RE: Necessity of NST Protection Filters and Safety Gaps

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

Original poster: Terry Fritz <teslalist-at-twfpowerelectronics-dot-com>

Hi Luke,

Inductors can "ring" or not work when put in series with teh NST's giant 
inductance.  See the papers at:

http://hot-streamer-dot-com/TeslaCoils/MyPapers/rlcfilter/rlcfilter.html

http://hot-streamer-dot-com/TeslaCoils/MyPapers/rcfilter/rcfilter.html

http://hot-streamer-dot-com/TeslaCoils/MyPapers/

Cheers,

         Terry


At 08:53 PM 1/16/2004, you wrote:
>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