Dual Coils
We created these dual coils for use in school demonstrations. The coils are tuned 180 degrees out of phase. The leads from the base of each secondary are tied together to avoid the grounding normally required of a Tesla Coil. These coils resonate at kHz.
Construction
The secondaries are 3 in dia X 10-1/2 in lg consisting of 1000 turns of #30 ga wire. The primaries are 5" dia, 7 turns of 1/4 in copper tubing. The toroid is 8 in OD X 2-1/2 in dia. 3 SISG4 boards are used for the Semiconductor based spark gap. They trigger at 10,800 vots. The unit is powered by 2 Microwave Oven Transformers and a voltage doubler. The tank Capacitor is 37.5 nF.
Close up of Coil
Internal Components
On the left is the tank cap enclosed in PVC pipe. It is made up of (2) strings of (8) 150 nF 2000 volt CDE caps in series. On the right, the black heat sinks for the SISG IGBT's can be seen. In the lower middle a fan to cool the heat sinks is visible.
Another View
The MOT's can be seen in this picture immediately below the coil. The two MOT's are stacked in this design and separated by an acrylic sheet. The MOT secondaries have been isolate from the cores.
Streamer Pictures
The 100 ohm 100 watt resistors can be seen on the left hand side. The diodes are not visible, but just to the right of the resistors. The following streamer pictures are taken at progressively faster shutter speeds.
