8 wire half or Serial ? ( was Speed - Parallel vs serial ( was Re: Motor

Hi Mariss,

I am beginning to get a grip on this. I've been searching the past
posts for how to wire an 8 wire in serial and have come across quite
a few related posts.

Seems that the amps have a lot to do with accuracy of th icrostepping
as well. one a stepper approaches the saturation point, it seems the
not only is more energy being applied with no additional work, but
the steps lose their seperation and start bunching up. bad.

In my application, I am replacing the NEMA 23's with NEMA34's for
physical constraints, but want to run the 8 wire 34's serial.

I've assembeled a few posts that are very topical and will post them
to the files section once I have completed the compilation. Well,
after I get a few of you guys to review it for accuracy too.

Dave

--- In CAD_CAM_EDM_DRO@y..., "mariss92705" <mariss92705@y...> wrote:
> Dave,
>
> On the series / parallel thing. Here is the reason series needs
half
> the current of a parallel connection.
>
> Torque is equal to current multiplied by the number of turns of
wire
> it passes thru. This is called "ampere-turns" naturally.
>
> In series, current passes thru twice as many turns of wire than it
> does in parallel, so only 1/2 the current is needed for the same
> torque.
>
> Some might think "why not keep the current the same and get twice
as
> much torque?". The reason why not is because of magnetic saturation.
>
> You can think of iron being composed of countless microscopic bar-
> magnets, all randomly oriented. These "magnets" are
called "magnetic
> dipoles" Because of their random orientation, iron has no net
> magnetism.
>
> When you wind a coil around iron and pass current thru it, some of
> these magnetic dipoles align with the coil-generated magnetic
field,
> strenghtening it. When you double the current, twice as many
dipoles
> align. At some threshold current though, all the dipoles are
aligned.
> This is called "magnetic saturation". Any further increase in
current
> cannot increase the magnetic field.
>
> Step motors are designed to operate at about 80% of magnetic
> saturation when rated current is passed thru its windings. To keep
it
> at that point, half the rated current must be used if the number of
> wire turns is doubled (series or full-winding operation).
>
> Mariss
>
>
>
> --- In CAD_CAM_EDM_DRO@y..., "turbulatordude" <davemucha@j...>
wrote:
> > Hi Peter and all,
> >
> > It seems that half coil offers a simple solution and would let me
> run
> > straight away.
> >
> > Now my ignorance will become abundantly clear.
> >
> > using 2 coils, like a 6 wire stepper, center connected, one end
un-
> > used, would use nameplate amps.
> >
> > getting the correct pairs and matching them and wiring up each
pair
> > as if it were one coil (again like an center connected 6 wire
> > (parallel)but now using the 'other' end wire/circuit) would use
> > nameplate amps.
> >
> > finding the correct 2 pairs and series wiring would use half
> > nameplate, and run half as fast. Like an end connected 6 wire.
> >
> > Miswiring which pairs (not shorting out wires or other mistakes)
> > would only make the motor miss.
> >
> > The idea of powering two sets of coils in series with half
current
> > has't integrated itself in my thinking as yet. Seems two series
> > lightbulbs at full voltage would burn half as bright, but if the
> > voltage were halved they would be really dim. My thinking is
that
> > I 'want' to double the power at series. I am intelegent enough to
> > follow the directions and use half current.
> >
> > Dave
> >
> >
> >
> >
> >
> >
> >
> > --- In CAD_CAM_EDM_DRO@y..., "cadcamcenter" <cadcamcenter@y...>
> wrote:
> > > > I did that first. an 8 wire stepper uses 2 sets (pairs) of
> > coils,
> > > it
> > > > does not go into how to decide which two pairs to connect.
> > > >
> > > > Dave
> > >
> > > This question occurs quite frequently. Let's see how one can
> > > approach. The combined wisdom of this list says best is to wire
> in
> > > half-coil.
> > >
> > > 8 wires stepper are 4 coils terminated at both end with
separate
> > > wires, forming 4 pairs of wires. With a multimeter, it will be
> easy
> > > to find these 4 pairs. Let's call them A, A' and B, B'.
> > >
> > > Wiring in half coil mean that 2 of these 4 pairs will be
> connected
> > to
> > > the driver, leaving the other two open. This mean there are
only
> 4
> > > possibilities and they are:
> > >
> > > A and A' no good
> > > B and B' no good.
> > > A and B good
> > > B and A' good
> > >
> > > The question is, what happen when you connect A and A' and B
and
> > B'?
> > > I guess the motor will not turn, but no harm will be done to
the
> > > driver/motor provided voltage, current setting are within
> > permissible
> > > limits. (hope the experts will elaborate on this)
> > >
> > > When wired in the other 2 (good) possibilities, the motor will
> > turn,
> > > only thing is, if polarity is wrong, motor will turn opposite
to
> > > intended sense. A simple remedy will be to reverse the pair
> > > connection or reconfigure the controller.
> > >
> > > In any case, I believe the way to approach this is
> > >
> > > 1. determine the paired wires with multimeter
> > > 2. pick any 2 pairs, connect them to the driver.
> > > 3. Test. If wrong pair motor will not turn, probably make
noise,
> > but
> > > no harm done. (experts please correct if wrong)
> > > 4. Make a note, pick another 2 pairs.
> > > 5. At most, you need only 3 trials before you get the motor
> > turning,
> > > and at most 4 to get them turning correctly.
> > >
> > > Hope I did not give inaccurate info. (disclaimers apply)
> > >
> > > Peter
> > >
> > >
> > >
> > >
> > >
> > >
> > > --- In CAD_CAM_EDM_DRO@y..., "turbulatordude" <davemucha@j...>
> > wrote:
> > > > <snip>
> > > >
> > > > >
> > > > > For wiring 8 wire stepper motors, go to www.geckodrive.com
> and
> > > look
> > > > at their
> > > > > white paper on stepper motors.
> > > >