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Alex G

Strange Magnetic flux correlation

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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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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?


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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:



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



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.

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