EV Engineering News

“Electrical steel” allows electric motors to run at much higher frequencies


The DOE’s EV Everywhere initiative, announced in 2012, has set goals of bringing EV battery costs down to $125 per kilowatt-hour, and electric drive system costs to $8 per kilowatt.

To help make this a reality, the feds are investing some $59 million in 35 research projects around the country. One of these is led by Jun Cui, an Iowa State University Associate Professor and a Senior Scientist with the DOE’s Ames Laboratory. Cui’s team has won a $3.8 million grant to address the demand for better materials and performance in electric motors.

The task is tougher than it sounds – electric motors have been around since the 1830s, and the easy improvements were discovered long ago. “The hard stuff is material-related,” Cui said. “It’s the demand for better materials.”

Cui’s research team is working to develop motors with a stator core manufactured with thin layers of a new “electrical steel.” The new steel will be an iron alloy containing 6.5% silicon, twice the amount used in most electric motors today. Cui said the extra silicon increases the electrical resistivity of the material by about 50%, reducing eddy currents, heat and power loss.

Cui envisions these motors running at much higher frequencies – as much as 400 hertz, compared to today’s typical 60 hertz. This will produce a much higher motor power density, enabling motors to be made smaller, lighter and more powerful.

However, running at higher frequencies lowers motor efficiency. Cui’s new electrical steel is designed to reduce those efficiency losses, but there’s a catch: steel with extra silicon is brittle and expensive to manufacture. The Iowan researchers will study different processes for making electrical steel so it’s more ductile and cheaper to make.

This is forward-looking research with a long time horizon: “In about 10 years, if we’re lucky, we should see these motors on the road,” says Cui.


Source: Iowa State University

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