Tech Briefs Magazine - October 2023 - Comsol-35A

SIMULATION-BASED PRODUCT DEVELOPMENT
can be compensated for. Using the
COMSOL Multiphysics®
software, we have
investigated a number of these effects,
including:
* Fringing effects
* Torque ripple reduction by means
of rotor skew, stator skew, or the
application of grooves
A 2.5D model, consisting of
a stack of three 2D models.
This combined model is
able to approximate various
skew configurations.
CALIBRATING 2D
MOTOR MODELS
Once tested and conditioned properly,
2D and 2.5D motor models can be very
useful indeed, especially within the
context of topology optimization or
parameter sweeping. Many 3D effects
can be replicated or approximated with
2D models. This can be done for radial
flux machines and, to some extent, axial
flux machines too.
2D models have a number of blind
spots, though. Traditionally, they have
had to be calibrated and verified using
very costly prototype development
cycles. Well-established manufacturers
have typically relied on data they
have gathered over many years,
sticking to familiar designs. Now, with
recent advancements in hardware
and software development, 3D motor
models can close the gap, enabling
considerable cost reduction and faster
product development.
An important preliminary step is to
develop trust in 3D models. This can
be done by looking at simple cases
for which the 2D solution is known to
be exact - like a 3D model that is no
more than a simple extrusion. These
configurations can be used to tune the
3D meshes and solver settings to find
a good compromise between solving
speed and accuracy. Comparing with
measurements is an option too.
From this point onward, the 3D
model can take many forms - with
or without skew, with or without
end turns, with or without magnet
segmentation cuts, and so on - and a
comparison between these forms can be
used to isolate certain effects. The next
step is to determine to what degree
they can be replicated in 2D and, if they
cannot be, if there is some underlying
logic that can be used to augment
the 2D models to better reproduce
the 3D results - and ultimately, the
measurements.
When doing so, the 3D models will
be very useful to map the key points
of interest: Even if we do not know
precisely which materials are going to
be used or which thermal conditions are
going to apply, we can still investigate
which input parameters have a strong
influence on the performance of the
machine and which can be ignored -
or can be used to save costs.
Finally, it is important to keep
in mind that the electric motor is a
multiphysics machine. Therefore, an
optimal design will take into account
mechanical, acoustical, and thermal
performance as well.
2D VS. 3D MOTOR
MODELING
Historically, 2D motor modeling has
been dominant because it has provided
sufficient accuracy for very little
computational effort. However, in recent
years, the demand to fully resolve 3D
phenomena has increased. Together with
enhanced motor modeling software and
increasingly powerful hardware, this
demand opens up a whole new market.
Full-fidelity 3D modeling provides
valuable insight into many effects that
otherwise are difficult to reliably quantify.
Some of these can be replicated in 2D,
some can be approximated, and some
* Flux leakage between step-skewed
rotor segments
* Eddy currents in the magnets and the
effect of magnet segmentation cuts
for suppressing them
* Resistive effects, inductive effects,
and loss in the end turns
* Skin and proximity effects inside and
between the turns
* Electric field singularities increasing
the risk of electromagnetic
breakdown
In addition, there are several
multiphysics effects to consider, such as
those related to heat transfer, structural
mechanics, acoustics, and fluid dynamics.
A move toward 3D motor modeling
seems inevitable but should not
be seen as a solution on its own. In
practice, the best development strategy
involves a combination of 2D modeling,
3D modeling, and prototyping.
Computationally demanding research
such as topology optimization studies will
typically still be done using heavily finetuned
2D models before going back to
3D. In this context, the 3D models serve as
the missing link between the 2D models
and the prototypes: they allow designers
to gain a more profound understanding
of the machine, help them to better
interpret the measurements and calibrate
the 2D models, and - most importantly
- aid in making better design choices.
3D MOTOR MODELING
RESOURCES
The COMSOL Multiphysics motor
modeling capabilities have been extended
in recent years, resulting in better
performance and usability, and better
example models. For free access to a
collection of detailed resources on 3D
motor modeling, visit:
www.comsol.com/model/110261.
COMSOL NEWS 35a
http://www.comsol.com/model/110261
Tech Briefs Magazine - October 2023

Table of Contents for the Digital Edition of Tech Briefs Magazine - October 2023
