Re: Fwd: [jlnlabs] TESLA COIL REVISED

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

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;
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>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



>Jaro