Original poster: "david baehr" <dfb25@xxxxxxxxxxx> In your opinion, whats highst practical KW input for a 4" dia. coil ? I mean, there comes a point in the quest for longer sparks , that its just more practical too increase dia. for more output. I run 3kw into such a coil, and, feel Im reaching the limit. I may have reached close to 5 feet , with a huge toroid. ( static gap only ) any other 4" coilers out there want to coment ?
I think you're around the limit now. Not an absolute limit of course, but a practical limit. By making the coil tall, and using large toroids, long sparks can be obtained up to a point, but losses may become somewhat high too at some point. I used to get up to 65" sparks at 1500 watts or so with my old 4" research coil but the coil was on the verge of breakdown (and often did break down). The secondary winding was 23" long.John