JEC COMPOSITES MAGAZINE - Special Issue Composites for mobility - May 2020 - 32

APPLICATION standard
test 400-V e-drive systems. The conclusion of many successful tests is that
the industry is slowly preparing for this
big step towards an 800-V onboard
supply system as the future standard
for high-performance electric vehicles,
most probably in the next 10 years to
come.
Increasing efficiency and profitability with 800-V systems
Assuming a constant power level, the
required current can be reduced by
50% in an 800-V system compared to
a 400-V system (power=voltage*current). As a result, less copper is used,
which benefits the overall system costs
as well as the vehicle weight.
A welcome side effect is that the charging plug and the charging socket no
longer need to be cooled, as an increase in the voltage in the cable does
not increase the heat in the charging
system, but the charging process itself
is faster.
Von Roll is working intensively on the
introduction of new materials to meet
the requirements of an 800-V vehicle
electrical system. This includes, for
example, new types of impregnating
resins and insulation systems for electric motors, which have improved
thermal conductivity and thus lead to

higher efficiency in the engine. Due to
faster processability and shorter curing
times, which are possible at ambient
temperature, such an electrical insulation system is much more user-friendly. This means that electric motors can
be manufactured quicker, which in the
long term leads to massive time and
energy savings as well as lower manufacturing costs.
Problem: today, all the necessary under-the-bonnet components are not
yet available in their high-voltage version. But the investments quickly become profitable. Let's take an e-drive
motor at a cost of EUR1500: the Von
Roll insulation system can procure
10% more performance which results
either in using less material or using
a smaller e-drive motor. The cost per
piece would be reduced down to
EUR1350; at one million cars produced p.a., this saves EUR150 million
straight into the pocket thanks to the
high-performance insulation system,
without changing anything on the
e-drive motors themselves yet.
Mastering high voltage, mastering the upcoming challenges of
e-drives
Increased stress on the motor, like fast
rise time pulses of up to 50kV/µs, caus-

Focus
Von Roll offers automotive manufacturers two technologies with different advantages: polyesterimide- and epoxy-based resin systems for impregnating the stator in the e-motor, which can be applied in a trickle
process or by potting. The resin should cover the copper winding in the
motor while enclosing the air gap pockets of the electrical windings, up
to 100% (ideal case). Polyesterimide-based resins are used when the
manufacturer is looking for high temperature resistance in the engine
system, fast curing times and a quick impregnation process. Epoxy-based
resins can be used when the manufacturer is particularly looking for high
mechanical strength and resistance against external influences such as,
for example, the cooling agent in the engine. Two different application
processes are possible: either the trickle process, where the resin is trickled on the stator, which is a quick process with short process times; or
the complete potting process, which offers a higher fill factor but takes
more time. The quicker trickle process is used for standard cars produced
in high volumes and the longer, more ambitious potting process is more
commonly used for car production with lower volumes such as Formula
1 or other niche models.

jec composites magazine / SPECIAL ISSUE Mobility / May 2020

es encumbrances with power peaks
challenging the insulation system's and
e-drive motor's performance. Let's
have a look at the phenomenon of partial discharges and how to cope with it
in order to extend the motor's and car's
lifetime massively starting with a 400V system and particularly in an 800-V
system.
Partial discharges (PDs) are small
electrical arcs (also called "corona")
in voids inside or on the surface of
the insulation ignited by high electrical fields. During the impregnation
process, the air between the copper
wires is supposed to be filled entirely
with resin. However, some of the air
bubbles do remain in the resin and
between the wires. Depending on the
geometry, the air pressure and temperature inside these voids - conditions
for corona presence - may result in
degraded insulation, harmful corona
effects and, finally, motor failure.
Applying pulses using a pulse-width
modulated inverter with a high voltage level (800 V and higher) increases
the possibility of PD creation and the
power of PDs, resulting in premature
insulation failure. In short, without an
improved e-drive motor design and
appropriate insulation systems, partial discharges may cause significant
damage during the lifetime of the machine. Therefore, the manufacturers of
tomorrow's vehicles are already testing
and driving at higher voltage levels
since this will bring many advantages.
Over 100 years of experience in the
high-voltage business with lab tests
up to 100,000 V for various market
segments such as wind power, hydro
or even, in the past, coal, nuclear or gas
power, make Von Roll an unmatched
specialist in this field. The most important criteria and learnings from
these industries make it possible to
achieve 100% security, durability and
absolute robustness in a zero-failure
environment. Evaluating the thermal
and electrical stresses on insulation
systems, selecting proper insulation
materials, assessing the compatibility

JEC COMPOSITES MAGAZINE - Special Issue Composites for mobility - May 2020

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