Re: RSG and NST's

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>

Hi Gary, Dr,

I'm not too sure which one of you are "right" on this ;^) I have
experienced near cascading failure of an NST farm when try-
ing to run an asynch rotary gap with them! I'm not too sure
what the BPS rate was but I think it was in the 300 to 350
range - 6 rotary electrodes on a 3450 rpm motor. Anyway,
I had (6) 15/30 NSTs in parallel and almost as soon as I
fired it off, the output quickly went down to almost zero. In-
spection revealed that one of the transformers had failed.
Once this transformer was removed and I was operating
on 5, the same thing happened again almost immediately
after power up. So now I had 4. Didn't take long to figure
out that this was NOT going to work :^O I don't think 300
or so bps would be considered LOW bps. One thing that
I am pretty sure of is that whether or not high bps is more
stressful on the transformer from resonant rise or whatever,
it is more stressful on the primary capacitor due to higher
RMS currents. This particular .083 uFd, 84 kV cap was
quite robust though and never even "hiccupped" then or
for the next several years after that after I had finally upgraded
the transformer(s) to a single 10 kVA, 14,400 volt pole
pig and got bright, thick 8 to 10 ft. sparks for runs of se-
veral minutes of non-stop operation at a time. So for me,
NSTs are just too fragile for serious coiling and since
using pole pigs, transformer failures have ceased , with or
without any type of protection/filter circuitry ;^)

David Rieben

----- Original Message -----
From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, November 26, 2004 9:35 PM
Subject: RE: RSG and NST's


> Original poster: "Lau, Gary" <gary.lau@xxxxxx>
>
> Hi Dr.
>
> I don't agree that the hazard associated with async RSG's and NST's is
> due to excessively high break rates.  With an NST, as an RSG's break
> rate increases, the bang voltage will go down, making it LESS stressful
> to everything.  The same effect may be achieved by reducing the spacing
> of a static gap - lower bang voltage and higher bang rate - and I think
> all agree that narrow static gaps are the least stressful.  Even if bang
> voltages did not diminish with increasing BPS, I still don't see how the
> NST would be any more stressed at higher BPS.
>
> On the other hand, it's easy to demonstrate via simulation the
> consequence of having a too-slow BPS, resulting in mains resonant-rise.
>
> I'll be the first to admit that my opinions are based solely upon theory
> and simulations, and I have not personally attempted an async RSG and
> seen an NST fail. If you have experience demonstrating that high BPS is
> in fact more stressful, I would enjoy hearing it, as well as your theory
> as to the actual stress mechanism that increases with BPS.
>
> Regards, Gary Lau
> MA, USA
>
>  > -----Original Message-----
>  > From: Tesla list [mailto:tesla@xxxxxxxxxx]
>  > Sent: Friday, November 26, 2004 8:07 PM
>  > To: tesla@xxxxxxxxxx
>  > Subject: Re: RSG and NST's
>  >
>  > Original poster: "Dr. Resonance" <resonance@xxxxxxxxxx>
>  >
>  >
>  > Technically, a NST is designed to provide an ignition voltage for a
> plasma
>  > tube, ie, 9-15 kV to quickly ignite the gas in the tube, and then the
> xmfr
>  > voltage drops back considerably, usually down to 400-600 VAC to
> sustain the
>  > plasma.  At this point it becomes a current source to keep the plasma
>  > bright.
>  >
>  > In short, a NST is not designed to provide a continuous source of HV.
> They
>  > do, and they work well with TCs firing 120 bks/sec.  They will also
> work at
>  > higher break rates but one must be very very careful to provide
> excellent
>  > filtering to prevent ANY high freq transients from getting back into
> xmfr
>  > windings.  A "Terry Filter", named in honor of its inventor, Terry
> Fritz, is
>  > commonly employed to provide this high level of filtering.  Perhaps
> Terry
>  > could post this location in his extensive archives collection.
>  >
>  > http://hot-streamer.com/TeslaCoils/Misc/NSTFilt.jpg
>  >
>  > The other area, that must be carefully monitored, is the total spark
> gap
>  > setting when running a NST.  Usually 0.220 to 0.250 is the absolute
> MAXIMUM
>  > total spark gap setting that should be used with a NST.  Larger gaps
> invite
>  > problems and failures on the NSTs.  It's always advisable to keep your
> total
>  > gap setting at the maximum size (or less) that provides the
> performance you
>  > want.
>  >
>  > RSGs can run asynchro IF you use a good filter with safety spark gaps
> and
>  > total gap settings in the recommended range.  Not using all these
> cautions
>  > invites trouble.  I would suggest less than 400 bks/sec as a max for
> NSTs.
>  >
>  > I've been working for quite some time now for a reliable replacement
> for the
>  > NST especially since the 60 mA units seem to be disappearing rapidly
> from
>  > local suppliers.  Our unit contains two separate 8 kV coils and a LOT
> of
>  > mylar under both coils so they can be either operated as a CT ground
> unit
>  > (like NSTs) or, the coils may be connected in series, for a 16 kV to
> ground
>  > unit.  These units are designed to be operated in oil so that the
> final
>  > product should be quite robust.  A standard "Tupperware" type plastic
>  > container will serve as a suitable xmfr tank.  For greater mobility,
> we
>  > intend to offer a steel tank with a phenolic top that is sealed with a
>  > gasket.
>  >
>  > There has been a lot of delays.  We finally received the two sets of
> test
>  > coils and are awaiting the laser cut cores from Magnetic Metals.  We
> hope to
>  > have them in our lab and tests completed prior to Dec. 20th.
>  >
>  > After that, we can start ordering production quantities which will
> determine
>  > final pricing of these units.
>  >
>  > Dr. Resonance
>  >
>  >  >
>  >  > Several posts lately are discussing the use of rotary spark gaps
> with
>  > NST's.
>  >  > I was under the impression that a RSG was not for use with NST's as
> they
>  >  > cause them to fail.  Is this not right?
>  >  >
>  >  > randyaz
>  >  >
>  >  >
>  >  >
>  >
>
>
>