Re: [TCML] Solid state efficiency, was: mini Tesla coil specs

[Steve Ward <steve.ward@xxxxxxxxx>]

Hi Ken,

It sounds like our intuitions about spark growth agree.  I convinced myself
that the faster energy rise was better because you spent less time wasting
energy making little corona on the rising edge of the voltage rise.  What
led me to believe this was that the secondary voltage in my comparison test
was essentially the same (simulated, not measured), and the spark length was
the same, but it took less time (and thus energy) to make the spark.  I
doubt that our resonator drivers will ever be "too fast" for spark
propagation.  One thing to watch for would be exciting those nasty
transmission line modes on the secondary, which seem to cause the racing
sparks, etc...  Interestingly, i believe it is because the SS excitation of
the system is "slow", that you can build small DRSSTCs that really put out
huge sparks with out much fuss.  Some small coils have produced spark
lengths exceeding 5X the secondary winding length, my best has been about 4X
getting 45" sparks from an 11" tall secondary winding.  This is something
ive never seen with a SGTC, usually racing sparks would just destroy the
secondary if you attempted to cram that much power into one.

Steve

On Thu, Nov 12, 2009 at 10:57 AM, Ken or Doris Herrick <kchdlh@xxxxxxxxx>wrote:

> Steve Ward writes, "[I] think energy transfer time to the spark is very
> important" for maximizing spark length.  I agree and repeat here an opinion
> I posted a few years ago:  As compared to a solid-state coil, the relatively
> much-higher rate-of-rise of the initial half or whole cycle from the abrupt
> shot of energy thru a spark-gap will allow charge to be crammed onto the top
> electrode before the spark has a chance to proceed very far.  A research
> paper I have a copy of has found spark propagation in air, measured over 1
> inch of distance, to require about 50 ns of time.  That extrapolates to
> about 20 inches of travel per microsecond.  So with a high rate of
> voltage-rise, more charge can be applied to the electrode than can bleed off
> through the spark during its first several inches of travel.
> Ken Herrick
>
> [snipped]
>
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