RE: Safety Gap Question

["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>

My comments interspersed:


>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.

The fact that the safety gap firings seem weaker is due to the energy
being
dissipated in the resistors as well as the safety gaps.  

Even if the safety gap fires through the protection resistors, it will
discharge the
Tank cap pretty fast.  Running it through a simulation, a .03uF cap
charged to
21kV, discharging through a 2K resistor, will discharge to 10.5kV after
only 
36.5 usec.  If the gap is set correctly, it will prevent 60 Hz resonant
rise
regardless of the presence of the resistor.

>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.

Are you saying that the output of your protection network resistors feed
the
CAP?  The consensus is that the main *GAP* should be fed from the NST or
protection network, as the gap shunts the tank circuit RF from being
applied to the NST.  If you have safety gaps directly across the tank
cap,
then you certainly will have "explosive" firings, since the discharges
are in
no way current limited.  This is extremely taxing on your cap!

>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.

The value of R is not relevant so far as preventing 60Hz NST/tank cap 
resonant rise, and tank frequency resonant rise is not an issue with
spark
gap coils.  

>Peter Lawrence.

Regards, Gary Lau
MA, USA