Re: Strike rails/safety gaps IMPORTANT

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

Original poster: "uk-teslacoil.co.uk by way of Terry Fritz <twftesla-at-qwest-dot-net>" <duncanr-at-uk-teslacoil.co.uk>

I agree, strike rails are important and shouldn't be left out of any design,
My first tesla coil NST was fried after several strikes to the Primary coil.

Duncan
----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, July 12, 2002 4:17 AM
Subject: Strike rails/safety gaps IMPORTANT


> Original poster: "Mr Gregory Peters by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <s371034-at-student.uq.edu.au>
>
> Hello all,
>
>
> I am SICK SICK SICK and tired of people saying "well, I don't use
> safety gaps and strike rails and have had no problems". You are playing
> Russian Roulette here. These devices don't only protect your equipment,
> they protect YOU!! Don't forget that a nice 200kV streamer makes a very
> nice conductive path for the output of your pole pig, or even the 240v
> mains! You DON'T want it getting into your control/power circuitry. The
> little effort in making a simple safety gap and strike rail are well
> worth the bother. These devices don't HAVE to look good. Fencing wire
> will do. I have included part of an old post from Richard Quick (A very
> successful old school coiler) below. I urge you all to read it:
>
> "Well I have seen a coiler or two who did not use contactors to
> remotely switch their 60 cycle mains. I have operated coils at
> 1.5 kVA without contactors. But let me tell you about the one
> time I had an incident that "resolved itself" inside the power
> cabinet. The experience changed my mind.
>
> Everything happened too fast to really give a "blow by blow"
> description, but basically what started it was the secondary
> discharge struck a primary that was not equipped with an RF
> grounded strike shield. The secondary discharge shorted the
> primary turns, and the main tank circuit ran away. By "run
> away" I mean that the oscillator shifted to a much higher
> frequency due to the arc shorted primary. The primary/secondary
> field flux collapsed when the tune was lost. All of the input
> energy, the field flux energy, and the energy already in the
> secondary, appeared to feed back into the tank circuit; in any
> case it looked like discharger had become a vacuum cleaner and it
> sucked in the five foot streamers. All of the conductors in the
> tank circuit sprouted six inch long sparks and corona at the same
> time the safety gap and capacitor terminals went to flames.
>
> What happened next I do not rightly know, but just when my finger
> hit the switch to shut the runaway oscillator down, there was a
> tremendous explosion inside the power cabinet. It was so bright
> that I had spots in my eyes even though I did not directly see
> the flash. The smell of ozone and electrical burn were strong in
> the cabinet when I opened the back to peer inside. At first I
> could not see anything wrong. But given the intensity of the
> flash, I was determined to disassemble everything if required.
>
> A careful examination of every inch of the wiring revealed a
> small hole in the insulation on the bottom side of a 60 cycle
> main. The hole was located about 1/2 inch from the first line
> filter, closest to the coil. Apparently kickback had made it
> inside of the cabinet and the impedance of the filter was
> sufficient that the kickback blew out the insulation and left the
> conductor entirely. The line filter, having been bypassed, was
> undamaged! Looking around some more I found fine arc tracks
> scored into the surface of the polyurethane coated plywood mount
> board. The arc had left the wire and traveled nearly four inches
> across a surface of poly-coated plywood while spreading into a
> "fan" of fine arcs that struck all along the main ground strap.
> The delicate fan-like spark pattern was nearly the size of a
> man's hand!
>
> As it turns out nothing in the cabinet was damaged. I tried to
> power up later, but a neon in my bank had gone south. I assume
> that the neon broke down internally, and the kickback had jumped
> to the 60 cycle primary.
>
> After all that I completely re-thought, re-designed, then re-
> wired everything. BTW, I just happened to be standing on an
> insulated platform, which I rarely do when I am at the controls.
> Had I not, I firmly believe I would have been jolted to my
> backside.
>
> Richard Quick
>
>
>
> Greg Peters
> Department of Earth Sciences,
> University of Queensland, Australia
> Phone: 0402 841 677
> http://www.geocities-dot-com/gregjpeters
>
>
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