Unexplained arcing current

To: tesla-at-pupman-dot-com
Subject: Unexplained arcing current
From: Gary Lau 21-May-1999 2229 <lau-at-hdecad.ENET.dec-dot-com> (by way of Terry Fritz <twftesla-at-uswest-dot-net>)
Date: Sat, 22 May 1999 07:51:38 -0600
Approved: twftesla-at-uswest-dot-net
Delivered-To: fixup-tesla-at-pupman-dot-com-at-fixme

I just saw something I can't explain.  For as long as I've been coiling,
the resistors in my NST protection circuit have been getting hotter than
expected.  The power defined by I**2 R, I being the NST current, never
came close to explaining how hot they got, so I assumed that the
additional wattage was due to a reverse transformer action.  After the
gap quenches, the energy in the secondary could couple back to the
primary, although it won't be tuned any longer now that the gap is open...
Not a very good theory, I know.

Tonight I shorted my gap, essentially shorting the NST, but having the
current pass through my RC network.  My R's are each 1.6K, 113W, non-
inductive.  C's are 450pF.  Metering the current, I got 73mA (mine is a
15KV/60mA NST), and the resistors barely got warm.

Next I removed the short across the gap but broke the connection between
the tank L and C, so that the gap arcs, but no cap charging/discharging.
Now the resistors get hot as a pistol in no time.  I tried measuring the
current to the gap, but my digital meter just wigged out, I'm probably
lucky it still works.

So, what's different that causes the R's to see so much more power going
to an arcing gap?  It's just down to 60 Hz stuff now.

Gary Lau
Waltham, MA USA