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RE: TC Spark Energy



Original poster: "Malcolm Watts" <m.j.watts-at-massey.ac.nz> 

On 10 Mar 2004, at 17:00, Tesla list wrote:

 > 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.
 >
 > 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 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?

Because the length of spark per JOule is highly dependent on the coil
design. Pumping 1J into a high-C secondary is not going to give the
same sparklength as pumping 1J into a low-C one is it? Just for
starters, the output voltages will be quite different.

 > 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?

I fail to see what the voltage developed by 1J into a small
capacitance vs the voltage developed by putting 1J into a large
capacitance has to do with efficiency.

?
Malcolm