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Re: Weird ideas
From: Bert Hickman[SMTP:bert.hickman-at-aquila-dot-com]
Reply To: bert.hickman-at-aquila-dot-com
Sent: Sunday, November 30, 1997 10:26 AM
To: Tesla List
Subject: Re: Weird ideas
Good questions, Ted. My answers are included below.
-- Bert --
Tesla List wrote:
>
> From: Ted[SMTP:tedric-at-generation-dot-net]
> Sent: Saturday, November 29, 1997 6:59 PM
> To: tesla-at-pupman-dot-com
> Subject: Weird ideas
>
> Hi all,
>
> Here are some ideas and questions:
>
> 1) Earlier this month, we had discussion on using water as a dielectric.
> >From Jim Lux's post, we learned that water is a "slow" conductor. Will it be
> practical to use water as choke by filling water in poly tube? If not, why not?
>
I assume you were referring to the RF chokes used for blocking high
frequency RF from the transformer? Water would perform very well as a
choke but could perhaps be used as a series damping resistor. The
problem is that the water will be conducting the relatively heavy 60 HZ
current going to charge the tank cap. There's be LOTS of ions present to
conduct both the 60 HZ and any RF currents. Water works well as an
insulating medium only for relatively quick pulses - of the order of
nanoseconds or microseconds. BTW, once the water begins conducting, it
may also generate gases that must be allowed to vent, else your water
resistor might blow up...
> 2) As the capacitance increases, high frequency current will pass through a
> dielectric more easily. So, by putting poly between the primary and the
> secondary, instead of insulating the two, will it actually create more problems?
>
It can, but for a slightly different reason having to do with e-fields
and dielectric circuits. When you put a material with a dielectric
constant k > 1 into an air gap (k = 1) stressed by a high AC electric
field, the presence of the material actually INCREASES the E-field
stress in the remaining air gap. If you were right on the edge of air
breakdown before adding the poly, adding the material may now actually
cause air breakdown to occur, immediately followed by punch-through of
the poly insulation! Multiple dielectric systems can be tricky!
> 3) I want to do some ball lightning experiment with microwave (I know about
> the candle trick, it works!). Similar to what the Corums did, who excited
> two resonators will one primary, I am going to put two resonators in a
> microwave and excite it with one magnetron. Is microwave tranformer shunted?
> Some say yes, but other say no. Who should I trust?
Virtually all home microwaves are driven by relatively cheaply
constructed shunted transformers. However, that still doesn't mean that
it's impossible to damage the magnetron under certain conditions. What
were you planning to use for resonators? Simple wire-wound coils don't
behave as resonators at this frequency...
>
> 4) Superconductor again! It is a known fact that intense magnetic field will
> ruin superconductor. But before the entire "breakdown" happens, the current
> that is allowed to pass through the superconductor decreases, yet it still
> has zero resistance. The ultimate "breakdown" for a ceramic superconductor
> will be becoming an insulator. Read the last sentense again! Either
> superconducting or insulating, doesn't that sounds like a perfect switch to
> you? I am currently pondering if it is possible (of course it is!) to
> replace the spark gap with a magnetically contolled "Superconducting
> Switch". One example is by using rare earth magnet to approach the threshold
> of the "breakdown", and by putting the superconductor under the (tesla)
> coil, when the "switch" fires, the magnetic field from the coil itself
> "quenches" the superconductor, a true self-controlled soild state tesla coil!
>
> Also, you can use superconductor as a current limiting device. (someone
> had proposed this before I did!) :(
I suspect a superconducting switch would have a hard time trying to
operate as a high-power repetitive switch. Whenever a superconductor
begins to transition through the region between being a normal conductor
(or insulator in some cases) to a superconductor, it goes through a
region where is has finite resistance (i.e., all of the material doesn't
suddenly transition to being superconducting at the same time). If we
try to drive any appreciable current through it at this point, power
losses (I^2*R) will quickly heat the semiconductor above its
superconducting transition temperature. Now, you MIGHT be able to switch
off a heavily-conducting superconductor ONCE, IF the resulting power
dissipation upon quenching didn't destroy it. You'd then have to wait
until it cooled down to the point where it again became superconducting
before repeating this.
>
> BTW, why bother with tubes? Frankly, I found that they are so incredibly
> inefficient, think about this for a moment: First, you have to put enough
> energy to "boil" enough electrons. Then, you are applying electric field
> (energy) to constantly accelerate the electrons, not only did the electrons
> did not slow down as they approach the anode, they travel at full speed. At
> last, you stop the electrons and most of its energy become heat. Heat is
> generated in both the "boiling" and "stopping" process, it sounds to me like
> a electron welder.
>
That's why semiconductors were invented. :^)
Seriously, for certain applications tubes may be relatively inefficient,
but they're the only game in town. One of these areas is in high-power
RF. One of their more endearing features is their robustness in the the
face of current and voltage transients and severe overloads that would
cause a semiconductor to instantly whimper and silently go "belly up"...
Some on this list have become quite proficient at torturing their tubes
JUST the edge of destruction with excellent (coiling) results..
> Any comment are welcome. (I figure out that I better to add this since my
> post "Terminal Capacitance" remains unanswered, bother to look at it again?)
We all must have missed this post... sorry!
>
> Ted
Safe coilin' to you, Ted!
-- Bert --