Demagnetization risk of Neo magnets in repel mode?

[gyulasun]

Iv'e been having two N50M neos in repel mode for 3 month now and I measured them yesterday to
see if they had lost any of their strength. Well, they hadn't lost anything. They were as good as new.

The originally measured 0.51 tesla on the surface and 3 month later in repel they still measure 0.51 tesla.
Maybe they won't become demagnetized when just sitting still. Perhaps motion is required???
I might build a rotating repel test machine later on to see if they can handle that to.

Hi Honk,

Thanks for showing this.  May I suggest to check the magnets temperature when you first try the same test with motional Neos.  IF eddy currents are involved they will heat up the Neos and this may cause some demagnetization in time.

Gyula

[markdansie]

I thought I might ask here (sorry of topic)
does anyone know of a good 3d fem software for magnet research
My email is mark.dansie@advatel.biz
Thanks

[Honk]

I got some new information from a source connected to the manufacturing of neodymium magnets.

Quote:
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The force field in a magnet is static even if the magnet is moving, That has got to do with the source of the force.
The source of the force field in a magnet is the magnet itself, due to the molecular alignment. Hence the description "static".
In an electromagnet, the force is "dynamic" because there is a flow of current. It's the Amperes that demagnetise the magnet.
And to demagnetise it, the whole magnet must be inside the force field of the electromagnet. In a rotating motor only the poles/tips
are exposed, hence degradation is not present. There is always some shape degradation (natural los of power) but that is irrelevant.
For Neo magnets its around 5-10% in 100 years. That's all.
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This seems to make real sense. There is no demagnezitation of Neodymium magnets in repel mode. End of story.

Now all of you repel mode builders can start building your motors without any risk of demagnezitation. Good luck.

[Low-Q]

There is a lot of people telling us that placing magnets in repel mode will demagnetize them.
But many of those people have used inferior magnets in their test, like cheap ferrite.
And then we hear over and over again that repelling magnets will demagnetize them.
But that might not be true if you are careful and use neomagnets of the same size,
shape and strength in repel mode. Then the fields are equal in strength.

Please read the question at this link. It explains my concern.
http://www.overunity.com/index.php/topic,2451.msg39543.html#msg39543
I think we have to sort out the risk when using good quality NdFeB magnets.

So, if we have two equally strong neo magnets of the same size and shape
they should be able to operate in repelling mode without demagnetization.

I have attached a demagnetization graph on several types of magnets.
But I have trouble understanding how to read it. Can someone here explain
how to see what type of field it takes to demagnetize the N38 in the graph?
It might clarify wether it can withstand or not to be demagnetized of a similar
external field as the N38 holds.

My experience is that one stronger magnet can demagnetize another weaker magnet.
Not even two ferrite magnets with same stregth can demagnetize each other, but if you take a neo magnet, and a ferrite magnet, the ferrite magnet will change polarity instantly when the neo magnet are close enough.
I have glued two small disc neomagnets together, equal poles facing. Then I putted them in my drawer, and after a very long time I forgot it was there, so recently I found them in my drawer. I separated them but the magnetism dont seem to weaken much. They must have been together for a year now.
My experience.

Vidar

[hoarybat]

Repel motor using N50 here  ran for 4 days and  dead.

Alittle bit about demag, Sorry its not much .

http://video.google.com/videoplay?docid=1681787127575536292&q=Walter+Lewin&total=91&start=0&num=10&so=0&type=search&plindex=3

The demagnetized motor you talking about is it a magnet only motor (stator rotor setup with magnets) with no electricity applied?  Or an electromagnet motor as Honk suggested above?

THanks