Re: current limiting power supply for stepper?

Hi Grant,

I love research and would never tell people not to try something.

If you go back and read some of the posts on this topic, you'll find
that most chopper style drivers feed the power into the motor with an
inital high voltage, once the watts are reached, the voltage is
reduced to keep the current there. the chopper, micorstep will not
use near the listed power of the motor itself. ie: a 4 amp driver
will rarely use 4 amps.

also, with multiple motors, one would typically use one power supply
to feed 3 motors. if one is running at slow speed, the power
requirements are less than three, all at high acceleration.

Since the power requirements are so widely varied, current limiting
the power supply may not be needed, it certanly would rarely if ever
be used.

just my opnion, but it would be neat if you found some method of
making it easier for us to make power supplies.

Dave

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "grantfair2001
<grant.fair@s...>" <grant.fair@s...> wrote:

> Hi Dave-
>
> The power supply I am thinking of using has adjustable voltage and
> current limiting. When the specified current limit has been met the
> voltage lowers (and maximum current remains constant).
>
> (This is from National Semiconductor's datasheet on the LM317, p

14).

>
> So for a given stepper I would adjust the max. current to the max
> current rating for the motor, but use a higher voltage than the
> nominal motor voltage rating. The current would not exceed the

motor's

> max.
>
> I know this is not the way it is usually done, but I am wondering if
> there is any reason not to try it.
>
> Grant
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "turbulatordude
> <davemucha@j...>" <davemucha@j...> wrote:
> > Hi Grant,
> >
> > there is a maximum current you can pump into a motor. voltage is
> > limited(chopped) to keep the power on the upper end of the

curve.

> > current monitoring is how it is done.
> >
> > for reasons why 25 times nameplate is the max as far as voltage

goes,

> > read the white paper at www.geckodrives.com
> >
> > Dave