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Re: potential gain vs. power in TC systems



Original poster: "Antonio Carlos M. de Queiroz" <acmdq@xxxxxxxxxx>

Tesla list wrote:

Original poster: Steve Conner <steve@xxxxxxxxxxxx>
Hi Paul, all,
I would go one step further and say that anyone tuning a magnifier empirically would end up avoiding that condition by a country mile. If the entire output voltage appears across the extra coil at any time, then the extra coil would flash over before the system reaches the maximum "Watts number" it would be capable of with a tuning that gave a more even voltage gradient along both coils. So I believe Richard Hull's magnifier couldn't have been "correctly" tuned and would have self-destructed spectacularly if it was.

Empirical magnifier designs always leave a significant part of the
initial energy trapped in the capacitance between the primary and
secondary coils and at the transmission line. The waveforms in the
system then resemble the ones in a conventional Tesla coil, but for
the same input and output capacitances the peak output voltage is
always smaller in the magnifier. A correctly tuned system will reach
higher voltage, because the "ideal" tuning not only removes the
wasted energy from the secondary capacitance, but produces faster
energy transfer, minimizing losses. I agree, however, that in a
magnifier built just for producing sparks, the separation between
the output terminal and the primary circuit is the main objective
of the structure.

My own current belief is that as long as you make the characteristic impedance of the resonator anywhere between 50,000 and 150,000 ohms, the coil will perform well. I used 50,000 for my last DRSSTC and it has produced sparks 4.3 times the length of its secondary. If I was constructing a magnifier I would make the secondary and tertiary of more or less the same diameter and wire gauge. To all intents and p urposes I would be taking a 2-coil system and cutting the secondary in two pieces. I would also use a DRSSTC driver to excite one of the two lower frequency modes, where the secondary and tertiary resonate together almost as if they were a single coil, and avoid the higher frequency mode that (AFAICS) generates a lot of voltage on the transmission line without contributing much to the output.

I have investigated "TRSSTC" systems, but didn't like the results.
It seems impossible to drive the system in a way that concentrates all
the energy in the output capacitance after a certain number of cycles,
driving the system with zero-current switching. Without zero-current
switching, it is possible to achieve this with switching between the
second and third resonance (better), or above the third resonance, only.
Of course it is possible to drive at any of the three resonances,
but this spreads energy everywhere in the system with just a fraction
going to the terminal, and easily results in huge primary currents.
The use of primary current feedback to ensure zero-current switching may
be problematic due to the three resonances, that may cause some
current reversions to be missed, because they don't cross the zero
current limit.

I would also minimize the transmission line capacitance to keep this unwanted mode as far in frequency from the wanted one as possible. The idea would be to distribute the voltage evenly across the whole coil system and so get the highest output voltage before flashover.

Or, to have a system that operates as a double resonance Tesla coil.
Possible, with low primary-secondary coupling (to increase distance
and reduce capacitance) and short "transmission line". But this
results in large number of cycles for energy transfer.

Antonio Carlos M. de Queiroz