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Thermal Performance of Additively Manufactured Hollow-Conductor Windings in Electrical Machines for Propulsion

Lookup NU author(s): Dr Rafal Wrobel, Dr Zaynah Ahmad

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Abstract

© 2015 IEEE.High-specific-power electrical machines for transportation applications require effective thermal management to enable elevated power density and efficiency. Hollow-conductor windings offer direct internal cooling, reducing temperature rise and increasing allowable current density. This paper investigates the thermal performance of copper hollow-conductor windings fabricated using additive manufacturing (AM) and evaluated via reduced-complexity motorette demonstrators. The windings were produced using a filament-copper AM process, enabling continuous hollow channels along the full conductor length. Experiments demonstrate winding-to-coolant heat transfer exceeding 2000 W/m2K, corresponding to a 0.7l/min corresponding to a 37 × increase in allowable winding power loss relative to a baseline design employing conventional round copper conductors with liquid-cooled housing. Complementary theoretical analysis of complete machine variants shows that hollow-conductor cooling can significantly enhance machine operating envelope and efficiency, extending high-efficiency regions and torque-speed capability. The findings illustrate that direct cooling of hollow-conductor windings, enabled by AM, provides a viable route to higher specific output and improved thermal robustness in propulsion-relevant electrical machines. Practical considerations for integrating hollow-conductor windings into full machine assemblies are also discussed, including manufacturing, assembly, and thermal design implications.

Publication metadata

Author(s): Wrobel R, Ahmad Z

Publication type: Article

Publication status: Published

Journal: IEEE Transactions on Transportation Electrification

Year: 2026

Pages: epub ahead of print

Online publication date: 15/06/2026

Acceptance date: 02/04/2026

ISSN (electronic): 2332-7782

Publisher: Institute of Electrical and Electronics Engineers Inc.

URL: https://doi.org/10.1109/TTE.2026.3703538

DOI: 10.1109/TTE.2026.3703538

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