ORNL team uses 3D printing and WBG semiconductors to make smaller, more powerful inverter (update w/ metrics)
|Prototype inverter. Click to enlarge.|
Using 3-D printing and novel silicon carbide (SiC) wide band gap (WBG) semiconductors, researchers at the Department of Energy’s Oak Ridge National Laboratory (ORNL) have created a prototype power inverter for electric vehicles that achieves a much higher power density than currently available along with a significant reduction in weight and volume—almost meeting, and in terms of efficiency, beating, DOE’s 2020 targets.
The prototype stems from a two-year $1.45-million DOE-funded project to integrate wide bandgap (WBG) technology and novel circuit architectures with advanced packaging to reduce cost, improve efficiency, and increase power density.
|Metric||DOE 2020 target||ORNL prototype|
|Power density||13.4 kW/L||13.33 kW/L|
|Specific Power||14.1 kW/kg||11.5 kW/kg|
Power inverters convert direct current into the alternating current that powers the vehicle. Wide bandgap technology enables devices to perform more efficiently at a greater range of temperatures than conventional semiconductor materials, said ORNL’s Madhu Chinthavali, who led the Power Electronics and Electric Machinery Group on this project.
Specific advantages of wide bandgap devices include: higher inherent reliability; higher overall efficiency; higher frequency operation; higher temperature capability and tolerance; lighter weight, enabling more compact systems; and higher power density.
Additive manufacturing helped researchers explore complex geometries, increase power densities, and reduce weight and waste while building ORNL’s 30 kW prototype inverter.
With additive manufacturing, complexity is basically free, so any shape or grouping of shapes can be imagined and modeled for performance. We’re very excited about where we see this research headed.—Madhu Chinthavali
Using additive manufacturing, researchers optimized the inverter’s heat sink, allowing for better heat transfer throughout the unit. This construction technique allowed them to place lower-temperature components close to the high-temperature devices, further reducing the electrical losses and reducing the volume and mass of the package.
Another key to the success is a design that incorporates several small capacitors connected in parallel to ensure better cooling and lower cost compared to fewer, larger and more expensive “brick type” capacitors.
The research group’s first prototype, a liquid-cooled all-silicon carbide traction drive inverter, features 50% printed parts. Initial evaluations confirmed an efficiency of nearly 99%, surpassing DOE’s power electronics target (>94% by 2020) and setting the stage for building an inverter using entirely additive manufacturing techniques.
Building on the success of this prototype, researchers are working on an inverter with an even greater percentage of 3-D printed parts that’s half the size of inverters in commercially available vehicles. Chinthavali, encouraged by the team’s results, envisions an inverter with four times the power density of their prototype.
Others involved in this work, which was presented at the Second IEEE Workshop on Wide Bandgap Power Devices and Applications (WIPIDA 2014) in Knoxville, TN this week, were Curt Ayers, Steven Campbell, Randy Wiles and Burak Ozpineci.
Research for this project was conducted at ORNL’s National Transportation Research Center and Manufacturing Demonstration Facility, DOE user facilities, with funding from DOE’s Office of Energy Efficiency and Renewable Energy.
Madhu Chinthavali, Curt Ayers, Steven Campbell, Randy Wiles, and Burak Ozpineci (2014) “A 10-kW SiC Inverter with A Novel Printed Metal Power Module With Integrated Cooling Using Additive Manufacturing” (WIPIDA 2014)
Madhu Chinthavali (2014) “Inverter R&D” (US DOE Merit Review 2014 APE053)