The World’s Fastest Interior Permanent Magnet Synchronous Motor

The World’s Fastest Interior Permanent Magnet Synchronous Motor

By: David Waterworth

The shape of the longest railroad bridge in South Korea has inspired University of New South Wales engineers to design a new high-speed motor. The prototype interior permanent magnet synchronous motor (IPMSM) has achieved speeds of 100,000 RPM, making it the world’s fastest interior permanent magnet synchronous motor. IPMSM motors are used in the traction drives of electric vehicles.

📷: University of New South Wales Associate Professor Rukmi Dutta and Dr. Guoyu Chu.

The new technology has been developed by a team headed by Associate Professor Rukmi Dutta and Dr Guoyu Chu from the University of New South Wales School of Electrical Engineering and Telecommunications.

“An IPMSM type motor has magnets embedded within its rotors to create strong torque for an extended speed range. However, existing IPMSMs suffer from low mechanical strength due to thin iron bridges in their rotors, which limits their maximum speed. But the UNSW team have patented a new rotor topology which significantly improves robustness, while also reducing the amount of rare earth materials per unit power production,” the team states.

“The new design is based on the engineering properties of the Gyopo rail bridge, a double-tied arch structure in South Korea, as well as a compound-curve-based mechanical stress distribution technique.” 

The motor’s impressive power density at around 7kW per kilogram potentially offers improved performance for electric vehicles where weight is extremely important.

“Every EV manufacturer is trying to develop high-speed motors and the reason is that the nature of the law of physics then allows you to shrink the size of that machine. And with a smaller machine, it weighs less and consumes less energy and therefore that gives the vehicle a longer range,” says Dr. Chu.

“If an electric vehicle manufacturer, like Tesla, wanted to use this motor, then I believe it would only take around 6 to 12 months to modify it based on their specifications.”

Dr. Chu kindly answered additional questions for CleanTechnica:

1. What would be the estimated increased range per charge compared to current EV motors?

“We believe if we scale and optimize the motor design for EV applications, it is expected to be 10%–20% lighter and 2%–5% more efficient than motors used in existing EVs. The inverter will also benefit from the high speed and become lighter and smaller. The reduced weight and improved efficiency will contribute to an extended range — the ballpark estimation is around 5%–10% longer.”

2. Which rare earth minerals would be needed in lower quantities other than neodymium?

“The UNSW high-speed motor technology can help to reduce the total volume of permanent magnets required to provide a specific power. So, it can help to reduce the use of overall rare earth and critical minerals in high-energy permanent magnets. Our technology can help to reduce the use of samarium and cobalt if SmCo magnets are used for the motor. Samarium is a rare earth mineral and cobalt is a high-demand critical mineral.”

3. How long would such a motor be expected to last compared to current EV motors?

“Because the UNSW high-speed motor has a significantly strengthened rotor structure, it could achieve a mechanical safety factor 1.5–2 times higher than current EV motors. Consequently, it is expected to be more mechanically robust and should have a longer life span.”