Welcome to this
Ansys Innovation Course on
multi-material inductors.
In our previous videos, we showed the design
and simulation of a multi-material
inductor under specific DC current - 10 A.
However in most power applications,
the load usually varies from time to time.
Accordingly, the dc bias at the inductor
also varies from time to time.
Thus, the inductor dimension designed for 10 A
may not be suitable for changing DC bias.
So, what would be the best multi-material
inductor design
for a converter with changing load?
Let's take a look at this graph.
Inductance of an inductor usually drop
with DC bias,
but can have different slopes depending
on inductor design.
If a converter works a lot at light load
which means the inductor works a lot at
low DC bias,
We'd like the L-I curve to be steep.
So, the inductance at low DC bias is high
and that at high DC bias is low.
But it's not that important.
If the inductor works a lot at high DC bias,
we'd like the curve to be more flat
so that inductance does not drop too much
at high bias. Therefore, we'd like to see
how the variation in inductor design
changes the L-I curve so we'll know what the
best inductor design for the converter is.
Now let's take a look of how to simulate
and optimize L-I curves for the
multi-material inductor in Ansys Maxwell.
Open the simulation file we created in
the last video.
Let's make "r1", "r2" variables
in a multi-material design.
"r1" as the outer radius of the inner ring
"ring3".
So double click create cylinder under
"ring3" tab.
Change the radius to "1.15 mm + t1"
where "t1" is the wall thickness of the inner ring.
"r2" is outer radius of the middle ring
so follow the previous steps to change
the radius under "ring2"
to "1.15 mm + t1 + t2", where "t2" is
the wall thickness of the middle ring - "ring2".
Now we have two
dimension variables for the inductor core.
Since we're going to sweep DC current
to get the L-I curves,
we need to create another variable -
"Idc" for sweeping DC current.
Go to excitation, double click the
defined currents
and change the current value from 10A
to "Idc".
Set the nominal value to 0A.
Now let's add parametric analysis to
sweep the three defined design variables.
Right click optimetrics > add > parametric.
Under sweep definition tab,
click "add". Choose variable "t1".
Let's sweep "t1" from 0.1 mm to 1 mm
with a linear step size of 0.3 mm.
Click "add".
Then select "t2" to sweep it from 0.8 mm to
1.7 mm with a linear step size of 0.3 mm.
Finally, choose the sweep "Idc" from 0 A to 20 A
with a linear step size of 5 A.
You can check the defined sweeping
points for all variables under "table" tab.
Click "ok".
Validate and analyze the setup.
Once the analysis is completed
to plot the L-I curves,
right-click result > create magnetostatic
report > rectangular report.
For y-axis, under category choose "L"
and choose "Matrix1.L(group1,group1)".
For x-axis use "Idc".
To plot L-I curves under different "t1" and "t2",
click "families".
Make sure all values are included for
both t1 and t2. Click "new report".
We can see multiple L-I curves under
different t1 and t2
are plotted. Choose the L-I curve that best
suited the working condition of your converter.
You can calculate the weighted average
inductance for each curve
based on the percentages of
time of each dc bias on the inductor.
To get the data, right click on the plot
choose "export" to get the setup points.
For example, if inductor works at 5 A DC
current for 10% of the time,
at 10 A for 30% of the time
and at 20 A for 60% of the time,
then we can use the data to calculate
the weighted average inductance and find
the highest weighted average inductance
is when t1 equals to 1 mm
and t2 equals to 1.7 mm.
So r1, r2 for the multimaterial inductor
should be 2.15 mm and 3.85 mm respectively.
From this example we can see that
for changing DC bias,
we cannot simply calculate
r1, r2 by Ampere's law,
but need L-I plots under different conditions.
To extrapolate the best group of r1 and r2
by using Maxwell we can quickly obtain
plenty of L-I plots for our use.
So far we have shown the design of a
novel inductor using Maxwell.
Ansys Maxwell can help us quickly
predict inductance for an unconventional
multi-material inductor design
and quickly optimize the design
by concurrently sweeping
multiple variables which is difficult to
be done by hand calculations
and allow user to import custom
material properties
to ensure more accurate results which is
very important to this kind of inductor design.
Besides, we showed one example in this
course but depending on your applications
the r-in,
r-out, height, number of turns or even the
inductor shape can all be different.
The number of material can also be more
than three to get even
higher inductance density
which can all be quickly evaluated by
Maxwell simulation.
Thank you for watching this course,
for more information on Ansys Maxwell
or any of our simulation tool, visit our
Ansys learning channel -
ansys.com/courses today.