Re: [CAD_CAM_EDM_DRO] Check my math and reasoning....

Brady,

You need to separate the calculations for stepper motors and servo motors.

I would suggest that you build two power supplies. One for the stepper
motors and one for the servo motors.

One of the limiting voltage factors will be the drivers that you are going
to use. The Gecko drives have an 80 volt limit. I would keep it at about 70
volts.

I would recommend that you look for 100 volt capacitors. You can always hook
them in parallel to get more capacitance.

Bob Campbell
Bob@...
www.campbelldesigns.com
Breakout board
THC board sets
CNC router plans
Stepper Motors
VisualMill Basic

----- Original Message -----
From: "braidmeister" <braidmeister@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Monday, June 27, 2005 5:04 PM
Subject: [CAD_CAM_EDM_DRO] Check my math and reasoning....


> OK gang,
> I am trying to piece together my power supply and have a few
> questions regarding the rated voltage for a capacitor. I am finding
> that most use 50v caps and they are cheap and available...I am
> wondering at this point if I am missing something...here's where I am
> and where I want to go with the PS:
>
> I am running Sigma N42 motors on the Bridgeport and the manual says
> that they are 6.8A. I would like to build a power supply with enough
> juice to power these 3 steppers AND an 11A Servo for the 4th axis
> down the road. I will eventually need to run 4 of these 11A servos @
> 70v ~ so I am thinking why not just build one supply and be done with
> it?
>
> Right now I have 2 50v (what decal says on each...but advertised as
> 55v when I bought them) 800VA torid transformers. I bought 2 at the
> time so that I would have enough amperage to run the 4 servos. Now
> comes the question of capacitors...I need caps are rated by voltage
> after being rectified, right?...In this case at least 80v...not 50v,
> right??? I searched around on here and didn't see any reference to
> this.
>
> So...If my math is correct, I will need (using the servo motor draw
> as a guideline) Assuming 50v rectified to 70v by the 2 torids:
>
> 44Amps * 67% (from Campbell's pdf) = 29.5A
>
> C= (80,000 * I) / V)
> (80000 * 29.5) / 70 = 33691 uF
>
> Could I get away with 3 P10653-ND from DigiKey? They are 12,000 uF @
> 100v +/-20%.
>
> Did I do my math right...or am I missing something???
>
> Thanks!!!
> -Brady
>
>
>
>
> 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@... davemucha@...
> [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
>
>
> Yahoo! Groups Links
>
>
>
>
>
>