Re: More on spark delay

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

Original poster: "Peter Lawrence by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>

Ken,
    certainly some of the more interesting observations to surface recently

first lets see if we have the time-base correct:

140KHz -> 7.1us AC cycle time.  100us = 14 cycles.  5ms = 704 cycles.

your wording below leaves me totally confused, can you fill in a simple
time line with voltages:

cycle voltage
----- -------
0     100%
1     70%  (aka a "30% drop")
2
3
...
14    ??? stable value ???

I might make some comments on the spark formation theory after I have a
good mental picture of whats on your oscilliscope!

thanks,
Peter Lawrence.




>
>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Kchdlh-at-aol-dot-com>
>
>I've put forth my hypothesis more than once that the relatively high
>rate-of-rise of spark-gap-coil voltage is the reason that spark-gap sparks are
>longer than SSTC sparks.  I've proposed that that high rate allows the toroid
>voltage to rise higher during the time it takes for the spark to propagate. 
>That time period exists due to the necessity to heat and displace the air
along
>the spark's path.
>
>The notion has received scant attention.  I may be repeating myself but here's
>an observation I just made today:   In my SSTC, the toroid voltage's rise &
>fall is extremely stable from spark to spark.  So, I can sync the scope to it
>and accurately gauge the rise and fall.  I find, at commencement of the spark,
>that the toroid voltage falls abruptly, at first, to about 70% of the level
>that it holds during the remaining 5 milliseconds of the spark's duration.

does it climb back up from 70% to 100% during those 5ms, or did you mean it
falls to 70% relative to the peak voltage just before the breakout?

 
>That fall seems to take place well within 1 cycle of the excitation, which is
>at ~140 KHz , and it always occurs at a negative half-cycle (indicating to me
>that the spark initiates when the toroid is 'crowded" with electrons and not
>otherwise).  It then takes just about 100 microseconds longer for the voltage
>to decline further to the steady level.

here you seem to be saying it continues to drop, so I assume you meant that
a) during a 7.1us cycle the voltage drops almost instantaneously to 70%
b) during the next 14 cycles the voltage continues to drop, finally to ???%
>
>Clearly, at the instant of the 30% drop, the impedance of the initial
spark has
>appeared in parallel with the impedance of the capacitance between the toroid
>and ground.  But at the end of that instant, the spark impedance is still
>relatively high since its presence in the series circuit of
>ground/secondary/toroid:ground capacitance/ground (across "toroid:ground
>capacitance") has diminished the toroid voltage by only that 30%.  The spark
>impedance then relatively-slowly decreases during the following 100 us,
causing
>the toroid voltage to correspondingly diminish.
>
>So my supposition remains:  It is the capability of spark-gap systems to
>deliver higher power during the (at least first part of) 100 us or so that
>allows for the longer sparks.  And it is the physical/thermal inertia of the
>air in the path of the spark that causes the 100-us phenomenon to exist.
>
>But perhaps this is old-hat to spark experts.  Comments?...
>
>Ken Herrick
>
>