RE: Metal Screws and Salt Water Caps

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

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

Hi Sean:

I think you hit the nail on the head.  The primary winding is 169V 
above/below mains-ground.  But if the NST core is tied to RF ground, 
depending upon how good that RF ground is, that could be hundreds, maybe 
thousands of volts above mains-ground.  This is why:
1) EMI filters are used between the NST and the mains, and
2) A good RF ground, particularly with higher powered coils, is important.

Is it possible that the RF ground at the Teslathon was less robust than 
usual, and once that primary-to-core breakdown was made, subsequent repair 
efforts were largely ineffective?

Gary Lau
MA, USA

 >>Original poster: "Sean Taylor by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <taylorss-at-rose-hulman.edu>
 >>
 >> IF anyone knows why the primary core or coil is generating enough potential
 >> to form an arc through at least 600v of insulation, please let me know!  I
 >> do not have any protection but a safety gap.  Maybe i need an RC type
 >> filter?
 >>
 >> Steve Ward.

 >Hi Steve,
 >
 >I don't KNOW :-) but I'll venture a guess . . .
 >
 >You're primary of the NST is at ground level (well, or at +/-169 V max from
 >the AC line voltage).  Depending on what you have grounded where, you're
 >coil MAY be pulling the ground potential far away from that.  If the core of
 >the NST is ground to AC line ground, ie earth ground, then you may be
 >dumping considerable power into that ground, pulling its potential up
 >relatively high, wrt the AC hot/neutral, and blowing through the insulation.
 >Also, if this is true, you may have your safety gap tied to the earth
 >ground.  If so, every time the safety fires, your sinking a lot of energy
 >into that ground, probably pulling the potential quite high (of that
 >ground), again, blowing the insulation between the primary and core.
 >
 >If the core is tied to RF ground, then that maybe be floating above/below
 >the earth ground, and AC reference, causing a large differential, and
 >blowing the insulation.
 >
 >I hope that actually made sense :-)  Any one else have any ideas about what
 >I said? or do my thoughts only make sense to me?
 >
 >Sean Taylor