Re: [TCML] 1KVA Pole Pigs?

["David Rieben" <drieben@xxxxxxxxxxx>]

Hi Conor,

These transformers sound like the instrument transformers
that are often seen with PFC (capacitor) banks on utility
primary power lines. As with all oil-filled transformers
used by the utility power companies, their KVA rating is
based on a 100% duty cycle, with typically up to a 65*C
temperature rise, at 30*C ambient temperature (about
86*F).  This translates to being able to run them at a
few times their nameplate KVA rating for relatively short
runs and in this situation, something like 5 - 10 minutes of
continuous running could still be considered a "short" run.
The shear mass of their coil and core assembly causes
significant delay to the thermal rise from a reasonable over-
shot of their KVA rating.


My best "guess" for the Fixed Load Transformer is that
the transformer is designed for a static, or unchanging,
load.?

David Rieben



----- Original Message ----- 
From: <ConorPerry@xxxxxxxxxxx>
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, November 24, 2008 8:55 PM
Subject: [TCML] 1KVA Pole Pigs?


I was looking at a large coil (24" secondary) tonight which uses two 7200 
volt pole pigs in series.  The tags showed "1.0 KVA" and "1 KVA" on the 
other at 7200.  One had a weight listed of 88 pounds.  I've previously 
measured these transformers pulling 20amps each (120 each feed from two legs 
and neutral of a 208 3-phase system).  Now running them phase shifted 
doesn't seem like a good idea, but I have no science to backup why I think 
so.

My question is, "1 KVA" really?  I didn't think they made pigs that small. 
How did they survive at all running nearly 2.5 times their rating?  One is 
now dead with a shorted secondary. Looks like it will be hard to find 
another to matchup this pair again.

One pig is labeled "Fixed Load Transformer", what does that mean?

CP8071
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