New YASA electric motor promises more power from less mass

YASA electric motor

It turns out that the YASA axial flux electric motor has been in development for about 20 years, but a video just found its way into my algorithm. Likely as a result of the attention we gave to the solid-state battery and Donut motor from Verge Motorcycles in the last few weeks.

In any case, the Yokeless and Segmented Armature (YASA) motor design is fascinating, next-level axial flux electric motor that offers a number of advantages over radial flux motors currently in use.

Interestingly they were first envisioned in the 19th century, but manufacturing constraints led to the more widespread adoption of radial designs, which are far more easily built.

Tim Woolmer

Enter Tim Woolmer, who in 2005 decided to focus on advanced motors for electric vehicles for his PhD thesis at Oxford University. The result are motors that are 1/6th of the length of a radial flux design.

This allows the motor to be mounted nearer a electric vehicle’s (EV’s) wheels.

The design reduces the motor’s diameter 50%, and it pushes out four times the power relative to its mass.

YASA motors have a pancake shape with two rotors on either side of a stator and by removing the heavy iron yoke, YASA reduces stator mass by 60-80%. The stator is segmented into independent pieces, enhancing efficiency and cooling.

Woolmer focused on and solved the manufacturing difficulties inherent in axial motor designs, earning his PhD. YASA, along with Mercedes-Benz, has built a 60,000 sq ft facility in the UK to mass-produce the motors.

Video links

Despite leaning on images of gasoline engines when talking about large electric motors, this first video offers a more detailed look at the YASA design.

This led to a second video that features Dr. Woolmer talking about the motor. However, it is effectively a commercial for Mercedes-Benz, who are building and developing the motor for a next round of EVs.

Between the potential of the solid-state battery from and advances in electric motors, there is a better, lighter-weight, greater range and faster charging future ahead for EVs.

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