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Sector symmetry on a 1/5 3D electro motor

Posted Jan 2, 2013, 9:57 a.m. EST Low-Frequency Electromagnetics, Geometry, Parameters, Variables, & Functions Version 4.3a 5 Replies

Akmal
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Hi All,

i have a 3D model that shows only 1/5 of whole motor. It has 3 phase and 5 pool pairs. i'm using rotary machinery modul 3D.

if i disabled all continuity BC on the outer slice surface, it converge. but it cant be right.

if continuity BC are used, it wont be converged.

there is also sector symmetry. on the documentation there only some sentences about it. if i'm not mistaken, i need to define "sector" = 5 because i have only 1/5 of it.
has any body deal with this BC?

thx and happy new year!
akmal

5 Replies Last Post May 31, 2013, 5:04 a.m. EDT
brockap3
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Posted: 1 decade ago Jan 21, 2013, 10:52 a.m. EST
Akmal~

I am currently working on a similar problem. Mine is a model of a toroidal inductor (single wire wrapped 25 times around a core, for a 25 turn inductor - calculations of inductance on a model like this can easily be done analytically), with the picture attached to this post. This is more proof of concept than anything else at this point, but we would like to understand how the inductor reacts with the core and optimizing turns and things of that nature. I should specify that this is a microinductor, on the scale of <0.5 mm tall, by <10 mm diameter. I saw your post and decided to try for a 1/5 sector as well. I can't even get the model to begin solving, forget converging. I will try it without boundary conditions as well, and I am in contact with COMSOL support personnel, but I will let you know if I find something. Do share your knowledge as you attain it as well.
Akmal~ I am currently working on a similar problem. Mine is a model of a toroidal inductor (single wire wrapped 25 times around a core, for a 25 turn inductor - calculations of inductance on a model like this can easily be done analytically), with the picture attached to this post. This is more proof of concept than anything else at this point, but we would like to understand how the inductor reacts with the core and optimizing turns and things of that nature. I should specify that this is a microinductor, on the scale of
Akmal
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Posted: 1 decade ago Jan 22, 2013, 3:58 a.m. EST
Hi Brock,

try to use MEF (magnetic and electric field) because you need no multi-turn-coil, that rotary machine provide. how you will define electricity through coil? current density or voltage. and so on.

regards
Hi Brock, try to use MEF (magnetic and electric field) because you need no multi-turn-coil, that rotary machine provide. how you will define electricity through coil? current density or voltage. and so on. regards
brockap3
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Posted: 1 decade ago Jan 29, 2013, 12:32 p.m. EST

Hi Brock,

try to use MEF (magnetic and electric field) because you need no multi-turn-coil, that rotary machine provide. how you will define electricity through coil? current density or voltage. and so on.

regards


Akmal~

After speaking with COMSOL support, I was able to glean a lot of information that would otherwise have left me lost about the different coils and different application uses.

To answer your post, it's not even that I don't need multi-turn coil, I can't even use multi-turn coils for my models (i need to model losses in the copper of the inductor and it is a single-turn toroid core anyway. I learned that MF does not appear to be working for me, I think I am struggling to understand how to apply the current through the coil.

However, when using MEF, it works quite nicely up to fairly high frequencies (due to thin copper cross-section, can withstand lower skin depths). I apply the current through a boundary defined as "magnetic insulation." The magnetic insulation boundary can then have sub-boundaries defined in which I use the terminal and ground. This I can do because my model has leads out to the edge of the model (magnetic insulation only works on outer boundaries). And since it is a terminal, I can hold it to a specific current, and COMSOL handles the rest. Any other questions?

Lastly, the model seems fairly accurate with the sector for larger sections of the coil (I tried going to smaller - 1 turn, 2 turns - sections to see if it still works), but I still have more to do on that front. For me, I don't get to use the sector symmetry. I can use a function that is in the results section once the model is solved that basically takes the model and repeats it around the circle, but the model does have to work with all the pieces rotated around (number of repetitions needs to be an integer for the model (25 turns only divisible to 5 sections or 25 sections, etc.)). Hope that answers that somewhat. Sorry my situation isn't as applicable to your own.

~Brock
[QUOTE] Hi Brock, try to use MEF (magnetic and electric field) because you need no multi-turn-coil, that rotary machine provide. how you will define electricity through coil? current density or voltage. and so on. regards [/QUOTE] Akmal~ After speaking with COMSOL support, I was able to glean a lot of information that would otherwise have left me lost about the different coils and different application uses. To answer your post, it's not even that I don't need multi-turn coil, I can't even use multi-turn coils for my models (i need to model losses in the copper of the inductor and it is a single-turn toroid core anyway. I learned that MF does not appear to be working for me, I think I am struggling to understand how to apply the current through the coil. However, when using MEF, it works quite nicely up to fairly high frequencies (due to thin copper cross-section, can withstand lower skin depths). I apply the current through a boundary defined as "magnetic insulation." The magnetic insulation boundary can then have sub-boundaries defined in which I use the terminal and ground. This I can do because my model has leads out to the edge of the model (magnetic insulation only works on outer boundaries). And since it is a terminal, I can hold it to a specific current, and COMSOL handles the rest. Any other questions? Lastly, the model seems fairly accurate with the sector for larger sections of the coil (I tried going to smaller - 1 turn, 2 turns - sections to see if it still works), but I still have more to do on that front. For me, I don't get to use the sector symmetry. I can use a function that is in the results section once the model is solved that basically takes the model and repeats it around the circle, but the model does have to work with all the pieces rotated around (number of repetitions needs to be an integer for the model (25 turns only divisible to 5 sections or 25 sections, etc.)). Hope that answers that somewhat. Sorry my situation isn't as applicable to your own. ~Brock
Xuezhou Wang
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Posted: 1 decade ago May 28, 2013, 3:36 p.m. EDT
Hi Akmal,

I met the same problem as yours. Have you handled it? I set the boundaries as shown in the attachment.
Look forward to your reply.

Best regards,
Xuezhou
Hi Akmal, I met the same problem as yours. Have you handled it? I set the boundaries as shown in the attachment. Look forward to your reply. Best regards, Xuezhou

Attachments:

akmal
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Posted: 1 decade ago May 31, 2013, 5:04 a.m. EDT
Hi,

Xuezhou Wang, periodic BC can be ignored if the slice made respecting symetry. just like brock did.

Brock, dont forget to define air domain between coil dan soft iron.

regards
akmal
Hi, Xuezhou Wang, periodic BC can be ignored if the slice made respecting symetry. just like brock did. Brock, dont forget to define air domain between coil dan soft iron. regards akmal

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