Re: Safety gap resistor?

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

Original poster: "Barton B. Anderson by way of Terry Fritz <twftesla-at-qwest-dot-net>" <tesla123-at-pacbell-dot-net>

Hi All,

Just wanted to say I support everything Ed said here. This is exactly how I
have my
own safety gaps setup (at transformer and across rotary gap). This is good
info for
those using rotary gaps.

Bart

Tesla list wrote:

> Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>"
<Esondrmn-at-aol-dot-com>
>
> In a message dated 8/6/01 3:12:12 AM Pacific Daylight Time, tesla-at-pupman-dot-com
> writes:
>
> <<
>  >Do you current limit your primary to keep the discharge current from
>  damaging your cap?
>  >I have NEVER seen a cap destroyed by a safety gap yet. I HAVE however
>  seen many caps go to the great beyond for the lack of a safety gap!
>  >The first question I ask someone who has just blown a capacitor is "were
>  >you running a safety gap on the cap?", and almost invariably the answer is
>  >no. I personally will use a safety gap every time!
>
>
>
>  Someone please straighten me out on this! It makes since to use a current
>  limiting resistor for the MMC caps, but... WHERE should I put the resistor?
>  Are we talking about the resistors in the Terry filter (that I am using), or
>  should there be another resistor in series with the cap gap, or a resistor
>  in series with the primary coil? And if so, WHAT value and wattage resistor
>  should I use? Save my caps! Kevin
>   >>
> There seems to be some confusion on safety gaps for the primary tank
> capacitor.  Having lost an expensive commercial cap due to a lack of a safety
> gap, I speak from experience.  My opinion:
>
> If your system uses a static gap for the main primary spark gap, you need a
> safety gap at the H.V. transformer output terminals and no safety gap for the
> tank capacitor.  The main tank circuit spark gap already serves this purpose
> - just be careful not to open it up too far.
>
> For a rotary gap system things are different.  Due to gap phase control
> settings, rotary gap speed, or undesireable primary resonance problems, you
> definitely need a safety gap to protect the primary tank capacitor.  This
> safety gap should be installed directly across the rotary gap.  When it
> fires, all the current goes through the primary inductance and no current
> limiting systems or impedance matching components are required.  Just don't
> mount a safety gap directly across the main tank capacitor - which I had
> originally done.  It goes off like a rifle shot and is really hard on the
> capacitor.
>
> Ed Sonderman