Truck & Off-Highway Engineering - December 2023 - 19

ELECTRIFICATION FEATURE
BorgWarner targets more-sustainable
E-MOTORS
System optimization and
lifecycle analysis are key
to taking heavy rare earths
out of next-gen motors for
commercial EVs.
by Ryan Gehm
A
ll components of an electric propulsion system
- the motor, battery pack and inverter,
in particular - are interrelated and optimized
for a system function. Still, there are
significant trade-offs in cost and what's best for sustainability
when developing today's e-drive systems,
according to David Fulton, director of rotating electric
machines, PowerDrive Systems at BorgWarner Inc.
" The dominant design for motors today is probably
the worst for sustainability in terms of KPIs [key performance
indicators] as well as highest in cost. But it
serves the greater good of the system [by enabling]
the lowest cost for the battery pack and inverter, "
Fulton said at the 2023 SAE COMVEC conference, during
his presentation on next-gen motor technology for
commercial vehicles.
The majority of current motors are rare-earth-magnet
types on the rotor side, he said. These designs use heavy
rare earth (HRE) elements that allow them to be used at
high temperatures without demagnetizing. " This is a
concern because of how short the supply is globally for
these, and they virtually all are found in China or near
China, " Fulton said. " This is going to be a short-term
supply problem very soon. So, heavy rare earths are going
to be the first to be taken off the table. "
Dysprosium and terbium are two HREs commonly
used as additives in neodymium (Nd) magnets.
Though light rare earths such as Nd are more plentiful
than lead, for example, higher BEV volumes and
increased wind power - not to mention unpredictable
shifts in geopolitics - likely will drive prices
higher, Fulton said.
TRUCK & OFF-HIGHWAY ENGINEERING
BorgWarner's 800-volt
HVH320 electric motor for
commercial vehicles features rare-earth
magnet and aluminum induction rotors.
" Rare earths in general are well known to have high environmental
impacts, " he said. " They might be only 3% of the mass fraction of the
motor but over 20% on the carbon footprint, because of all that has to
happen to process those materials. " The recyclability of rare earth metals
also poses a challenge - it's difficult and not particularly cost-effective.
" People would rather dig them out the ground and make more new
magnets than recycle, " Fulton said. " If we did something like gradeto-grade
recycling - as we separate plastics into categories and recycle
those - and just change the dimensions of the magnet in the
future but not what they're made of, that could help enormously. But
the problem with that, of course, is at end-of-life for these motors, is
that magnet grade going to be competitive? My hope is that we find
entirely different magnets altogether that are much lower cost to
recycle by that point in time. "
Rotor development for next-gen motors
Different types of rotors that are more sustainable have been gaining
traction in the automotive industry. Copper induction rotors offer
higher conductivity and greater efficiency than aluminum induction,
according to Fulton. Wound rotors essentially replace the magnets
with electromagnets. " That means we have to provide current to the
rotor and need a special excitation board in the inverter to do that, "
Fulton explained. " That's not a problem. "
Another option is non-HRE rotors. Several automotive OEMs have
moved in this direction. Fulton referenced General Motors and its Chevy
Volt hybrid, which uses ferrite magnets, as one example. But there's a
catch with these higher-sustainability solutions: higher system costs.
December 2023 19
BORGWARNER
Truck & Off-Highway Engineering - December 2023

Table of Contents for the Digital Edition of Truck & Off-Highway Engineering - December 2023
