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Permanent magnet machine modelling!

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I am simulating a permanent magnet generator, in 2D Comsol, 'emqa', 'ALE' mode. But there is a problem concerning magnetic circuit saturation as the followings:

- My programs are convergent with linear permeability, but converge in some cases
- In static mode, there are no problems; my program is convergent with any types of BH curves (using analytical function of BH curve or piecewise line or table).
- While generator is no load, my program is not convergent with BH curve using table interpolation; even BH curve is made so smoothly and corrects the natural of physical.
But my program converges with a few analytical functions, not all; if analytical function of BH is identical to measured BH curve, my program does not work.
- While generator operates with load, having electric current in winding, my program is not convergent. Even I operated my program in right way: first run with linear permeability, and then...However, if the remanent flux density of magnet is reduced to certain value, e.g (Br=0.8T), my program is convergent. It is so strange!

I also discussed with my colleagues using other FEM soft wares; it seems like having the same problem. Are there any limitations of FEM-softwares?

I would like to receive suggestion from Comsol experts.

Thanks in advance.


8 Replies Last Post May 15, 2013, 7:46 AM EDT

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Posted: 10 years ago Nov 18, 2009, 4:27 PM EST
Hi

Difficult to give a clear answers, but I do not beleive it's any limitation related to the FEM as such, it hears more like a "stepping" issue for the non-linear solver.

Have you tried to select "highly non linear" in the solver tab ? and read carefully through the manuals on solver settings for non-linear solving ?

Try to understand how the solver si moving along your non linear curves, probably it's stepping to quickly and does no get to follow the gradients of your curves.

Good luck
Ivar
Hi Difficult to give a clear answers, but I do not beleive it's any limitation related to the FEM as such, it hears more like a "stepping" issue for the non-linear solver. Have you tried to select "highly non linear" in the solver tab ? and read carefully through the manuals on solver settings for non-linear solving ? Try to understand how the solver si moving along your non linear curves, probably it's stepping to quickly and does no get to follow the gradients of your curves. Good luck Ivar

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Posted: 10 years ago Nov 19, 2009, 8:04 AM EST
Dear Hung,

Please run the model that does not converge again and send me the
surface plots of normB and of mur that you obtain at the last computed
solution. Based on previous experience, I expect that the value for
normB becomes too high and the the value for mur becomes too low
in certain regions of the geometry. I would like to see whether we can
solve the non-convergence using either a finer mesh or by rounding
sharp corners in the domain (using fillet). The fact that the simulation
does work for the permanent magnets included in the model can be
possibly due to the fact the field of the permanent magnets prevents
the values of normB becomming too large. So, please send me the two
figures.

Best, Domenico.

Dear Hung, Please run the model that does not converge again and send me the surface plots of normB and of mur that you obtain at the last computed solution. Based on previous experience, I expect that the value for normB becomes too high and the the value for mur becomes too low in certain regions of the geometry. I would like to see whether we can solve the non-convergence using either a finer mesh or by rounding sharp corners in the domain (using fillet). The fact that the simulation does work for the permanent magnets included in the model can be possibly due to the fact the field of the permanent magnets prevents the values of normB becomming too large. So, please send me the two figures. Best, Domenico.

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Posted: 10 years ago Nov 19, 2009, 8:20 AM EST
Hi,

Thanks for your useful information. I took some time to play with it and will try more.

Thanks again.

Hung
Hi, Thanks for your useful information. I took some time to play with it and will try more. Thanks again. Hung

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Posted: 10 years ago Nov 19, 2009, 8:22 AM EST

Hi Domenico,

Thanks for your information. I am collecting that you required and will send you as soon as possible.

Regards, Hung
Hi Domenico, Thanks for your information. I am collecting that you required and will send you as soon as possible. Regards, Hung

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Posted: 8 years ago Feb 17, 2011, 5:24 AM EST
Hi All,

i have quite the same problem.

and looking forward to hear from the experts

regards
akmal
Hi All, i have quite the same problem. and looking forward to hear from the experts regards akmal

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Posted: 8 years ago Feb 17, 2011, 5:33 AM EST
Hi,

With Comsol version 3.5a or newer, you can solve nonlinear transient problem of a permanent magnet machine efficiently. Let try with different solvers to find good one.

Good luck.

Hung.
Hi, With Comsol version 3.5a or newer, you can solve nonlinear transient problem of a permanent magnet machine efficiently. Let try with different solvers to find good one. Good luck. Hung.

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Posted: 6 years ago May 15, 2013, 7:39 AM EDT
Hello Hung,

I met the same problems as yours. I am wondering whether you have solved these problems.

One interesting thing is that my problem is not convergent with HB curve in stationary study while you have finished on it. Would you mind to share your steps with me? Thank you in advance.

Best regards,
Xuezhou
Hello Hung, I met the same problems as yours. I am wondering whether you have solved these problems. One interesting thing is that my problem is not convergent with HB curve in stationary study while you have finished on it. Would you mind to share your steps with me? Thank you in advance. Best regards, Xuezhou

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Posted: 6 years ago May 15, 2013, 7:46 AM EDT
Hello Domenico,

I guess these are the same problems I met with. However, Hung made it converge with any type of BH curve in stationary case while I failed. How about the progress on this issue?

Look forward to your reply. Thanks in advance.

Best regards,
Xuezhou
Hello Domenico, I guess these are the same problems I met with. However, Hung made it converge with any type of BH curve in stationary case while I failed. How about the progress on this issue? Look forward to your reply. Thanks in advance. Best regards, Xuezhou

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