Re: 2 phase, 6 wire motors connections

Hi,
There really is no problem (amps wise) running a 5 Amp unipolar
rated stepper motor at 2.5A in series winding mode. You can get full
uni-polar rated torque from the motors in this configuration. The
problem isn't the amperage at this point, it is the voltage. The
maximum running voltage for the Xylotex drive is 30VDC (35VDC abs.
max.). With a 5 amp stepper running in series at 2.5A, you want to
double the voltage from what the 5 amp would normally require. THIS
factor (the voltage the drive can handle), not really the amperage,
is what would be the deciding factor on what to choose. While the
Xylotex can handle such a motor in series mode, and give full rated
torque at slower speeds (metal cutting speeds), if you need faster
motion (wood router cutting speeds/fast G0 rapids), then you need a
higher voltage to get higher top end speed from the motors. At that
point you really want to look at the higher end drives. Ones rated
at 80V & 7A like Geckos will of course give you much better
performance. It's nice to be able to shop for a Chevette or a
Corvette, and choose the "drive" to fit your needs and income
source. Many people are actually driving around in their "Ferarri"
with 3 cyinder Suzuki motors, and are quite happy just "tooling"
along!

In regards to this question:

>Am I correct to think, if I hook up in the stepper motor in half
>winding, I'm going to get higher speeds, lower torque. Full
>winding, slower speeds, more torque?

If you are running the motors with a microstepping drive, then you
really do not want to try to push the motor much past the unipolar
current rating anyway. The idea: series - more torque, half winding -
more speed, is a generalization that not always true. If you keep
the amperage ratio the same (5A vs 2.5A for example) and your drive
can handle 5 A/phase, then running 5A/phase will get you FULL
unipolar toruqe AND higher speed (assuming a fixed voltage). The only
way you get MORE torque (than the unipolar rating) from the "full
winding" mode is to run ABOVE the 2.5A/phase (since the wires can
handle it), on up to an amperage of about 3.5A, BUT you then loose
all of the microstepping capabilites since you are most cetainly
saturating the motor core. If you stick with limiting the current to
5A/phase - half winding, or 2.5A - series winding, you will not get
more torque from series mode (assuming your drive can handle 5A/phase
for half-winding).
In most cases, if you have a microstepping drive, you do not want
to sacrafice the smoothness of microstepping to get the extra torque
you can acheive by going to an amperage much higher than 2.5A/phase
in series mode (you end up running with FULL step characterstics).
The extra torque you get at the motor will often be lost to machine
vibrations and oscillations and you end up with less power at the
cutting tool than sticking with running at the normal unipolar rating
(2.5A/phase series in the above example).

Jeff
http://www.xylotex.com


--- In CAD_CAM_EDM_DRO@yahoogroups.com, "rotarysmp"
<mark.wrathall@l...> wrote:

> Hi Lloyd,
>
> A six wire motor was designed to be driven unipolar, therefore it
> generates it's rated torque with one coil energized. Wiring both
> coils of a phase in series will not generate more torque, just the
> same torque at 1/2 the rated current. The trade off is a much
> steeper torque drop off with speed.
>
> The only reason to use both windings in series is to match a low
> inductance motor to a low powered drive like the Xylotex or

L297/298

> based ones.
>
> If you think about that case, say you have a 5A motor and Xylotex
> 2.5A driver, you are powering a ferrari with a three cylinder

suzuki

> motor :)
>
>

http://geckodrive.com/ycom/documents/C163R21_step_motor_white_paper.pd

> f
>
> Regards,
> Mark
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Lloyd Leung" <lloyd@l...>
> wrote:
> > Am I correct to think, if I hook up in the stepper motor in half
> winding,
> > I'm going to get higher speeds, lower torque. Full winding,

slower

> speeds,
> > more torque?
> >
> >
> >
> > Thanks
> >
> > Lloyd
> >
> >
> >
> > [Non-text portions of this message have been removed]