Hi Gary,Adding a spark gap would be superfluous and counterproductive to your objective of creating "undamped or partially damped oscillations in the helical resonator."
An SISG can be adjusted so that it transfers the initial bang energy within the primary to the secondary and then traps it there, permitting the resonator to ring down slowly (assuming no breakout). Only a series of damped waves is achievable with an SISG, since the tank cap must still be recharged between bangs.
Referring to the the schematic of Terry's original 900 volt SISG stage (at http://www.teslaboys.com/SISG/SISGSchematic.pdf) it can be seen that reducing the value of the discharge resistor (R4) allows "tuning" the ON time of the IGBT so that it is slightly longer than the one-way energy transfer time between primary and secondary (the "first notch"). At this point, all of the available system energy resides within the secondary resonator and toroid. Switching off at this point reflects an ideal "quench". Note that, with moderate coupling and no spark loading to help remove secondary energy, "first notch" quenching is unachievable with ANY kind of spark gap. The problem is that the previously conducting gap cannot recover sufficient dielectric strength quickly enough to prevent reignition and subsequent energy flow from secondary to primary.
In Tesla's day, spark gaps were the ONLY way to "disruptively" (suddenly) switch charged high voltage capacitors into inductive loads and then open the discharge loop to permit recharging for the next "bang". Today, there are combinations of solid state devices that can, for TC system purposes, mimic or outperform spark gaps. Solid state switches offer lower On-state losses and improved quenching. In particular, solid state Tesla coil designs that store initial bang energy within a tank cap and suddenly switch it into the primary inductor (i.e., OLTC's or SISG's) provide superior output, and quenching, than spark gap switched systems operating at similar input power. Adding a spark gap (of ANY type) to a ideally timed SISG circuit will simply add losses without improving quenching.
Whether the above solid state switched coils are "disruptive" or not is more of a semantics issue than a real one. Historically, disruptive systems were spark gap-switched systems. Indeed, "disruptive" may be an antiquated term that we may want to consider leaving to previous centuries...
Bert -- *************************************************** We specialize in UNIQUE items! Coins shrunk by huge magnetic fields, Lichtenberg Figures (our "Captured Lightning") and out of print technical Books. Visit Stoneridge Engineering at http://www.teslamania.com *************************************************** Gary Peterson wrote:
Re: http://www.tfcbooks.com/images/lectures/1892-02-03/017.gifThere is no "Tesla coil", there is no "high-voltage terminal."The Tesla coil is labeled "TRANSFORMER" and the high-voltage terminal is labeled "PLATE SUSPENDED." Getting back to my question, do you have an opinion on the placement of an adjustable hyperbaric spark gap, sulfur hexafluoride filled spark gap, or magnetically quenched spark gap in between upper end of R1 and the collector of the first IGBT to provide SISG quenching? _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla
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