Soft magnetic composites are enabling lighter, smarter, and more efficient motors—without the constraints of traditional materials.
Manufacturers of products as wide ranging as e-mobility vehicles, drones, HVAC, industrial automation, hand tools, lawn and garden equipment, and more are demanding smarter, lighter, more efficient motor solutions. As the use of electric motors evolves, one material stands out for its ability to transform motor topologies: soft magnetic composites (SMCs).
SMCs are redefining what’s possible in electric motor design, enabling innovative topologies like axial flux, yokeless axial flux, and trapezoidal radial flux. The real breakthroughs emerge, however, when these materials are paired with conventional laminations to create hybrid stators that elevate efficiency, reduce weight, and unlock new design features previously considered impractical or too costly.
Let’s dive in and see how this approach is reshaping what motors can do.
Why Rethink Traditional Motor Topologies?
Traditional radial flux motors, which are built around stamped electrical steel laminations, were defined by the limitations of a different era. While they’ve served well, their 2D geometry constraints now stand in the way of progress, especially in high frequency, compact, or three-dimensional flux designs, where performance demands are outpacing legacy solutions. Soft magnetic composites are reshaping the rules, offering a bold alternative to traditional designs. Made from iron powder particles coated with an insulating layer, SMCs enable 3D magnetic flux, reduce eddy current losses, and allow near-net shape manufacturing.
Despite their advantages, SMCs also bring trade-offs such as lower mechanical strength and heat dissipation limitations. Understanding these strengths and weaknesses is critical as we explore how new topologies— especially axial flux, yokeless axial flux, and trapezoidal radial flux motors—can be optimized using SMCs.
Axial Flux Motors: Compact Powerhouses
In axial flux motors, the magnetic flux flows parallel to the axis of rotation—unlike the more common radial flux motors where it flows perpendicularly. This shift in direction opens up a world of design efficiencies:
- Higher torque density: This is ideal for e-mobility, drones, aerospace, and beyond.
- Shorter axial length: A pancake-like shape fits tighter design envelopes.
- Improved cooling: Flat surfaces enhance heat dissipation, increasing motor longevity.
How SMCs Help
For axial flux motors, 3D stator shaping isn’t just an advantage; it’s a performance enabler. SMCs make this possible by supporting the following innovations:
- Intricate stator teeth that optimize magnetic performance while also controlling back EMF
- Reduced eddy current losses across high-frequency ranges (400 Hz–10 kHz)
- Increased maximum saturation flux density
- Greater cradle-to-grave sustainability
Challenges and Considerations
To take advantage of the benefits of SMCs, designers of axial flux motors must also address these limitations:
- Lower mechanical strength: If used in a rotor, careful consideration must be given to sustain the high stresses generated.
- Thermal trapping: SMCs can retain heat if not well managed.
- Lower magnetic permeability: This can limit peak flux density at low currents, making SMCs less ideal for low frequency applications.
Yokeless Axial Flux Motors: Less Material, More Innovation
Yokeless axial flux motors take the axial flux architecture a step further by eliminating the stator yoke. This design allows magnetic flux to travel directly between opposing stator teeth through the rotor, reducing core material usage, lowering losses, and enabling a more compact, lightweight motor that’s ideal for next-generation applications.
Key Benefits
- Up to 30% weight reduction: Lighter weight is essential for e-mobility and space-constrained applications.
- Simplified assembly: Automated stator winding and motor assembly reduces labor, materials, and production complexity.
- Higher efficiency: Reduced copper and iron losses translate to more power output per watt and less heat to manage.
Where SMCs Shine
- Enabling yoke-free and trapezoidal stator geometries allows for cost-effective production.
- SMCs reduce core losses at high speeds and frequencies.
- SMCs enable unique shape making to reduce back EMF and the possibility of magnetic fringing at the stator tips.
Engineering Caveats
Yokeless designs amplify the need for careful engineering:
- Flux saturation risk: Stator teeth carry more magnetic load. SMCs are well suited to the greater saturation flux density because they have inherently higher maximum flux saturation. Select SMC grades with high permeability.
- Structural reinforcement: If higher structural integrity is a requirement, mechanical interlocking or epoxy bonding can strengthen the design.
- Cost-performance balance: While material costs may drop, tooling and assembly complexity can rise. However, the use of pre-wound bobbins can simplify winding and enable fully robotic assembly of the motor stator.
Real-world inspiration: Koenigsegg’s “Dark Matter” motor—a yokeless axial-radial hybrid—uses SMCs to deliver 800 hp from just 40 kg of motor mass.
Looking Ahead: Hybrid Designs & Segmentation
The real magic often comes from combining SMCs with traditional laminated steel—a hybrid approach that balances innovation with practical engineering. These hybrids provide the following advantages:
- Improved magnetic efficiency as a result of combining SMCs in stator slots with laminations for improved motor performance
- Lower material waste and capacity for more sustainable production
- Ability to create more compact, copper-optimized designs
Scaling these ideas, however, requires smart hybridization strategies, which we’ll cover in Part 2 of this series. There, we’ll explore how to make large, complex SMC parts manufacturable through modular designs—and how customers like Koenigsegg and niche aerospace programs are proving that the impossible is becoming possible.
Final Thoughts: Design Freedom Comes with Responsibility
Topologies like axial flux, yokeless axial flux, and trapezoidal radial flux motor concepts offer revolutionary performance, but they demand new design thinking. Soft magnetic composites open up this world, but only when their unique advantages are fully utilized and any potential limitations are minimized or eliminated with sound engineering designs. At Horizon Technology, we don’t just manufacture SMC parts; we collaborate with engineers to solve their hardest design problems.
The question we leave you with is this: What would your motor look like if traditional limitations no longer applied?
