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Re: terry filter theory
Original poster: "resonance" <resonance@xxxxxxxxxxxx>
The caps serve as a rapid ground source for the high freq transient
currents due to their very low high freq reactance. The resistors
destroy the circuit Q factor and reduce the transients. The
varisters serve as a direct overpotential safety value to allow
excessively high resonant potentials a direct path to ground. The
safety gap serves as a final safety valve but these are not usually
required as the varisters serve the same purpose ---
provide a quick, safe path to ground.
I usually split the resistors into two 500 Ohm, 50 Watt resistors,
one on each side of the series caps to ground. From the tank circuit
the oscillation first hits a resistor, then the series caps to ground
(low reactance), then another 500 Ohm, 50 Watt resistor, then the
varisters to ground, and finally a safety gap to ground. This will
stop almost anything that could damage your nst. Be sure to use one
of these systems off each xmfr bushing. The power reduction is so
slight it does not adversly effect the TC output spark length.
Terry's original circuit used a 100 Watt, 1,000 Ohm resistor.
Some transformers can develop a ferro-resonance with a tank capacitor
and this type of filter prevents this ferro-resonance while
simultaneously destroying any reflected oscillatory currents from the
tank circuit, e.g., the pri cap and pri inductor.
Dr. Resonance
parts for this filter I would like to grasp the theory behind the
design of your filter. Do the capacitors store excess current that
would otherwise damage the nst? Are the movs' there to protect the
nst from surges? Will the 1k ohm resistors reduce the input voltage?
Does it take an arc at the safety gap to operate the terry filter in
the first place? Is it overkill to add more components? Will extra
components reduce the spark length?