RE: and oddity or a normality?

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

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

I agree with Dan's comments.  One thing I would add is that a strike rail 
should be constructed to minimize bumps and projections that would 
precipitate corona.  I would wager that in Dan's photo of Terry's coil, the 
points on the strike rail that have the corona coming from it would 
correspond to an alligator clip ground connection, or some similar 
projection.

Gary Lau
MA, USA

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

This is very common phenomenon, especially on coils running with relative
high power and a relatively short secondary.
The following picture is of Terry Blake's PT powered tesla coil at the
Rochester Teslathon 2003.  This is a great example of
toroid to strike rail corona.

http://www.spacecatlighting-dot-com/ratcb2003/bigimages/240-4022_IMG.jpg

One thing to note, that this corona is a direct current path from your
output to ground.  This will have two direct effects on your tesla coil:

1.  Prevent the toroid from reaching its maximum obtainable voltage.  You
will be discharging prematurely before the voltage can get high enough.

2.  Ultimately reduce the output of the system.  This corona can be modeled
as a resistor to ground and represents a considerable loss of power of which
could
be used better elsewhere, like in the formation of a longer arc.

I suggest increasing the height of your secondary, or reducing the height of
the strike rail to eliminate this corona discharge.  Insulating material may
also work if you can't do
the former.

Dan



  > A couple of hours after first light, it was finally dark enough
  > outside that I could finally fire it up again, and see all that
  > the streamers were doing, big and small.
  >
  > That's when I noticed something that intrigued me severely... there
  > was a constant corona discharge going on, between the top secondary
  > winding and the strike rail.  Not intense enough to form a full-on
  > streamer, but more of a lavender glow, that was all the way around
  > like an electric veil/curtain.
  >
  > Is this a common phenomenon?  Or am I seeing something rare?
  > ---
  > Christopher 'CajunCoiler' Mayeux
  > http://www.cajuncoiler.tk
  >
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