Re: COMPLETE 3 axis CNC electronics package (plug-n-cut, ready to go)

There is no significant difference between half-winding and parallel-
winding performance. Current passes thru the same number of turns
either way; the parallel connection will just have 1/2 the resistance
of a half-winding connection. Inductance is the same either way too.

Let's compare: Say you have an 8-wire NEMA-34 4A motor with a half-
winding resistance of 1 Ohm. The voltage drop will be 4V.

Connect it in parallel, resistance is 0.5 Ohms and the voltage drop
is 2V.

Now let's say you are using a 40V power supply. Running the motor
very slowly makes no difference in torque. The motor needs 4V in half-
winding, 2V in parallel. You have 40V available.

Run the motor now at high speed and load it to just short of
stalling. If it's a "round" motor, supply current will be 2/3 of 4A.
Each winding draws 1/3 of 4A or 1.33A.

The half-winding motor coil (1 Ohm) has a 1.33V resistive voltage
drop, the parallel-winding coil (0.5 Ohm) has a 0.66V resistive
voltage drop.

The half-winding voltage drop is 0.66V higher than than the parallel
connection. Performance of the half-winding motor would be identical
to the parallel motor if you made up this voltage drop by raising the
supply voltage to 40.66V.

This is a 1.6% difference in performance between the two.

So here's what you can take away from this:

1) Full-winding is exactly equal to series-winding performance.
2) Half-winding is at least 98.5% of parallel-winding performance.

Mariss







--- In CAD_CAM_EDM_DRO@yahoogroups.com, Aaron <aaron.groups@...>
wrote:

>
> Mariss,
>
> I'm confused. Assuming we are talking about an 8-wire motor...
>
> Wasn't Alan comparing the *speed* of paralleling both windings vs.
> only a half winding connection?
>
> Wasn't your explanation on *power* directed more towards a

comparision

> of the half winding connection vs. a series connection of the
> windings?
>
> Aaron
>
> On 5/3/06, Mariss Freimanis <mariss92705@...> wrote:
> > "Alan Marconett" wrote:
> > > Windings in parallel are said to have the best speed. But only
> > >slightly better then just using 1/2 the winding.
> >
> > Yes they are. In fact twice as good.
> >
> > Inductance increases as the square of wire turns (mutual

inductance)

> > so a full winding has 4 times the inductance of a half winding.
> >
> > Motor power output is proportional to Vs / SQRT L . A half-winding
> > motor produces twice the power of a full-winding motor for the

same

> > power supply voltage. You'd need to double the power supply

voltage

> > (Vs) on a full-winding motor to recover the loss in performance.
>