RE: TC Spark Energy

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

Original poster: "Lau, Gary" <gary.lau-at-hp-dot-com> 

Here we go again...

 >Original poster: "John H. Couture" <couturejh-at-mgte-dot-com>
 >
 >Dr. Resonance -
 >
 >As you know the topic of TC spark energy has been discussed before on
this
 >List. Little progress was made because of the confusion over the
difference
 >between power and energy. The TC spark energy test is very simple, only
an
 >input wattmeter and tape measure are required. The operation is
continuous
 >and the same as typical TC operation. Just add a wattmeter at the input
and
 >measure the spark length.
 >
 >Because the operation is continuous the wattmeter (power) indicates
watts
 >per second (energy). All you need is the number of sparks per second to
find
 >the number of watts seconds or energy per spark. The number of equal
sparks
 >per second is not an easy number to come by. However, it can be
determined
 >provided the coiler adjusts the TC spark output to give 120 equal spark
 >lengths per second (for 60 Hz). The spark should be horizontal and to a
 >suitable ground.


A Watt meter reads Watts, which is the same as Joules per second.  If it
could read watts per second (or Joules per second per second, which is a
meaningless concept), it would say so on the meter face.  Energy is
Watt-seconds, or just Joules.

I assume you're talking about a static gap?  I agree that the Variac
setting will determine the average bang rate, but how do you determine
when you have 120 BPS?  The interval between bangs may on average work
out to 120BPS, but the actual interval will rarely if ever be 1/120th
second, so you won't be able to hear that frequency, even if you have a
very golden ear.


 >In my test I adjusted the variac to get a continuous wattmeter reading
of
 >120 watts or watt seconds. The sparks were adjusted until the spark was
 >continuous and of equal length at 120 sparks per second. Energy = watt
 >seconds = joules.
 >
 >    Joules per spark = 120 joules/120 sparks = 1 joule per spark
 >
 >The spark length was measured and found to be 8.5 inches. This then
gave me
 >a Tesla coil rating for my Tesla coil of 8.5 inches per joule of
energy.

It is an invalid assumption to think that if you were to double your
bang size to 2 joules, that you would get a 17 inch spark.  John Freau's
formula clearly shows that the expected spark length is proportional to
the square root of the input power - not a linear relationship.

 >It is obvious from the above that if the wattmeter had indicated 175
watts
 >with a 10 inch continuous spark and at 90 sparks per second the TC
would be
 >rated
 >
 >      175/90 = 1.94 joules per spark
 >
 >      10 inch/1.94 = 5.16 inches per joule.
 >
 >This TC would have been less efficient because it is producing less
spark
 >length per joule of input energy. All very simple. So why is it that
coilers
 >have seldom rated their TCs this way?
 >
 >The answer is also very simple. This rating method gives low ratings
for
 >large TCs,  only a couple inches per input joule. In other words large
TCs
 >appear to be very inefficient. This is a problem. Any comments?
 >
 >John Couture

That larger coils generate less streamer per Watt has never been in
dispute or seen as a problem.  Death and taxes are problems, but none of
this is going to change.

Gary Lau
MA, USA


-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Tuesday, March 09, 2004 8:58 PM
To: tesla-at-pupman-dot-com
Subject: Re: TC Spark Energy


Original poster: "Dr. Resonance" <resonance-at-jvlnet-dot-com>



Perhaps we can all supply John with some data from each of our coils and
he
could do a tabulation and find an average or statistical value.

Dr. Resonance

   >
   >
   > For over twenty years the coilers on the List have used output spark
length
   > to compare their coils. The input is usually shown as a total input
watts.
   > The problem is that this does not give the coiler any indication of
the
   > actual energy per spark to give a true comparison of Tesla coils. To
my
   > knowledge no coiler (see below) has ever determined the TC input
energy
   > (joules) per spark for these comparisons. Do any coilers know how
this
could
   > be best accomplished?
   >
   > The overall engineering efficiency is represented by
   >
   >     Percent efficiency = 100 x Spark Length/Input Energy (joules)
   >
   > The spark length could be in centimeters, inches, etc, and the input
energy
   > in joules or watt-seconds. The energy in the spark output is a
complex
   > parameter so would have to be a compromise. In past postings the
approximate
   > losses in the TC system have been determined and the characteristics
of
the
   > spark have been estimated. The preliminary tests I have made gave
8.5
   > inches (21.59 cm) per joule of input energy. Has any other coiler
made
these
   > tests?
   >
   > John Couture
   >
   > --------------------------------
   >
   >
   >