RE: TC Spark Energy

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

Original poster: "David Thomson" <dave-at-volantis-dot-org> 

Hi John,

 > I like to distinguish between sparks to ground and streamers that
terminate
 > in the air. The length of streamers in air are random and can not be
 > controlled. The length of sparks to ground can be controlled and the
number
 > per second assumed to be 120 or 100, etc. I agree this is debatable.

OK, I can agree with the terminology.  And I also agree that streamer length
is too variable to be of much use without some kind of sophisticated
measurement system.

 > Energy per spark length is useful because it can be an indication for
rating
 > a TC.
 > Input power per streamer length has problems. Power is an instantaneous
 > parameter and streamer length is random. Shock frequency is a term I have
 > never heard before so cannot comment on it.
 >
 > Can you show the calculations for comparing a 1000 watt TC with a 500 watt
 > TC using your method?

Basically I would do it the same way you did.  Multiply the input power by
the spark length.

But I think we can go further with the equation.  It is quite easy to
calculate or measure the resonant frequency of the secondary coil.  Also,
the force exerted by the spark on the atmosphere must be constant (with
slight variation for various atmospheric conditions) because both the
electricity and the atmosphere behave as incompressible fluids.  If we can
determine this force constant, we can determine the amount of power being
output in the secondary.

force_constant * secondary_frequency * spark length = secondary_power_output

Comparing the secondary power output to the primary power input could tell
us just how efficient the coil really is.  As such, a whole new way of
looking at coiling would surface.  Instead of seeking long sparks by
building the biggest coil with the mostest bucks, we would have a benchmark
for building the a coil with the most bang for the buck.

In the equation I give above, the force against the atmosphere is a
constant, the resonant frequency of a given coil is fixed, so the only
variable is the spark length.  The spark length would be directly
proportional to the secondary power output.

Essentially your good idea for calculating energy directly by using the
input power and spark length is similar to my idea of back calculating to
get a power ratio.  The key difference we need to work out is how we
determine frequency.

You are saying that the frequency will always be 120 bps (100 bps)
regardless of the frequency of the secondary and that the spark is an
accumulation of stored energy.  So if we had a 120kHz secondary coil
breaking at 120 bps, you're saying the total energy is stored at the rate of
1000 secondary oscillations per spark.  If that is the case, then the energy
value you come up with needs to be divided by the ratio of the secondary
frequency to the break rate.

On the other hand, I was saying that the energy per spark was based on the
secondary oscillations.  But obviously I'm wrong on that since, as you point
out, the energy is stored in the capacitor and only breaks 120 times per
second (or whatever actual break rate the system produces).  So in my
equation the secondary frequency needs to be divided by the break rate.

I'm glad I did this exercise.  It made me realize that any given spark in a
Tesla coil has a frequency of 1/120 of the secondary resonance.  I might be
able to exploit that in some way.

Dave