Re: Stepper current - how bad is underdriving a motor?

--- In CAD_CAM_EDM_DRO@yahoogroups.com, Tony Jeffree <tony@j...>
wrote:

> At 12:18 21/12/2002 +0000, you wrote:
> >I just acquired a NEMA42 stepper,
> >
> >840 oz-in,
> >1.45V
> >15.2amps !!
> >
> >I was wondering how much torque I
> >sould expect out of it when running
> >on a Gecko at 7A? I do know that
> >whatever torque I get will stay
> >there to a rather high speed, thanks
> >to the very low voltage.
>
> You would expect to get approx 1/2 the torque at low
> speeds, but as you say, the low voltage gives plenty
> of headroom to get good performance at high speeds.
>
> You haven't said whether the motor is 4, 6, or 8 wire.
> If it is 6 or 8 wire, the alternative is to use it in
> full coil (6-wire) or series connected (8-wire) at 7A;
> you should then get close to the rated torque at low
> speeds.
>
>
> Regards,
> Tony

Duh! Why didn't I think of that! It is six wire. So
full coil turns it into a 2.90V, 7.6A motor. That's
almost perfect. With a 48V supply, I'll have 16.5x
voltage, so I should get good high speed performance,
and 7A into a 7.6A motor will deliver nearly full
torque. Thanks Tony!

John Kasunich