Re: [CAD_CAM_EDM_DRO] stepper current

In a message dated 26-Apr-01 06:51:29 Central Daylight Time,
rsidor@... writes:

> Question do I set the current for .5 amps now due to
> twice as many ampere turns?
>

No, you can still push one amp through 'em. But maybe they will heat up a
bit more than before, since "all the copper" is conducting. However, the
MAIN consideration is that the INDUCTANCE is now FOUR times as great
(proportional to the square of the number of turns), so the maximum
stepping-rate will be SEVERLY reduced. You just have to experiment, since
there would be no "specs" for this lashup, it never having been
intended/anticipated by the original motor's designers.

So long as you don't exceed twice the max. (half-) coil voltage at
stand-still, and never exceed 1 amp, I guess all should be OK, if you don't
need to step faster than, say, 200 or 300 steps/second.

My first experience with steppers was with unipolar motors (center-tapped
windings), and I got a "feel" for the kind of torque at a given current and
coil-voltage. Then a couple of years back, I built two lathes with bipolar
motors of the same physical size as those unipolars I had used before, and
WOW! They have FOUR times as much torque, and use LESS current at
stand-still (driver drops current back to 50% after several milliseconds of
no steps being received). MUCH better! My max stepping-rate on my machines
is about 450 sps.

Lotsa luck! Jan Rowland



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