VOLTAGE DOUBLER FOR TESLA COIL USE
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I found two more MOTs (some little 2 kV output units). Because I have some big silicon diodes, I decided to build a 12 kV source for my tesla coils. I know that the silicon are sensible and the 4 or 6 MOT packs are recomended, but I dont want to mess with oil insulation and I hope that my big diodes will keep well.
ELECTRIC SCHEMA
INFERIOR STAGE (MOTS AND INDUCTIVE BALLAST)
The MOTs have the secondaries connected in series and the primary in antiparallel. The inductive ballast is made with three ballast coils (used for high presure mercury lamps (250 VA each),in parallel, which can be connected separately to the circuit. I tested this stage with 20.1 vac from my variac and the output was 337 vac (so the transformation raport Uout/Uin = 16.76. So, for a 220 vac input I will have a 3687.2 vac output. Using the same input (20.1 vac), I rectifyed the output (because my meter can measure only DC currents) and get a current value = 33.3 mA at 337 vac (475.17 vdc after rectifycation). Considering that u = i * Z (where Z = impedance of the setup output), I got for Z a value around 10 kohms. For the maximum output voltage, this gave an approximative current capability of 368 mA. Anyway i have enough current to pass through the level shifter.
LITTLE MOVIE WITH THE OUTPUT ARCS FROM THE BALLASTED MOTs
SUPERIOR STAGE (CAP AND DIODES)
  - two big UGE2206 diodes in serie, protected with 1 nF @ 12 kV MMC in parallel
   - 1 uF @ 6.3 kV oil-paper cap (used initially for phase correction in a power plant).

The maximum output for 220 vac input would be around 10.3 kV, and up to 12 kV for 250 vac input from variac.
LITTLE MOVIE WITH THE ARCS FROM THE VOLTAGE DOUBLER
The output current can be increased by completely removing the ballasts from circuit.
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