How can I find out which type of magnet Is?

[FarshidKamran]

I repair electrical motors in a workshop and sometimes I must repair PMDC motor and other motors that their poles are made of permanent magnet.I need to specify type of permanent magnet (Ferrite or Alnico or rare earth or ...)by a simple methode.Is there any idea about it? Thanks.

 

[oldfieldguy]

I think I'd go out and grab my nearest ChemE or a chemistry major and talk to them. It's pretty easy to differentiate between ferrite and metallic, but between various metallic formulations is more difficult.

old field guy

 

[MagMike]

If the magnets are part of the rotor, they almost certainly are rare earth magnets such as NdFeB or SmCo. Since there are dozens of different grades of rare earth magnets, I recommend sending a sample to a reputable magnet distributor and let them know you want them to quote a particular quantity. It would be ideal if you could send an intact magnet. It is a simple matter to non-destructively determine the material type and grade. I do this all the time, returning the sample after testing.

 

[DRWeig]

Is there a good resource for the densities of different magnets? If they differ enough, an accurate balance and a graduated cylinder to measure volume can be used. We do that with gold jewelry to determine 18k vs 14k vs the occasional 24k ring, chain, and other odd-shaped things.

Best to you,

Goober Dave

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[MagMike]

Density will only tell you if it is SmCo or NdFeB, not the grade of material.

FWIW: SmCo has a density of ~8.4 g/cc. NdFeB has a density of ~7.6 g/cc

 

[FarshidKamran]

Hi MagMike! Are you sure that “If the magnets are part of the rotor, they almost certainly are rare earth magnets such as NdFeB or SmCo. “? but I've seen some rotors with Ferriet magnets. evidently there is no simple, inexpensive and non-destructively way to determine the material type and grade.

 

[MagMike]

You'll have to send it to a reputable magnet vendor and it is a fairly simple matter to determine the grade of magnet material and it is nondestructive.

 

[FarshidKamran]

Thank you for your replys.