Oak Ridge Labs Develops New Device For Lighter, Faster Cars

U.S. government scientists have developed a lighter, stronger and more efficient power inverter – “the heart of an electric vehicle” – that could make electric cars a lot like the inverters themselves: lighter, more powerful and more efficient.

The U.S. Department of Energy’s Oak Ridge National Laboratories reports that its scientists used unusual semiconductors and 3-D printing to create their inverter, which transforms direct electric current from the car’s battery into the alternating current needed by the motor.

The unusual semiconductors include silicon carbide, which is known as a “wide-bandgap” material that can function properly at high temperatures and more efficiently than traditional semiconductors. As a result, Oak Ridge’s 30-kilowatt prototype inverter has a much higher power density with a significant reduction in weight and volume.

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This greater heat, though, can drain electrical conductivity in nearby parts that need to be cooler, so the researchers turned to the precision of 3-D printing, also called additive manufacturing, to improve the design of the device’s heat sink to keep the inverter cooler.

“With additive manufacturing, complexity is basically free, so any shape or grouping of shapes can be imagined and modeled for performance,” said Madhu Chinthavali, who led the Power Electronics and Electric Machinery Group that developed the new inverter.

Using the 3-D printer also allowed the researchers to reduce the weight of the device as well as the amount of power it wastes. As for wide-bandgap silicon carbide, its benefits are many, including improved efficiency and reliability, tolerance for higher temperatures, lighter weight and greater power density.

“Wide-bandgap technology enables devices to perform more efficiently at a greater range of temperatures than conventional semiconductor materials,” Chinthavali said. “This is especially useful in a power inverter, which is the heart of an electric vehicle.”

The new power inverter isn’t only about 3-D printing and silicon carbide, though. Chinthavali’s team also came up with a design that includes several small capacitors – which accumulate and hold electrical charges – that are lined up in parallel rows. The capacitors’ size and their arrangement make them run cooler than larger, costlier capacitors used in conventional inverters.

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Oak Ridge’s prototype has 50 parts that were created on a 3-D printer, which lead to a power-transfer efficiency of nearly 99 percent. The team now plans to use additive manufacturing to create all the parts in its next effort.

This isn’t the first time Oak Ridge has been involved in using additive manufacturing in automotive research. It recently teamed up with Local Motors of Phoenix, Ariz., to develop a large 3-D printer to manufacture an entire car, called the Strati.

This small two-seater appears to be fairly successful for a prototype. It has a range of 120 miles before needing a recharge, but only achieves a speed of 40 mph. By comparison, another electric car, the Chevrolet Volt, has only one-third the Strati’s range, but can accelerate up to highway speeds.

By Andy Tully of Oilprice.com

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