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The e-mobility laboratory
A premises in Switzerland is proving to be the go-to place for evaluating and testing
the insulation systems of drive-fed motors against the new generation of PWM drives
Electric mobility is on the rise
aroun d the world. What’s
more, e orts to increase the
e iciency of the technology are
ongoing. However, increasing the
voltage level (up to 800VDC) and
pulse slew rate (up to 50kV/us) of
e-vehicle drives subjects their
insulation systems to greater
electrical and thermal stress.
This research topic suits the Von
Roll Institute perfectly. In 2018, an
e-Drive lab was set up at its
premises in Breitenbach,
Switzerland, to evaluate, analyze and
develop the full range of insulation
systems used inside motors in
electrified vehicles. In addition, to
cover the large volume of requests
from world-leading automotive
companies to also assess every
detail of the insulation systems, the
Von Roll Institute’s e-Drive lab is
being expanded and better
equipped. Many automotive OEMs
already rely on the institute’s
facilities and advice for their
e-mobility products. A glance at the
testing possibilities at the e-Drive
lab shows why.
The range of testing that can be
undertaken at the innovative
institute is extensive, starting with
basic UL1446 standard tests to
ascertain the fundamental
compatibility and thermal resistance
of components. In addition to basic
resistance checking, it is also
necessary to ensure that the
di erent insulation materials used
in a system are chemically
compatible with one another to
prevent unwanted reactions
between various insulation types.
A host of other equipment is at
the disposal of the institute for
testing drive-fed motor insulation
materials. For example,
environmental test chambers allow
simulation of specific climactic
conditions, with maximum
The Von Roll e-Drive lab can assess the lifetime of insulation systems under electro-thermal stress
temperatures of up to 662°F (350°C),
a minimum of -49°F (–45°C) and up
to 100% humidity. The e ects of
thermal aging can also be simulated
using one of 15 furnaces, capable
of accepting parts up to 750mm
long and weighing 66lbs (30kg).
A vacuum chamber with high
temperature up to 212°F (100°C)
serves for tests.
These latter tests are particularly
useful when it comes to drive-fed
motors – specifically, the latest
generation of 800V systems – in
analyzing and preventing partial
discharge, which is a common
source of failure in high-voltage
motors. Until recently, motors
employed in electric cars did not run
at su iciently high voltages to
experience partial discharges, which
produce ozone. This ionized oxygen
chemically reacts with many
insulation materials. Over a long
period of time, the ozone corrodes
196 // July 2019 // www.electrichybridvehicletechnology.com
insulation, causing premature failure
in the winding insulation system.
Accordingly, the e-Drive lab has
been equipped with various pulse
generators up to 5kV amplitude and
30kHz pulse repetition rate. The
slew rate of the produced pulse is
at least 20 kV/us. The voltage
endurance test consists of placing
test components in a furnace with
temperatures up to 428°F (220°C)
to simulate real operating
temperatures, and subjecting the
components to high-frequency
square-wave voltage.
The institute has also developed
a system specifically for performing
voltage endurance tests on
insulation for drive-fed motors that
run at high frequencies. This
high-frequency sine-wave voltage
supply, with a maximum test
frequency of 1000Hz and up to 7kV
RMS value, along with high
temperature up to 428°F, can also
detect partial discharge problems
and show resistance against them.
In addition, a variety of other test
procedures can be carried out,
including vibration tests,
measurement of partial discharge
under surge voltage stress,
insulation resistance measurement,
mechanical tests such as tensile and
compression tests up to 100kN, and
assessment of thermal aging under
pulsed current loads.
Evaluation of partial discharge
events, AC and pulse conditions,
insulation resistance measurement,
insulation withstand tests constitute
diagnostic tests that can be
implemented by aging tests in a
cycle to thoroughly evaluate the
lifetime and durability of the
drive-fed motors.
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