Automotive Engineering - February 2023 - 8

TECHNOLOGY REPORT
PROPULSION
ZF introduces complete e-drive system for
passenger, commercial vehicles
The ZF Group said its new e-drive system
architecture that is more compact,
offers greater energy density and is easily
adaptable will appeal to manufacturers
introducing new battery electric vehicles
when it is ready for production in
2025. In late 2022, the company showed
key details of the new modular-concept
system that can be configured to run at
400V or 800V. Executives speaking to
global media in a virtual workshop said
the customization-friendly system that
includes matched motor, inverter, gearbox
and software would offer shorter
Assembly of incumbent-tech high-voltage
battery packs at the BMW plant in Dingolfing,
Germany.
law makes EV consumer tax breaks
conditional on final assembly taking
place in the U.S., with critical battery
minerals sourced from America or its
free-trade partners.
" For now, North America is the most
difficult place to obtain materials, "
Schuster acknowledged. " But we have
to have localized materials. "
BMW's global plans envision six cylindrical-cell
gigafactories around the
world - two each in the North American
zone, Europe and China - each with at
least 20 gigawatt-hours of capacity, for
a total 120 GWh. In October, BMW and
Japan's Envision AESC announced
plans for an $810-million, 30 gigawatthour
battery factory in South Carolina
- powered by 100% net carbon-free
energy - to supply cells to BMW's massive
Spartanburg, S.C. factory. BMW
plans to have Spartanburg cranking out
a half-dozen EV models by 2030, ideally
with enough affordable batteries
and consumer tax sweeteners to keep
business humming.
Lawrence Ulrich
8 February 2023
development times for OEMs.
" ZF is positioned very well to meet
both current and future challenges, "
said Markus Schwabe, product line
manager of electric systems. ZF, traditionally
a transmission powerhouse, has
been making increasing investments in
electrification and in 2019 began supplying
the entire electric propulsion
system for the Mercedes EQS SUV. For
the new system, engineers focused on
improvements in four metrics: cost, EV
range, torque and power density.
The system is designed to be as plugand-play
as possible. ZF predicts that 80%
of customer uses can be met directly offthe-shelf,
with the remainder being easily
customized to fit any application. One key
to the new technology is that the different
needs of, say, 400V and 800V systems, is
handled on the controller chip and via
inverters with individual power switches.
The company asserted that this architecture
results in fewer components than
today's power modules. " We can serve
different market requirements faster and
more precisely, " said Otmar Scharrer, head
of electric drive technology development.
The system starts at 100 kW (134
hp) per axle and can go up to 300 kW
(402 hp).
On its new motors, ZF engineers said
that a new braided wiring design was a
large contributor to increasing the power
density of its systems. " Hairpin wiring,
the state of the art today, was introduced
five to seven years ago, [and]
ZF has improved on previous offset gearboxes
by using two planetary gearsets to achieve a
50/50 power split.
requires hundreds of laser welding
points, " said Roland Hintringer, head of
e-motor product lines. He said ZF's
braided wiring is formed and braided in
one step, saving time and requiring less
space. " It only requires 24 welding
spots, " he said. The braiding also reduces
the raw material used by 10%.
ZF engineers focused heavily on cooling
as another path to increased power
density. In addition to the water-cooled
motor housing, cooling oil is pumped not
only around the metal of the stator, but
through slots in the braided windings
themselves. Hintringer said the result is
an 85% increase in peak performance
and a 50% increase in power.
Getting power to the wheels is a new
coaxial reduction gearbox that draws on
the company's planetary-gearbox expertise
to use two planetary gears to generate
the desired axle ratio and a 50/50
power split. The bonus is that it also includes
a fully integrated differential function,
said Robert Peter, head of engineering
product line for axle drives. Peter
said that compared to two-stage offset
helical gear solutions that have been in
use since 2011, the new gearbox requires
25% less installation space, has higher
power density and offers a 10% reduction
in weight with 20% lower transmission
losses. NVH is on par with offsettype
gearboxes or better, he claimed.
Chris Clonts
AUTOMOTIVE ENGINEERING
BMW
Automotive Engineering - February 2023

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