Re: TESLA COIL REVISED 2

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

Original poster: "S & J Young" <youngs-at-konnections-dot-net> 


Jaro,
With all due respect to you and Mr. Tesla, I recommend you construct a few
coils and determine for yourself the same modern wisdom gained by thousands
of hours of experimentation by hundreds of modern day Tesla coil builders,
some of which clearly demonstrate that Tesla was not always correct in what
he wrote.  Tesla was a brilliant advocate of alternating currents, and with
the limited resources at hand (poor insulating materials, very limited
measurement equipment, etc.), he made some wonderful advances and laid the
foundation for our AC power distribution system.  But not everything he
concluded is absolutely true, as more recent experiments and simulations
have proven.  A study of the Tesla List archives will yield a wealth of
empirical data.  Yes, you can get relative high voltages from a low number
of secondary turns (the coil at Griffith Observatory only has a few hundred
turns), but much recent experience shows that 1000 to 2000 turn secondaries
are more "efficient" (less mains input power needed to achieve a given
output streamer length).  Bottom line - try your ideas by constructing coils
(e.g. 50 turn secondary) and determine for yourself if they have merit.
Avoid the mistake many make, which is that everything Tesla said must be
100% true.  He had a good batting average, and the world has greatly
benefitted from his discoveries and developments, but he also made a few
erroneous conclusions.
--Steve Y.

----- Original Message -----
From: "Tesla list" <tesla-at-pupman-dot-com>
To: <tesla-at-pupman-dot-com>
Sent: Friday, January 02, 2004 9:00 PM
Subject: TESLA COIL REVISED 2


