Game-Changing Lightweight E-Motor Design Enables Unrivalled In-Wheel Drives and Other Applications

Conference paper
Part of the Proceedings book series (PROCEE)


This paper presents latest developments and applications of a new electrical motor design which delivers highest power and torque density, while keeping weight and cost at a minimum. This allows for direct drive applications like wheel-hub motors or other mobile drives, where very low weight is mandatory. The motor’s air-gap-winding design reduces the amount of iron and copper and consequently it’s weight and cost significantly. Slotless design completely avoids cogging torque and shows a very smooth operation. The simple geometric design based on two thin-walled hollow cylinders, supports an automated production, which also contributes to very low cost. A flat slotless stator design stands for a homogenous temperature distribution and very efficient cooling, which allows high shortterm overload. In a first application a 40-kW wheel-hub-motor for a 15-inch rim was developed, built and tested. It delivers nominal torque of 300 Nm over the complete range of speed up to 1350 rpm. Total weight of this prototype is only 20 kg. Further applications for an E-Scooter, a Wheel-Hub Generator, an E-Flyboat and an E-Motorbike will be presented. Combining air-gap winding with an additional slot winding boosts torque and power of the motor substantially, without any relevant increase of weight and cost. Both windings share the already existent permanent magnetic field and cooling system, and both contribute to the torque. Converting an existing wheel-hub motor of generation 1 showed a proof of concept by delivering a nominal torque of 450 Nm and nominal power of 60 kW keeping the same size and nearly the same weight. First generation 2 prototypes providing a nominal torque of 600 Nm in a 16-inch wheel rim and a power of 70 kW is designed, built and validated on test stand.


Lightweight E-Motor High power In-wheel-drives 


  1. 1.
    Rix AJ, Kamper MJ (2012) Radial-Flux permanent-magnet HubDrives: a comparison based on stator and rotor topologies. IEEE Ind Electron 59(6):2475–2483CrossRefGoogle Scholar
  2. 2.
    Moreels D, Leijnen P (2018) High efficiency axial flux machines, May 2018.
  3. 3.
    Woolmer TJ, McCulloch MD (2007) Analysis of the yokeless and segmented armature machine. In: 2007 IEEE international electric machines & drives conference.
  4. 4.
    Martini F (2015) World-record electric motor for aircraft, Siemens press, 24 March.[]=Corp. Accessed 13 June 2016
  5. 5.
    Borchardt N, Heinemann W, Kasper R (2012) Design of a wheel-hub motor with air gap winding and simultaneous utilization of all magnetic poles. In: IEEE International Electric Vehicle Conference (IEVC), Greenville, USA; 4–8 March 2012, pp 1–7, USA; 4–8 March 2012.
  6. 6.
    Fraser A (2011). In-wheel electric motors the packaging and integration challenges. In: 10th international CTI symposium, pp 12–23Google Scholar
  7. 7.
    Borchardt N, Kasper R (2016) Nonlinear design optimization of electric machines by using parametric fourier coefficients of air gap flux density. In: IEEE/ASME international conference on advanced intelligent mechatronics, pp 645–650Google Scholar
  8. 8.
    Borchardt N, Hinzelmann R, Pucula DS, Heinemann W, Kasper R (2016) Winding machine for automated production of an innovative air-gap winding for lightweight electric machines. IEEE/ASME Trans. Mechatron 21(3):1509–1517. Scholar
  9. 9.
    Kasper R, Borchardt N (2016) Boosting power density of electric machines by combining two different winding types. In: Proceedings of the 7th IFAC symposium on mechatronic systems, Loughborough University, UK, September 5–8, 2016, pp 322–329Google Scholar

Copyright information

© Springer-Verlag GmbH Germany, part of Springer Nature 2020

Authors and Affiliations

  1. 1.Head of MechatronicsOtto-Von-Guericke UniversityMagdeburgGermany

Personalised recommendations