Re: [CAD_CAM_EDM_DRO] Re: Power Supply and Capacitor Questions Help!!

Mariss and Jon,

Yes, I entered those values from memory and when I rechecked they were different. Sorry about the confusion. After much preparation and scavenging I got my CNC control assembled enough to test it today. I wired the transformer with the two sets of taps in SERIES and I'm getting about 63 volts DC off the 3 100 volt DC capacitors wired in PARALLEL ( I knew I'd get that right eventually). I wired up one Gecko and followed the Instructions , tuned it the best I could without a scope and after much dithering and oscillation I finally got it smoothened out. Much to my amazement, this is going to work. These DC brush servo motors are very powerful, fast and responsive. I dont have them belted to the axies yet but this bridgeport is going to work very well. The Gecko which I have mounted on a heatsink, even with this large motor, delivered the torque and did not even begin to get warm. Bob Campbells Mach2 breakout performed flawlessly as well. Tomorrow I am going to build Mariss's
e-stop/dump circuit. One question I do have, Is it possible to accurately tune the Gecko's without a scope? One characteristic my motors are displaying is erratic motion at very slow jog rates. Or is something else causing that? I need to get that resolved and I should be out of the woods then.

Ron

Jon Elson <elson@...> wrote:


Mariss Freimanis wrote:

>Jon,
>
>You might want to check your numbers. Kt is always 1.351 * Kv.
>
>

Right, you showed me that one a while ago. These numbers came right off
the original poster's question, and I didn't check them. And, then,
there is
something VERY wrong with these numbers! I was a bit surprised at
his Kt value, which would give 800 in-Lb at 20 Amps. That is a VERY
high torque motor. So, either his Kv or Kt is wrong.

His original description of the motor is as follows :

40 in/lb DC brush type servo motors that are
rated 40v/K at 2500 rpm 13.7 amps maximum current.

Later, he clarified it a bit as :

40 lb/in per 2500 rpm max and 13.0 continuous amps,
30 amps peak. 40 volts per k of rpm.

I took the 40 Lb/In to be the Kt, and the 2500 RPM as a separate
rating. But, 40 Lb-In/Amp is a huge torque, and clearly incompatible
with the Kv, which seems to be pretty clearly stated as 40 V per K RPM.
So, if the Kv seems like it has to be 40 V/KRPM, which sounds quite
ordinary for mid-size servo motors, then the Kt has to be
54 Oz-In/Amp, a FAR cry from the previous number. Ah, but
54 Oz-In * 13 A is 702 Oz-In, or 43.9 Lb-In. So, the whole line
is really the rating at 13 A. Now it is starting to make sense.

So, his continuous torque is 702 Oz-In, and his peak torque, at
20 A (the Gecko 320's limit) would be 1081 Oz-In, a VERY respectable
output, but not as wild as the numbers that I was coming up with
before.

Thanks for spotting my error in interpreting the somewhat confusing
ratings he gave.

Jon



Addresses:
FAQ: http://www.ktmarketing.com/faq.html
FILES: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO/files/
Post Messages: CAD_CAM_EDM_DRO@yahoogroups.com

Subscribe: CAD_CAM_EDM_DRO-subscribe@yahoogroups.com
Unsubscribe: CAD_CAM_EDM_DRO-unsubscribe@yahoogroups.com
List owner: CAD_CAM_EDM_DRO-owner@yahoogroups.com, wanliker@..., timg@...
Moderator: pentam@... indigo_red@... [Moderators]
URL to this group: http://groups.yahoo.com/group/CAD_CAM_EDM_DRO

OFF Topic POSTS: General Machining
If you wish to post on unlimited OT subjects goto: aol://5863:126/rec.crafts.metalworking or go thru Google.com to reach it if you have trouble.
http://www.metalworking.com/news_servers.html

http://groups.yahoo.com/group/jobshophomeshop I consider this to be a sister site to the CCED group, as many of the same members are there, for OT subjects, that are not allowed on the CCED list.

NOTICE: ALL POSTINGS TO THIS GROUP BECOME PUBLIC DOMAIN BY POSTING THEM. DON'T POST IF YOU CAN NOT ACCEPT THIS.....NO EXCEPTIONS........
bill
List Mom
List Owner



Your use of Yahoo! Groups is subject to http://docs.yahoo.com/info/terms/



---------------------------------
Do you Yahoo!?
Yahoo! SiteBuilder - Free, easy-to-use web site design software

[Non-text portions of this message have been removed]