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What is the best soft iron disc thickness for 22mm x 3mm disc magnets

Hi, I am building a wind turbine with 12 , 22mm diameter x 3mm thick magnets on 6inch diameter soft iron disc and 9 coils on a wooden stator? Is the thickness of the soft iron magnet discs critical? Is 3.5 mm too thin or 10mm too thick?


The dimensions of your magnets are important, but their field strength is also controlled by what kind of material they are made of. Are they ceramic, neodymium, samarium, or something else? What grade material- C8, N32, N58, S26, or something else?

Meaured in inches, your magnet is a bit smaller than 7/8 inch by 1/8 inch. If it is grade N42 neodymium, it might have a BrMax of 13,200 gauss like this one.

If the iron is thick enough for your magnets, the field loops between north and south poles of your magnets will flatten out against it, piling up to a high density. Your coils will then be able to cut through many field loops at once.

But if your magnets are powerful enough, some of the magnetic field loops will pass straight through the metal, spreading out into empty space where your coils are never going to touch them. That is, you would not be making full use of your magnet's strength.

frollard8 years ago
Strength is important - the 3.5 is easily strong enough. More weight is more flywheel capacity however; and helps to reduce the effects of 'cogging'