RE: Necessity of NST Protection Filters and Safety Gaps

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

Original poster: "Luke" <Bluu-at-cox-dot-net> 

May I ask why inductors are not used instead of the resisistors since
the react with frequency?

What is a MOV?

And what is the method to properly set the safety gap?
Are you talking about the safety gap at the Main spark gap or the safety
gap in the NST protection circuit?

Luke Galyan
Bluu-at-cox-dot-net

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, January 16, 2004 5:03 PM
To: tesla-at-pupman-dot-com
Subject: Re: Necessity of NST Protection Filters and Safety Gaps

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