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Magnetic flux density

Posted Feb 5, 2016, 12:43 p.m. EST Low-Frequency Electromagnetics Version 5.1 1 Reply

Jianbin Chen
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I followed the tutorial then made this magnetic flux density distribution. I modified the dimension and made some changes to the file but I found that the magnetic flux only came out from one line instead of the whole block. What is happening?
Please see the attached pictures

Thank you
1 Reply Last Post Feb 8, 2016, 10:18 a.m. EST
Mark Harradine
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Posted: 8 years ago Feb 8, 2016, 10:18 a.m. EST
Your magnetic structures are quite different in the 2 models. Your "original.jpeg" image uses a Halbach style arrangement where neighbouring magnetisations are rotated 90 degrees to eachother. The other image shows alternating polarity radially oriented magnetisations. In this "6 poles..."model, high flux densities are achieved at the boundaries between neighbouring magnets, which makes the field coming from the main body of the magnet seem much smaller. Also, the permeance is much higher in the magnets in the "original.jpeg" model, (larger magnetic length to pole width ratio would be a simplistic way of looking at this) which leads to the majority of the flux "flowing" at the edges of the magnets. The low magnetic length to pole width ratio (or low permeance) in the "6 poles...." image will produce the flux distribution as shown in your image, with the low reluctance path for the magnetic flux around the contact points of neighbouring magnets.

As far as I can tell, both models are set up correctly, but you may need to experiment with the plot ranges to allow your images to show the field distribution a little more clearly. Also a logarithmic representation of the arrow plot may help your "6 poles..." plot look a little more intuitively correct.

Mark
Your magnetic structures are quite different in the 2 models. Your "original.jpeg" image uses a Halbach style arrangement where neighbouring magnetisations are rotated 90 degrees to eachother. The other image shows alternating polarity radially oriented magnetisations. In this "6 poles..."model, high flux densities are achieved at the boundaries between neighbouring magnets, which makes the field coming from the main body of the magnet seem much smaller. Also, the permeance is much higher in the magnets in the "original.jpeg" model, (larger magnetic length to pole width ratio would be a simplistic way of looking at this) which leads to the majority of the flux "flowing" at the edges of the magnets. The low magnetic length to pole width ratio (or low permeance) in the "6 poles...." image will produce the flux distribution as shown in your image, with the low reluctance path for the magnetic flux around the contact points of neighbouring magnets. As far as I can tell, both models are set up correctly, but you may need to experiment with the plot ranges to allow your images to show the field distribution a little more clearly. Also a logarithmic representation of the arrow plot may help your "6 poles..." plot look a little more intuitively correct. Mark

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