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RE: 3 phase to single phase, transformer wiring VTTC

Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>


Maybe good news... the transformer is not potted, furthermore, all windings
have both legs out to the connection block and are separate. The input has
separate taps, the outputs have one of each pair screwed together at a
common point under the connection plate. It seems like it should work to me.
Of course I'll ohm out all the windings to be sure. 3X current, yes? Am I
missing something? It is a nice transformer!

Jim Mora

-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Friday, August 25, 2006 10:46 AM
To: tesla@xxxxxxxxxx
Subject: Re: 3 phase to single phase, transformer wiring VTTC

Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>

If the leads to each winding are easily separated and
not all expoxy encased and/or welded together, then
you *can* do *something*, but you can't just parallel
all the windings.  That'll just give you a big short
circuit, AFAIK, no matter how you phase things :-)
Here's what you *might* do:

Just so we have some real numbers, let's say this is a
208Y-to-4160Y transformer.  That means your "input"
phase voltage is 120V and your "output" phase voltage
is 2400V.

With all the windings disconnected from each other,
you should be able to (one example) put 120V into the
center LV winding (the one on the center "leg" of the
core), then you could phase the outer two HV windings
in series, giving you 4800V.  Or, you could place the
outer two HV windings in parallel for 2400V.  This
2400V would *not* be good for the full KVA of the
transformer.  It would have to be derated.  I'm
forgetting how three-phase KVAs are calculated right

Aaron, N7OE

--- Tesla list <tesla@xxxxxxxxxx> wrote:

 > Original poster: "Jim Mora" <jmora@xxxxxxxxxxx>
 > Hello,
 > I know that alike transformers can be wired to
 > create three phase output,
 > can the converse be done? I have a large 3 phase (90
 > Lbs) dry 240 to 4K+
 > plate transformer. What would be the ramifications
 > of paralleling the inputs
 > and outputs? Will the windings oppose each other
 > since they share the same
 > core? I'm thinking of buying one of the mongo
 > Russian Power tubes on
 > ebay.such as this one.270022234745. Yikes.
 > Making the filament transformer would be interesting
 > as it wants a couple
 > hundred amps.
 > The recent talk of VTTC is raising my interest
 > again. I have some vintage
 > 833a parts...future... My big coil is baking in the
 > sun, as the Santa Ann's
 > ... Santana's (devil winds) (hot and dry) are
 > blowing here and it's inside
 > work for awhile to stay cool.
 > Jim Mora
 > Ojai, Ca