Automotive Engineering - March 2024 - 20

EV energy
management
POWERS-UP
COVER STORY
Vishnu Medisetty, director of power electronics for Bosch in
North America.
" It's always the cost, " he said. " OEMs are focused on
three important things: cost, cost, cost. "
Ozpineci said he worked with a team in 2017 to develop
a roadmap for 2025 targets, which included cutting
costs by 50% compared to 2015. At the North
American International Auto Show in Detroit at the
beginning of the project, he noticed that many hybrid
vehicles there had an extra box in the trunk, reducing
cargo area.
" Talking to the OEMs, we heard about their interest
in power destiny, too, " he said. " At that point, it almost
sounded like power density was as important as cost.
So, we focused on improving the power density by
eight times by 2025 compared to 2015. But over the
years, though, any time I bring up power density, they
always say it's the cost. Power density is really important,
but cost is still the number one. "
VTO looks for merit
The DOE's Vehicle Technologies Office (VTO) has a
mission to support R&D efforts that " lower the cost
and improve the performance of power electronics in
electric drive vehicles. " It funds and works on dozens
of power-electronics projects to do that. A glance at
the VTO's Annual Merit Review submissions shows the
many ways companies and the government are working
on these next-gen devices. Some are working on
integrating more components - heatsinks, power
20 March 2024
In 2021, GaN Systems offered this comparison of gallium-nitride performance
versus silicon and SiC semiconductors.
modules, control circuits - into the inverter, with the benefit of reducing
the overall size so it won't require as much space on an OEM's
skateboard EV chassis. Capacitors in an inverter could also be made
smaller. Some projects use AI to redesign heat exchangers to potentially
cool devices better in smaller packages.
Since 2020, American Axle & Manufacturing has been working
with the VTO to eliminate the need for heavy rare earth materials in
its motors. So far, this project has designed a highly integrated 650volt
inverter to eliminate phase leads and has developed a sintering
method to attach discrete SiC devices to heat sinks for better thermal
efficiency.
Another approach could come from new ways to cool power electronics
using dielectric fluids. In 2018, the DOE started a $1.6-million
project to improve thermal management in EV power electronics as
part of the DOE's Vehicle Technologies Program. The project's objective
is to develop thermal-management techniques to help reach that
100-kW/L power density target. In mid-2023, the National
Renewable Energy Laboratory said it had demonstrated that a new
two-phase dielectric fluid concept, designed specifically for EV cooling,
could perform better than more familiar water ethylene glycol
(WEG) systems when used with a custom SiC module.
Bosch's Medisetty confirmed that advancing thermal-management
techniques are critical to improving its power-electronics devices.
" There is a separate group at Bosch that looks into thermal management
- that's a vehicle-level thermal-management team. What I'm
talking about is purely on the thermal-management side of the power
electronics and there are other advancements that we are looking at,
AUTOMOTIVE ENGINEERING
FROM LEFT: BOSCH; GaN SYSTEMS
Automotive Engineering - March 2024

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