Researchers at North Carolina State University (NCSU) have developed a new type of inverter that they claim offers greater efficiency in a smaller, lighter package – a hybrid and electric vehicle manufacturer’s dream.

While conventional inverters use silicon-based components, the researchers at the Future Renewable Electric Energy Distribution and Management (FREEDM) Systems Center at NCSU have developed one using off-the-shelf silicon carbide (SiC) components. SiC, as you know, is a wide bandgap material that offers much higher power density.

“Our silicon carbide prototype inverter can transfer 99% of energy to the motor, which is about 2% higher than the best silicon-based inverters under normal conditions,” said Iqbal Husain, ABB Distinguished Professor of Electrical and Computer Engineering at NCSU and director of the FREEDM Center, in a press announcement.

“Equally important, the silicon carbide inverters can be smaller and lighter than their silicon counterparts, further improving the range of electric vehicles,” says Husain, who co-authored two papers related to the work. “And new advances we’ve made in inverter components should allow us to make the inverters even smaller still.”

Husain-inverter-2016-HEADER-992x558 Figure 1: The new inverter, made using off-the-shelf SiC components. Photo by Iqbal Husain.  

Range is an important issue because so-called “range anxiety” is a major factor limiting public acceptance of electric vehicles. People are afraid they won’t be able to travel very far or that they’ll get stuck on the side of the road.

The SiC-based inverter can convey 12.1kW/L, which is close to the U.S. Department of Energy’s goal of developing inverters that can achieve 13.4kW/L by 2020. Compare this with a 2010 electric vehicle that can achieve only 4.1kW/L.

Additional boost from new SiC components

What’s more FREEDM researchers have recently made new, ultra-high density SiC power components that they expect will allow them to get closer to DOE’s 13.4kW/L target once it’s incorporated into next generation inverters.

What’s more, the design of the new power component is more effective at dissipating heat than previous versions. This could allow the creation of air-cooled inverters, eliminating the need for bulky (and heavy) liquid cooling systems.

“We predict that we’ll be able to make an air-cooled inverter up to 35kW using the new module, for use in motorcycles, hybrid vehicles and scooters,” Husain says. “And it will boost energy density even when used with liquid cooling systems in more powerful vehicles.”

The current SiC inverter prototype was designed to go up to 55kW – the sort of power you’d see in a hybrid vehicle. The researchers are now in the process of scaling it up to 100kW – akin to what you’d see in a fully electric vehicle – using off-the-shelf components.