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[TCML] capacitance and efficiency questions

I have been reading over Ritchie's site, particularly the section on rotary gap analysis for internally shunted supplies. In the section on choice of primary tank capacitance, the equation is given, Cp = 150xCmatched/BPS. What does the 150 figure represent?

I ran the numbers for my 9000V 90mA NST with a 120BPS sync rotary through this equation. The capacitance came to 33.125nf. This is much different than the figure acquired from JavaTC and from the 2.5xCres suggestion. I assume the larger capacitance suggestion is to load down the transformer and to minimize voltage stress on the cap and transformer. Is there a point where increasing the cap size is counterproductive to arc production?

I have been running my 2" diameter twin coil at 60nf and I am only getting approximately 20" arcs from either side. JavaTC calculates arc length to be a little more than 40". I think someone mentioned that this figure should be 1.4x greater with the bipolar setup, so 56" or 28" per side is what I was expecting. Does this sound right? If so, where is the remainder of the energy being spent? It seems the rotary gap should be more efficient than that. Is 1/8" copper tube not adequate for the primary wiring in this system? Would lowering the Cp value help reduce the inefficiencies?  Is the relatively low 9000V input adding that much to the gap's inefficiencies?

Thanks for your help, guys. I know there are a lot of questions in this message, but I really am starting to understand this stuff better.


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