RE: [CAD_CAM_EDM_DRO] RE: Stepper questions

Alan:

The way I understand it is, because the bipolar drive actually reverses
the polarity of the voltages to the winding, it can reverse the field
more quickly than if one end of the winding is at circuit ground.

________________________________________
Andy Wander |


-----Original Message-----
From: CAD_CAM_EDM_DRO@yahoogroups.com
[mailto:CAD_CAM_EDM_DRO@yahoogroups.com] On Behalf Of Alan Marconett
Sent: Wednesday, May 03, 2006 11:17 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] RE: Stepper questions

HI Dave,

That's an interesting point! I don't recall reading anything like that,
I
could be wrong. Basically the windings do not interact as far as I
know.
Actually, one would think that "turning around" a winding, as in a
bipolar
drive would take longer. The field would have to collapse before it
could
build up in the opposite direction. Therefore wouldn't a unipolar
drive,
with its four windings have the advantage? And I'd think that the
unipolar
stepper would have the further advantage of having two windings
available
for microstepping. Half-stepping of a unipolar stepper is relatively
easy!
Just alternate one winding on and two windings on! Ever see a 5 phase
stepper? I still haven't figured out the stepping sequence for that,
but
they do 400 steps!

I'd like to see the "dual" specs for such a stepper. I'm guessing that
they
rely on a difference in current, and possibly some dissipation
differences
between the two modes. Same current * turns = same torque!

I have the opinion that it's better to use ALL of the windings
available.
But maybe it doesn't matter.

Alan KM6VV

> > A bipolar drive will provide more torque to a given motor than
> > unipolar. This is why we see the "same" size 23 double stack 3amp, 1
> > ohm motor nowadays labeled with either 280 oz.in. (bipolar) or 200
> > oz.in. (unipolar).
> >
> >
> I was under the assumption that on a uni-polar, one coil with a
> decaying charge prevents the other coil from attaining the same power
> as fast as a bi-polar drive ?
>
> Dave

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