The Wheel Hub Motor Revolution: How SMCs Are Changing the Game

The concept of the wheel hub motor isn’t new. In fact, Porsche pioneered the technology in the early 1900s with the Lohner-Porsche, an electric car that housed motors inside each of its four wheels. However, the technology never took off due to limitations in materials, manufacturing, vehicle design, and the electric infrastructure to support fully electric vehicles.

Fast forward to today, and advancements in motor and suspension designs are redefining electric vehicle (EV) propulsion by eliminating traditional drivetrain components. Wheel hub vehicle designs utilizing new motor topologies such as axial flux, yokeless axial flux, and trapezoidal radial flux offer greater efficiency, space and weight savings, and superior control delivering power directly to the wheels. These promising new design technologies also present challenging manufacturing logistics. With the ever- increasing acceptance of soft magnetic composites (SMCs), how can this new manufacturing methodology further the adoption of wheel hub motors?

The Key Benefits of Wheel Hub Motors

Wheel hub motors offer several game-changing advantages over conventional electric powertrains:

• Greater efficiency—By eliminating mechanical drivetrain losses, power is delivered directly to the wheels, improving overall energy efficiency.
• Compact space-saving design—Removing transmissions, differentials, and driveshafts frees up interior space and allows for more creative vehicle designs.
• Superior handling & performance—Individual wheel control enables vehicles with enhanced torque vectoring capabilities for better handling, stability, and traction.
• Sustainability & simplicity—Fewer moving parts mean lower maintenance, longer component lifetimes, and more sustainable vehicle design.

These advantages are pushing in-wheel motors toward mainstream adoption, but challenges remain. Could new materials combined with new motor topologies be the missing piece?

Challenges to Market Adoption

While the benefits of wheel hub motors are clear, their widespread adoption faces key hurdles:

• Thermal management—In-wheel placement increases exposure to heat and environmental conditions, impacting efficiency and lifespan.
• Weight concerns & unsprung mass—Adding weight to the wheels can affect ride quality and suspension performance. However, axial flux, yokeless axial flux, and trapezoidal radial flux designs mitigate this issue by making motors more power-dense and lightweight.

The Role of SMCs in Unlocking New Possibilities

SMCs are a key enabler for more efficient and compact motor designs. These advanced magnetic materials offer significant advantages over traditional laminated steel cores:

• Lower energy losses—Traditional laminated steel cores experience eddy current losses at high frequencies. SMCs reduce these losses, improving overall motor efficiency.
• Improved power density—SMCs allow for unique shapes, facilitating three-dimensional magnetic flux paths and enabling more compact and efficient motor designs.
• Better thermal performance—With reduced core losses, SMCs generate less heat, improving motor durability and reliability.

Enabling New Motor Topologies

SMCs open the door for innovative motor architectures that address current limitations in wheel hub motors:

• Axial flux & yokeless axial flux motors offer higher power density and efficiency, reducing overall weight and addressing unsprung mass challenges.
• Trapezoidal radial flux motors are an emerging topology that uses the radial flux design but with unique rotor and stator architecture that reduces mass and increases power density.
• Hybrid electrical steel lamination paired with SMCs enables unique shapes and optimal magnetic performance. (Yes, you really can have your cake and eat it too!)

These unique AC motor designs optimize magnetic flux flow and distribution. Creating 3D magnetic flux paths, SMCs improve motor efficiency and torque output, making Lohner-Porsche’s design ready for today’s demanding applications.

What’s next?

Are we on the verge of a wheel hub motor revolution? Advanced motor topologies, including trapezoidal, yokeless axial flux, and hybrid SMC designs, are redefining in-wheel propulsion for everything from ebikes to off-highway equipment. The automotive industry is at an inflection point, and the wheel hub-motor is transformational, allowing us to reimagine a new generation of vehicles.

At Horizon Technology, we’re pushing the boundaries of soft magnetic composite materials to enable the next generation of high-efficiency electric motors. Learn more about how SMCs are driving the future of electric mobility!