stepper voltage ( was Re: Simple PSU stuff

Jan,

Couldn't have said it better myself.

Mariss

>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, JanRwl@A... wrote:
> > In a message dated 12/13/2002 5:52:38 AM Central Standard Time,
> > echnidna@y... writes:
> >
> >
> > > Assuming each motor may operate simultaneously, the transformer
> for your
> > > power supply is not large enough to handle 3 - 2 amp bipolar
> motors.
> >
> > Bob:
> >
> > I thought this way, too, when I first bench-tested my first

(only,

> so far)
> > bipolar-CHOPPER Gecko-drives (G210). Mariss explained to me why
> the MAGIC I
> > observed: I had about 30 Volts, unregulated but filtered
> ("smoothed" in
> > English-English; We Yanks call that "filtered"), DC feeding two
> G210's,
> > those driving two 3+ amp motors, with two 3+ volt windings, each,
> i.e., about
> > 20 watts per motor. With BOTH motors stepping simultaneously,
> meaning that
> > neither was drawing only 1/3 current "at standstill" like the

Gecko

> drives do
> > after a second or so pause, the DC from the 30 V supply was less
> than two
> > amps! Yet, both motors had "full rated torque". Mariss pointed
> out that the
> > supply was supplying WATTS, as the chopper-drive still puts-out
> about 30
> > volts with this supply to the motor-windings, but "chopped", to
> average the
> > current down to the 3+ amps rating.
> >
> > If I dare attempt "the math": Say the supply IS exactly 30 VDC,
> and the
> > current-rating per winding for the motor in question is exactly

3.0

> amps, and
> > the rated winding voltage is exactly 3.333 volts. I.e., exactly

10

> watts per
> > winding, or 20 watts for this motor. Now, to keep only 20
> watts "into" the
> > motor with a 30 VDC supply, we must "chop" the voltage/current to
> maintain 20
> > watts total to the motor, so, with 20 W./30 V. = 0.67 amp, less
> than ONE
> > winding's rated current! Yet, it "appears" that 3 amps is

flowing

> in BOTH
> > windings (and it is!). It's the WATTS, not the apparent total
> current, as
> > the VOLTAGE is much higher than the 'rated" voltage (which would

be

> 3.333 V.
> > at rest).
> >
> > Yep, it took me a few minutes and some pencil-scratching to "get
> this", but
> > it is now (nearly) clear in MY feeble mind!
> >
> > HOPE this clarifies for you! (Mariss: Did I get it
> right???)
> > Jan Rowland
> >
> >
> > [Non-text portions of this message have been removed]