News: Microelectronics
2 October 2024
NREL to design silicon carbide-based power inverters for US ground combat vehicles
To transform US military ground combat vehicles, the US National Renewable Energy Laboratory (NREL) has been selected to redesign a critical component: the traction inverter, which controls the flow of electricity between a vehicle’s battery, motor and drivetrain. The new silicon carbide (SiC)-based propulsion system will double the range of Army vehicles with a footprint four times smaller than its predecessors.
The three-year, $6m project has been fully funded by the Operational Energy Capability Improvement Fund (OECIF), which guides energy innovations for the US Department of Defense. It will be led by the US Army Combat Capabilities Development Command (DEVCOM), with researchers from both NREL and the Army Research Laboratory (ARL) providing technical expertise.
NREL’s power electronics researchers will lead the development of a SiC-based power inverter dubbed PICHOT — a power inverter that is compact in scale and functions at a high operating temperature — that can offer 200% more range to US Army ground combat vehicles.
The inverter will be designed, fabricated and characterized in-house at NREL prior to evaluation at the US Army Ground Vehicle Systems Center’s test labs. Its modular design will allow it to slot into many different hybrid-electric ground combat vehicles, from light- to medium-wheeled vehicles to Abrams and Stryker battle tanks. SiC-based semiconductors and novel thermal management will give it unmatched power density, allowing vehicles to travel further with less fuel.
Reimagining propulsion system power electronics
NREL says that, to create PICHOT, its power electronics are reimagining nearly every aspect of conventional power inverters.
First, researchers studied the current leading traction inverter used by US Army ground combat vehicles: the 200kW Zeus inverter, created by DEVCOM for high-power applications. Then, based on NREL’s research into power electronics thermal management, they determined everything they could strip away from the predecessor technology — from the cooling equipment to the connectors.
Because traction inverters are typically installed next to other heat-generating elements in a combat vehicle, they need to be able to withstand high operating as well as ambient temperatures. This usually requires them to be packed with bulky cooling technologies, like cold plates or coolant reservoirs.
PICHOT will require none of these heavy cooling solutions. Instead, it will link to the existing engine coolant system, eliminating the need for additional coolant loops. In turn, unlike conventional silicon-based inverter systems — which become essentially powerless when exposed to operating environments over 70°C — PICHOT will be able to function at full power in environments of 105°C.
Due to NREL’s expertise in power electronics packaging, PICHOT will be capable of the same 200kW output as its predecessor Zeus but at a quarter of the size — small enough to fit in a shoebox. Also, while most inverters require a plethora of electrical wiring for communication, PICHOT’s main communication will be a tailored wireless system featuring remote control and monitoring while ensuring robust data security. It will also come equipped with a ‘smart’ feature that allows it to monitor its own state of health, predicting component failure before it occurs.
Compared with existing technologies, PICHOT is expected to enable 53% fuel savings, so Army vehicles will be able to stay in the field for nearly twice as long before needing to refuel. Combined with silent performance thanks to the hybrid-electric engine and electromagnetic interference shielding, Army ground combat vehicles are should become safer, longer-range and higher-performing than before.
“NREL is home to a highly skilled thermal management research group,” notes Faisal Khan, chief researcher of power electronics in NREL’s Center for Integrated Mobility Sciences, who will be principal investigator for the project. “Given the complexity of this project — designing a high-power-density traction inverter with stringent thermal management that can function in extreme environments — we are well equipped to handle this challenging work.”
Three-year timescale for design, fabrication and evaluation
PICHOT will take three years to design, fabricate and evaluate. In the first year, NREL researchers will build a computer-generated model of the inverter and simulate its operations in the real world, ensuring that it will operate as planned.
Then they will build it using the laboratory’s end-to-end prototype fabrication pipeline and demonstrate its effectiveness versus other combatants’ standard vehicles.
Finally, the blueprints will become available to manufacturers at a forthcoming industry day. The final design will be manufactured at scale, with the potential to be leveraged in multiple kinds of US Army ground combat vehicles.
Also, as the Army prepares to implement climate strategies aligned with the USA’s shift to lower-emitting vehicles, it is expected that new solutions, powered by clean energy, will provide more power, reliability and sustainability than before.
NREL’s thermal management design boosts power density of SiC inverters for heavy-duty vehicles
