Re: Check my math and reasoning....

Thanks Bob. What would be the result of running the larger ampacity
supply (@70v) over one that had less amps for the steppers?

Drives will be 202s for the steppers and 320/340s for the
servos...same 70v requirements just different ampacities.

-Brady

--- In CAD_CAM_EDM_DRO@yahoogroups.com, "Robert Campbell" <bob@c...>
wrote:

> 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@c...
> www.campbelldesigns.com
> Breakout board
> THC board sets
> CNC router plans
> Stepper Motors
> VisualMill Basic
> ----- Original Message -----
> From: "braidmeister" <braidmeister@y...>
> 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
> >
> >
> >
> >
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