Design considerations of a brushless open-slot radial-flux PM hub motor

Rafal Wrobel*, James Goss, Adrian Mlot, Phil Mellor

*Corresponding author for this work

Research output: Chapter in Book/Report/Conference proceedingConference Contribution (Conference Proceeding)

11 Citations (Scopus)


Initial sizing of a brushless radial-flux permanent magnet (PM) machine is typically based on assumptions regarding the electric-and magnetic-loading together with the motor's active volume. Additional design assumptions include the winding current density and magnetic flux density within the core pack. These initial design decisions are crucial as they largely define the resultant electromagnetic and thermal behaviour of the motor. The general rules regarding the choice of the initial design parameters are well known. However, the effects of the initial sizing on the final motor performance are not widely reported.

This paper presents an analysis of design considerations for a brushless open-slot radial-flux PM hub-motor. A number of alternative motor designs are compared to demonstrate the effect of the initial design decisions on final motor performance. Both the electromagnetic and thermal aspects of the motor design are considered. The design variants are characterised by the same electric-and magnetic-loading together with active volume while the winding rated current density and no-load/open-circuit magnetic flux density within the core pack are varied. The employed sizing methodology combines the classical approach with a non-linear magneto-static finite element solver and an optimisation routine. A prototype hub-motor has been manufactured to validate the theoretical findings from the design process. The experimental data shows good agreement with the theoretical findings.

Original languageEnglish
Title of host publicationIEEE Energy Conversion Congress and Exposition (ECCE 2012)
Place of PublicationNEW YORK
PublisherIEEE Computer Society
Number of pages8
ISBN (Electronic)978-1-4673-0801-4
ISBN (Print)978-1-4673-0802-1
Publication statusPublished - 15 Sep 2012
EventIEEE Energy Conversion Congress and Exposition (ECCE) - Raleigh, New Caledonia
Duration: 15 Sep 201220 Sep 2012


ConferenceIEEE Energy Conversion Congress and Exposition (ECCE)
CountryNew Caledonia


  • Brushless motors , Copper , Iron , Stator windings , Thermal analysis , Windings

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