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Re: buying a pole pig

Original poster: Don Murray <don@xxxxxxxxxxxxxxx>

Jim,
Don't let the two phase concern you much. I understand it's pretty rare. I don't know what load it's serving, maybe locks or bridges, or some old manufacturing plants. About 10 years ago I read in Electrical World T/D, (Transmission and Distribution), a trade magazine by McGraw-Hill, that there are still some oddball frequencies out there, from before the nation settled on 60HZ. Some 25HZ, and some 40HZ systems still existed at that time. I've been a lineman for 34 years, and I've never come across anyone that has any firsthand knowledge of 2 phase or these oddball frequencies, and I would very much like to hear from anyone that does. 

Don

Tesla list wrote:


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


Don,
Thanks for the excellent reference material. Wye, delta, and zig-zag, and
now two phase is somewhat, no, down right confusing to this signal guy :-)
Jim Mora
-----Original Message-----
From: Tesla list [mailto:tesla@xxxxxxxxxx]
Sent: Wednesday, June 07, 2006 4:03 PM
To: tesla@xxxxxxxxxx
Subject: Re: buying a pole pig
Original poster: Don Murray <don@xxxxxxxxxxxxxxx>
Justin,
   What the Y means is that if you are going to connect that
transformer to a 12470 volt system you must connect it Y. Each end of
that Y is one phase of a 12470 volt system and each leg of the Y
would be one 7200 volt coil. On a delta system each corner of the
triangle is one phase of a 7200 volt system and each side would be a
7200 volt coil. Draw it out and you will see. What determines if we Y
or delta the high side is coil rating and primary voltage, if they
are the same it will be delta, if primary is higher it will be Y or
star as they are the same. And what determines if you get a delta or
Y low side is the service voltage you want. If you want 120/240 it
will be delta, if you want 120/208 it will be Y.
On the high side of a Y connected bank of transformers you don't
always ground it. Some times you let it float. And you don't always
have to have 3 transformers, you can have open delta and open Y with
2 transformers.
I have some transformer connections on my web page that I put up for
a discussion on a usenet group, thought they might help some. The
Scott connection at the bottom of the page is for 3 phase to 2 phase.
They take special transformers and are pretty rare.
http://murrayranch.com/Electricity.htm
Don
Tesla list wrote:
 >Original poster: Justin <rocketfuel@xxxxxxxxxxxxx>
 >
 >Hi All,
 >Just an update, here are the specs on the pig:
 >15KVA
 >Rated Volts: 7200/12470Y        120/240
 >2.2% impedence
 >Orto Filled
 >http://jay.g-cipher.net/pig2.jpg
 >http://jay.g-cipher.net/pig1.jpg
 >
 >I'm curious what the Y means in the "12470Y"...any ideas?
 >
 >Thanks as always!
 >Justin
Snip>