Re: [CAD_CAM_EDM_DRO] Arc Welder Power Supply for steppers

In a message dated 6/2/2003 10:43:42 AM Central Standard Time,
sariddle@... writes:

> Another related question I have is on the rule of thumb I see often
> of supplying 20-25 times the rated voltage on the stepper motor. Does
> this always hold true and for all Volt steppers. The reason I ask is
> that I see some steppers rated for 12V. This would yeild 240+V power
> supply requirements. From what I understand this higher voltage is to
> get better responce from the steppers. At what point do you limit the
> voltage. One sure limiter is the driver boards voltage limit but are
> there others?

>

Scott: A welder DC-supply is WAY-overkill, and there is likely some
electrical detail of its design that will do damage or at least drive you nuts, when
you attempt to use it for stepper power.

You might experiment and remove the TRANSFORMER from it, and try using the
lowest-AC secondary to feed to a full-wave bridge rectifier and a capacitor of
l0,000 or more µF.

Perhaps a couple years back, most stepper systems specified a 24 VDC supply
be used, the "off the shelf" steppers having winding-voltage-ratings from, what
about 2 to perhaps 12 volts, mostly in the 2-5 volt area. Nowadays, there
are good stepper-drivers with ratings up to 80 volts. I would call that "the
upper limit" (in MY opinion!). I don't quite understand these rules of thumb
suggesting 20-25 TIMES the winding-rating for a power-supply! But that might
well apply in some situations, such as a very popular S.E. motor wants about 3+
VDC per winding, so this would mean up to 75 volts or more for the "raw DC"
supply. On the other hand, I have built some small machines with 5 volt/1 amp
stepper-windings, and used 24 VDC supplies, and that works perfectly, a ratio
of only about 5, instead of 20-25.

It may be unscientific, but the silly addage, "Whatever works!" seems
"scientifically valid" to me!

But no, NO stepper supply should EVER exceed, what, 100 volts, even if
drivers were designed to handle that! SUCH over-kill, with SUCH danger! NO way!

JRR


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