Re: Pole Pig Question

To: tesla-at-pupman-dot-com
Subject: Re: Pole Pig Question
From: "Edward Wingate" <ewing7-at-rochester.rr-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sun, 20 Feb 2000 13:07:40 -0700
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

Tesla List wrote:

> 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.  Aside from that, what are differences?  (I guess
> I'm asking for the theory behind the different phases of AC current.)
> Also, some of the transformers have primary voltages that I can understand.
>  For example, 12470 volts.  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.
>
>         Thanks,
>             Ryan
>

Ryan,

Single phase pole transformers come with either one or two bushings, the number
of bushings having nothing to do with the phase of the transformer.  A single
bushing transformer has one end of the high voltage winding tied to the case.
If you get a single bushing transformer, BE ABSOLUTELY CERTAIN, that the case
is grounded, otherwise it (the case) will be at high voltage potential. It is
best to find a two bushing transformer.

The Gnd Y/Y designations are for power company connections between one leg of a
three phase line and ground. The transformer will only produce the voltage
without the Y designaton, which is the lower of the two voltage ratings, when
run in reverse for Tesla coil operation.

Ed Wingate RATCB