Re: Necessity of NST Protection Filters and Safety Gaps

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

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

Basically you just want a HV RC filter.  500pF and 1k R works out well to 
most NST sizes.  Smaller NSTs should use lower value resistors - don't want 
to waste too much power in the resistors on a small coil.  The "Terry 
Filter" is a solid design using HV PP film capacitors identical to the MMC 
capacitors (only smaller in value) and a "big" wirewound enameled power 
resistor (25-50W is big when you're used to 1/2W or less).  And to throw in 
some extra protection, some MOVs are added to clip any voltage spikes that 
made their way through the filter.

I built one for my first coil, and I think was one of the first to ever 
destroy one....  I guess I forgot to set the safety gaps 
properly....  oops....  The MOVs are somewhat pricey and are only there as 
"one last line of defense" so I have no problems recommending that the 
budget concious omit them.  But I will say that replacing $20 in MOVs was a 
lot easier than replacing 2 NSTs.  ;)

http://hot-streamer-dot-com/TeslaCoils/Misc/NSTFilt.jpg

Although *I* may use them, The Geek Group has never used one, and hasn't 
had a problem since we learned to properly set the safety gaps before every 
run (that was before even *I* was a member).

Cheers.

Mark Broker
Chief Engineer, The Geek Group



On Fri, 16 Jan 2004 12:01:26 -0700, Tesla list <tesla-at-pupman-dot-com> wrote:

>Original poster: "Luke" <Bluu-at-cox-dot-net> That's good to hear bout your NST's 
>not burning up.  That is something I
>will have to tackle soon.
>
>Do I want a protection circuit?
>If so what is the best style and why?
>And if so how do I choose my values for the components and why?
>
>If you feel like giving any input ill gladly check it out.
>If not I may be posting some questions later after I do a little
>reading.
>
>
>Luke Galyan
>Bluu-at-cox-dot-net