Re: [jlnlabs] TESLA COIL REVISED

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: FutureT-at-aol-dot-com 

In a message dated 1/2/04 3:14:03 PM Eastern Standard Time, 
tesla-at-pupman-dot-com writes:

Jaro,

Am I correct that you have not actually built and compared coils
with various number of turns?  Regarding your comment about
the point of a Tesla coil being brush-like discharges, I believe
that each person has their own idea of what the point of a Tesla
coil is.  Of course Tesla's photos of his Colorado Springs coil
were time lapse photography so they made the sparks look a
lot bushier than they'd look in person.  But if you want bushy
discharges, yes a high frequency may help that.  A high break
rate may help too.  Tesla's Colorado Springs coil however
ran at a low RF frequency of about 50kHz ballpark.  I don't
remember the exact frequency.

Regarding the Q of a coil, it's not really that important as long
as the Q is reasonably high.  Making the Q super
high won't really give a noticeable improvement.  It's a coiling
myth that the resonator rings up higher and higher as the coil
runs.  The ring-up is limited by conservation of energy issues.
The resonator is not being constantly pumped by input energy,
but is limited by the charge in the energy discharge capacitor.
Because of all this, the coil voltage will not exceed the equation's
prediction regardless of how high the Q is.  Of course once the
sparks emit, the dynamic Q plummets.
Although it's true that thick wire reduces the losses in the secondary,
it tends to force the use of fewer turns in the primary which
increases the gap losses.  Tesla got away with this because
his coil was large in diameter, so the primary inductance was
still reasonably high.  Nevertheless, it's always a tradeoff between
gap losses and wire losses.  In any case voltage is not the whole
story anyway.  To create long sparks takes a certain amount of
both voltage and current.  Regarding what Tesla said, do you
believe that everything that Tesla said was correct?  If so, I assure
you it was not.  He simply didn't have the equipment necessary
to verify some of his conjectures.  Tesla coil knowledge and
understanding has come a long way since Tesla's day.  None
of this is intended to take away from Tesla's wonderful achievements.
It's just the simple reality.  Let me say in closing that there's a whole
*heap* of misinformation out there about Tesla coil theory.  Much
important theoretical and empirical work has been done by folks
on this mailing list.  The research continues.....

John


>Original poster: "Trans-world" <jaro-at-surfside-dot-net>
>
>You're right that higher inductance ratio will produce higher output
>voltage, but it will also reduce resonant frequency. My proposed
>50-turn secondary coil has at least 100 times lower resistance, and 35
>times lower inductance than your 1000-turn coil. That results in MUCH
>SMALLER resistance losses, and MUCH GREATER frequency and greater Q.
>
>The point of Tesla coil isn't the highest voltage, but providing a
>BRUSH-LIKE discharge. Otherwise it's just a fancy lightning generator.
>And for that special discharge you need AT LEAST SEVERAL HUNDRED
>kiloHertz frequency. And you can't get much more than about 100 kHz
>from your high-inductance secondary coil. If you don't believe it,
>here's what Tesla said about it:
>
>http://www.pbs-dot-org/tesla/res/res_art05.html
>
>Also, doesn't higher Q of a coil, translate into more powerful
>resonance, and with it, HIGHER VOLTAGE? Remember that the lower the
>resistance losses, the higher the voltage due to resonance will be.
>
>And the problem with your "Output (gain) = Einput x sqr (Ls/Lp)"
>equation is that it doesn't include the Q of the coil. It will be true
>for two coils made with the same diameter wire, but NOT TRUE if the
>coils are made using different wire gauges. That's because you can
>increase wire thickness without increasing coil's inductance, and
>thicker wire will output higher voltage because of higher Q, than your
>equation would predict.
>
>Jaro