how to "repair" a motor magnet?

H

Herbert Widlok

Guest
Hi
Is it possible to remagnetize permanent magnets on stepper motor
rotor, that was partially demagnetized, when I have pulled it out of
stator? I knew that this could happen, but I never believed that this
will happen to me. And how they are mounting such motors in industry?

Thanks,
Michael
 
Sad to say but you may need to replace the complete motor as an assembly.
Unless you can get the manufacturere to send you a replacment magnet set.
"Herbert Widlok" <widlok@uci.agh.edu.pl> wrote in message
news:3F56F03E.D9EEBD8C@uci.agh.edu.pl...
Hi
Is it possible to remagnetize permanent magnets on stepper motor
rotor, that was partially demagnetized, when I have pulled it out of
stator? I knew that this could happen, but I never believed that this
will happen to me. And how they are mounting such motors in industry?

Thanks,
Michael
Click to expand...
 
Herbert Widlok <widlok@uci.agh.edu.pl> writes:

Is it possible to remagnetize permanent magnets on stepper motor
rotor, that was partially demagnetized, when I have pulled it out of
stator? I knew that this could happen, but I never believed that this
will happen to me. And how they are mounting such motors in industry?
Click to expand...
In theory, it is possible. But as a practical matter, probably not.

They have to use a "keeper" when removing the rotor to maintain the
field.

--- sam | Sci.Electronics.Repair FAQ Home Page: http://www.repairfaq.org/
Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/
+Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm
| Mirror Site Info: http://www.repairfaq.org/REPAIR/F_mirror.html

Important: The email address in this message header may no longer work. To
contact me, please use the Feedback Form at repairfaq.org. Thanks.
 
Herbert Widlok wrote:

Is it possible to remagnetize permanent magnets on stepper motor
rotor, that was partially demagnetized, when I have pulled it out of
stator? I knew that this could happen, but I never believed that this
will happen to me. And how they are mounting such motors in industry?
Click to expand...
You could try replacing the magnet with a neodymium/rare earth magnet.
Those are much stronger than the ferrite stuff used in most motors, so a
much smaller magnet than the original one would do. Check out
http://www.wondermagnets.com/cgi-bin/edatcat/WMSstore.pl?user_action=list&category=Magnets_and_Magnetism%3BPermanent_Magnets%3BNeodymium

Neodymium magnets can also be found in hard drives, crack one open if
you have an older one lying around and take out the magnets to get a
feel for those beasts.

HTH,

Andi
 
It's not that easy. A magnet is not just a magnet. Typically, the
magnetic material is installed on the rotor and placed in a magnetizing
fixture. The magnetizing coils are energized and this places the
desired pattern on the magnets. You can't necessarily tell what the
magnetizing pattern is by looking at the magnets (N-S are not always at
the ends). To further complicate things, the rotor was probably skewed,
meaning the magnetic "charge" on the rotor was not parallel.

In your case, you will definitely have to install magnetized magnets -
unless you build a magnetizing fixture. Either reverse engineer what's
remnant on the rotor or get a new motor.



Andreas Schmidt wrote:
Herbert Widlok wrote:

Is it possible to remagnetize permanent magnets on stepper motor
rotor, that was partially demagnetized, when I have pulled it out of
stator? I knew that this could happen, but I never believed that this
will happen to me. And how they are mounting such motors in industry?


You could try replacing the magnet with a neodymium/rare earth magnet.
Those are much stronger than the ferrite stuff used in most motors, so a
much smaller magnet than the original one would do. Check out
http://www.wondermagnets.com/cgi-bin/edatcat/WMSstore.pl?user_action=list&category=Magnets_and_Magnetism%3BPermanent_Magnets%3BNeodymium


Neodymium magnets can also be found in hard drives, crack one open if
you have an older one lying around and take out the magnets to get a
feel for those beasts.

HTH,

Andi
Click to expand...
 
Thanks You all for replays. It seems that I will have to get new motor or
use old one that now have 50% of normal torque. I hope that this will
suffice for me.

Michael Widlok
 
You must log in or register to reply here.

Welcome to EDABoard.com

Sponsor

Back
Top