The BMW iFE.18 drivetrain: Unprecedented teamwork between motorsport and production development.

Munich. On 15th December, the new BMW iFE.18 and
the BMW i Andretti Motorsport Team will contest their first race in
the ABB FIA Formula E Championship in Ad Diriyah (KSA). At the heart
of the car, which was developed for Season 5, lies the drivetrain:
The Racing eDrive01. It brings together the pioneering spirit,
innovation and technological expertise of both BMW Motorsport and
BMW i. In an unprecedented collaboration, engineers from motorsport
and production development have incorporated the knowledge and
experience of BMW i in a high-performance motorsport drivetrain.
Here is an overview of the technical details behind the Racing eDrive01.

 

Development of the Racing eDrive01 and technology transfer.

Work on developing the BMW drivetrain for Formula E began in early
2017. The Racing eDrive01 began with pre-development for production
drive systems and was produced in the same prototype construction
facilities as the next generation of BMW i series drives. As such, it
benefits from the experience of the production engineers in the areas
of manual and mechanical manufacturing of electric motors and their
components. More than a quarter of the pre-development team is also
working on the Formula E project. The first concepts for the Racing
eDrive01 were on the test stand for the first time in mid-2017 – the
same test stand that is used for pre-production. After the delivery of
the test chassis and standard battery, work started on assembling the
test car at the start of 2018. By the time it came to the roll-out of
the BMW iFE.18 in April 2018, the drivetrain had undergone many rounds
of development and optimisation during extensive bench tests.

 

While the Racing eDrive01 benefitted greatly from the experience of
production engineers during its development, the knowledge gained by
BMW i Motorsport engineers in the tough competitive environment of
Formula E flowed straight back into the development of future E-drives
for BMW production vehicles. Motor racing makes it possible to test
new materials, technologies and methods in extreme conditions and
without having to take into consideration restrictive factors. This
way, the technology transfer between motorsport and production
development comes full circle. This technology transfer is more
intensive in the Formula E project than ever before in the history of
the BMW Group.

 

In particular, the fact that the BMW Group developed the fifth
generation of their electric drive themselves again, thereby creating
an excellent infrastructure for production and development, provides
great advantages for the Formula E project. This development factory
makes it possible to provide technological solutions tailored
specifically to motorsport within a very short period. In the
particular case of Formula E, for example, dozens of development
variants were generated mathematically and via simulation almost
overnight, from which the engineers could accurately select the
solution perfect for the project.

 

Drivetrain components: Electric motor, cooling system and inverter.

The Racing eDrive01 consists of the electric motor, cooling system
and inverter. The goals when designing all these components were
maximum efficiency, the highest possible energy density, and a
lightweight design that is as compact as possible. These goals were
primarily achieved by using state-of-the-art materials, technologies
and processes.

 

The electric motor is primarily made up of three
parts: The rotor, the stator and the casing. In order to reduce weight
and for strengthening, among other things, the rotor has supports made
of fibre composites. In addition, innovative materials such as highly
thermally-conductive resins, titanium and ceramic are used. The
combination of all the state-of-the-art technologies used results in a
high gravimetric energy density.

 

The electric motor is cooled by a virtually 360°
cooling geometry in aluminium casing manufactured via the additive
manufacturing procedure. In addition, materials with high thermal
conductivity – such as ceramic and resin – are used. Thanks to CFD
optimization, the pressure loss is minimal and maximum efficiency is guaranteed.

 

The inverter converts direct current from the
standard battery into alternating current, which powers the electric
motor. Parts of its casing are also made from fibre composites.
Multiple MOSFETS (metal-oxide-semiconductor field-effect transistors)
with state-of-the-art silicon carbide technology are used on the
inside for the semiconductor. Thanks to this technology, the inverter
achieves very high dielectric strength while having a reduced size and
minimal energy losses, and is thus smaller and lighter. An effective
cooling system and low-loss circuit layout help make the inverter as
efficient as possible.