twin coil

Because of the limited space of my new appartment I decided to build a small bipolar tesla coil, also called "tesla twin".

In this special configuration one uses two identical secondaries to archieve a standing wave of λ/2. The effect is a minimized base current and a better control of the streamers.

Schaltung einer Tesla Twin

Because of limited space the twin is designed for a maximum power consumption of 600W which leads to voltages near 500kV.

current status:

Power Supply

At the moment the coil is powered by two OBITs (each 10kV/20mA). Tey are filtered with a symmetric low pass consisting of a 2nF/16kV-MMC string and a 230Ohm/11W resistor.

Gap

Below 1kW a double static series gap provides sufficient quenching of the primary resonant circuit.

The hot ionized air ca be succed out of the gap by a vacuum cleaner.

Cap

This is the MMC. It has a capacity of 10.3nF and is rated at 16kVdc. In the past I had some trouble with the insulation between the strings of caps but now it's working fine.

coils

Though the secondaries look quite ugly on the picture, they are machine-wound without the slightest mistake. After that I spent three days with painting the coil with epoxy resin. The outer diameter is 4cm and the winding length is 23cm. I used 0.25mmCuL.

At the moment the topload of one coil is just a 6cm steel ball. But their capacity is far to small for an efficient transfer of energy. So two toroids of 15cm diameter will be built in future...

Because of the high resonant frequency I built two helical primaries two archieve the maximum coupling between the two resonant circuits. With 8cm diameter Ihad problems with rising arcs and corona discharges. With 3.5 windings in total on a 10cm PP form, the output at 400W are 25cm steamers.

With the new toroids (and real primaries...), I hope to have streamers of 30-35cm.

23cm Spark