Rated temperature for magnets 1

[Clyde38]

How is the rated temperature for magnets established?

Clyde Hancock
Design & analysis of electric motors and generators

http://www.motorconsultants.com

 

[EdStainless]

Two methods.
One is to run full demag curves at various temps.
This takes time and money but it gives very reliable information.
You then decide how much reduction in properties you will consider acceptable.
The other method is to build small fixtures that place the magnets at various operating conditions (demag) and then expose these to different temperatures.
Or of could you could just copy with other people publish and assume that it is good for your material.

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P.E. Metallurgy, consulting work welcomed

 

[Clyde38]

Thanks, I understand but I am curious as to how the published data is determined. In other words, what does he magnet vendor due to establish the values they publish?

Clyde Hancock
Design & analysis of electric motors and generators

http://www.motorconsultants.com

 

[IRstuff]

I think Ed answered your current question in his last sentence. ;-)

TTFN (ta ta for now)
I can do absolutely anything. I'm an expert!

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[MagMike]

The rated temperature is oftentimes called maximum operating temperature and it is more of a marketing concept. I don't like it very much, but it has gained widespread acceptance amongst laypeople.

That said, when the concept was introduced it was defined as the temperature when a magnet with a B/H ratio of 1.0 would weaken by a certain percentage. As time passed, manufacturers 'stretched' these criteria and nowadays most of the industry has settled with the data you see on most websites.

Hope that helps.
-Mike

 

[Clyde38]

Thanks Mike, that's what I was looking for.

Clyde Hancock
Design & analysis of electric motors and generators

http://www.motorconsultants.com

 

[EdStainless]

If you hunt some you can find temperature coefficients for Br, Hc, Hci, and EP.
Then knowing the characteristics of your application you can estimate the drop in field with temperature.
Most devices will stop working long before you ruin the magnet, unless you are using Neo.
For fun we built a thermometer using NdFeB magnets, their output varies that much.

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P.E. Metallurgy, consulting work welcomed