Discussion Forum

Hi

I would sugest to either make the magnet by a series of adjacent disk segments, and define two set of magnetic material polarized (magnetisation) alternately,

or set up a cylindrical coordinate function and multiply the magnetisation by this alternating sign polar development.

Both should be similar, I believe.

A good thing to check and pls report back so we all can learn someting interesting

--
Good luck
Ivar

Hi Ivar,

Thank you for your response.

I have already finished the modeling but the problem is that the solution does not converge. So, I will be thankful if you help me and verify my approach in this model.
My model is composed by a Permanent magnet disk and a rotating copper disk (see the attached file Permanent magnet disk).
To do that, I created a sphere, a disk and another disk divided in four parts (see fig2: the red one is the copper disk and there are four magnet under the copper disk alternately magnatized).

I have used 2 physics: 1/ Magnetic fields no currents (mfnc), in order to create the permanent magnets. (domain selection = all domains)
2/ magnetic and electric fields (mef), in order to define the induced current and then calculate the resulting torque in the roatating disk . (domain selection = all domains)

In the mfnc, I created the four parts of magnet alternately mgnatized
and in the mef, I have defined the the velocity of the disk (-y*w,x*w,0) and the external current density Je = sigma * w * B * (x,y,0). (sigma = conductivity and w is the angular velocity).
See the attached file fig3 for the physics part.

I used an extra fine mesh for the disk and the four magnets, and a fine mesh for the remaining domain(the sphere)
For the study, I have done 2 stationary simulations: for the first simulation I deselected the mef physics interface and for the second I select mef and deselect mfnc (See fig4).

when I simulated the model, an error message appear: out of memory in stationary solver.
In the other hand, could you please tell how to calculate the torque applied to the copper disk (my objective in this project is to calculate the torque in the roating disk).

Thank you in advance.

Best Regards.

John J.

Hi John,

do I understand you correct that you define Je on the perment magnets?

I would set the Lorentz-term on the copper disk (with the appropiate rotation) and set a conductivty via
the material settings. And no explicit external current, because the eddy currents are computed by Comsol.


Regards

Jens

Hi Jens,

I want to simulate this magnet (see attached file) and then see the effect of the induced magnetic field in a conducting disk that is situated under the magnet. I choose the magnetic and electric filds (mef) physics.
I have again the error message: singular matrix
Thank you in advance.
Have a nice day!

Regards.

John J