From Mon Jul 28 13:48:01 1997 Date: Mon, 28 Jul 1997 13:24:58 -0400 From: Chip Atkinson To: choke_faq

How does a choke work? how does it protect the transformer? how about using a sparkgap, would that take place of a choke or should they both be used?

Chokes act like shock absorbers and protect the HV windings of the transformer from the RF generated in the tesla primary tank circuit. This RF can easilly cook the insulation of the transformer which results in breakdown.

A choke works by having a high resistance/impedance to rapidly changing voltage but has a low resistance to DC. This allows the relativly slowly changing AC from your transformer to pass through, but acts as a block to high frequency AC. (all due to self induced voltage)

I wind my chokes on plasic tube single layer (like small TC secondary) and these perform very well. I must admit I have tried and failed using toroids chokes, I could not stop the arcing between turns (toroid chokes use fewer turns thus more volts per turn).

Yes you should use a spark gap on the transformer outputs to protect against any RF that gets through. You set the gap to be just large enough to prevent arcing when full output voltage is present but no TC in operation.