Re: Chokes vs Safety Gaps

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

Original poster: Mark Broker <mbroker-at-thegeekgroup-dot-org> 

I hadn't seen the NSTWinding paper.  But I think the real frequencies of 
interest are the ones over 1MHz, which are generated by the spark 
gap.  Indeed, the Terry Filter is "tuned" to these higher harmonics, not 
the fundamental resonant frequency.

It has been a while since I read the RLC paper, but I'm not so sure anymore 
about the results.  I think that any NST filter should be two center-tapped 
filters, a la the "Terry Filter."  Putting a resistor (albeit a large 
wirewound) on one leg of the NST, an inductor on the other leg, and a 
capacitor between the two that isn't tied to ground is not indicative of a 
real world filter.  I would be interested to see if the test results 
changed significantly if a "double pole" filter was used.  (ducking to 
avoid a swing from Terry :p ).

I would expect a fairly good filter design to feature an RLC filter with 
the inductors straddled by two resistors (NST-C-R-L-R-TC).  The resistors 
would kill the Q of the resonant circuits comprised of both the filter cap 
and inductor and main cap and inductor.  IMO this is practically executed 
by using a large wirewound resistor ;)

I would never run an NST-powered Tesla Coil without a safety gap, even with 
a static gap.  I also strongly encourage people to build at least an RC 
filter a la the "Terry Filter" minus the MOVs.

Cheers,

Mark Broker
Chief Engineer, The Geek Group


On Wed, 11 Feb 2004 08:05:52 -0700, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: "Steve Conner" <steve.conner-at-optosci-dot-com> Terry Fritz has 
>already done what seem to me the definitive experiments on
>this. He pinged a depotted NST with spark-gap pulse waveforms and examined
>the voltage distribution across the windings. He tried this with various
>chokes and resistors in series with the NST, and found (IIRC) that chokes
>were worse than useless. He wrote a couple of papers that you can find on
>hot-streamer-dot-com.
>
>The "Terry Filter" is the result of these experiments.
>
>Steve C.
>
>http://hot-streamer-dot-com/TeslaCoils/MyPapers/NSTWindingStress/NSTWindingStress.html
>
>http://hot-streamer-dot-com/TeslaCoils/MyPapers/rcfilter/rcfilter.html
>
>http://hot-streamer-dot-com/TeslaCoils/MyPapers/rlcfilter/rlcfilter.html
>