PMW pioneered the development of the in-wheel electric motor and have delivered many thousands of high-powered and compact in-wheel motors for robotic traction and hoist applications, along with samples and prototypes to a wide variety of customers in the marine, aerospace & defence, heavy industrial and commercial automotive markets.

PMW has a wide range of hub motors available for highly specialised applications. The in-wheel XR series (XR stands for eXternal Rotor) offers a glimpse into the future of powered wheel technology. We are happy to work with customers to develop, manufacture and supply wheel motors for these specialist applications.

In-Wheel XR Series Motors

The in-wheel XR series is a permanent magnet brushless motor with an external rotor. Permanent magnet brushless motors are generally the most efficient and highest torque density motors available today. The XR series gains from two distinct additional advantages: the magnets are positioned on an externally running rotor which gives the motor the fundamental geometric advantage that torque is being delivered on the outer-most point of the motor. Finally, the torque density of larger XR series is maximised by a high degree of slot fill. The high slot fill is achieved by winding each of the stator teeth individually before assembling them together into a stator.

Side by side view of direct drive in-wheel electric motors: XR20-12 in-wheel motor for automatic guided vehicle, XR32-13 for heavy duty off-highway vehicle and XR32-11 in-wheel motor for car.

Side by side view of direct drive in-wheel electric motors: XR20-12 in-wheel motor for automatic guided vehicle, XR32-13 for heavy duty off-highway vehicle and XR32-11 in-wheel motor for car

The stator teeth of larger XR series are modular and interlock in such a way that we can vary the diameter and length of the stator more or less infinitely to fit both the packaging and the power requirements of the application.  The in-wheel XR series can be liquid cooled or even oil filled for subsea applications that require underwater pressure compensation.

Applications for the XR Series in-wheel motors include substitution of large high torque hydraulic actuation systems with a compact efficient motor, industrial and marine winch systems, propulsion of industrial robots and other specialised electric vehicles and trailers, traction for commercial electric vehicles for example in mining, direct drive radar systems, direct drive railway vehicles, compact generators for auxiliary power units, and general hybridisation of vehicle propulsion systems.

Below are some examples from the XR Series in-wheel motor range:

XR Series MotorsMotor Ratings (Continuous)   
XR20-09 (water cooled)92033660314501.5drawingdatasheetSTEP
XR32-13 (water cooled)92101003223001875.87drawingdatasheetSTEP
XR44-16 (water cooled)914130025075360047drawingdatasheetSTEP

The following data sheets are available for the XR Series brushless DC in-wheel motors:

XR32-11 In-Wheel Motor PDF

Printed Motor Works XR32-11 direct drive in-wheel electric motor with disc brake mounting points

Front side view of XR 32-11 direct drive in-wheel motor for car (disc brake mounting points on rear face).

XR32-13 In-Wheel Motor PDF

XR32-13 in-wheel motor

Rear side view of XR32-13 direct drive in-wheel motor next to its wheel rim.




PMW Dynamics