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An air-cooled YASA motor for in-wheel electric vehicle applications

Lookup NU author(s): Dave Winterborne, Dr Nick Stannard, Dr Steven Jordan, Dr Glynn Atkinson



This is the authors' accepted manuscript of an article that has been published in its final definitive form by IEEE, 2020.

For re-use rights please refer to the publisher's terms and conditions.


In-wheel motors present a range of opportunities for innovation in electric vehicle design as the torque produced at each of two or four wheels can be controlled individually. A high-aspect ratio (large radius, short axial length) motor is required to fit within the wheel. Due to its location, liquid cooling of the in-wheel motor is difficult and undesirable, but a high power density is required to reduce the mass—which is particularly important as it is unsprung—and fit the space envelope. Furthermore, a high-torque density is required to eliminate the need for a gearbox. These constraints create a real challenge for the design of a machine for this application. An axial field machine using a yokeless and segmented armature (YASA) topology is designed to fit these requirements as such a machine has clear advantages when considering the high-aspect ratio. A soft magnetic composite material is utilized to carry the flux in its nonplanar path without incurring excessive losses or requiring a lamination design, which is difficult and expensive to manufacture. A novel cooling arrangement involving heat-spreading elements on each armature segment is employed to improve heat dissipation and, hence, power density. The design, analysis, manufacturing, and testing of the motor is described in this article to verify the concept against the requirements outlined earlier

Publication metadata

Author(s): Winterborne D, Stannard N, Sjoberg L, Jordan S, Atkinson GJ

Publication type: Article

Publication status: Published

Journal: IEEE Transaction of Industry Applications

Year: 2020

Volume: 56

Issue: 6

Pages: 6448-6455

Print publication date: 02/11/2020

Online publication date: 18/09/2020

Acceptance date: 06/09/2020

Date deposited: 12/11/2020

ISSN (print): 0093-9994

ISSN (electronic): 1939-9367

Publisher: IEEE


DOI: 10.1109/TIA.2020.3025267


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