A little experiment on demagnetization

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