How SMCs Can Unlock the Hidden Assets of Axial Flux Motors.

Posted by Eric Wolfe - November 30, 2022

We previously highlighted all of the benefits of axial flux motors high power density, shorter magnetic path, more torque, and better cooling – so why aren’t more people taking advantage of the topology?

Your current design might be doing the job, but what if we told you there was a way to get more out of your money? Here, we’ll illustrate additional assets of axial flux motors and how they can improve your bottom line. 

Benefits of the Axial Flux Motor

Axial flux motors have a variety of benefits, including:

  1. Increased performance 
  2. Simplified manufacturability
  3. Maximized magnet utilization
  4. Reduced bill of materials combining the best of green technologies

Increased Performance

Axial flux motors demonstrate increased performance over traditional radial flux motors, due to:

  • A higher torque density, leading to lower overall weight
  • A shorter flux path for more efficient use of magnet material
    • In a radial flux motor, the magnetic flux moves from one tooth to the stator, back to the next tooth, and to the magnets.
    • In an axial flux motor, the magnetic flux moves from one magnet, through the core, to another magnet.
  • More efficient use of copper, leading to reduced copper losses
  • The intrinsic design of the axial flux motor, providing exposed wire surfaces, leading to improved cooling

Simplified Manufacturability

As opposed to internal slot-inserted winding, the wound bobbin design of the axial flux motor is easier to produce and requires less specialized winding equipment.

Maximized Magnet Utilization

Because of the improved cooling of the axial flux motor, you may have the potential to use lower cost magnets, yet yield the same performance. Due to the shorter flux path intrinsic with the axial flux motor design, the path through the magnet is shorter, which essentially leads to less magnet material.

As we’ll discuss further below, the addition of soft magnetic composites (SMCs) allows for a more compact design with smaller magnets, further saving you money.

Reduced Bill of Materials: Combining the Best of Green Technologies

Axial flux motors are also more environmentally friendly than other types of motors. With the axial flux design, you can enjoy reductions in:

  • Energy consumption, while still enjoying higher performance
  • Waste through recyclability and utilization of material 
  • Copper usage (no end-turns)
  • Reliance on rare earth magnetic material
  • Weight for the same power output

If this isn’t enough, an SMC stator requires 15% less energy to produce over a steel laminated stator.

Cost Drawbacks of the Traditional Axial Flux Motor Using Laminations

As we’ve discussed before, laminations can be used in your axial flux motor design – but it comes with a variety of inherent weaknesses, including:

  • The axial flux machine stator is difficult to manufacture and automate, for the following reasons:
    • A rolled and machined concept utilizing welding involves significant waste.
    • A rolled and progressively stamped stator creates the same amount of waste in a more cost effective way, but the optimal shape is not possible.
  • Increased supply chain issues lead to longer lead times, making the process more expensive. Lack of available capacity to support projected market growth - further impacting lead times and increased cost.
  • Due to the varying thickness of lamination sheet steel, the effective stacking factor of the assembly will be 90-95%, thus lowering the saturation induction of the assembly.

Good News – SMCs Can Alleviate These Drawbacks

Through the use of SMCs, you can enjoy all the inherent performance advantages of an axial flux motor design, without the drawbacks of laminations. These include:

  • You can achieve a high tooth-to-tooth precision from pole to pole 
  • SMCs reduce the magnostrictive effect inherent in all magnetic materials. The magnostrictive effect is the inherent size change of magnetic materials with the application of an applied field. This growing and shrinking of laminations results in noise.
  • SMC components are readily available, so you won’t experience the same supply chain issues as with laminations

Ready to Maximize Your Electric Motor Performance with SMCs and Axial Flux Motors?

SMCs and axial flux motors are the perfect synergy of cost savings, efficiency, and performance. If you find this fusion intriguing and you really want to maximize your advantages, check out the yokeless axial flux design.

Editor's Note: This article was originally published in July 2022 and was updated on November 2022.

Topics: Powdered Metallurgy, Soft Magnetic Composite

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