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

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Alan Marconett" <KM6VV@...>
wrote:

>
>(sip)
>
> 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.

> It seems to me that it would be good to use the entire winding >

(other considerations aside), because the heat dissipated would be

>better distributed. But not at the cost of slower speed!

Center-tapped motor windings are bi-filar, making them thermally
intimate. It makes no difference thermally to use a half-winding 100%
of the (bipolar drive) versus both windings 50% of the time
(unipolar).

> I have seen a better fit for a stepper (current wise) by using the
>full winding, sometimes 1/2 the current can allow you to use a
>smaller driver if ultimate speed is not needed. It's good to have
>choices!

Always use 1/2 rated current for a full winding! The motor is an iron-
core inductor; full current thru a full winding results in magnetic
saturation and a percipitous drop in inductance. This can kill a
switching drive which relies on inductance to operate properly.

Secondarily, full current thru both half-windings doubles I^2 * R
losses,(twice the heat).

Mariss

>
> Alan KM6VV
>