Re: power supplies form those 24v transformers

The 75V is too high. multiply output by 1.414 to obtain the DC
voltage you would wind up with.

Dave


--- In CAD_CAM_EDM_DRO@yahoogroups.com, Marv Frankel <dcdziner@p...>
wrote:

> Les,
> I've been following this thread with interest, and asked the
> originator for a schematic, using two of the 24V transformers. I

also looked

> into the www.mpja.com web site, and saw a 48V @ 10A, and a 75V @

6.6A

> available, but at a much greater cost. Would mounting 4 or 6 of the

24V

> units in one case require a fair amount of ventilation, or wouldn't

there be

> that much heat generated?
>
> Marv Frankel
> Los Angeles
>
> ----- Original Message -----
> From: "Les Watts" <leswatts@a...>
> To: <CAD_CAM_EDM_DRO@yahoogroups.com>
> Sent: Sunday, January 19, 2003 8:57 AM
> Subject: [CAD_CAM_EDM_DRO] power supplies form those 24v

transformers

>
>
> > Some of my customers from the list have asked about
> > powers supplies for servos/amps. This concerns higher
> > voltage for the larger Bridgeport conversion type motors.
> >
> > I want to help my customers on this, but I want to
> > do it on list so others can help or use the information.
> >
> > Now, there was a thread about the economical 24v 10a
> > transformers. I have looked into a supply using four of
> > these for a nominal 66v 20a or six giving 66v 30a.
> >
> > But I think there is a problem with these. You see,
> > line voltages are speced a little differently in various
> > countries.
> >
> > The primary of these is listed as 110vac I think.
> >
> > We want a higher voltage supply, but some margin
> > away from an amplifiers maximum input voltage must
> > be allowed. This give some latitude for things like
> > normal line voltage variations, surges from nearby
> > equipment, and servo regenerative braking.
> >
> > So, considering using two of the 24v secondaries in series
> > we may get
> >
> > 48 vac
> >
> > x 117/110 (our nominal US line voltage)
> >
> > x1.1 (+10% normal line variation)
> >
> > x1.414 (after rectification and filtering)
> >
> > -1.4 (the forward voltage drops of the rectifiers)
> > = 78vdc
> >
> > I think this is a little too close to the Gecko 80v max input.
> > I talked with Mariss about this some, and he needs to have
> > the last word on this as they are his amps.
> >
> > If you are using something like Copley 412, 78v is fine.
> >
> > I suspect these transformers give 24v at 110, but our line

voltages

> > are often 120+. The power companies like to run high to sell more
> > power with less I^2R on their lines.
> >
> > Didn't someone measure higher open circuit voltages on these

things?

> >
> > So I am not going to recommend using the transformers in this way.
> > But if someone has some in hand and can ACCURATELY measure the
> > transformer output and line using the 220v primary and 240v line I
> > would like to know. Tim?
> >
> > Why 240? The KVA of a 30 amp supply is kind of pushing it for a
> > standard 120v 15a line considering surges.
> >
> > If the 24v transformers put out 24 with 120 or 240 in that
> > would yield a much more reasonable 73.5vdc max, 66v nominal.
> > But I don't think they do. It would be nice ,though, as they are a
> bargain.
> >
> > If they are to high, there are lots of other options. One
> > is Doug Fortune's Monster supply at
> > http://www.cncKITS.com
> >
> > Another is the toroidal power transformer kit at
> > http://www.toroid.com
> > They supply a 1.5 KVA toroid core with a pre-wired primary,
> > and you wind your own custom secondary.
> >
> > A further option is a snubber, higher current bleeder resistor,
> > or diodes.
> >
> > But I would like to see exactly what these transformers put out.
> >
> > Les
> >
> >
> > Leslie Watts
> > L M Watts Furniture
> > Tiger, Georgia USA
> > http://www.alltel.net/~leswatts/wattsfurniturewp.html
> > engineering page:
> > http://www.alltel.net/~leswatts/shop.html
> > Surplus cnc for sale:
> > http://www.alltel.net/~leswatts/forsale.html
> >
> >
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