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Re: Sparks to ground
Tesla List wrote:
>
> > Subject: Sparks to ground
>
> >From bert.hickman-at-aquila-dot-comTue Nov 19 22:05:36 1996
> Date: Tue, 19 Nov 1996 20:13:34 -0800
> From: Bert Hickman <bert.hickman-at-aquila-dot-com>
> To: tesla-at-pupman-dot-com
> Subject: Re: Sparks to ground
>
> Tesla List wrote:
> >
> > >From hullr-at-whitlock-dot-comMon Nov 18 20:06:15 1996
> > Date: Sat, 11 Mar 2000 02:35:50 -0800
> > From: Richard Hull <hullr-at-whitlock-dot-com>
> > To: tesla-at-pupman-dot-com
> > Subject: Sparks to ground
> >
> > All,
> >
> > It has been stated on this list that one an arc contacts ground that the
> > resonator Q goes into the hamper to near zip.
> >
> > I was reviewing some frame by frame video hits of maggey #11-E and note
> > that the arc channel develops over an extended period of time!
> >
> > I note a spark approaching the heavily grounded aluminum siding on my
> > house. The contact occurrs, let us say, at t0, in frame, f0. The arc
> > channel is fairly dim, but contact is made and the arc channel is 115"
> > long point to point. In the next frame, f1, (1/30 second later) the
> > channel doubles in brightness.(as measured by my light meter (spot
> > reading). In frame f2 the arc channel increases in brightness by another
> > 40% or so over the preceeding frame. In frame f3, the channel retains
> > about the same brilliance (white hot) as in f2 frame. In frame f4, the
> > channel starts to reduce its brightness and is about 65% of f2s level.
> > Frame f5 shows a greatly reduced channel intensity and is just about 10%
> > below that of f0s level. In frame f5, The channel is just a faint mist
> > of ionized vapor. Frame f6, shows the channel to have disappeared.
> >
> > Assuming 400 BPS (which is my normal break rate), This means that the
> > system has energy pops at the rate of about 13 pulses per video frame. so
> > we see that from time of contact to max brighness,(more or less), we
> > actually sent in about 52 energy pulses. Is the electronic Q of the
> > resonator system this slow to respond?!! Energy delivery to the arc
> > channel was consistently on the increase over this long period
> > (~120,000 usec).
> >
> > The rise to max channel current is rather slow, compared to the
> > extinguishing of the channel which never takes more than 2 video frames
> > (1/15 sec-60,000usec).
> >
> > I am making no judgments here, only reporting observational fact.
> >
> > Richard Hull, TCBOR
>
> Richard and All,
>
> Very interesting! Although my experience has only been with 2-coil
> systems, and maximum arc length only in the 60-65" range, I suspect
> that fundamental arc behavior is probably not much different. Storage
> scope measurements I've taken seem to suggest that Q declines
> dramatically during heavy arcs to ground. Are these measurements and
> Richard's videotape analysis inconsistent?? I really don't believe they
> are...
>
> Q may be defined as the ratio of stored energy divided by the amount of
> energy lost per radian. Resonator Q is a dynamic, real-time, reflection
> of energy losses from all sources. While total resonator energy
> typically changes very little over 1 radian, the denominator can change
> instantly (and dramatically), particularly if the rate of energy loss is
> large. For example, prior to breakout, resonator Q is typically quite
> high (say 150 -200). However, once active streamers form, Q declines
> significantly; I've measured "effective" secondary Q's of about 10-20 on
> my system, depending upon power level, BPS rate, and streamer
> variations. In general, the heavier the streamers, the lower the Q.
