Using 3-D printing and novel semiconductors, researchers at the Department of Energy’s Oak Ridge National Laboratory have created a power inverter that could make electric vehicles lighter, more powerful and more efficient.
At the core of this development is wide bandgap material made of silicon carbide with qualities superior to standard semiconductor materials. Power inverters convert direct current into the alternating current that powers the vehicle. The Oak Ridge inverter achieves much higher power density with a significant reduction in weight and volume.
“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. “This is especially useful in a power inverter, which is the heart of an electric vehicle.”
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-kilowatt prototype inverter.
“With additive manufacturing, complexity is basically free, so any shape or grouping of shapes can be imagined and modeled for performance,” Chinthavali said. “We’re very excited about where we see this research headed.”
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 percent printed parts. Initial evaluations confirmed an efficiency of nearly 99 percent, surpassing DOE’s power electronics target 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.
Highly integrated electric motor unifies powertrain components for an electric vehicle
German researchers present the prototype of an electric motor that may shape the future of electromobility: Small, light and efficient. The electric motor was created and constructed by the four German partners in the European research project “MotorBrain”: Infineon Technologies, Siemens, the Institute of Lightweight Engineering and Polymer Technology at the Technische Universität (Technical University) Dresden and ZF Friedrichshafen. The prototype is being presented at the Hannover Messe “MobiliTec” fair stand of the German federal government (Hall 27, Stand H51).
The MotorBrain prototype is a highly integrated electric motor that unifies the most important components of the powertrain for an electric vehicle. The researchers have succeeded in designing a highly compact electric motor with only three-quarters the size of models from 2011, the year when MotorBrain began. The electric motor prototype now being presented could easily fit in a conventional-sized laptop or notebook backpack. And on top of that, it’s lighter than before. By the integration of motor, gear drive and inverter the MotorBrain partners were able to cut down the weight of the powertrain by approximately 15 percent, from 90 kilograms to less than 77 kilograms. Reduced size and weight will benefit the future car owner: A lighter electric vehicle that brings battery power “to the street” more efficiently and has a longer range than the electric vehicles of today. A medium-sized vehicle with MotorBrain electric motor and performance of 60 kilowatts (equal to about 80 hp) would be able to drive a good 30 to 40 kilometers farther than today’s electric vehicles with their average range of approximately 150 kilometers per battery charge.
Furthermore, the partners succeeded in building the MotorBrain prototype without using rare earth metals, which are currently a fundamental cost driver in hybrid and electric vehicles. Today rare earth metals are an important component in the permanent magnet of any electric motor, generating a particularly strong, constant magnetic field. The stronger the magnetic field, the higher the performance capabilities of the motor. However, obtaining rare earth metals is extremely complicated and environmentally harmful. Also, rare earth metal prices are high and fluctuate widely. The MotorBrain electric motor therefore utilizes readily available and less expensive ferrite magnets. The lower performance level of ferrite magnets compared to those with rare earth metals is compensated for by the specially developed high-RPM (revolutions per minute) rotor of the MotorBrain electric motor.
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New electric vehicle technology packs more punch in smaller package
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