3D prints world’s best inverter
"We are hoping that in just a few years from now someone will come up with a way to mass produce 3D printer designs," ORNL’s Madhu Chinthavali told EE Times. He is leader of the ORNL’s Power Electronics and Electric Machinery Group’s first completed 3D project — a 3D printed power inverter for electric cars.
Power inverters convert the direct current from batteries into the alternating current electric cars’ motors use — for which ORNL used a wide bandgap material made of silicon carbide to improve power density while reducing weight and volume. By learning the ins and outs of 3D printing these devices, ORNL hopes to amass patents that will put it in the leading position worldwide in how to use 3D printers to solve real-world problems.
"I want to be the first to do this — a first-ever kind of deal," Chinthavali told us. "Eventually we want to put the specs you want into our CAD file and print out an entire inverter for you."
ORNL claims that its design would be impossible to manufacture in any other way, as a result of its using complex geometry to increase power density and reduce weight — packing a 30-kilowatt inverter into the palm of your hand.
"Some of the parts on the interior of the inverter are not manufacturable by any other means," Chinthavali told us. "This inverter combines germanium semiconductors with silicon carbide — that is what makes it different."
Chinthavali would not reveal the brand of the 3D printer(s) used, but admitted that it took several different additive material techniques to create the entire device. Additive manufacturing also allowed low-temperature devices to be placed near high-temperature devices, for instance, optimizing the heat sink to make the device cooler yet smaller. It also used several small capacitors in parallel, for easier cooling, compared with one giant capacitor, also further reducing its size.
His group is also experimenting with DC-to-DC converters. Its overall vision is to print inverters and other devices 100% — which would mean printing the semiconductors, too, "which is not there yet, so we are going to continue to integrate as needed," Chinthavali told us.
Chinthavali’s first prototype uses 55 percent printed parts to achieve 99 percent efficiency, but his group’s overall goal is to discover how to produce 100 percent 3D parts, and to overcome the limitations to mass production using 3D printers and solve them so that anything can be 3D printed en masse in the future.
Chinthavali’s next prototype will aim for using even more 3D-printed parts, producing a 30 kilowatt inverter that is half the size of the inverters currently used in electric cars — aiming for four times the power density of the current prototype.
Researchers who contributed to this work included Curt Ayers, Steven Campbell, Randy Wiles, and Burak Ozpineci. Funding was provided by the US Department of Energy’s Office of Energy Efficiency and Renewable Energy.
— R. Colin Johnson, Advanced Technology Editor, EE Times