Re: [CAD_CAM_EDM_DRO] Re: Voltage to steppers

this is the basic info that people need
can i post this on two other boards??

richard

----- Original Message -----
From: <david_mucha@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Thursday, January 16, 2003 9:08 PM
Subject: [CAD_CAM_EDM_DRO] Re: Voltage to steppers


> Hi,
>
> and I'm glad your interest brought you over here from the BasicStamps
> list.
>
> What I posted over there was something that many first time stepper
> users don't know about.
>
> Stepper motors have nameplates that list some basic information for
> calculations which is unlike standard electric motors which put
> maximums on the motor nameplates.
>
> using ohms law, you need to know some basics. resistance, amps,
> volts, watts, and inductance. with the basic lising of just a
> voltage and current, you can figure out all the rest.
>
> to charge the motor coil you need to pump current into it. higher
> voltage means that current gets there faster. higher voltage means
> faster motor speeds.
>
> double the voltage and you double the speed. your 12 volt motor will
> spin at 12 volts, it will do slightly more work at 24 and really
> start to come into the power band at 70 volts. or 5 times the rated
> voltage. If you want to run at 30 volts, a 1.5 volt motor would be a
> better choice.
>
> Power output increases proportionally with supply voltage. Losses in
> the motor increase with the square of the voltage. At some point the
> motor just gets too hot. This occurs at about 25 times nameplate
> voltage. most hobbiests think a 5 volt motor needs to run at 5 volts
> and 6 volts is too much.
>
> also, stepper motor output power is independent of speed. Since power
> is speed times torque, this means every time you double motor speed,
> torque is halved. steppers appear to loose power at higher speeds as
> on some machines the torque needed to move the assembly exceeds the
> delivered torque and the motor starts missing steps.
>
> One thing on the nameplate that should not be exceeded is the amps.
> if you connect both sides of one coil of a 6 wire motor so they are
> in parallel you use the full motor amperage. if you connect those in
> series, then you half the current as you doubled the resistance and
> 4x'ed the inductance. this also means you get the same power, but
> lose top end speed.
>
> i'm sure others will comment on this or other questions you might
> have.
>
> Dave Mucha
>
>
>
>
>
>
>
>
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "pwrcntrl <info@c...>"
> <info@c...> wrote:
> > I have a home-grown machine that uses small 55mm 12V steppers. I
> have
> > driven them with an embedded controler & Allegro driver chips,
> which
> > make it fairly straightforward. The setup uses round ground
> thompson
> > shafting and linear bearings and moves quite freely, however, the
> > little motors only have enough torque to drive consistently in
> either
> > 1/2 or wave drive. I would more importantly like to see some more
> > speed. during free moves...it doesn't need torque beyond what is
> > required to move itself around.
> >
> > From what I have been reading here while lurking (from people like
> > Dave M, of the Basic Stamp list - Hi Dave!) it seems that it is
> > common practice to drive steppers above their rated voltage, is
> that
> > correct?
> >
> > If so, what will driving my 12V motors at say 24V do? It seems you
> > guys were talking about 10X rated V, so I'm wondering what 2X will
> > do....
> >
> > Perhaps I should just change motors. Of course they will have to be
> > inexpensive say $20- and with 1/4 inch shaft. If I need to go over
> > the V rating of the driver chips, I may have to re-think
> everything...
>
>
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