Wagner Lipnharski wrote:

> I think that the difference between using a single coil or two coils
> in series attached to the *same* drive VCC, as you said, results in a
> half current, half dissipated power, but the torque *would not be the
> same*, it should be less.

  Well, half the current through twice the turns = same *static* force.
However, I then went on to consider the apparently "disproportionate"
effect on the inductance of using twice as many turns, which affects
stepping speed.

>  If this is true, than multiplying the coil turns by 100, it will go
> for an infinite low current and power, keeping the the same torque,
> what unfortunately I think is not true. I really wish you would be
> right :)

  This is *not* the same as considering the situation where you have two
coils already wound and are deciding whether to use one or both in
series.

  If you use 100 times as many turns on a given former, then each turn
has 100 times the resistance as before (you have reduced its cross-
section by that factor).  You have therefore increased the resistance
10,000-fold and the magnetic field and thereby torque of a motor is
*reduced* to one-hundredth.

> There must have a "perfect" relation between torque, maximum possible
> magnetic flux, core size (dictated by the winding coil size to
> generate the maximum magnetic flux with the maximum current), and heat
> dissipation.

  You've twigged to it.  That was essentially my reply to the original
posting; if a motor is used at its design target, then "simple" changes
like using two windings instead of one, or just "bumping up the drive
voltage a little" will *not* necessarily increase performance *at all*.

> A bipolar motor is designed to stand one coil of each net energized
> all the time, not both, so I think it is not a good idea to feed
> double VCC to the double coil (unipolar) fashion.

  That's what I was saying!

> First because the motor will dissipate double heat, second that it
> will be trying to generate a double magnetic flux, and the core can
> get saturated and the motor productivity would not be the same as in
> bipolar fashion.

  That's what I was saying!

> I use bipolar motors in "H" bridges, but always try to feed them with
> less than double voltage.

  That's what I was saying!
--
  Cheers,
        Paul B.