Automotive Engineering - December 2023 - BET-13

If satisfied with the energy conservation
results that the efficiency map shows,
the engineer will have optimized the
motor effectively and can begin the next
stage of development.
Improving Motor Noise Levels
In addition to optimizing the motor's
functionality and sustainability, a crucial
aspect must be taken into account: motor
acoustics. EVs are significantly quieter
than
their
conventional
factors, such as torque, iron thickness, and
temperature rise. Multiphysics modeling
and simulation make it easy for engineers
to see how the different physics phenomena
within an electric motor interact and
optimize their design accordingly.
COMSOL Multiphysics is a registered
trademark of COMSOL AB.
This article was written by Beth Beaudry
of COMSOL (Burlington, MA). For more
information, visit www.comsol.com. 
counterparts,
which initially raised safety concerns due
to the difficulty in alerting nearby cyclists
and pedestrians. As a result, it has become
standard practice for EV designers
to
incorporate a warning sound.
Multiphysics modeling and simulation
can be used to manage this sound as well
as the overall acoustics of the vehicle,
enabling engineers to ensure that it produces
ideal sound before spending time
and money to make a prototype.
To determine the acoustic behavior,
there are three analyses the engineer
should perform. First up is a transient
analysis to determine the electromagnetic
forces in the time domain for a
given rotation speed. A time-dependent
analysis is needed for electric machines
since time-harmonic analyses do not account
for motion.
Next, the Fourier transform can be
used to convert the time-domain forces
into frequency-domain harmonics. This
allows for an efficient computation of
the vibrations and noise emitted from
motor housing.
The third step is to perform a vibroacoustic
analysis of each harmonic at
different speeds of rotation. These harmonics
can be plotted using a Campbell
diagram (Figure 6), which shows loudness
as a function of speed and frequency for
a set of harmonics. With this, the engineer
can find the frequency and intensity of
the emitted noise (also known as the
sound pressure level).
With COMSOL Multiphysics, the engineer
can export the noise plots to WAV
files and hear how the motor will sound.
Depending on the results, they can make
any adjustments they wish to the rotor
slot sizes, position, and shapes until the
motor produces ideal noise.
The optimization of an EV motor involves
a careful examination of numerous
Battery & Electrification Technology, December 2023
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13
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Automotive Engineering - December 2023

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