In recent years, the automotive world has experienced a dizzying transformation. The shift from combustion engines to electric powertrains has brought new technological challenges where efficiency, power, and weight reduction are key aspects. Precisely in this context appears one of the most promising technologies on the current scene: the axial flux motor.
Although not a new technology—its origins date back to the 19th century—the axial motor is experiencing a second youth and is shaping up to be the logical evolution compared to the traditional radial flux motor. Its implementation is gaining more ground in high-performance electric vehicles and is developing beyond the experimental realm. Here we are going to tell you what it is, how it works, and why it is set to revolutionize electric mobility.
What is an axial flux motor?
An axial flux motor is a type of electric motor whose magnetic flux travels parallel to the axis of rotation. This characteristic distinguishes it from the radial flux motor, in which the flux moves perpendicularly to the axis. Its configuration allows for a disc-shaped architecture, more compact and lighter, making it an ideal solution for sectors where space and weight matter, such as automotive, aerospace, or even robotics.
Unlike classic motors, where the stator surrounds the rotor, in axial motors, both components align facing each other. This means less volume, reduced weight, and high efficiency at lower revolutions.
How an axial flux motor works
The key lies in the direction of the magnetic flux. In axial motors, the magnetic field generated by the stator passes through the rotor parallel to the axis, allowing all the energy to act directly on the axis rotation. Thanks to this arrangement, a higher torque density and better thermal performance are obtained.
In many designs, such as those developed by companies like YASA, the motor features a dual-rotor and intermediate stator architecture, which further improves the distribution of magnetic and mechanical stress. These motors integrate a pancake structure –a flat disc– that maximizes the use of available space.
Advantages over the radial motor
Axial flux motors offer a series of benefits that explain their growing presence in next-generation electric vehicles. We highlight some of their main advantages:
- Superior power density: Compared to radial motors, axial ones are capable of generating more power in a smaller volume. For example, YASA’s most advanced motor offers up to 80 hp/kg, marking a turning point.
- Higher thermal efficiency: Thanks to its design, heat is dissipated better, and it withstands continuous thermal loads without performance dropping.
- Weight reduction: Smaller dimensions and optimized materials allow for lowering the vehicle’s weight, which also impacts greater range.
- Ease of integration: Its flat format facilitates inclusion in various mechanical configurations, providing freedom to vehicle designers.
The challenges of the axial motor
Despite all their advantages, axial flux motors are not exempt from certain limitations and technical challenges. Historically, the main obstacle has been their manufacturing complexity and associated high costs. Unlike radial motors—easier to mass-produce—axial ones require more precise industrial processes and more sophisticated components.
In pioneer models like the Koenigsegg Regera or the McLaren P1, the use of axial motors has been possible thanks to generous budgets and very limited production. However, brands like Mercedes-Benz, through its subsidiary YASA, are already working to democratize this technology in their future electric AMG range.
Real-world use cases
Real implementation of axial motors is starting to be reflected in commercial models. For example, the Ferrari SF90, McLaren Artura, and prototype models like the Mercedes AMG GT XX Concept, have demonstrated the potential of these systems.
One of the most impressive technical milestones is found in YASA’s latest axial motor, which achieves 750 kW of peak power (around 1,000 hp) with only 12.7 kg of weight. This not only improves acceleration and efficiency but also allows for reducing other elements such as suspensions, battery, or braking systems, due to the lower total vehicle weight.
Comparison with radial motors
| Metric | Radial Motor | Axial Motor (YASA) |
|---|---|---|
| Power density | 20 kW/kg | 59 kW/kg |
| Torque density | Up to 133 Nm/kg | 400 Nm (with 25 kg motor) |
| Cooling | Passive / air | High thermal contact oil |
| Format | Cylindrical | Flat disc |
Technological design keys
The most significant advance has come from the hand of the YASA architecture, which is based on a segmentada armature without yoke (‘Yokeless and Segmented Armature’). This design eliminates a large part of the iron present in traditional stators, reducing weight by 80% and, incidentally, magnetic losses.
In addition to lightening the assembly, the use of less copper, iron, and permanent magnets also reduces manufacturing costs. In the long term, this technology is shaping up as a more economical and ecological alternative.
Environmental and design repercussions
The use of axial motors not only improves electric car performance but has a positive effect on the entire system. Being more compact and efficient, the quantity of materials needed is reduced, and the design of more optimized cooling systems is facilitated. This contributes to cutting the carbon footprint of production, as well as costs associated with electricity and maintenance.
Furthermore, it allows for designing smaller batteries without compromising range, thanks to lower energy consumption. The lower vehicle weight also impacts energy efficiency, allowing for a saving of up to 200 kg in total weight.
The future of the axial motor lies in industrialization
One of the keys for this technology to extend to popular vehicles is the capacity to mass-produce. Currently, processes are complex and still not very scalable, but manufacturers like Mercedes-Benz are working on it. Thanks to the open innovation lab opened by YASA and its collaboration with brands like Ferrari and Koenigsegg, a clear path toward industrial production is already being glimpsed.
The European MAXIMA initiative, with the participation of universities and research centers such as the UPC (Spain), works on overcoming these challenges through new developments in electromagnetic, mechanical, and thermal fields. Their goal is to offer viable solutions that bring axial motors to the street in affordable commercial models.
The development of axial flux motors presents itself as one of the most dynamic and advanced branches of the electric sector. Although it is still in the mass market adoption phase, its advantages, both at a functional and environmental level, represent a quantitative leap in the performance of next-generation electric vehicles. The improvement in mass production capabilities will be key for this technology to reach a wider scope and greater integration in vehicles of all types, from utility cars to high-performance sports cars.