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RE: Output
The Sphere Spark vs Kilovolts Fig 25 graph shown in the Tesla Coil
Construction Guide is based on Tesla coil empirical data and not on any
standard sphere gap table. As Jim points out these standard tests are made
with very special setups. The empirical data I used came from coilers who
had tested their coils under much different conditions. With this data I
obtained an equation (non linear) by mathematical regression (least-squares)
and used this equation to generate the graph.
The graph has proven to be reasonably accurate in the past. However, because
of the many variables involved and the different test conditions only a
rough approximation of spark length vs kilovolts can be realized in making a
graph of this type. I have also modified the graphs to show spark lengths vs
kilovolts for neon sign transformers (NST) which are slightly shorter spark
lengths.
My books also show many other types of graphs for other Tesla coil
parameters based on empirical data. As no one has ever made similar graphs
of some of these graphs it is not possible to make comparisons in most
cases.
The JHCTES Tesla coil computer programs use information from these graphs.
John Couture
------------------------------
-----Original Message-----
From: Tesla list [mailto:tesla-at-pupman-dot-com]
Sent: Wednesday, August 30, 2000 4:16 PM
To: tesla-at-pupman-dot-com
Subject: Re: Output
Original poster: "Jim Lux" <jimlux-at-jpl.nasa.gov>
>
>I do recall a Dicovery Channel special on lightning that had a clip
>showing Richard Hull's 11-D magnifier in operation for the man-
>made lightning segment and the narrator stated, "these 2 million
>volt sparks leap 10 ft. thru the air and are an awsome reminder of
>the raw power of electricity". I know because I have it on tape. Al-
>so, John Couture's "Tesla Coil Construction Guide" on pg. 14-9
>has a "Sphere Spark vs Kilovolts" log graph which seems to show
>that ~50" represents 1 million volts. I believe this is referring to
>electrostatic DC charges built up on very large radius spheres,
>though and was the only comparison data available to John C. -at-
>the time of printing (1994). If I'm not mistaken, John stated this
>himself? Also, this same graph shows that 100" sphere sparks
>are considerably less than 2 million volts ( KVs vs spark length
>is NOT a linear progression).
Sphere gap vs voltage is a fairly linear function as long as the gap is MUCH
smaller than the diameter of the sphere. But, as the gap starts to get to
be a signficant fraction of the sphere radius, it gets really nonlinear.
Take a look at http://home.earthlink-dot-net/~jimlux/hv/sphgap.htm for a much
fuller discussion, and a link to a standard sphere gap table.