RE: Safety Gap, Grounding, and Secondary Questions

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

Original poster: "Lau, Gary by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Gary.Lau-at-compaq-dot-com>

Hi Jake:

Asking if the NST case should be connected to RF or 3rd wire ground is like
asking Mary Ann or Ginger.  There are compelling arguments for both ways.

First, the case for RF ground.  It is important to note that due to the RF
ground and connections to it being less than perfect, very high voltage
transients will develop between one's RF ground at the coil and the 3rd wire
ground.  If your NST case is connected to RF ground, these high voltage
transients will exist between the NST case and the NST primary.  Two issues
here:
1) There is a possibility that the insulation between the NST primary and
the core may break down and arc.  However, I've never heard of this failure
mode occurring in an NST.
2) Since the NST core is energized with high voltage, high frequency
transients, these will capacitively couple to the NST primary and will
generate common-mode interference being into your mains wiring.  A good,
properly wired EMI filter should do a fair job of cutting this down however.

I have my NST case connected to RF ground, and suspect this may be the more
common practice.

Malcolm Watts and others suggest that it makes more sense to connect the NST
case to 3rd wire ground, and to connect only the secondary base and any
discharge targets to the RF ground.  This is much cleaner as far as keeping
things quiet on the NST primary and AC mains.  The problem I see is if a
streamer strikes the primary, it will couple via safety gaps into the 3rd
wire ground.  It's possible to use RF-grounded barriers to head off primary
strikes, but this seems less than certain to be effective at preventing a
primary strike.

The shorter answer is, folks have been successful with both ways.

I'm not sure I understand about the "tiny pin-prick sparks on the
secondary".  

Gary Lau
MA, USA


Original poster: "Jake Draper by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<cybermecium2-at-home-dot-com>

Hi, I was running my 3"x12" coil tonight and it occurred to me that I didn't
have any safety gaps on my prized 15/60 Franceformer. So I made some safety
gaps to ground. So I have 2 questions about grounding NST's:
 
1) Do you connect the ground screw on the NST to the earth ground in your
home
(3rd prong)
2) If the NST is not grounded, will a firing safety gap kill it because it
just
shorts the overvoltage     through its own winding?
 
NOTE: As of now, my NST has the ground screw connected to the 3rd prong in
the
recepticle.
 
I also have a question about my secondary, When I was running it, I noticed
some tiny pin-prick sparks on the secondary so I put some glue over it as
extra
insulation. Will this kill my secondary or is it something that happens
alot?
    -Jake D.
    <mailto:cybermecium2-at-home-dot-com>cybermecium2-at-home-dot-com
    http://taradev.cjb-dot-net