>
> Once we initiate a heavy toroid-ground discharge, the rate of energy
> loss climbs dramatically. In previous measurements, virtually all of the
> energy in the resonator/toriod was lost in about 1.5 uSec, or about 1/8
> of one cycle at Fo, This translates to an effective Q of less than 1
> while the ground arc was firing. In effect, the arc became a
> prodigious energy sink for all the energy the resonator could deliver! I
> have little doubt that if we were still transfering energy to the
> resonator at the time of the discharge, the additional energy would
> _also_ get unceremoneously dumped into the arc.
snip
> Its also possible that the camera was integrating an increasing number
> of
> successful ground hits per frame. As a previous arc-path leaves its ion
> trail ghost, there may be greater opportunity for lower-energy "bangs"
> to
> fully bridge the path blazed by their larger predecessors. The
> progression from frame 1 could reflect only the "bigger" bangs
> connecting at first, followed by more/all successive bangs connecting in
> frames 2 and 3, until the discharge path begins to be disrupted in frame
> 4. This situation might occur as ground arc length approaches the
> maximum sparklength for the coil. Once the channel begins breaking up,
> only the larger bangs still connect (but just barely). In any case, I
> don't see anything in the above scenarios that conflicts with the
> changes in Q I've measured versus type or strength of discharge. Food
> for thought! :^)
>
> Why does arc breakup seem to take a shorter time than the buildup to
> full strength? This may be related to turbulence which may be more
> prevalent around a higher temperature, fully formed, multiple-strike arc
> channel. In the power industry, turbulent mixing between the arc plasma
> and a cooler media is used with great effectiveness to rapidly
> extinguish arcs in high power/high voltage circuit breakers. Another
> area for future TC research! :^)
>
> My best wishes to you Richard, and safe coilin' to you all!
>
> -- Bert --
>
> P. S.
> Richard, could you provide a little description of how you made the spot
> lightmeter readings? The "brightness" of a videotaped arc image should
> be related to the sum of the individual strokes. The more strokes/frame,
> or the greater the current/stroke, the brighter the resultant image.
> However, this would seem to presume that the camera tube's target isn't
> saturating from the brilliance of the discharges...
Bert,
Much of what you have noted above, I agree with. However, as a video
expert (my electronics engineering specialty), I understand fully what is
taking place in the video imaging process.
All the arcs recorded are dead horizontal, on screen. What little arc
droop or radiusing that occurs, occurs totally within 20 scan lines.
(vertically interlaced horizontal lines) The video frame is never
continuously exposed for the 1/30 sec as in a common photo, even though
the frame is, indeed, a 1/30 of a second exposure!! The horizontal lines
(about 525 of 'em) are scanned in no more than 60usec per line . As the
scan is interlaced, this entire group of 10 'key'lines in each field (two
1/60sec fields of alternating lines per frame) are scanned in about 625
usec! As the rep rate (500BPS)is about one discharge per 2000usec, the
normal exposure, of a standard video frame, will show only a single
'active' discharge channel of the resonator and never two. There is
nothing to integrate!!! There are no successive arcs to pile up on the
video camera's CCD sensor.
It is even highly likely (3:1 odds in favor) that no actual active arc
channel is recorded in any video frame!!!!! Thus, we are mostly seeing
the result of heated air in the multi-thousand degree range with each
successive video frame. This is a very close mime of the actual averaged
arc channel current levels when the arc is on!
It is also possible, with chance occuring sync locks, to record the
coils violent white hot arc ativity without capturing a single 'active'
arc channel over multiple 1/30 second exposures!! I know it sounds
weird, but it happens. If you place a camera on high speed shutter,
where the luminence integration winds up severely depressed, it is
possible to film a running coil and never see an arc on the film (total
darkness). The chances of such a perfect and continuous sync lock are
rather slim. This is the reason that high shutter speed video shots of a
coil are of almost zero value without full knowledge of the sync point.
Regular old 30 hertz (~1/30 sec) frame rates are virtually ideal
indicators of arc energy content.
The light meter readings were taken with a Lumi-pro professional 'spot'
meter in contact with the CRT face of a high qualtiy Panasonic BT-S901
professional video monitor and not a standard old crummy TV set.
Richard Hull, TCBOR