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Re: Coil Efficiency (and true wattmeter)
From: David E. Sharpe[SMTP:sccr4us-at-erols-dot-com]
Reply To: sccr4us-at-erols-dot-com
Sent: Saturday, August 02, 1997 10:52 PM
To: Tesla List
Subject: Re: Coil Efficiency (and true wattmeter)
Tesla List wrote:
>
> From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
> Reply To: bert.hickman-at-aquila-dot-com
> Sent: Friday, August 01, 1997 2:06 AM
> To: Tesla List
> Subject: Re: Coil Efficiency (and true wattmeter)
>
> Tesla List wrote:
> >
> > From: David E. Sharpe[SMTP:sccr4us-at-erols-dot-com]
> > Reply To: sccr4us-at-erols-dot-com
> > Sent: Tuesday, July 29, 1997 11:51 PM
> > To: Tesla List
> > Subject: Re: Coil Efficiency (and true wattmeter)
> >
><<SNIP >>
> Dave,
>
> Thanks for the clarification on Vcap - now I understand what you're
> saying.
>
> There's a common misunderstanding of the effect of k - for coupled
> resonant circuits, the energy transfer "efficiency" is actually a
> function of the Q's of the primary and secondaries. "Lossy" systems will
> lose energy all during the time that the primary energy is being
> transferred to the secondary. Loose coupling means that the amount of
> time it takes to transfer all the primary energy to the secondary is
> longer. With lower Q, this means that more is dissipated while the
> transfer is occuring. leaving less that eventually gets to the
> secondary. Thus, most coilers assume that the reason for poorer
> efficiency is low k, while the REAL reason is dissipative losses (mostly
> in the primary circuit, and mostly in the gap).
>
> In the electrostatic coupling experiments, was the base of the test
> resonator grounded, and what kind of resonator output did you see? Did
> it seem to be like an impulse excitation to the resonator the instant
> the gap fired, or did it more follow the primary voltage swings? Sounds
> like an interesting experiment!
>
> Safe coilin' to you, Dave!
>
> -- Bert H --
Bert
Your comments on primary circuit losses are well founded. On my
current magnifier project, I'm using aluminum roof flashing in 3"
wide strips, separated by 0.060 LDPE, as a transmission line
sandwich (Al,PE,Al,PE,Al). Since RF likes to run on large
surface areas, busses of very high power transmission capacity
can be easily (and CHEAPLY :^) ) built. The only negative with
this type construction is corona at the sharp edges, but even this
could be reduced by rolling the edges of the transmission bus.
The TCBOR back in the early nineties (Richard, hop in!) began
researching free coil systems as the next progression of understanding
magnifiers from two coil systems. A regular two coil system would
be abnormally heavily top loaded, and the primary tank circuit
retuned to maintain system resonance, and power gradually increased
until the overloaded two coil system was radiating ('E' field wise)
strongly, but was not breaking out with streamers. An unconnected
resonator was placed in close proximity to the operating system
(4-6 feet away with power in of 0.5 to 1.0kVA.) The base was connected
to local RF ground, and the coil tuned by placing very small capacitive
loads (toroids, spheres, anything) on the system until resonance was
achieved. This experiment was originally performed by Alex Tajnsek
of the TCBOR.
The observed Q and response of the "free coil" would often times
produce sparks greater than the driven system was capable of producing!
Tesla indicated the reason for this was condition was there was
no primary around the base of the free coil to influence the
secondaries response (as a parasitic load, and dropping of the
resonator's Q due to this parasitic load).
In other experiments, an aluminum plate was placed between the
driving system and the free coil resonator. As long as the intermediate
aluminum plate was not grounded, significant output spark was seen
(the spark length was reduced from the control condition of no plate).
If the intermediate aluminum plate was grounded (Faraday ground plane)
the free coil's output immediately was killed, strongly suggesting that
'E' field excitation was the mechanism of exciting the free coil. The
mentioned experimental series was fully documented on TCBOR videos.
Since these coils were spaced up to 6 feet apart, magnetic coupling
was virtually non-existent (we attempted to measure, and couldn't).
This series of experiments lead to the logical conclusion that if a
separate two coil "driver" system, directly drove the base of a
third "extra coil" uninductively, and system resonance was maintained,
much higher power output and output voltage would result. Much of the
past 4-5 years of research of the TCBOR spring boarded from these
experiments.
Regards
DAVE SHARPE, TCBOR