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A new composition of the primary coil for a Double Resonance Solid State TeslaCoil (DRSSTC). It is a combination of wire and capacitors. By making the coil like this you get rid of all the parasitic inductions of the capacitor bank, it reduces wire length and saves a lot of space. Calculating the resonance frequency also becomes much easier. I hereby dub this coil configuration: The Eindhoven Primary. |
A double resonance solid state teslacoil is a well known principle, the primary circuit always consist of a combination with a coil and a capacitor bank. The improvement that I made is that the capacitor bank is integrated into the coil itself.
Another description for this coil configuration is the ohmic coil, this term in itself shouldn't exist, but it's a coil and at the resonance frequency it is also an ohmic load. It might seem a little premature to name it right away, but as far as I know this hasn't been done before, I still have yet to encounter anything like it.
I came up with the idea when I was constructing a test setup for my IGBT half bridge, the connection wires were so long that my calculations for its resonance frequency could never be accurate. In stead of calculating the extra wires etc. I came up wit this idea: make the coil itself out of capacitors, and use the parasitic inductance! This has many advantages.
A few images of the coil in setup:
A video of the first tests, it seems to work pretty well:
The arcs on the video are made with the half bridge setup, the pictures above are of my new full bridge setup (yet to be tested).
An example of how to use it:
I need a 3 Turn coil (110mm) with resonant freq fo=235,6kHz, calculations tell me I need a 240nf capacitor bank. Usually a capacitor bank consist of a series/parallel circuit combination and requires extra wire length and space. This will change the inductance of the circuit and thus change its resonance frequency. By making the capacitors part of the coil itself, this whole problem doesn't even apply. The only parasitic inductance left is the connection between the coil and the IGBT bridge.
To get 240nf I take 9 MKP capacitors of 2.2uF in series, this comes to a total of 244.4 nF which is close enough for my tests.
Naturally, any combination can be made with coils and capacitors, 2 or 3 parallel capacitor strings is also possible (to reduce internal resistance).
Some frames cut out of the video, input voltage of the half bridge is 166V (max is 270):
