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,
    thanks for the clarifications.
    
I'ld REALLY like to match up your SSTC with a streak-photograph of the spark
formation!!! (I've got the machine shop to make the streak-camera (and I've
built a turbine engine, so high RPMs are not an issue), but..., my girlfriend
just moved in and there are so many boxes around the house and shop that I
can't even get to anything right now... :-)))

I can only wonder and speculate about whats happening during those:

32 cycles ring up
1 cycle break out (people say feeder sparks grow in nano-seconds, not 7us)
15 cycle ring down
700 cycle steady ringing


? how much energy is built up in 32 cycles, and how much expended in that
  first 30% drop in Vp-p

? how far does the spark grow in that first (nano seconds) break out, during
  the 15 cycle ring down, during the 700 cycle steady ringing
  
? how much corona develops around the spark during the 15 cycle ring down,
  during the 700 cycle steady ringing

? how much brighter does the spark get during...

? what happens after the 748 cycles, do you stop feeding input or does the
  spark extinquish by itself (if so why)



? what would happen if you pumped your TC for only 33 cycles, for 33+15 cycles,
  for 48+... cycles

? is the SSTC different from SGTC because of long ring up time, if so can we
  simulate this with a SGTC with a really low K coupling value (one could do
  this experiment with a SGTC by raising the secondary a bunch of inches - but
  then will gap losses start to eat up so much energy that comparisons are
  meaningless?) 
   
? 

so many questions, so little time...!!!

-Peter Lawrence.


(ps,
 A comment about the notion of inertial confinement, the air heats up as
 a consequence of the current flowing through it, this lowers its
 resistance and a higher current brighter spark forms. But from basic 
 physics the _expansion_ of the air/plasma actually _cools_ it. I'm not
 saying that inertial confinement cannot be having an effect, I just don't
 myself see how it would. The lowering of resistance of the air is not a
 function of it expanding, at least as I see it. Perhaps high pressure plasma
 does have a high resistance compared to 1-Atm, I don't really know, but I
 always presumed that plasma already had disassociated electrons and thus
 low resistance regardless of pressure...?
)



 
>
>
>Original poster: "by way of Terry Fritz <twftesla-at-qwest-dot-net>" <Kchdlh-at-aol-dot-com>
>
>Peter (& all)-
>
>Comments interspersed...
>
>[snipped]
>
>
>>
>> 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 ???
>
>
>
>
>Right--  I'll try to be clearer this time:
>
>1.  Rise to breakout voltage (Vp-p), ~230 microseconds =~ 32 cycles of
>exact-secondary-Fr excitation.  Breakout is from a polished 6" x 24"
Landergren
>toroid.
>
>2.  Toroid-voltage drop from -Vpk to ~-0.7Vpk in 1 cycle, i.e., from 1
negative
>1/2-cycle to the next.  Sometimes accompanied by a rise of the next +Vpk to
>~+1.14Vpk (And I don't seem to see that for every spark.  Also, it might
be the
>preceding  +1/2 cycle rather than the following one: can't be sure.).  Voltage
>measured via a nearby scope probe--and I suppose it may not strictly be
"toroid
>voltage" but rather, may have a "coil voltage" component.
>
>3.  Decline from Vp-p to ~0.17Vp-p over ~100 us =~ 14 cycles.
>
>4.  Continuation at ~0.17Vp-p for the ~5 milliseconds duration of the
>pulse-burst.
>
>Repeating my hypothesis:  1.  Given sufficient dV/dt, the toroid voltage will
>increase, above what it would be otherwise, during (at least, the first part
>of) the ~100 us time period, thus producing a longer spark.  And 2.  The ~100
>us time period is caused by the necessity to heat the air and push it out of
>the way (so to speak).
>
>It may be mostly the heating, because of this:  In the past, I had
contrived to
>incorporate a mode of operation in which I gated my ~5 ms pulse-burst on &
>off.  Sixty-four cycles on, 64 off, etc.  That was just for the hell of it and
>I have quit that, at least temporarily, because I had a rash of MOSFET
failures
>that I--probably mistakenly--attributed to that mode of operation.  But I
>noticed that the ~0.17Vp-p level did not change from one 64-cycle "on"
event to
>the next one.  And further, I could clearly hear the "musical note" that was
>created by that on & off characteristic during the ~5 ms follow-on time
>period.  That would imply that the air, "pushed out of the way" during each
>64-cycle "on" period, rushed back again--at least, in part--during each
>subsequent "off" period.  But it stayed hot, with the interrupted spark
>continuing to go along the same path for the full ~5 ms period (as I
observed),
>because the ~0.17Vp-p level r! emained essentially constant.
>
>More food for thought, I hope...
>
>Ken Herrick
>
>
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