Re: new coil

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>

Hi Gary,

If the safety gap was directly across the NST, then when it fires, I'm
thinking it may be hard on the filter caps.  If the safety gaps are located
at the main gap side of the filter, it will limit the voltage into the
filter.  May have the same result.  When the safety gap does fire, the
discharge of Cp will be current limited by the TC primary inductance just
like when the main gap fires.

In this configuration, yes the safety gap would be backup to the main gap.
The main gap will also limit the voltage if it is not set too wide or a RSG
misfire doesn't occur.  The only disadvantage I can think of to this
location is with a SRSG.  Safety gap firings in this case will mess up the
timing of the SRSG causing rough running.

> Original poster: "Lau, Gary" <gary.lau@xxxxxx>
>
> My thinking is that the filter is there to protect the NST, and the
> 3-ball gap is an absolute voltage limiter applied across the thing we're
> trying to protect.  Having the safety gap in parallel with the main gap
> seems redundant, since the lower voltage gap will always fire first.
>
> Why then wouldn't the main gap be an equally effective voltage limiter,
> making the safety gap redundant?  Good question and I don't have an
> excellent answer.  It has been suggested that mechanisms exist that can
> generate high voltage transients across the wires between the main gap
> and the NST if they're at all long-ish, so that the NST might see a
> voltage higher than the main gap.  I personally haven't measured or
> studied this, but it's enough for me to realize that I want a clamp as
> close as possible to the thing I wish to protect.

I dont disagree with your thinking on this,  I like to keep my wires short
to keep stray pickup down.  The filter caps should shunt the RF anyway.  The
RC filter in anycase should be as close to the NST as possible.  If it
wasn't for the filter caps, I guess I would put the safety gap across the
NST (I would need to think about the power dissapation in the resisters when
the safety gap fires).

If the NST was far away from the main gap, I would locate the safety gap on
the filter end of the long connection (transmission line effects might start
to come into play).  Maybe have a safety gap on both ends of the long cable
so the safety gap protects the capacitor bank too.

Thankyou for sharing your thinking,

Gerry R.




>
> Regards, Gary Lau
> MA, USA
>
>  > Original poster: "Gerry Reynolds" <gerryreynolds@xxxxxxxxxxxxx>
>  >
>  > Hi Gary,
>  >
>  > Thats how I read it also.... and that is how I think it should be
> connected.
>  > ie, safety gap in parallel to the main gap.  Comments??
>  >
>  > Gerry R.
>  >
>  >
>  >  > Original poster: "Lau, Gary" <gary.lau@xxxxxx>
>  >  >
>  >  > Perhaps I'm reading it wrong, but it appears that in the photos,
> the
>  >  > 3-ball safety gap is not across the NST terminals, but across the
>  >  > filter's output, essentially in parallel with the main gap?
>  >  >
>  >  > Gary Lau
>  >  > MA, USA
>  >  >
>  >  >  > Here is a way "too" beautiful one!!  I wish I could just take
> the
>  >  >  > "pictures" half that good ;-))
>  >  >  >
>  >  >  > http://www.peninsulators.org/Tesla/nstfilt1.jpg
>  >  >  >
>  >  >  > http://www.peninsulators.org/Tesla/nstfilt2.jpg
>  >  >  >
>  >  >  > But just use old bolts or bent wire for the safety gaps.  You
> just
>  >  > want
>  >  >  > it to arc over if the voltage on the NST starts to go way too
> high.
>
>