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Re: Pole Pig Question
Hi Ryan,
Comments interspersed.
> Original Poster: "Ryan Ries" <spud-at-wf-dot-net>
>
> Hey. In my search for a distribution transformer, a
>couple of questions came to my mind. First of all, I
>have observed that single-phase transformers only
>have one high voltage terminal, while triple-phase
> transformers have two.
No, not quite. A 3 phase pig will have to have at least 3
horns, possibly 4, depending on the internal configuration.
A one horned pig (single phase) has one input terminal
connected to the case of the pig. This means you need
less insulation (cheaper, easier to do). Similar to a MOT
configuration, where the inner core winding is held at
ground potential. The two horned pigs have no connection
(on the HV side) with the case,which needs better
insulation to survive, but they are NOT 3 phase units.
snip
> Others have weird things like 7200/12470Y, or 12470GY/7200.
> Could you please explain this to me also? I have a feeling
> it has to do with the 1-phase and 3-phase thing, but I don't know.
Correct. In a three phase circuit (using the above example)
you will have 7200 volts between a phase (R, S or T) and N (or
ground for insulation purpose) and between two phases (like R &
S) you have 12470V. The Y means a "Y" configuration used in
wiring 3 phases. Picture each leg of the Y as a coil of the
transformer or, in most cases, 3 sets of transformers. The GY
means grounded Y circuit AFAIK, where N is also connected to
ground.
For headache free operation stay away from single framed 3
phase xformers as you canīt series or parallel the winding easily,
which means you would need to rectify the three phases and
go for a DC setup. Of course ONLY step up to a pig if you have
gathered lots of experience in the HV field. They donīt hurt you,
they kill you.
Coiler greets from Germany,
Reinhard