I am wanting to build some type of high voltage air core resonant transformer (tesla coil) and have seen some designs with a stable spark gap and a rotary spark gap with a motor. I was planning on using the stable spark gap idea, but I see a lot made with the rotary.
How does the rotary spark gap work?
And what advantage does it give over the stable type consisting of 2 metal balls for the spark to go across?
And for a QUAD-MOT tesla coil, would a rotary spark gap be the best option?
Rotary spark gaps are self-quenching, since the gap is only small for a very short period of time.
Also, a rotary gap is significantly self-cooling, since one half of the gap is rotating at a very high rate.
Last, and probably most significantly, a rotary spark gap basically lets you control the arc rate, since you generally only get one spark per gap closure. Therefore, you can control the repetition rate by varying the rotor speed.
With the multi-kilowatt, pole pig driven Tesla coils, the design features required for a stationary gap to reliably switch and quench make it impractical and the the rotary gap becomes the most practical choice. For smaller NST driven systems, a stationary gap can still be constructed within practical limits that will allow it to function properly although some coil builders still opt for a synchronous rotary gap for better phase and timing control than a stationary gap can provide.
