Tech Briefs Magazine - June 2022 - 19

ESR in Ohm
monic analysis with COMSOL Multiphysics®
0.01
0.005
measurement
0.002
COMSOL
simulation
0.001
for the frequencies of the current
spectrum. Then we sum up our losses
for every harmonic. "
0.0005
104
105
f in Hz
106
Figure 6. A plot of the ESR curve, as calculated in the simulation, compared with ESR values derived
from measurement of a live prototype. Alignment of these curves helps validate the model for further
analysis.
Kessler's design process validates simulation
models against measured results,
where possible, and then uses the
validated models to pinpoint potential
problems. " By helping us locate hot
spots in the model, the simulation helps
us avoid issues that would have appeared
late in the development process,
or even after production had started, "
he said. " Instead, we can get specific results
and make adjustments early in the
process. "
" We perform EM modeling and validation
of every new design. We compare
the calculated equivalent series resistance
(ESR) curve with the ESR curve as
measured from a prototype (Figure 6). If
these curves are aligned, we can set up
boundary conditions for stationary and
transient heat calculations, " said Kessler.
" We can compare the temperature curves
from our thermocouples with the results
of probes in the COMSOL Multiphysics®
model. If they match, we can then simulate
all the critical points where we must
keep temperatures within limits. " The
curve data is put into the COMSOL Multiphysics®
MATLAB®
Findings
from their analyses can then
lead to design changes. Kessler explained
that each new capacitor design
typically undergoes three rounds of testing.
" With simulation, the improvement
curve gradient is much steeper from one
phase to the next. Our knowledge grows
quickly, and this is reflected in the final
product. " The latest generation of Bosch
inverters promises 6 percent greater
range and a 200 percent jump in power
density compared to previous designs.
Electrification Shifts into High
Gear
As automakers convert more of their
product lines to electric propulsion, Kessoftware
via the LiveLink™ for
interfacing product.
" Before we can do this, we have to
think about which factors should be incorporated
into the model. Some of the
variables we receive from the OEM,
such as maximum DC link voltage, are
not very relevant to our simulation, "
said Kessler. " But the current, switching
frequency, e-machine values, and modulation
schemes all help define a current
spectrum. We need to calculate the
current spectrum for all three phases of
our output to establish power losses.
Once we have this, we can do the harsler
believes that the need for rapid,
cost-conscious R&D will also increase.
" Electric mobility is growing up now. We
expect that the OEMs will come to us
with more varied needs, for inverters in
different power classes and that meet
tighter spatial constraints, " said Kessler.
" I do think that the number of products
that require new capacitor designs will
keep expanding. With our simulation-driven
development methods, we
are confident that we can keep up with
this growth, " he added.
MATLAB is a registered trademark of The
MathWorks, Inc.
This article was written by Alan Petrillo,
content writer, COMSOL (Burlington, MA).
For more info visit http://info.hotims.com/
82322-121.
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Tech Briefs, June 2022
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Tech Briefs Magazine - June 2022

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