Re: Power versus Spark Length

From: 	John H. Couture[SMTP:couturejh-at-worldnet.att-dot-net]
Sent: 	Thursday, July 24, 1997 2:08 PM
To: 	Tesla List
Subject: 	Re: Power versus Spark Length

At 05:44 PM 7/23/97 +0000, you wrote:
>From: 	FutureT-at-aol-dot-com[SMTP:FutureT-at-aol-dot-com]
>Sent: 	Wednesday, July 23, 1997 3:41 AM
>To: 	tesla-at-pupman-dot-com
>Subject: 	Re: Power versus Spark Length

   John F, All -

   Your excellent description of Tesla coil operation points out the
problems of trying to give a rating to a Tesla coil from an engineering
standpoint. It is obvious from your report that sparks from the TC secondary
must be evaluated as free air length or continuous length. 

  First of all it should be understood that a spark length rating is a
different test than an efficiency rating. This is because spark length
cannot be reasonably converted into the output energy or watt seconds
necessary for efficiency determination. This means that two ratings are

  To find the efficiency of a Tesla coil the "energy in" and "energy out"
must be found. I will use watt seconds because this also is energy. The
"watt seconds in" can be found by electronic meters and the "watt second
out" can be found by using an incandescent lamp and light meter. Note that
the lamp and meter could also be used for the input. The lamp and light
meter give reasonable accuracy from DC to RF frequencies.

  There are several possible methods of rating a Tesla coil using the
secondary terminal output spark. The input could be the same as for the
efficiency rating. The output rating could be either the maximum free air
spark length or the continuous spark length. This could also be used to give
the TC a rating in watts per foot of spark. The input watt seconds could
also be devided by the breaks per second to give a watt second per spark rating.

  The importance of accurate ratings of TC's is to ensure that the TC
improvement is actually a gain in TC output over input to compare various
coils including magnifiers. This would also show a true increase in
efficiency or input to spark length. Without these standards the estimating
of what a builder thinks is an improvement in his coil cannot be verified
because different tests give different results..

  Regarding your 15 KV, 60 ma neon coil, how long did you run it and was
there overheating?  I made a JHCTES printout of your coil with a 2600 watt
input and the program showed  a 55 inch continuous spark. This is in close
agreement with your 65 inch free air spark. 

  As for computer simulation the JHCTES computer program is flexible enough
to be modified to agree with the empirical data as it comes in from coilers
using the above standards. The program would then become public property.
The program now includes most of the necessary TC parameters including
toroid size.

  John Couture  

==========================================  big snip

>If we can describe a mathematical model of spark formation, and relate
>it to power input, break-rate, toroid size, etc., then we will be approaching
>a complete analysis of TC behavior.  This is the TRUE scientific approach.
>Still, I suspect there must be an easier way that we're missing.  It might
>be possible to do some kind of computer simulation also?
>Comments welcomed,
>John Freau