 > Original poster: "Trans-world" <jaro-at-surfside-dot-net>
 >
 > Folks you don't have to take my word for it, that a 50-turn thick wire
 > secondary should work even for a small Tesla coil, here's what Tesla
 > had to say on the subject:
 >
 > "Here is a coil which is operated by currents vibrating with extreme
 > rapidity, obtained by disruptively discharging a Leyden jar. It would
 > not surprise a student were the lecturer to say that the secondary of
 > this coil consists of a small length of comparatively stout wire; it
 > would not surprise him were the lecturer to state that, in spite of
 > this, the coil is capable of giving any potential which the best
 > insulation of the turns is able to withstand; but although he may be
 > prepared, and even be indifferent as to the anticipated result, yet the
 > aspect of the discharge of the coil will surprise and interest him.
 > Every one is familiar with the discharge of an ordinary coil; it need
 > not be reproduced here. But, by way of contrast, here is a form of
 > discharge of a coil, the primary current of which is vibrating several
 > hundred thousand times per second. The discharge of an ordinary coil
 > appears as a simple line or band of light. The discharge of this coil
 > appears in the form of powerful brushes and luminous streams issuing
 > from all points of the two straight wires attached to the terminals of
 > the secondary (Fig. 1.) Now compare this phenomenon which you have just
 > witnessed with the discharge of a Holtz or Wimshurst machine -- that
 > other interesting appliance, so dear to the experimenter. What a
 > difference there is between these phenomena! "
 > http://www.pbs-dot-org/tesla/res/res_art05.html
 >
 > Note especially this part "in spite of this, the coil is capable of
 > giving ANY potential which the best insulation of the turns is able to
 > withstand".
 >
 > So according to that, "a small length of comparatively stout wire" is
 > capable of producing ANY potential/voltage which the best insulation
 > can handle. In other words, according to Tesla, a small number of turns
 > of a thick wire will provide ANY output voltage that the coil's
 > insulation can handle.
 >
 > Of course the limiting factor will be the resistance losses in the
 > secondary coil. And these losses aren't small because of the high
 > voltage as someone said, because Tesla wouldn't talk about using a
 > THICK (stout) wire, if a thin wire would also do the job.
 >
 > So, clearly then, using a THICK wire secondary coil will lower the
 > resistance losses enough, to allow more powerful resonance which will
 > build up output voltage to any level. The only problem with a small
 > 50-turn 12" diam secondary, would then be its very high frequency (in
 > the MHz range).
 >
 > The third, tertiary coil is then used to reduce the coil's resonance
 > from MHz range to several hundred kHz. And that's what I propose for a
 > small Tesla coil. 1-turn primary, 30-50 turn secondary of a thick 8 ga.
 > wire on 12" diam., and a tertiary coil made of 100-200 turns of 20 ga.
 > wire on a 1" diam core. Also, in order to compensate for the added
 > resistance of the tertiary coil, Litz wire may be needed for the
 > primary loop.
 >
 > That should provide as high output voltage as a 1000-turn Tesla coil,
 > but at several times higher frequency (about 300kHz+).
 >
 > Jaro
 >
 > --- Tesla list <tesla-at-pupman-dot-com> wrote:
 >  > Original poster: Terry Fritz
 >  > <teslalist-at-twfpowerelectronics-dot-com>
 >  >
 >  > Hi,
 >  >
 >  > I am not sure who the original writer is, but...
 >  >
 >  > At 07:48 AM 12/30/2003, you wrote:
 >  >
 >  > >Note: forwarded message attached.
 >  > >
 >  > >
 >  > >__________________________________
 >  > >Date: Sat, 27 Dec 2003 06:54:13 -0800
 >  > >Subject: [jlnlabs] TESLA COIL REVISED
 >  > >Reply-To: jlnlabs-at-yahoogroups-dot-com
 >  > >Content-Type: multipart/alternative;
 >  > >
 >  > boundary="7sXqLKCsjnyYoY64pxfTPFI2R0ZhKSZJleFSmA1"
 >  > >Content-Length: 1751
 >  > >
 >  > >I have a problem with today's Tesla coils. The way
 >  > they're built these
 >  > >days, is with the secondary made with SEVERAL
 >  > HUNDRED turns of thin
 >  > >wire, which is WRONG. When Nikola Tesla made his
 >  > coils, they only had
 >  > >50 to 100 turns of a THICK wire as the secondary.
 >  >
 >  > Tesla used a three coil system while most of today's
 >  > Tesla coil builder's
 >  > use two coil systems.  They are considerably
 >  > different machines made for
 >  > different environments.  However, the basic
 >  > principles are the same.
 >  >
 >  >
 >  > >The problem with hundreds of turns of a thin wire
 >  > is that they have
 >  > >many times bigger resistance than Tesla's original
 >  > coils. This big
 >  > >resistance increases losses, and so minimizes
 >  > voltage increase due to
 >  > >resonance. Thick secondary wire will have small
 >  > losses which allows the
 >  > >resonance to build higher voltages.
 >  >
 >  > Due to the high voltage, the resistance loss in the
 >  > secondary is small and
 >  > not a major energy loss.
 >  >
 >  >
 >  > >Here's how Tesla's Colorado Springs coil was built.
 >  > Primary were 2
 >  > >turns of a thick cable, and secondary 100 turns of
 >  > No. 8 wire with a
 >  > >diameter of 51 feet. That's 1:50 ratio between
 >  > primary and secondary.
 >  > >Input was 50 kV into a .004 mF capacitor which was
 >  > connected to the
 >  > >primary coil through a spark gap. It could resonate
 >  > at frequencies from
 >  > >45 to 150kHz.
 >  >
 >  > His think secondary actually had 17 turns of wire.
 >  > He had a third coil 12
 >  > high 6 feet diameter 160 turns of #10.  It was a
 >  > magnifier with a modern
 >  > example at:
 >  >
 >  > http://www.ttr-dot-com/model13.html
 >  >
 >  >
 >  > >Tesla's power-transmission coil patent shows almost
 >  > the same coil,
 >  > >except that the diameter was 8 feet, and secondary
 >  > was wound as a flat
 >  > >coil (also no. 8 wire), and resonance was around
 >  > 250kHz, producing 2 to
 >  > >4 million volts.
 >  > >
 >  > >So if Tesla's coil could be reduced from 51' diam.
 >  > to 8' diam., while
 >  > >keeping the 1:50 primary/secondary ratio, then it
 >  > should be no problem
 >  > >to reduce that coil further to about 1' diameter,
 >  > using only 50 turns
 >  > >of a thick wire as a secondary.
 >  > >
 >  > >The only problem would be the 50kV input that Tesla
 >  > used, but even
 >  > >using only 5kV from a neon transformer should
 >  > produce 200 to 400kV
 >  > >using the 1:50 ratio, since 50kV input produced 2-4
 >  > million volts.
 >  >
 >  > See the above model 13 details at www.ttr-dot-com.
 >  >
 >  >
 >  > >Also, using a 1' diam. secondary will reduce its
 >  > inductance, which
 >  > >will increase resonant frequency to several MHz.
 >  > And using a very thick
 >  > >wire, copper pipe or Litz wire would be needed to
 >  > reduce high frequency
 >  > >losses.
 >  > >
 >  > >So, using a 1-turn primary and 50-turn secondary on
 >  > a 1-foot diameter
 >  > >air-core, should make a TRUE Tesla coil which will
 >  > have lower losses
 >  > >and more powerful resonance than today's "Tesla
 >  > coils". Plus that makes
 >  > >it much easier to make than winding hundreds of
 >  > turns.
 >  >
 >  > Winding hundreds of turns is not that hard ;-)  But
 >  > most of the losses
 >  > (40%) go into the spark at the gap.  The other
 >  > system losses due to coil
 >  > heating and cap losses are very small compared to
 >  > the spark gap.  "Modern"
 >  > Tesla coils are optimized for spark length given
 >  > commonly available input
 >  > power and size requirements.
 >  >
 >  > Of course, if one can make a better Tesla coil, just
 >  > do it!!! :-))
 >  >
 >  > Cheers,
 >  >
 >  >          Terry
 >  >
 >
 >
 >