Truck & Off-Highway Engineering - December 2023 - 20

BorgWarner targets more-sustainable
E-MOTORS
" The dominant design for motors today is probably the worst
for sustainability in terms of KPIs as well as highest in cost.
But it serves the greater good of the system. "
David Fulton, director of electric
machine innovation at BorgWarner.
" Smart engineering " - a term
repeatedly used at the SAE
COMVEC conference - is necessary
to find cost-neutral solutions
that satisfy performance and sustainability
goals. System optimization
tools and lifecycle analysis
will be key to evaluating the relevant
metrics and managing
trade-offs, according to Fulton.
" Having the right kind of toolset
to be able to not only [determine]
multiphysics optimization,
which we've done for years, but
also to look at cost models and
lifecycle analysis for each of these
components to weigh that all out
is important, " he said.
Material standardization can
help with costs as well. " But it's
only relevant in areas where
materials are relatively mature, "
Fulton said. " I think rare earth
magnets are probably in that
camp. Batteries, not so much. "
An alternative, less-than-ideal approach to smart engineering is
BorgWarner's current motors for commercial vehicles offer up to 97% peak efficiency, but development of
new rotor technology is ongoing.
Trade-offs must be managed for next-gen motors that feature more-sustainable rotors.
" brute force adaptation, " Fulton said, comparing a baseline HRE
magnet used in one of BorgWarner's commercial-vehicle motors to a
redesigned zero-HRE magnet. " This [baseline] is very lean on the use
of heavy rare earths - as lean as you can get today using the diffusion
processes. If we used the best possible non-heavy rare earth
magnet for sustainability reasons, we're redesigning it to get the
same function - the same performance, same maximum speed rating
and same protection against demagnetization, " Fulton explained.
" But when we do this, we're handicapped right from the beginning
by losing half the coercivity of this magnet material at high temperature.
As a result, to protect the magnet against demagnetization you
20 December 2023
see how much thicker it becomes [see graphic on next
page], and that's the outcome of brute force adaptation, "
he said. " So even though the cost-per-kilogram
is lower, the cost of the magnet is quite a bit higher,
over 50% higher. And the magnet is, of course, a significant
fraction of the bill-of-material cost of these
permanent magnet motors. "
Fulton said engineers can take a step back and employ
the five-whys technique to determine new solutions.
" Why does the magnet have to tolerate such high
temperatures? Why can't we deal with something that
is not so high temperature? Of course, that begs the
TRUCK & OFF-HIGHWAY ENGINEERING
CLOCKWISE FROM TOP LEFT: SAE/RYAN GEHM; BORGWARNER; BORGWARNER

Truck & Off-Highway Engineering - December 2023

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