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Peak cap voltage, was 12kV, 30ma TC specs, 42" spark
From: Malcolm Watts[SMTP:MALCOLM-at-directorate.wnp.ac.nz]
Sent: Monday, September 22, 1997 6:08 PM
To: tesla-at-pupman-dot-com
Subject: Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark
Hi John, all,
Great notes below and useful information....
> From: FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
> Sent: Monday, September 22, 1997 3:46 AM
> To: tesla-at-pupman-dot-com
> Subject: Re: Peak cap voltage, was 12kV, 30ma TC specs, 42" spark
>
> In a message dated 97-09-22 01:08:07 EDT, you write:
>
> <<
> > Hi John,
> > I may have an explanation of why the sync gap does better
> > than the static. Unlike the static gap, the rotary electrodes are
> > drawing closer for a time while primary is oscillating and I would
> > think their losses are going down during this time (unlike my spark
> > blowing exercise where the losses (already high because of gap
> > distance) were being blown upwards.
>
> Hi Malcolm, all,
>
> This sounds reasonable, and I think there are also additional
> advantages: Using the static gaps, the gaps have to be run a little
> closer than optimal to ensure steady firing, this limits the voltage
> that the cap can charge to, to something below what can be reached
> using the sync-gap. It's also limiting the time available for cap
> charging, and I think this is what prevented steady 120 BPS firing
> from occuring in my static gap trial ( a smaller cap may have helped
> here, since I have found in the past that a small decrease in cap size
> doesn't reduce the output spark much.) Also, with wide static gaps,
> the likelihood of "skipping" a firing is high, and that will allow the
> tranny voltage to go sky high under resonant charging conditions. It
> may be this "skipping" of firing (and the accompanying resonant rise,
> that is the major cause of failure). Often folks use extra air blasts to
> help their quenching, esp. in magnifier systems. This extra air is
> even more likely to cause firings to be "skipped", and this may explain
> the frequent neon failures under these conditions.
Well, I did the verboten over the weekend. I must stress that the
transformer failed some time after I did this though and I don't
think it was responsible. I ran an async rotary (BPS at least 4x
Fmains) with a static gap planted firmly across it to catch misfires.
First point of note was that the coil never emitted sparks until the
variac was turned well up. Second was that while I got a pleasing
tone, I always obtained the single waving streamer from the sphere
with virtually no variation and the ionization was severely clamping
the output. If I'd known the transformer was going to fail later that
day, I would have let the coil discharge to a ground under these
conditions to see exactly what sort of attached discharge it would
produce.
> > The sync-gap never seems to skip a firing, thereby limiting the
> resonant rise to perhaps about 1.5 times the peak "normal" voltage.
> It is possible that a neon tranny can withstand this voltage. The
> regularly timed firings of the sync gap may also discourage other
> chaotic resonances from occuring?
Strongly agree.
> > BTW, the neon sign people confirmed that tar tracking in neons is
> > a major cause of failure and realized straight away the implications
> > of resonant charging.
>
> I agree that carbon tracking is a major cause of failure. But my
> question would be; just what is it that most promotes carbon tracking?
>From anecdote I would say the fact that it is present at all :(
> I have seen folks destroy a neon in 5 minutes by opening their gaps
> wide while obtaining wimpy 12" sparks. Yet, I have been running my
> sync-gap system for months with no problems. I try to limit my runs
> to 20 or 30 seconds, but often I have run much longer while doing
> quench measurements, etc. This transformer has experienced
> punishing abuse before I installed in onto this TC, yet it survives.
>
> There may be some combination of events, as mentioned above,
> that allows a neon to survive in a synchronous environment. Time
> will tell how long my trannie will survive. But even if it fails, it will
> not give a conclusive answer because of three reasons; 1, the
> trannie was used, maybe it was about to fail. 2, it had been punished
> in chaotic TC work previously. 3, neon trannies often fail during TC
> use despite all precautions (safety gaps, chokes, bypass caps,
> resistors, narrow gaps, smooth running, etc.) So I think that only
> large scale, long-term tests, will gradually give the true scoop on
> how well neon trannies can survive in resonant mode sync-gap TCs.
>
> I do agree that a neon should not be run in resonant mode with
> widely spaced static gaps; operation becomes just too erratic, and
> destructive. This sort of operation may also permit more destructive
> RF to enter the transformer compared with sync-gap operation?
It seems clear from my failure that it pays to adjust k carefully
before letting it totally rip or risk leaving a significant amount of
energy in the system to impinge itself on the transformer. No simple
answer here. If the gap quenches well and the secondary can't unload
fast, major problem. I now wonder whether Dr Resonance's observation
that low frequency systems seem to cause less kickback is related to
streamer formation speed.
?? Heaps o' questions,
Malcolm