# Re: 3 phase to single phase, transformer wiring VTTC

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

(sorry for the double-spam; correcting myself)

Thinking again, the *parallel* option (for 2400V)
below is silly, since the legs of the three-phase core
all have the same cross-sectional area.  To me, that
suggests you ought to be able to expect just as much
current if you were to simply derive the 2400V from
the high side of whatever leg you put 120V into (e.g.,
you supply 120V to the center LV winding, get your
2400V from the center HV winding).  The only advantage
of using two HV windings would be the *series* option
for 4800V.

I think.

Regards, (again)
Aaron

--- "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
wrote:

> 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
> now...
>
> Regards,
> 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
> >
> >
> >
>
```
>
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