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Re: [Amps] HV transformer and Variac

To: amps@contesting.com
Subject: Re: [Amps] HV transformer and Variac
From: Robert Arenella <rja12@comcast.net>
Date: Wed, 22 Jul 2015 11:02:52 -0400
List-post: <amps@contesting.com">mailto:amps@contesting.com>

## The difference between the hypersil pole pigs and say the dahl plate xfmrs 
is... on the pole pigs,
the primary is the 7200 vac winding.... which is called the primary.   The 
primary always goes on the inside
of the core..with the secondary wound on top. Sec of course is the   240 /120 
vac side.

Do a bing search of "How It's Made: Pole transformers" and you will see that the low voltage side is wound first, with the HV winding wound over the LV winding. The neutral side of the HV winding is wound closest to the primary winding for safety reasons.

I have a 14.4 KV pig that I'm going to use for a rather large Tesla coil. It is wound as described above. It also has taps on the HV side for 12.8 KV & 13.2 KV.

For amp use, look for a Superior electric 1256D Variac. 0-280VAC @ 28 amps continuous. For intermittent operation, you can easily draw twice their rated current & they just get a little warm.

I have one that I use to power a very large X-Ray transformer powered Jacobs ladder. The transformer is rated at 0-300 VAC in, 125KV @ 300 mA out. The filament transformer & diode stacks were removed & 12" porcelain insulators replaced the federal plugs. I run it at 280 V out, with the primary of an arc welder in series with the primary of the X-Ray transformer, for current limiting. It draws 56 amps @ 280 V. The core of the variac gets moderately warm after a 1 minute run. Arcs are from 24" - 30"....Lots of fun on Haloween.

73,
Bob
N2OAM
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