RE: NST protection filter

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "C. Sibley" <a37chevy@xxxxxxxxx>

Excellent explanation, thanks!


--- Tesla list <tesla@xxxxxxxxxx> wrote:

> Original poster: "Lau, Gary" <Gary.Lau@xxxxxx>
>
> The benefit of the R-C filter has little to do with
> attenuation of the
> coil's resonant frequency.  It turns out that when
> the gap is firing, it
> (the gap) does a splendid job of keeping the coil's
> resonant frequency
> out of the NST, since it's essentially a short
> circuit at that point in
> time.  The real benefit is in attenuating high
> voltage, high frequency
> (multi-megahertz range) parasitic oscillations that
> occur at each
> zero-current crossing of the resonant frequency,
> when the gap briefly
> ceases conduction.  This is why having an R-C cutoff
> frequency in the
> neighborhood of the resonant frequency is not a
> problem - it's actually
> orders of magnitude lower than the frequencies of
> interest!
>
> This is a topic that receives scant attention on
> this List, even though
> it was Terry who first observed these transients, so
> I've described the
> underlying mechanisms on my web site.  Please refer
> to
> http://www.laushaus.com/tesla/protection.htm
>
> Regards, Gary Lau
> MA, USA
>
>
>  > Original poster: "C. Sibley" <a37chevy@xxxxxxxxx>
>  >
>  > I've learned my lesson and am in the proscess of
>  > adding a "Terry Filter" to my coil, along the
> lines of
>  > the one at
>  >
>  > http://www.hot-streamer.com/temp/NSTFilt.jpg
>  >
>  > If I did the math correctly, it has a cut-off
>  > frequency of approximately 290KHz.  I assume that
> the
>  > frequency response is adjusted up or down based
> upon
>  > the resonant frequencey of the coil?  Is there a
>  > discusstion/web page somewhere along these lines?
>  > Doing a web search find a lot of hits but none
>  > specifically describing the filter and it's
>  > application for different frequencies.
>  >
>  > Seeking advice...
>  >
>  > Thanks,
>  >
>  > Curt.
>  >
>
>