Re: Safety Gap =

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

Original poster: "Harold Weiss" <hweiss-at-new.rr-dot-com> 

Hi All,

On my 6" coil primary I have measured a 7X voltage rise at resonance, when
injecting signal across the gap.  At 12KV it could rise high enough to blow
my Fair Radio caps (100KV).  That coil also has a nasty habit of wanting to
fire at 1/2" spacing on the SRSG for a total of 1" of total gap.(1/2" below
alignment)  I have put a JF phase controller on it in hope that I could
could close that gap, but the T filter gap keeps firing at the 9KV point.
(my project for this summer)  Before this I had a RC filter that broke down
accross the primary side terminals thru 10" of canvas phenolic with some
help from the humidity.  Had I had no protection, I would have two dead
12/60 NSTs.

David E Weiss

 > Original poster: "Gerry Reynolds" <gerryreynolds-at-earthlink-dot-net>
 >
 > I'm glad you have not had any failures.  I wonder if one realizes that
 > resonate rise could take the voltage above 40KV.  A spice simulation of a
 > 12KV NST (with winding resistance in the model) at mains resonance (using
a
 > 6.2nf cap and no voltage limiting) could grow to above 100KV.  Now I'm
sure
 > that other effects like core lose would keep the rise below this high
level
 > and certainly the NST would smoke well before this.
 >
 > Gerry R
 >
 >  > Original poster: "Gary  Weaver" <gary350-at-earthlink-dot-net>
 >  >
 >  > I built my caps almost bullet proof.  They are all rated 40,000. volts
 > each.
 >  > I want my coil to be maintenance free.  I think overkill is better than
a
 >  > DEAD cap that has to be replaced.  I have not used safety gaps in so
long
 > I
 >  > have forgotten that people use them.  I assume it would be wise to use
a
 >  > safety gap on caps that need the protection.  Richard Hall once said if
 > you
 >  > build your caps with a voltage rating of 2.5 times the transformer
voltage
 >  > safety gaps are not necessary.  After loosing a few caps I took his
advise
 >  > and built all my caps 40KV rating and I have not lost a cap sence.
 >  >
 >
 >
 >