Pier,
Assuming that you are able to resolve the issues of properly quenching the shorter spark gap that would be associated with the lower voltage of 7 kV vs. 10 kV, the maximum obtainable spark length of a Tesla coil is mostly based upon the square of the input power. So the 7 kV @100 mA (700 VA) transformer should be able to produce a slightly longer spark output than the 10 kV @ 50 mA one (500 VA). John Freau's formula states that - spark length, in inches = 1.7 x sq. rt. input VA. Example: for ease of quick calculation, let's assume a 900 VA input power. Applying this formula, we could expect about a 50" maximum output spark length from a properly designed and tuned coil that is fueled at this power level (1.7 x 30 = 51). This is pretty much based upon the theoretical MAXIMUM spark length that you can obtain from a given power input, though, and your coil would probably not quite attain this level of performance. Bottom line, though, is that if you wanna double your spark length, you pretty much have to quadruple your power throughput. Therefore, MORE power is BETTER. :^)
David Rieben
On Thursday, November 12, 2015 6:35 AM, Pier Aisa <pier.aisa@xxxxxxxxx> wrote:
Dear Teslalovers Hi to everybody,
I have to choose between the two Transformers 7KV-100mA or 10KV-50mA.
What will be the best choice in order to obtain longer sparks ?
Thank you in advance
Bye
Pier Aisa
PS:Some details about my present 300VA TeslaCoilin on my youtube channel
https://www.youtube.com/watch?v=JPIcQOf2P30
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