RE: potential transformer question

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Trimmell" <humanb-at-chaoticuniverse-dot-com> 

This is very correct. Do not run the PT over +20% if you plan on keeping
it. For instance, I have a Westinghouse 120/7200 oil filled PT 110KV
BIL, interestingly this is rated at only 750VA-at-30C, but I can run it for
hours at +2500VA. BUT, once I go over 140V in it starts groaning and at
160V in it is sucking over 6-7 amps with no load! Just try a TC load and
you'll end up with one dead PT! Really, a 0-140V supply is what only
works with these instrument transformers wired in reverse...

Regards,

David Trimmell


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, October 07, 2003 8:28 PM
To: tesla-at-pupman-dot-com
Subject: Re: potential transformer question

Original poster: dhmccauley-at-spacecatlighting-dot-com

You are playing with fire there.  Assuming the transformer is 240VAC,
that
is 2x the rated voltage.  Thats a big NO NO unless you want to ruin your
"expensive" transformer
in a very short time.  BIL is NOT the DC Hi-Pot level.
BIL is short for BASIC IMPULSE LEVEL.  It is the rating that the
transformer
can withstand under transient conditions such as a voltage surge or
lightning hit etc...  This
rating simply allows power engineers to design a proper insulation
capability in their power system.  A good design will always have a
"safer"
path during transient conditions than
allow the transient to voltage to reach and exceed the BIL of the
transformer.

So in short, if you put 500V into your transformer, YOU WILL DESTROY IT!
Maybe not right away, but pretty quickly, especially if its a 120VAC
input
transformer and not a 240VAC
input.

However, you can push these to 2x the rated power for short periods.
Typically, 1.5kVA potential transformers can easily run at up to 3.5kVA
for
short periods.

Dan

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