Re: [CAD_CAM_EDM_DRO] Stepper Voltage and Current question

starcast82 wrote:

> I am currently starting to design my stepper drive and wanted to make
> sure of a couple things. I hate to see smoke. First off I have 3
> volt, 2 amp unipolar stepper motors.
>
> 1. I plan on using 25 volt supply, is this enough or should I jump up
> to 50 volts ? I read I can go 20 times the rated voltage.

25 V is marginal, and will limit top speed.

> 2. As far as current limiting goes, since I have 2 amp motors, from
> what little I found from reading, does this mean I can run 2 amps
> through each of the 4 coils <what I read> or does this mean I can
> run .5 amp through each coil ?

Neither. There really are 2 phases in a standard stepping motor. In
your case, with an 8-wire motor, each phase has 2 coils that can
be connected in series or parallel. I think the way they are all rated,
is the same as a unipolar configuration, where each coil half can take
rated current. If you run them in series (not recommended because of
inductance) you could run .5 A. Using just one half of the coil, you
would run 2 A. Using both coils in parallel (very little benefit, here)
you could run 2A also, and the motor will run just slightly cooler.

So, the 2 amp rating refers to 2 amps for EACH phase.

If your motors are really 6-wire unipolar ONLY motors, you hook them
up to use only half the coil, and use a bipolar drive feeding one end
and the center tap. This gives much better performance than unipolar
or bipolar drive using the full coil, due to lower inductance.

Jon