Re: Single-bushing 14.7kV pigs. Thoughts?

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

Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com> 


Using pole xmfrs our procedure is to always ground one lead and keep one
hot.  We use five 200 watt, 1000 Ohm resistors (Digi-Key Electronics) so as
to have an effective resistance of 200 Ohm at 1000 Watt rating.  I also use
a large 3 inch dia. toroid with 3-4 turns of 12 AWG.  This starts the
clipping process before the transients hit the Q spoiling resistance.

I also want to share with the group something to never do:  On an early pig
xmfr we used a coax cable to connect both the hot and ground approx 12 feet
over to the coil.  When we fired the coil up the capacitance formed a
powerful resonance with the xmfr's inductance.  The result was hot long
sparks that fired across the entire large 14.4 kV bushing on the xmfr.  It
formed a sort of blumlein and developed over 125 kV across the bushing!

Dr. Resonance

Resonance Research Corporation
E11870 Shadylane Rd.
Baraboo   WI   53913
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Sunday, February 08, 2004 10:05 PM
Subject: Re: Single-bushing 14.7kV pigs. Thoughts?


 > Original poster: "J. B. Weazle McCreath" <weazle-at-hurontel.on.ca>
 >
 >
 > At 04:02 PM 08/02/04 -0700, you wrote:
 >  >Original poster: "J. Aaron Holmes" <jaholmes-at-silicon-arcana-dot-com>
 >  >
 >  >Thanks for the encouraging words, Weazle!  So, if I rig up some
 >  >protective filtering on the output, it'll end up looking like
 >  >half of what I did for my NST, yes?  For example, I would only
 >  >choke the single hot lead, only have one side of the typical
 >  >three-legged saftey gap, etc.
 >  >
 >  >73, Aaron, N7OE
 >  >
 >
 > Hi again Aaron,
 >
 > I don't use a choke...that's a subject of much debate on the
 > list, and the general consensus is that they can create more
 > problems than they cure.  If you look closely at the shot of
 > the PDT on my website you'll see a horn gap sitting atop the
 > transformer.  That is all the protection I use, and it works
 > just fine, firing only very occasionally when the coil is a
 > bit out of tune due to environmental changes.  The leads to
 > the gap are short and direct and the gap itself is made up
 > of scrap 1/4 inch tubing left over from my primary.
 >
 > 73, Weazle, VE3EAR/VE3WZL
 >
 > Details of my "Hyperbaric Gap" and Tesla coil are at:
 > http://www.hurontel.on.ca/~weazle
 >
 >
 >