Re: SSTC does 10 foot sparks

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

Original poster: Sean Taylor <sstaylor-at-uiuc.edu> 

I've gotta reply to this . . .

On Wed, 23 Jun 2004 11:21:47 -0600, Tesla list <tesla-at-pupman-dot-com> wrote:
>if you are rating
>your TC in power units (watts) it does not make engineering sense to say 
>the efficiency is equal to anything. Efficiency refers to energy units not to
>power units.  However, if you are rating your TC in power units it does 
>make sense to say it has a power gain of a certain amount. You can then 
>use this number to compare with other TC's.

Giving an efficiency in power makes perfect sense.  Most devices are rated 
in this way.  A motor has a certain electrical power in, and a certain 
mechanical power output.  The efficiency is defined as Mechanical power out 
/ electrical power in.  A heater, lightbulb, and many other devices can be 
given an efficiency rating the same way!  What doesn't make sense is to say 
we have a motor which has a certain power output, and then try to calculate 
the energy output by lifting a mass, or some other means and at the same 
time monitoring the input power and integrating - much more of a pain, and 
will arrive at (approximately, due to measurement error) the same result.

>The above, of course, does not solve the problem of how to properly test and
>rate a Tesla coil when using spark length as the TC output. In the past only
>a few coilers could rate and test their coils properly. This resulted in
>shorter sparks. However, everyone was more impressed by that random extra
>long spark so any tests that gave shorter sparks were not popular.
>The problem was the true input energy that actually created that special
>extra long spark could not be determined so true TC comparisons could not be
>made. Only continuous sparking with fixed lengths made sense. But it does
>not appear that we will ever get away from that mysterious random extra long
>spark test with an unknown input ( except maybe for one shot tests).
>
>John Couture


What is rating a coil "properly"?  The only way to have a relatively 
constant bang energy is to use a triggered type of gap (rotary, etc.) and 
then how do you calculate the energy in and out?  What is rated "properly" 
such that the coil ran with a "constant" length spark?  As line voltage 
fluctuates, and environmental conditions change, so will the spark length 
on the output, and there is no "rating" that will change that.  I am 
interested to know what you are suggesting changing on a coil that would 
"rate it properly".  Do you have any documented proof that this was done, 
or what was changed?

In your other post regarding the energy in a single spark, I'm sorry to 
say, but that is complete bull.  There are several problems with the logic 
- 1) How was the breakrate known to be 120?  2) The system definitely isn't 
lossless!!!  3) Wattmeters don't give you Watts/sec, just watts, that's 
it!  4) There is streamer growth over successive bangs, so unless you know 
the voltage you charged the tank gap too, are running ina single shot type 
of set up, and know the exact losses of the system, there is no way to know 
the energy in the 8.25" arc!!  As you state, there IS a lot more, but the 
problem is this isn't even a start towards really figuring anything 
out.  The energy in an arc is not solely determined by its length either, 
as you can have different amounts of current flowing through the arc, and 
thus very different amounts of energy.

I'm not trying to insult you, John, but there are several very fundamental 
mistakes in the calculations you have done (specifically in calculating 
voltage, current, etc. in the secondary), and you should really try to read 
up on how the quantities interact/relate.  One definite flaw was "Secondary 
current = joules/voltage".  I'm not going to use more time/bandwidth of the 
list, and I'm sure several people are getting tired of this discussion, so 
I'll leave this discussion with this:  True power ratings are a very good 
estimator of how much power is getting to the actual coil for the same 
type, ie SGTC, SSTC, etc.  To compare Steve's ISSTC to a SGTC with the same 
power input that gets half of the spark length tells me that either a) The 
losses in the ISSTC are much lower, or b) the output waveform of ISSTC is 
such that it is able to facilitate streamer growth to a much greater extent 
than the SGTC, and for the purposes of the hobby, I would consider either 
scenario to be much more efficient than the SGTC!

Sean Taylor
Urbana, IL