Hi Gary,
The "out of tuning" I'm referring to is the classic Tesla quarter wave
hypothesis. Tesla's serious coil work was meant to avoid sparks at all cost
so as to maximize the stored energy in the resonator, such that the
electric field at the top load was maximized, and that the topload could
handle the high potential without leaking it. He only posed for those long
exposure photos at Colorado Springs for publicity purposes. Unfortunately,
many people end up thinking that Tesla's main contribution to science is
making long sparks. Just look at all the "high tech" movies that
characterize ufos, time travel technology, and even magic as Tesla coil
streamers. It's all eye candy, with no science, and no practical use other
than to "earn" Tesla some funding and make money for movie producers.
Tesla's serious coil work was primarily purposed to harness resonance in
the coil, and tune it to resonance in the environment. That is how he lit
the lamps at great distances from the lab. The transformer and capacitors
were carefully chosen to match the resonator, and the resonator was
designed to match the Earth's Schumann resonance as we all know well.
Not having done any calculations on the eBay coil, my experience in working
with the geometries of coils reminds me of my own failures. I, too, burned
out a couple transformers on tall solenoid coils. Tesla ultimately isolated
the power circuit to the primary by making the spark gap totally
independent of the transformer frequency, such that he could generate
pulses at whatever rate he chose. I don't know how he did it, but I recall
him discussing this either in his Inventions book, or the Colorado Springs
Notes. The key to his eventual success was the shortest pulse at highest
energy and the right rate.
He used this on his quarter wave coil at Wardenclyffe. The Wardenclyffe
resonator was a tertiary coil where the secondary had a large flat spiral
coil with a tall skinny solenoid connected to it. The tall skinny solenoid
coil also had a long, narrow conductive mast added to it, and that mast was
calculated as part of the inductance for the solenoid coil. The wound wire
in the flat spiral portion of the secondary was one fourth the total
inductance of the entire secondary system from ground to topload. The flat
spiral of the secondary needs to be as close to the ground plane as
possible. I believe Tesla used variable inductors in the flat spiral
section of the secondary coil for tuning purposes.
The primary, of course, was tuned to the total resonance of the secondary
from ground to topload. I mention all this because the geometry of the flat
spiral and tall solenoid secondary coil is important to maximize the stored
energy in the system by minimizing the impedance. I can describe the
reason for this, but it often gets my posts censored on this list.
The bottom line is that nothing but a super sized transformer will be able
to pump electrons up and down that solenoid (for long) with that small of a
primary. Without a perfect spark gap to block the AC of the transformer
from coupling to the AC of the primary, the tall solenoid coil will fill
the transformer with magnetic interference. It will burn the transformer
out with hysteresis and high current.
Here is the experiment that culminated from my research into the
combination flat spiral and tall solenoid combination secondary.
https://tesla-coil-builder.com/spiral-solenoid-combination-coil
David Thomson
On Fri, Feb 1, 2019 at 5:36 PM Gary Lau <glau1024@xxxxxxxxx> wrote:
> Umm, I beg to differ... I think the experience of most here has the
> longest sparks occuring when the coil is *IN* tune. When a coil is OUT of
> tune, the power from the transformer is not coupled to the secondary and
> delivered to sparks, so it is dissipated in capacitor dielectric, spark
> gaps, and other loss mechanisms, and THAT's when things are more likely to
> die. The width ratios don't matter - coupling and matching resonance do.
> By what failure mechanism do you believe the transformers fail?
>
> Gary Lau
> MA, USA
>
> On Fri, Feb 1, 2019 at 11:33 AM David Thomson <aetherwizard@xxxxxxxxx>
> wrote:
>
> > If you want to extremely spill electrons all over the place, then you
> need
> > to sacrifice something. A Tesla coil with lots of sparks is out of tune
> by
> > definition. In this case, the exaggerated secondary width compared to the
> > primary width, and the exaggerated height of the coil is hungry for
> > current. This coil will forever feast on transformers.
> >
> > David Thomson
> >
> >
> >
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