Axial Flux vs Radial Flux Motors: What's the Difference?
Nearly every electric motor in service today — including the motors in most electric vehicles — is a radial flux machine, a concept that dates back roughly 200 years. In a radial flux motor, the magnetic field crosses the air gap perpendicular to the shaft, from a cylindrical rotor to the stator that surrounds it.
An axial flux motor turns that geometry on its side: the magnetic flux runs parallel to the axis of rotation, between disc-shaped rotors and a flat stator. The result is a short, wide "pancake" machine whose active magnetic surface sits at a large radius — and because torque scales with the cube of diameter, that geometry extracts significantly more torque from the same mass and volume.
Side-by-side comparison
| Aspect | Axial flux | Radial flux |
|---|---|---|
| Magnetic flux direction | Parallel to the axis of rotation | Perpendicular (radial) to the axis of rotation |
| Typical form factor | Short and wide ("pancake"), large diameter, short axial length | Long and cylindrical |
| Torque density | Higher — torque scales with the cube of diameter; the large active radius produces more torque per kilogram | Lower for the same mass and volume |
| Flux path | Short, one-dimensional flux path; yokeless designs remove stator iron entirely | Longer, two-dimensional flux path through the stator yoke |
| Cooling | Windings are close to the outer surface; direct liquid cooling can be integrated at the heat source | Heat must travel from buried windings through the stator stack to a cooling jacket |
| Manufacturing maturity | Emerging — requires new processes such as SMC cores and segmented stators | Very mature — over a century of industrialised production |
| Typical uses today | High-performance EVs, aerospace, marine, robotics, in-wheel drives | Most production EVs, industrial drives, appliances |
Why hasn't everyone switched?
If axial flux machines are lighter and more torque-dense, why do most EVs still use radial flux motors? Two reasons: manufacturing and thermal management. Radial flux motors benefit from more than a century of industrialised production, while axial flux designs need newer processes — segmented stators, soft magnetic composites, precise air-gap control between spinning discs. And packing more power into less volume concentrates heat in the windings, so cooling becomes the limiting factor for continuous performance.
The Axialis approach: yokeless, SMC cores, direct liquid cooling
Axialis is developing a yokeless axial flux motor that addresses both challenges. Independent stator segments made of SMC (Soft Magnetic Composite) are sandwiched between two rotors, so no stator yoke is needed — removing iron mass and the losses that come with it. Concentrated windings wound from rectangular copper wire raise the copper fill factor, and integrated direct liquid cooling takes heat out right at the windings instead of through a distant cooling jacket.
The current prototype delivers 71 kW of continuous power at 5,000 RPM and 150 kW peak, with a maximum speed of 8,000 RPM. The technology is being developed for automotive traction within the EU-funded project "Development of New Axial Flux Electric Motor Technology" (Recovery and Resilience Facility, 2024–2026). See the full prototype specifications or a deeper look at the technology.
Frequently asked questions
What is an axial flux motor?
An axial flux motor is an electric motor in which the magnetic flux between rotor and stator runs parallel to the axis of rotation, instead of radially as in conventional motors. This allows a short, disc-shaped ("pancake") construction with a large active radius, which produces more torque per kilogram than a comparable radial flux machine.
Why are axial flux motors more power-dense than radial flux motors?
Torque grows with the cube of a motor’s diameter. Because an axial flux machine places its air gap at a large radius and uses a short flux path, it extracts more torque from the same mass and volume. Yokeless designs go further by removing the stator yoke iron, cutting weight and iron losses.
What is a yokeless axial flux motor?
A yokeless axial flux motor sandwiches a series of independent stator segments between two rotors. Flux passes axially from one rotor to the other through the segments, so no stator yoke is needed to close the magnetic circuit. Removing the yoke reduces mass and iron losses, improving both power density and efficiency. This is the topology Axialis is developing, using SMC (Soft Magnetic Composite) stator cores and concentrated windings with rectangular copper wire.
How are axial flux motors cooled?
Thermal management is the main engineering challenge of compact axial flux machines: high power in a small volume concentrates heat in the windings. Because the windings sit close to the outer surfaces, liquid cooling can be integrated directly at the heat source. The Axialis prototype uses integrated direct liquid cooling, which allows a continuous output of 71 kW and a peak of 150 kW from a compact, lightweight package.
Are axial flux motors used in electric vehicles?
Yes, and adoption is growing. Most production EVs still use radial flux motors, but axial flux machines are appearing where power density matters most: high-performance cars, aviation, marine propulsion and in-wheel drives. Axialis is developing yokeless axial flux motor technology for automotive traction within an EU-funded project running from 2024 to 2026.