Re: [jlnlabs] TESLA COIL REVISED

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

Original poster: "Harold Weiss" <hweiss-at-new.rr-dot-com> 

Hi All,

My old 15" coil was 545 turns of #14 with a 20x5" torrid, and driven by a
15/120 supply.  Best spark was 3 1/2-4' in still air.  My 6" coil is 620
turns of #20 with same torrid, and 12/120 supply.  Best spark so far is 54"
and improvements continue.  Both of these coils use low turns and large
conductors compared to most other coils on this list.  It seems that these
coils are much more inefficient than coils running 1000+ turns, although, a
decent pulse type cap or MMC might make some difference over the Fair Radio
caps.  Also, the higher the frequency, the shorter the spark length will be.
Tesla could do this only because the diameters were large, which gave higher
inductance for the number of turns.  High inductance in the secondary seems
to be the key.  For small diameters this requires small wire and many turns
to get the best output.

David E Weiss

 > Original poster: Tom Stathes <newphreak_16-at-yahoo-dot-com>
 >
 >
 > 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.
 >
 > 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.
 >
 > 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.
 >
 > 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.
 >
 > 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.
 >
 > Jaro
 >
 >
 >
 >