RE: Necessity of NST Protection Filters and Safety Gaps

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

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

Thanx for the links
That answers my question about inductors in the filter circuit.
Using ohms law with a 60 ma NST the voltage drop across each resistor
would be about 60 volts totaling 120 volts.  Does this hurt performance?
Or is the 120 volts (0.8% of the NST output) small enough to be
considered negligible?

And why is the capacitor value across the NST not needed to be any
particular value?


Luke Galyan
Bluu-at-cox-dot-net

-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Friday, January 16, 2004 8:25 PM
To: tesla-at-pupman-dot-com
Subject: RE: Necessity of NST Protection Filters and Safety Gaps

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