Re: 12740Y/7200

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: David Dean <deano@xxxxxxxxxxxxxxxx>

On Thursday 28 December 2006 22:05, you wrote:
> Original poster: "Chip Ford" <chipford@xxxxxxxxxxxxxx>
>
> What does it mean when a rating on a transformer says 12740Y/7200.
> Someone please explain this to me...Thanks...Chip Ford
It means The primary voltage is 7200 phase to ground, 12470 phase to phase.
All single phase pole mount transformers are connected Y to Y in 3 phase, If a
pad mount 3 phase TRANSFORMER IT WILL BE Connected Delta to Y. In single
phase all power distribution transformers are connected   from one phase
primary to one phase secondary. All pole pigs rated 12470Y/7200 Are connected
to a single 7200V line. Only 3 phase transformers are connected 12470 Delta
on the primary side, and all of them that I have seen in the real world are
Pad Mount. Of the possible ways transformers can be connected there are Y -
Y, Delta Delta, Y delta. Y - Y is a no no for a three phase transformer. Any
imbalance in currents will result in neutral currents that will destroy the
transformer. Using three single phase transformers in Y - Y is OK because the
cores are not connected and the neutral of the secondary can be connected to
the neutral of the primary and no neutral current will flow if there is an
imbalance.

Anyway that is the theory.
later

deano