Re: Safety Gap Question

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

Original poster: "Malcolm Watts by way of Terry Fritz <twftesla-at-qwest-dot-net>" <m.j.watts-at-massey.ac.nz>

Hello Jason,

On 5 Oct 2001, at 12:39, Tesla list wrote:

> Original poster: "Jason by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<jasonp-at-btinternet-dot-com>
> 
> Generally the best ides is to put the PSG across the Main SG. That way the
> impulse that needs to travel to the protective SG doesn't have to go through
> your filter resistors. If it goes through the resistors it may damage them
> or worse. Me, I play it safe and put a safety gap across my main gap and my
> xfmr, but i have only had the xfmr gap fire once on me, after I exploded a
> cap.

If the safety gap is placed directly across the main gap, why is it 
needed at all (think about it)? The real problem occurs when the 
transformer is positioned some distance away from the main gap. The 
long leads running between the gap and transformer form a 
transmission line which is quite capable of generating high voltages 
with very little energy given the high shunt impedance of the 
transformer terminating it at the far end. Ergo, the safety gap 
should be placed directly across the transformer secondary terminals 
and secondary ground if the secondary is grounded. 

Regards,
malcolm
 
> Jason
> ----- Original Message -----
> From: "Tesla list" <tesla-at-pupman-dot-com>
> To: <tesla-at-pupman-dot-com>
> Sent: Friday, October 05, 2001 4:35 AM
> Subject: Re: Safety Gap Question
> 
> 
> > Original poster: "Shaun Epp by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> <scepp-at-mts-dot-net>
> >
> > Ok, so I'm building a tesla coil and I'm using 500 pF doorknob caps for my
> > filter.  Would it be better to put the safty gap at the transformer or at
> > the main spark gap?  my thoughts were that, if I put it at the
> transformer,
> > it protects the transformer from over voltages.  Please correct me if I'm
> > wrong while we're discussing this topic.
> >
> >
> > ----- Original Message -----
> > From: "Tesla list" <tesla-at-pupman-dot-com>
> > To: <tesla-at-pupman-dot-com>
> > Sent: Wednesday, October 03, 2001 5:57 PM
> > Subject: Re: Safety Gap Question
> >
> >
> > > Original poster: "Peter Lawrence by way of Terry Fritz
> > <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>
> > >
> > > Dave,
> > >      I too have pondered this question. Here are some of my
> observations,
> > > which are based on using a static main gap so they may not be relevant
> for
> > > your SRSG situation...
> > >
> > > 1) safety gap next to NST (therefore power resistors between primary cap
> > and
> > > safety gap) results in "weak" spark in safety gap when it does fire,
> > leading
> > > me to wonder if it is really bleeding off much energy from the primary
> cap
> > > and if it is really protecting against resonant rise in the primary or
> > not.
> > >
> > > 2) safety gap next to CAP (therefore power resistors between safety gap
> > and
> > > NST) results in "explosive" safety gap firing. For sure this prevents
> any
> > > resonant rise in the primary, but I wonder about the abuse to the
> primary
> > cap
> > > due to the virtually unimpeded very high current pulse.
> > >
> > > I'm personally sticking with (2), until someone can show by direct
> > electrical
> > > measurements that (1) does eliminate resonant rise in the primary (and
> can
> > > show by EE what the resistance of the power R should be. And I try to
> keep
> > > my main spark gap adjusted so that the safety gap fires only
> > occassionally.
> > >
> > > Peter Lawrence.
> > >
> > >
> > >
> > >
> > > >Original poster: "Dave Kyle by way of Terry Fritz <twftesla-at-qwest-dot-net>"
> > > <dave-at-kyleusa-dot-com>
> > > >
> > > >Last weekend I completed construction of the neon transformer
> protection
> > > >module. It consists of two 1K 100 watt resisters and 4 small doorknob
> > caps
> > > >wired in the usual RC configuration and a safety gap. I elected not to
> > > >include the MOV devices at this time. My question is should the safety
> > gap
> > > >be on the neon side or the primary side of the resistors? I have seen
> it
> > > >shown both ways and I am curious what the arguments are for ether case.
> I
> > > >will be using a SRSG with a three x 15KV-at-30ma neon farm if that has any
> > > >baring on the answer.
> > > >
> > > >Dave
> > > >
> > > >
> > > >
> > > >=========================================
> > > >Dave Kyle
> > > >Austin, TX USA
> > > >Email: dave-at-kyleusa-dot-com
> > > >
> > > >
> > >
> >
> >
> >
> 
> 
> 
>