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Re: [femm] how do I model a torroidal transformer ?
Robert,
Drawing point currents like this is quick and easy.
It took me a whole 5 minutes to do this entire model.
Perhaps you are not aware of using the radial copy
and mirror functions?
First you center this whole thing on
the 0,0 origin. Put in two points for the toroid
thickness on the 0,a - 0,b line. Select them with
a right click. Then do mirror copy about the y axis.
Then you enter two 180 arcs on top for the ID and OD.
Then you mirror those two about the x axis. Toroid is
done and takes about 30 seconds or less.
Next change the grid size to what you want for wire
diameter or something close. Put in two points say
inside and outside on the top. Then go to the copy
button and do an angular copy of 6 degrees and 29
copies. Bingo! Primary side is done. Do the same
thing again using -6 degrees and 29 copies. Then
delete the two initial points so you have a primary
and secondary separated by on empty spot top and bottom.
Next pick the block properties you want, air, M19 steel
for this case. Then set the point properties for the
coils. I used plus and minus 5 amps I think it was.
This whole process took about 2-3 minutes. Then simulating
and displaying it another minute. Overall it took about 5
minutes. So it doesn't take very long to set up point
currents and such once you learn some tricks.
In any case it seems there are other ways as well
based on what Keith and Mark came up with.
DRS
robert Macy wrote:
Brain dead here, that's set to median thickness,
But instead of point currents which take a lot of time to
draw in, how about more curves and then use the "circuit"
properties. That way you automatically get inductance per
turns squared.
- Robert -
On Mon, 25 Aug 2003 10:04:51 -0700
Dave Squires <djsquires@xxxxxxxx> wrote:
Come on guys. This is easy.
The attached file shows you how to do this.
Remember this is static, not dynamic. But this
will work fine for getting the field. This would
be a no load condition. For a loaded case you
would have to calculate the rate of change,
figure the voltage induced and the current based
on the load. Depending whether the field is
rising or falling in the primary you can determine
the Lenz reaction polarity accordingly to oppose
or assist the primary drive. I will leave that
up to the user to handle all the other details.
The main trick is to use point currents for the
coil windings. Just run the attached file.
David Meeker can fill you in on any other way
to do this. But this is one way.
DRS
robert Macy wrote:
> The torroidal transformer *is* axisymmetric, but
when drawn
> that way the currents go around the small circle and
the
> magnetic field is perpendicular to the page. I
don't think
> femm solves this situation.
>
> Instead and approximation is to draw the cross
sectional
> view in x-y form and set the total length to the
median
> circumference.
>
> The "crunching" of the field at the inside
curve won't show
> up, but it will get you started.
>
>
- Robert -
>
> On Mon, 25 Aug 2003 03:16:32 -0000
> "Dr Mark Snoswell"
<mark@xxxxxxxxxxxxxxx> wrote:
>
>>
>>
>>
>>How do I model the field of a torroidal
transformer? ...
>>it's axi
>>symetric but I can't quite see hwo to model it.
>>
>>
>>
>>
>>
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>>
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----------
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[Comment] = "Add
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