Tech Briefs Magazine - July 2021 - 11

Q & A
Wireless Charging for Electric Vehicles
Dr. Burak Ozpineci,
Section Head, Vehicle
and Mobility Systems
at Oak Ridge National
Laboratory, is developing
a dynamic wireless
charging system that
charges electric vehicles
while driving. The same technology
can be installed in your garage, so you
never have to remember to plug it in.
Tech Briefs: Did you develop the
three-phase rotating field design as
part of your wireless vehicle
charging project?
Dr. Burak Ozpineci: Electric traction
motors are three-phase systems in which
you generate a rotating magnetic field to
impart motion to the rotor. We decided
we could use the same technology in
wireless charging - we can get higherpower,
greater power-density, lowerweight
coils that way. We demonstrated a
120-kW, 85-kHz system for which the
coils weighed about 110 pounds. When
OEMs are already trying to save weight,
you cannot convince them to put a 110pound
coil in the vehicle - it's like
adding another passenger. That's when
we came up with the idea of using a
three-phase system. We take the threephase
power from the utility and convert
it to DC.
Tech Briefs: Where would the power
conversion cabinet be installed for
on-the-road charging?
Dr. Ozpineci: It would be on the side
of the road. We would have power lines
going under the pavement to the coil.
Eventually, we want to connect the cabinet
directly to the medium-voltage
power lines.
Tech Briefs: The system could be
installed on interstate roads?
Dr. Ozpineci: Yes - we're designing
for interstate speeds. A demonstration
that was done before ours used a 20-kiloTech
Briefs, July 2021
Cov
watt system for about a mile. They didn't
have any gaps - they covered the roadway
from the beginning to the end with
coils. We're thinking that if we multiply
the power by 10, we only need 10% of
the road covered. So, that's why we're
designing for about 200 kilowatts covering
about 10% of the road. We think it
would be easier to have a single drop
with high power, rather than long
stretches of 20-kW power distribution.
Tech Briefs: What voltage do you
deliver to the vehicle?
Dr. Ozpineci: For today's passenger
vehicles, if you want to achieve ex -
tremely fast charging at 350 kilowatts,
it's going to be around 800 volts. For
electrified trucks, it looks like battery
voltages could be between 1000 and
1500 volts. We will go to higher voltages
for newer vehicles.
Tech Briefs: What power range are
you aiming for now?
Dr. Ozpineci: For passenger vehicles,
we're aiming at around 300 or 350 kW
for stationary applications. For trucks,
we want to go to higher power levels.
Tech Briefs: For people to install the
charger system in a home garage,
would they have to install a new
power line?
Dr. Ozpineci: No, not necessarily. The
maximum at home is typically 11 kW but
normally it's about 7 kilowatts. I have an
electric vehicle and I plug it in when I
arrive but I'd rather not have to bother
with that. I'd rather just park my car and
have it charge automatically without me
knowing it - that's the vision I have for
the future. If we can have in-motion
charging, if we can have charging in our
garage, if we are charging while we're at
work, we would never have to worry
about the range of our vehicle.
Read the full transcript of this Q&A at
www.techbriefs.com.
www.techbriefs.com
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Tech Briefs Magazine - July 2021

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