Re: [CAD_CAM_EDM_DRO] Re: QUESTION ABOUT SERIES OR PARALLEL ON STEPPER MOTORS

Alper YILDIRIM wrote:

>Hi,
>Take a look to the following site:
>
>http://www.microkinetics.com/contab.html
>
>For the bipolar series and parallel connections the
>time constant L/R is same. For parallel connection,
>inductance lower 4 times but resistance lowers 4 times
>too. So the time sonstant does not change.
>Can someone explain why parallel wiring allows higher
>speeds according to this approach.
>
>

I've had this argument with Mariss Freimanis a couple of times,
and maybe I've still got it wrong. I don't think the R of the winding
is a major factor in the increase of the current in the winding.
(It is obviously a dominant factor in the decay of current when the
transistors are maintaining the flux.)

The equivalent circuit when charging is the power supply, the winding
inductance
and the winding resistance. the small winding resistance of most
steppers used
in this application is just minute. So, the time constant is essentially a
straight-line V/L charging curve. Less inductance = faster charging.
When you are charging from a 65 V or so power supply, and the winding
resistance in parallel is on the order of 1 Ohm, and the winding current is
4 A, then even at full current peak, the IR drop is only 4 V, or less than
1/10th of the supply voltage. So, the L and the supply voltage are
dominant.

Jon