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Re: Safety Gap




From: 	Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: 	bert.hickman-at-aquila-dot-com
Sent: 	Friday, November 14, 1997 8:09 AM
To: 	Tesla List
Subject: 	Re: Safety Gap

Tesla List wrote:
> 
> From:   Vivian [SMTP:V.C.Watts-at-btinternet-dot-com]
> Sent:   Thursday, November 13, 1997 1:05 PM
> To:     Tesla List
> Subject:        Safety Gap
> 
> Hi All,
>         Having read various comments in the list I feel I should have a
> safety gap to protect my neon especially as I want to open up my spark gap.
> I currently have two 3mH inductors one in each leg of the neon transformers
> secondary.  The connections goes transformer, inductor, capacitor, primary
> coil, inductor, transformer.  The spark gap is across the two inductors
> which closes the capacitor - coil circuit.  Their is clearly no point
> putting another gap across the spark gap so the logical place would be
> directly across the neon.  However I cannot see how this helps, as any
> energy to get into the neon has to come through the inductors which already
> have the gap between them, limiting the potential.
> 
> Can anyone explain.
> 
> Viv Watts UK.

Vivian,

The safety gap for your neons should actually consist of two smaller
gaps - each going to a center RF ground, which is also tied to the case
of the transformer(s). See the ASCII diagram below for safety gap SG: 

                                                     ---------
                                                     |       | Toroid
                                                     ---------
                                                         O
         X1                               C1             O
                           RFC           | |             O  L2    
           O---------------||||----------| |-----        O
         ||O    |                   |    | |    |   L1   O
         ||O    |                   |           |    O   O
   -----O||O    * SG                *           |--->O   O
        O||O----*---  to RF Gnd        G1            O   O
   -----O||O    *                   *                O   O
    to   ||O    |                   |                O   O
  Variac ||O    |                   |                O   O
           O---------------||||----------------------O   O
                           RFC                           |
                                                         |
                                                      to RF Gnd

This configuration protects you three ways. First, it protects the
transformer(s) from an accidental secondary strike to the primary
circuit, providing a low impedance path to ground (just like a lightning
arrestor). Second, it's also possible to encounter conditions where the
self capacitance of the RF chokes causes them to "ring", inducing
additive voltage transients through being "shock excited" when the main
gap fires. If these get too high, the safety gap should prevent taking
out the transformer. Finally, if the main gap is accidently opened up
too widely, properly adjusted safety gaps should prevent 60 Hz resonance
rise (between the transformer's apparent inductance and the tank cap)
from over-volting the transformer. BTW, the last phenomenon will be a
very real problem if you "size" the tank cap to the transformer (as most
Tesla programs do...), and is responsible for sending many a poor
trannie to an early death.

Safe coilin' to you!

-- Bert --