Re: A little experiment on demagnetization

Hi Mariss,

It looks like your emperical evidece:

106 in-oz Unmolested Motor
82 in-oz Opened (but perhaps rotor not removed? <NEAT>)
53 in-oz Opended (rotor removed)

suggests that
1) Just openeing the motor to look at/play with the wires (leaving
rotor remaining inside?) can cause a significant torque loss.
Question: Is this possibly becasue the rotor was allowed to touch the
stator? If the the rotor were somehow kept from comming in contact
with the stator when opened, might it retain full magnetization?

2) Disassembling it essentailly can cut torque in half. Again the
question: if the rotor were to be removed without touching the
stator, would is loose as much torque.

Any comments on the above?

Thanks,

Jeff

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
<mariss92705@y...>" <mariss92705@y...> wrote:

> Hi,
>
> An addendum to the previous post. Something bothered me about the
> data. The motors I used for the test came from a very nice 4" X,Y
> table I got from Tim Goldstein made by New England Associates
> Technology.
>
> Both motors had been modified by NEAT so that the wires came out

the

> front of the motors rather than the rear as is usual. That is the
> reason I didn't want the motors after I re-motored the table with
> some really nice Vexta PK268-03A "square" motors (sorry Tim).
>
> The thing that troubled me was 82 in-oz is low for that motor.
>
> I looked thru my vast motor harem until I found another 23D6209
> motor, this time with conventional leads.
>
> I ran the same setup on this motor and got 23.5W at 5 revs per

second

> for a torque of 106 in-oz. That is more in line with what I would
> expect for that motor.
>
> I would conclude both motors had been partially disassembled (and
> demagnetized) to make the wiring modifications. The actual torque
> loss is more like 50% rather than 33% when compared to a know good
> motor (106 in-oz vs. 53 in-oz).
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Mariss Freimanis
> <mariss92705@y...>" <mariss92705@y...> wrote:
> > Hi,
> >
> > When I don't know for sure, I run an experiment:-)
> >
> > 1) I took two identical motors, (Rapidsyn 23D6209, 4.7A @ 1.7VDC)
> > connected in full-winding mode and set the current to 2.4A per
> phase
> > on a G201. The power supply was 25VDC.
> >
> > 2) I removed the rotor from one motor, waited 5 seconds, then
> > replaced it. The other motor was unmolested and would serve as

the

> > baseline unit.
> >
> > 3) Both motors were then run on a dyno and data was taken at 5

revs

> > per second (1,000 full steps per second).
> >
> > 4) The baseline motor delivered 18.25W to the dyno at that speed
> for
> > a torque of 82.3 in-oz.
> >
> > 5) The molested motor delivered 11.75W for a torque of 52.9 in-oz.
> >
> > 6) The calculated torque (and power) output for the disassembled
> > motor was 64% of the intact motor.
> >
> > 7) I removed the rotor again, leaving it out overnight before
> > reassembling it for the second time and ran the above tests

again.

> > There was no additional deterioration in performance.
> >
> > Conclusions:
> >
> > 1) Demagnetization occurs immediately on disassembly.
> >
> > 2) The motor loses about 1/3 of its holding torque and and power

as

> a
> > consequence.
> >
> > This experiment applies to standard magnet motors. I have not

tried

> > it on the newer, rare-earth magnet motors. I like the ones I have
> too
> > much to find out. Any volunteers?
> >
> > Mariss