Tesla coil is a device producing a very high voltage with high frequency.
It was invented in 1897 by American physicist Nikola Tesla with Croatian origin.
(Hence its name). Description of its functioning can be read in detail on thousands
pages, so I will try to be brief: the capacitor charges to the point
when the spark gap discharge occurs. The capacitor is then connected to the PRIMARY
and the resulting damped oscillations (Figure below) of high frequency
many tens to hundreds of kHz. When the capacitor has
is low, discharge ceases to exist and everything is repeated. Repetition rate ignition spark
is tens of thousands of Hz. High frequency oscillations are induced in the secondary
and there is a very high voltage. Primary and secondary should be tuned to
same resonant frequency. This is done by changing the number of turns of the primary
or by changing the capacity of the capacitor. Primary is formed by a few turns of very thick wire or
Secondary is a cylindrical coil (solenoid) with several hundreds or thousands of threads.
Tesla coil secondary must be grounded.
Tesla coil is powered by a
soft supply of voltage of about 5 - 20kV (may be less, but the tension is able
jump only to a very small distance and thus there are problems with the construction of the spark gap).
Voltage can be either AC (50/60Hz) or DC. Very good is a
neon sign transformer, because it has the appropriate voltage and current and is soft (current limited).
You can also use another type of transformer, such as a microwave (the MOT, 2.1 kV + doubler)
but it is quite hard and you need to limit the current using a ballast.
The second option is the dc voltage from the switching power supply. Small Tesla coil can also be powered by a power supply with CRT television set
high voltage transformer,
like this 20kV Switching power supply.
My Tesla coil is also using this supply. Spark gap is about 1mm distance between the electrodes, the capacitor has a capacity of 10n, primary has 2 turns of tripple wire, and the secondary has 400 turns. Primary diameter is 11cm and secondary 6.5 cm. This is my first Tesla coil :).