Re: [CAD_CAM_EDM_DRO] power supplies form those 24v transformers

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@...>
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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