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Strange Magnetic flux correlation

Hi,

I've been trying to use the same model to obtain a 1T field at varying frequencies using a steady state ac model. I have iterated the current through a coil until the magnetic flux density averages 1T through the parts cross section, then changed the frequency and repeated.

I'm getting an anomaly that at low frequency, it requires more current to obtain the same magnetic flux. See results below:

Frequency	Current	Mag Flux (T)
5	5.5	0.98
50	4.8	1.02
100	5	1.03
200	5.5	1.00
400	6.5	1.01
1000	9.3	0.99

I can't think of anything that could cause this anomoly at 5Hz. Is there something in the software that I don't understand?

Any help is greatly appreciated.

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asoualmi

Hi,

Can you share your Flux project.

Best regards.

Alex G

Sure,

Please find attached my file using 5Hz.

Thanks for looking.
Alex

Unable to find an attachment - read this blog

asoualmi

Hi,

Thanks for the file. In which part you compute the value of the Flux density (on the 2D grid)? you take the max value?

Best regards.

Alex G

I do a 3D plot of the flux density - vector, through the 2D grid, then copy the values into an excel sheet and average.

Is there a better way to get the Flux Density?

Thanks
Alex

Alex G

Did you manage to take a look at my model?

Thanks for the help.

Alex

asoualmi

Hi,

Sorry for the delay. I checked the model that you send us. May be the problem come from the mesh. In your case you need to take into account of the skin depth effect. This means that for each frequency you have to take into acount of the skin depth effect. To do it in Flux there is an option to create mesh generator type skin depth:

file:///C:/Program%20Files/Altair/2020/flux/Flux/Help/english/UserGuide/English/topics/MaillageDunDispositifAEffetDePeau.htm?hl=skin%2Cdepth

The other ay to do it in 3D, you can use a ‘surface impedance condition’. For more details:

file:///C:/Program%20Files/Altair/2020/flux/Flux/Help/english/UserGuide/English/topics/LaConditionDimpedanceDeSurfaceSpecificite3D.htm?hl=surface%2Cimpedance%2Ccondition%2C3d

To compute the average value of the flux density, you can create a sensor type operation, applied operator: average, spatial formula: select B, computation support selects defined by 2D grid.

Best regards.

Ovando_RBB

Hi there,

I am not sure where you were trying to compute the flux density but I would recommend to integrate B over the surface cut of interest and divide the result over the total surface area where the integral was applied. That will give you a more reliable number.

Hope this helps!