Re-magnetizing stepper motor rotor?
The Wumpus, Mon Jul 10 2006, 10:43PMI have two nice, rather large identical stepper motors (unipolar 4 phase permanent magnet). Because I have no information about them I opened one and removed the rotor from the stator to find out how the leads were connected to the windings. I did find out the right stepping sequence to drive them, but apparently opening them was not too smart; being devoid of the metal encasing the rotor seems to have lost some of its magnetic flux
. I notice this because the detents when turning the axle are now much less pronounced compared to the unopened one. Also when running it the torque has decreased somewhat.Is it possible to re-magnetize a demagnetized rotor, using e.g. a Neodynium magnet or an electromagnet? The rotor is a standard two-section toothed rotor and seems to be made up of a large number of stacked iron disks. One end is the north pole and the other end is the south pole. Or will the motor never again see it's original capability?
I'm thankful for any answers.
Re: Re-magnetizing stepper motor rotor?
johnf, Thu Jul 13 2006, 03:14AM
I thought they put a huge current pulse through the windings after assembly to magntise the rotor. As to which windings and how they connected it I don't know
johnf, Thu Jul 13 2006, 03:14AM
I thought they put a huge current pulse through the windings after assembly to magntise the rotor. As to which windings and how they connected it I don't know
Re: Re-magnetizing stepper motor rotor?
The Wumpus, Thu Jul 13 2006, 01:47PM
Sounds reasonable. Huge current pulses are easy, maybe just putting it through all windings at once could work. The motor is rated for 3 amps per phase in normal use and the windings are about AWG 20-22, any idea of how large current pulse one could use without risk of destroying the windings?
The Wumpus, Thu Jul 13 2006, 01:47PM
Sounds reasonable. Huge current pulses are easy, maybe just putting it through all windings at once could work. The motor is rated for 3 amps per phase in normal use and the windings are about AWG 20-22, any idea of how large current pulse one could use without risk of destroying the windings?
Re: Re-magnetizing stepper motor rotor?
Madgyver, Thu Jul 13 2006, 03:27PM
The flux won't come back by this. You permanentley destroyed it, by opening it, making a slightly bigger airgap. This is a well known thing among robotbuilders, and so far no cure is known which can be performed by an amateur.
But on the otherside, most roboteers don't play with high amps like we do, so maybe give it a try.
Madgyver, Thu Jul 13 2006, 03:27PM
The flux won't come back by this. You permanentley destroyed it, by opening it, making a slightly bigger airgap. This is a well known thing among robotbuilders, and so far no cure is known which can be performed by an amateur.
But on the otherside, most roboteers don't play with high amps like we do, so maybe give it a try.
Re: Re-magnetizing stepper motor rotor?
Electroholic, Thu Jul 13 2006, 04:43PM
This got me thinking about how they put together a stepper in the first place. so i googled and got this
scroll down and you will see the remagnetizign station.
it can be done, but probably not at home.
and i guess you will have to clamp down the shaft, if the stator is multi-pole.
Electroholic, Thu Jul 13 2006, 04:43PM
This got me thinking about how they put together a stepper in the first place. so i googled and got this
scroll down and you will see the remagnetizign station.
it can be done, but probably not at home.
and i guess you will have to clamp down the shaft, if the stator is multi-pole.
Re: Re-magnetizing stepper motor rotor?
Madgyver, Thu Jul 13 2006, 05:03PM
Yeah your right, the have make them somehow =)
Still even problems like exact positioning and pressure clamping for remagnetisation are ridiculously harde to solve.
Madgyver, Thu Jul 13 2006, 05:03PM
Yeah your right, the have make them somehow =)
Still even problems like exact positioning and pressure clamping for remagnetisation are ridiculously harde to solve.
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