Discussion Forum

Hi
I'm sitting on a boat far from my COMSOL PC, so I cannot open your model, but from what you explain I suspect that you have some poorly defined BC's. In 3D it is important to define All required BC for ALL dependent variables. One thing one often forget is the voltage in MEF (but its often far easier and better, as well as sufficient to use MF without the voltage solved)

then you must ensure continuity of the current flow, COMSOl does not accept spontanous creation and dissapearing of the current, it must flow around in a vloop, be it over the outer model surfaces.

Then you have the material properties, in MEF you need to add some conduction even to the air 1-1000 S/m would do

The best to learn is to 1) test out and run several of the model librarie examples 2) start in 2D with MF (or 2D-axi) it solves so much quicker and hence is far easier to debug, then go to 3D.

Finally, check your initials conditions, by hitting the node Solve ... Dependent variables, right click and "Solve/ compute to selected", then run through the postprocessing to see the fiels, currents etc, and use the arrows plot to check tat your current flows correctly

--
Good luck
Ivar

Hi again and thanks for the answer :)

When will you be back at work on the PC? As of now, I used the default boundary conditions. This means, I have the magnetic Insulation, applied only to the air sphere surrounding the model. The air conductivity has been set to 1 S/m beforehand. I tried having an arrow plot but it only showed one arrow, so I have probably done that wrong - can you explain me how to do it? I also tried out the streamline option, which gave me some really wierd stuff, so I'm not sure about this either.

About the compute to selected, I tried doing it from two certain places in the solving sequence, but one generated me an empty plot, without any field anywhere, and the other generated an even wierder solution, so here too I may have misunderstood the instructions.

meanwhile I edited my model a tad, the core should be anisotropic so I got that, and I smoothed the geometry. I hope the anisotropy won't create more problems after we solve the isotropic case. I'm still stuck on the computing part - I want to add another coil, and the current in it has yet to be determined by the computation results..

thanks for your help, enjoy sailing your boat meanwhile :)

Shoval.

Hi again,
I've upgraded my program to 4.2, after recieving some help from the tech. support which recommended that. However, after recreating the model, and running it, it gave me the error again:

-_-_-_-_-_-_-_-_-_-_-_-_-
Failed to find a solution.
Divergence of the linear iterations.
Returned solution is not converged.
-_-_-_-_-_-_-_-_-_-_-_-_-
The log says:

Nonlinear solver
Number of degrees of freedom solved for: 168244.
Symmetric matrices found.
Iter ErrEst Damping Stepsize #Res #Jac #Sol LinIt LinErr LinRes
1 0.29 0.7500000 0.0061 7 1 8 50 0.064 0.00016
Solution time: 334695 s.
-_-_-_-_-_-_-_-_-_-_-_-_-
note the very large solution time. The model is attached, can anyone help me?

Hi once more,
seeing as no answers have been posted I'd like to update the problem. I found out that in the model I attached in the last post the air's electrical conductivity was 0; so I changed it to 1 and ran it again, hoping it would be of any difference(although I did not believe it would) and it recieved yet again the same error. It happened within only a few hours of computation(less than one night) and it eventually did give me some sort of solution plot, but I'm not sure if it's of any use.
so firstly, I still have the problem of

Failed to find a solution.
Divergence of the linear iterations.
Returned solution is not converged.

whcih needs to be resolved.
secondly, I have another question - if the computation stops with an error, but a Magnetic Flux Density graph IS shown, and is editable etc, is that plot correct? can I use it for things meanwhile - does it have a correct meaning in it?

attached the model once more.

Hii,

I am facing a similar kind of problem. Did you solve yours ??? Can you tell me how you did it ?

Regards,
Anup

hi Dear

I didn't solve my problem.I moved to other FEM software due to Administrative Problem. Sorry for inconvinience.



Regards
Nathu

No problem. Thanks a lot. I read somewhere to add a Gauge Fixing for A-field in the MF physics. I am trying that out now :)