RE: [CAD_CAM_EDM_DRO] Re: QUESTION ABOUT SERIES OR PARALLEL ON STEPPER MOTORS - ref post 52721

Guys:

I really appreciate the input. I'm a newbie at this and your discussion is
very helpful. As a follow on question:

I have the following challenges:
The DC power supply of the NC controller I'm cannibalizing puts out 130V. I
don't know if this eventually reached the motors or was reduced somewhere
else in the old NC drive section before reaching the drives. (There was a
short circuit somewhere in the unit, so I disconnected all the controls,
drives etc so I could work on the power supply). I can rewire the taps on
the transformer to give me either 62 or 68 volts DC, both of which fall
below the range of the 80v max of the CMD260 drives I bought.

Based on the input you guys gave (my NEMA 42 steppers are unmarked and
undocumented) I'm going to try running them in parallel. I really don't
want to generate sparks and a puff of smoke. What would you recommend the
current setting on the drives to be placed at (they go as high as 8 amps)?
Should I drive them with 62 volts or 68 volts?

Thanks in advance,

Jeff


-----Original Message-----
From: turbulatordude <davemucha@...> [mailto:davemucha@...]
Sent: Thursday, February 13, 2003 8:33 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: [CAD_CAM_EDM_DRO] Re: QUESTION ABOUT SERIES OR PARALLEL ON STEPPER
MOTORS - ref post 52721



The serial vs. parallel speed question was tossed around by the pros
from Dover a little while back.

This is real close of an explanation. if you want more, read the
whole thread.


Message 52721 "jeffalanp" <xylotex@h. . . > Date: Tue Nov 19, 2002
12:56 am Subject: Re: Running Unipolar steppers with a Bi-polar
driver?

"Mariss, OK, OK, I got it (I think). The inductive time constant for
both parallel and series motors will be the same (t=L/R, the time it
take to get to 62. 3%). But to overcome the increased inductance and
resistance in a series wound motor (compared to parallel), I would
need to double the voltage to achieve the same time as parallel. "

There was more on the post, time to charge the coil, discharge it,
then reverse direction, that sort of stuff. but this is enough data
for most of us to understand the differences.

Or the short and sweet, series goes thru a longer wire and that takes
more time. You can did deeper and get more data.

Dave





--- In CAD_CAM_EDM_DRO@yahoogroups.com, Alper YILDIRIM
<yildirimalper@y...> 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.
>
> Best regards
> Alper
>
> Jon wrote:
>
> ""Yes. In almost all cases, the parallel connection
> is better. It
> provides lower inductance,
> and therefore, higher speeds, than the series
> connection. The only
> time
> to use series
> is if your stepper driver cannot supply the current
> needed for parallel
> connection, and
> if high speed is not important. (The fix is to get a
> driver that CAN
> handle full rated
> current in the parallel mode.)
> Jon""
>
>
> __________________________________________________