Achieving maximum power density in electric motors requires careful consideration of topology and design choices. We’ll be exploring the five design decisions we’ve made in our design of the next generation electric motors to achieve massive gains in power density.

Core Design Elements that contribute to power density:

1. Axial Flux   

An Axial flux motor has a  shorter length and higher torque density than a traditional radial flux motors.  Due to their flat, disk-shaped geometry,  the active parts are placed  farther from the rotational axis, creating more torque for the same magnetic force.  The shorter magnetic path and more effective  use of materials also result  in a reduction in size and weight, which enhances  power density. 

2. Single Stator – Dual Rotor 

In a single stator-dual rotor design, there are two rotors placed on either side of a central stator.

By eliminating the stator yoke, this arrangement reduces weight and associated iron losses. This further increases torque and power density while reducing the motor’s overall weight and volume.

3. Iron-Cored Stator 

Compared to air-cored designs, iron-cored stator designs offer better magnetic coupling between the stator and rotor, significantly reducing the magnet weight and increasing the motor’s efficiency and torque. The drawback of increased core losses and weight is mitigated by optimising the magnetic and thermal properties of the core materials.

4.Concentrated Winding 

Concentrated windings are simpler, more compact, and reduce the copper loss by minimising the length of wire needed, boosting power density and efficiency. Additionally, this type of winding allows for the implementation of direct coil cooling.

5.Direct Coil Cooling

In high-power-density motors, heat dissipation is critical, and direct cooling allows heat to be removed at the source, enabling the motor to handle higher current densities without overheating, and enhancing power density by preventing thermal limitations.  

Companies like YASA and Traxial (subsidiary of Magnax) use this approach to achieve very high performance in compact designs. 

Overall Impact of These Choices

• Higher Torque and Power Density: Combining dual rotors with a single stator maximizes torque output for a given motor size. 

• Efficient Heat Management: Direct coil cooling ensures the motor can operate at higher power levels without overheating. 

• Optimized Material Utilization: Iron-cored stators and concentrated windings enhance electromagnetic efficiency while keeping the motor lightweight. 

• Compact Design: Axial flux topology and dual-rotor arrangements reduce the motor’s axial length, improving volume utilization and reducing weight. 

 Companies like YASA and Traxial leverage this combination of design choices to achieve some of the highest torque and power densities in the market, making their motors ideal for high-performance applications.  

Get the technical data sheet of our latest axial flux motor, the AXF300-85s

Do not hesitate to contact us for a brainstorm chat.