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Re: A new cap failure mode?



Tesla List wrote:
> 
> Original Poster: Terry Fritz <twf-at-verinet-dot-com>
> 
> Hi All,
> 
> A few thoughs on the safety gap resistor.
> 
>         I was thinking of just putting the resistor in the safety gap
circuit so
> it would only act when the safety gap fires.  If it were in the main tank
> circuit it would drastically affect the coils operation.
> 
>         I would think a 50 or 100 ohm resistor would work well limiting the
> current to a few hundred amps.  One of those big 225 watt Ohmite ceramic
> core wirewounds should work well for this I would think.
> 
>         I worry about using an inductor since that would just oscillate
at some
> huge level that may be worse since there is no well defined element for the
> power to be dissipated in.
> 
>         Terry
> 
> At 05:22 PM 2/7/99 -0800, you wrote:
> >Tesla List wrote:
> >>
> >> Original Poster: "Barton B. Anderson" <mopar-at-uswest-dot-net>
> >>
> >> <big snip>
> >> Bert,
> >>
> >> > Adding a series resistance in the gap circuit should
> >> > help damp these oscillations, limit the current peaks, and even knock
> >> > down the magnitude of the voltage reversal with minimal impact on the
> >> > overvoltage protection function... sounds like a pretty good idea! The
> >> > resistor must be physically large enough to withstand worst-case
> >> > voltage however.
> >> >
> >> > -- Bert --
> >>
> >> How big of a resistor are we talking about? When I consider the
magnetude,
> >> I sure
> >> can imagine a "huge" resisitor.
> >> Bart
> >
> >
> >       Adding this resistor will increase the primary loss and hence the
> >streamer output!!!
> >
> >Ed
> >
> >

	A year or so ago I did some simulations of the effects of several
different "NST protection circuits" on the peak voltage across the
transformer.  Most of the L-C filters did indeed result in increased
peak voltages, unless series resistance was added in series with the
TRANSFORMER SECONDARY!

Ed