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Re: [TCML] Matt tesla

On 5/17/13 6:43 AM, David Rieben wrote:
Overcoupling means that the inductive coupling between your primary and secondary coils is too tight. Think of a typical mains iron core transformer where the tightest inductive coupling between the adjacent coils is desired to have the most efficient transfer of electrical energy from the input to the output with a minimum in losses. However, this is not the case with the air cored resonantor design of a classic Tesla coil. The inductive coupling is already signifacantly reduced by the absence of a solid iron core, being replaced with only open air. If the secondary is dropped too low into the primary coil, then the coupling will still be greater than optimal for your coil and this will often manifest itself with those dreaded racing sparks along the surface of the secondary coil. A simple and pretty straight forward way to address this issue is to raise the secondary coil higher in respect to the plane of the primary coil. Try raising it at like
  half-inch increments until the racing sparks cease with normal operation. Lower it again until the racing sparks start again. Optimal coupling is the point at where the secondary is at its lowest elevation with respect to the primary coil plane and still runs racing spark free during operation. Most coilers determine optimal coupling emperically, but a good place to "start" would be to have the lowest winding of the secondary dead level with the plane of the primary coil's plane (assuming a flat Archemdian spiral shaped primary coil).


programs like JavaTC calculate a lot of the things you're interested in (coupling, resonant frequencies) and is probably good to a few percent.

David's description of how to adjust coupling is right on, but I'd spend a bit of time with JavaTC to work through your coils. You'll need to do it anyway for your SSTC.

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