T-shaped cross-sections, wedge-shaped conductors are proposed due to their advantages in manufacturability and hairpin bending. The cooling channels are sealed using expandable slot liners (ESLs), enabling efficient manufacturing with reduced material usage for the cooling system while maintaining electromagnetic performance. Electromagnetic finite-element (FEM) simulations show that the proposed wedge-pin geometry achieves up to 25 % lower AC losses than conventional rectangular pins. Thermal simulations indicate an average winding temperature reduction of 8 K compared to hollow conductors and 105 K compared to water-jacket cooling. Initial experiments confirm manufacturability and demonstrate reliable sealing of the ESL. This concept enables current densities above 30 A/mm2 without exceeding thermal limits.

Authors with CRIS profile

Tobias Zürrlein Lehrstuhl für Fertigungsautomatisierung und Produktionssystematik (FAPS) Anja Preitschaft Lehrstuhl für Fertigungsautomatisierung und Produktionssystematik (FAPS) Simon Stauber Lehrstuhl für Fertigungsautomatisierung und Produktionssystematik (FAPS) Roman Hahn Lehrstuhl für Fertigungsautomatisierung und Produktionssystematik (FAPS) Jörg Franke Lehrstuhl für Fertigungsautomatisierung und Produktionssystematik (FAPS) Florian Risch Lehrstuhl für Fertigungsautomatisierung und Produktionssystematik (FAPS)

Involved external institutions

Fraunhofer-Institut für Integrierte Systeme und Bauelementetechnologie (IISB) DE Germany (DE)

How to cite

APA:

Zürrlein, T., Walch, D., Gehring, J., Preitschaft, A., Stauber, S., Hahn, R.,... Risch, F. (2026). Direct Cooled Hairpin Winding via Expandable Slot Liner – The Wedge-Pin. In Proceedings of the 2026 International Conference on Electrical Machines (ICEM) (pp. 1-8). Funchal (Madeira), PT.

MLA:

Zürrlein, Tobias, et al. "Direct Cooled Hairpin Winding via Expandable Slot Liner – The Wedge-Pin." Proceedings of the 2026 International Conference on Electrical Machines (ICEM), Funchal (Madeira) 2026. 1-8.

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