Reply To: Nuplex.

[Aeronaut]

JimmyT wrote: Before the age of solid state ignition systems, those of us who are old enough, remember ignition coils. These worked via a pinch, although I never heard it called that. Input voltage 12 volts. Output voltage ~10,000 volts. I know that it’s dependent on the relative number of turns in the primary and secondary. But, I don’t think you can use any 4x or 5x the input voltage rule of thumb.

The plasma focus sort-of works as a step-up transformer in that sense. Concentrating magnetic forces.

I know that two of the factors that go into the induced voltage spike are: magnetic field strength and speed of field decay.
Beyond that: proximity of the field, geometry of the objects involved, and of course materials they are made of.

Anything more elaborate than that gets a little above my pay grade.

Oh, yeah, I remember coils, distributors, condensers, and breakers. You’re right about the speed of decay- the breaker simply cut the current, and the collapsing field created counter EMF. The high voltage had no current to speak of. All it had to do was spark the air/gas mixture.

I went thru the video this morning, since I’m almost positive that’s where Eric mentioned the 5 to 6 fold voltage spike to the caps. Missed what I was looking for, but am now a LOT clearer on the current flows, mag fields, and instabilities.

Going back to my tank circuit diagram, inserting a 2 bank cap controller for ignition and profit caps, and the diamond switch leaves just the FF reactor as the “coil” in the circuit. It leaves the rails when you try to add a coil or cap to explain how this “supercoil” puts out 1.8 x input. Since this isn’t a paper FF, less than 100% of the energy that’s made it this far makes it to the next instability/transfer. This means there is a residual magnetic field to discharge with a reverse current, or account for as an electrostatic charge. Works for me on runout, so far. I still need to sketch/note the whole process to be sure.