Automotive Engineering - March 2023 - BET23

Medium-Voltage Benefits
Delta Electronics developed the solid-state
transformer (SST), power cabinet,
and the charging stand/dispenser that are
vital to the project. The SST converts the
" medium voltage " (13,200V AC) into 1000V
DC. The power cabinet uses the DC voltage
to create a current source, providing up to
500 amps. The dispenser communicates
with the vehicle and provides current to
the battery pack.
Current-generation
fast
are
considered
low-voltage.
chargers
Tesla's
Supercharger, for example, runs at 480V.
The move to medium voltage presented
hurdles, explained Zhu. " Medium voltage
can jump a wider gap because of its
higher potential energy, " he said, noting
special wire, materials, and designs
were needed to accommodate the higher
voltages. From a safety standpoint, the
DoE-Delta extreme fast charger has a medium-voltage
switch to isolate the system
from the grid. A licensed electrician with
proper personal protection equipment
must close the switch.
" If something goes wrong, the 'blast radius'
is about 30 ft [91.4 m], which is why all
others must stand clear when the switch is
actuated, " Zhu said.
There are strong reasons to opt for
medium voltage, according to Zhu. " The
advantages that we gain from pulling
directly from medium voltage include
higher efficiency, as a conventional
transformer can be about 95 percent
efficient, " he said. A conventional
transformer needs to have energy pass
through a conversion stage - another
loss - to create the DC current needed
to charge a vehicle battery, he added.
The medium-voltage system provides
an approximate 96.5 percent output and
eliminates the conventional transformer
from the charging process.
" 13.8 kW medium voltage and charging
current up to 500 amps are key features to
enable energy efficient and highly scalable
extreme fast charging, " Zhu said.
Michael Standing, Delta Electronics
Program Manager for the extreme
fast-charger system, said that eliminating a
traditional transformer in favor of a power
conversion via a solid-state transformer
equates to about a 3 percent efficiency gain.
" When you're talking about 400 kW, three
percent starts to be significant. The losses
Battery & Electrification Technology, March 2023
Delta Electronics' Charles Zhu and GM's Jim Khoury recharge a GMC Hummer EV with the 400-kW
extreme fast charger during a demo at the American Center for Mobility. (Image: Delta Electronics)
go out in heat, and you pay for the electricity
that you're wasting, " Standing said, adding
that the extreme fast-charging system
would eventually be a less-expensive way
to charge a vehicle.
Delta Electronics has multiple extreme
fast-charger system patents relating to
power-conversion topology and control.
To reach production readiness, the system
would need to undergo additional development,
system integration, and testing.
Regulatory certification also is required.
Charging On-the-Go
Then there's the ultimate time-saver:
charging without stopping at all. A roadway-embedded
wireless charging network
for EVs is coming to a stretch of urban
highway in Detroit, marking a pilot-program
first on a U.S. public road. " Our
electric vehicle receiver units are modular
and compatible with passenger vehicles
and with light-, medium- and heavyduty
commercial vehicles, " said Oren Ezer,
CEO of Electreon, based in Tel Aviv, Israel.
Michigan is expected to operate the first
electrified roadway in early 2025.
Electreon's patented wireless in-road EV
charging technology already is in use in
various European demonstration projects,
including a 0.7-mile (1.05 km) intercity toll
road in Italy and a 1-mi (1.65 km) public
road in Sweden. Sweden's policymakers aim
to have 1,243 miles (2,000 km) of electrified
roadway in operation by 2030. Detroit's
electrified roadway will be near Michigan
Delta Electronics' Dr. Charles Zhu stands
next
to the extreme fast-charging stand.
(Image: Delta Electronics)
Central, a mobility-innovation district under
development by Ford Motor Co.
" The wireless charging infrastructure
will support a suite of use cases involving
various vehicle types, including
autonomous vehicles, and it will support
partners, like Ford, " said Jim Buczkowski,
the company's Executive Director of
Research and Advance Engineering.
Cloud-Based System Monitoring
The $1.9 million-plus Michigan project
involves one lane of public roadway for a
23

Automotive Engineering - March 2023

Table of Contents for the Digital Edition of Automotive Engineering - March 2023