Smaller, Lighter Axial Flux Electric Motor Extends EV Range
January 05, 2023 by Mike Falter
The Aircore Mobility Motor from Infinitum uses PCB stator technology to deliver high torque without using iron.
While much of the recent coverage of EV efficiency trends focuses on batteries and power conversion technologies, new motor technologies can significantly impact vehicle range, energy efficiency, and costs. This is where electric motor start-up Infinitum is looking to make a difference.
The company has unveiled its Aircore Mobility motor3, an axial flux propulsion and traction motor designed to more sustainably power passenger and commercial electric vehicles, along with other emerging e-mobility platforms like aviation, marine, and construction equipment.
According to Infinitum, the Aircore Mobility motor is 10% more efficient and 50% smaller and lighter than radial flux motors with comparable torque ratings. The axial flux motor design achieves this by using patented PCB stator technology that requires 66% less copper and no heavy iron.
The improved efficiency and lighter weight translate to longer operating ranges, smaller and cheaper battery packs, and faster charge times for EVs and other e-mobility platforms.
Axial Flux Motor Technology
Most electric motors are some variant of the radial flux motor that uses iron core stators and windings to generate a rotating magnetic field that moves the rotor within the stator. The iron helps to concentrate and increase the strength of the magnetic field but is heavy and adds significant weight to the motor.
In an axial flux motor, a rotor disc resides next to the stator, and axial magnetic forces (forces parallel to the axis of rotation) induce motion in the rotor. Axial flux motors generally have a high torque to weight ratio, which makes them ideal for mobility applications like EVs or even aviation.
Printed Circuit Board Stator
Key to the small size and light weight of Infinitum’s axial flux motor is the PCB stator. Infinitum’s air core motor does not use heavy iron and copper windings in the stator. Unlike traditional motors, copper coils are etched directly onto the PCB stator, allowing for a motor with 50% less weight and size than traditional designs.
In an EV powertrain application, drive electricity from the traction inverter passes through the fixed PCB stator windings to generate the axial flux, moving the rotors and powering the vehicle forward.
In addition to size and weight, other benefits of removing iron include reduced stator hysteresis and eddy current losses, which translates to better efficiency or more physical output per unit of electrical input. The PCB stator also improves motor reliability by eliminating potential points of failure associated with the copper windings and insulation in traditional motors.
Modular Design Is Scalable
The Aircore Mobility uses a modular design that allows it to scale to the power requirements of an application without changing the core motor structure. With this approach, multiple PCB stators and rotors can be combined as needed to meet the power needs of the application, from smaller passenger vehicles to Class 8 commercial trucks like the Tesla Semi. The design flexibility allows engineers to experiment with different configurations, adding stators and rotors quickly to see which configuration best suits their power and torque requirements.
According to Ramon Guitart, Vice President of Engineering at Infinitum, this scalability to a higher power is a key differentiator for Aircore Mobility compared with prior models.
“The difference is the scalability that we have been able to achieve. These particular units are 150 kW or 200 HP, more or less,” Guitart told EE Power.
On the cost front, the PCB stator can be manufactured using widely available, standard circuit board production techniques.
Cooling a High Power Density Motor
The ability to add multiple rotors and stators allows the Aircore motor to scale in power but also presents challenges in terms of managing heat in the compact space of the motor. For Infinitum, replacing air cooling with an oil-based system was the answer to meeting this challenge.
“We achieved that [higher power density] by using oil as the cooling element for the stator, which allows us to get five to six times the power we currently have in our other units. We can extract the heat much quicker using oil instead of the normal air,” Guitart told us.
Guitart further said that for its cooling system, Infinitum uses technology allowing it to “spray the oil right onto the stator to extract the losses very quickly.”
And, the oil used to cool the stators also provides lubrication to the bearings, which improves the reliability and operating life of the motors.
CES 2023 Innovation Awards Honoree Designations
For its work, Infinitum was recently recognized with three CES 2023 Innovation Awards Honoree designations, including an award for the Aircore Mobility motor in the outstanding design and engineering in the sustainability, eco-design, and smart energy category. Other honorees for Infinitum include its Aircore EC motor which earned two awards.
Founded in 2016 and based in Round Rock, Texas, Infinitum holds multiple patents to form the basis of its lightweight, axial air-core motor designs. Each year, more than 800 million new conventional electric motors are installed worldwide, which consumes more than half the world’s electricity, according to Infinitum.