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‘Soft’ magnetic materials could give lighter, faster motors

23 September, 2019

Researchers in the US are working on motor materials and designs that could reduce electric motor sizes by more than two thirds, while transforming the same amount of power.

Existing motors, usually made with cores made of silicon steels, are designed to operate at speeds where energy losses in the form of heat are barely tolerable. It’s not possible to make them smaller or spin them faster to convert more electrical energy into power because their materials heat up to the point where the motor could be damaged.

Professor Mike McHenry and his colleagues at the Carnegie Mellon University are developing “soft” magnetic materials that generate much less heat. Using these materials, it is possible to build motors that spin faster, increasing the power output by a factor of three or four compared to motors based on traditional silicon steels. Alternatively, motor sizes could be reduced by the same factor while converting the same amount of power.

“The faster you can switch the magnetic material, the faster you can spin the motor, the more power you get out of it,” explains McHenry, a professor of materials science and engineering at the university. “So, if I can spin the motor at higher and higher speeds, I get more and more power. That means I can use a smaller motor for the same job.”

The researchers are also designing novel motor topologies, including axial designs. The smaller, more powerful motors are potentially attractive for use in robot arms, which could become more agile by having less mass to move. McHenry and his team are developing a small motor that could soon be ready for use in robots.

A 3D-printed mock-up of soft magnetic motor showing the rotor and stator designs.
Image: Carnegie Mellon College of Engineering

They also want to work with industry partners to scale up the motors for use in larger applications, such as vehicles. Using this technology, any application that needs a motor could be seeing big efficiency, size, and cost savings in the near future, the researchers say.

“As a materials scientist, I wanted to use my expertise where it could have the most impact, so I got into the motors space,” says McHenry. “With 50% of the world’s energy going through a motor at some point in time, improving motor efficiency could have huge ramifications.”

•   According to a recent report from the market analyst Fact.MR, the market for soft magnetic composites for use in motors was worth more than $6bn last year. It says that manufacturers of motors for electric vehicles are shifting from thin laminations to these composite materials to cut eddy current losses. EV motors can run a speeds of up to 14,000 rpm and switch at frequencies above 1.8kHz, resulting in high eddy current losses.

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