Re: Primary spacing on large coil. (fwd)

---------- Forwarded message ----------
Date: Tue, 30 Apr 96 13:24:00 PDT
From: Richard Hull <RICHARDH-at-whitlock-dot-com>
To: bin <bin-at-poodle.pupman-dot-com>
Subject: Re: Primary spacing on large coil.

Robert, and others.

We at the TCBOR have fiddled with really high voltage in TC's.  The 
temptations and benefits are very tempting.  A very small capacitor can be 
used for very large powers and the output voltage from the TC will be much 
higher due to the increased energy.  The real rub comes from the fact that 
above 20,000 volts, corona and insulation of primary tank connections 
becomes a real bear.  At around 30,000 volts, only the most heroic efforts 
will succeed in properly containing the primary energy.

Tesla had the capability of 60KV in Colorado and this is often spoken of by 
people in the TC building field.  Tesla never used voltages above about 30kv 
more than once!  (this blew his caps up!)  He quickly reduced his normal run 
voltage to about 25 KV.  He used the term "a number of jars gave way" to 
delicately describe the catastrophic explosions in the tanks.  I wouldn't 
want to go finishing around in salt water to retrieve shattered shards of 
glass bottles!!  This was down time to Tesla and he never ran this 
experiment again.  He also complained of "flaming at the rotary" when even 
25,000 volts was used.  Admittedly, his gap system in Colorado was terrible, 
but  with high voltages, extra efforts must be poured into gap design.

My advice would mime yours Robert,  let someone else pioneer this sticky 
area for now.  We are just trying to do our best under 20,000 volts.  A lot 
of extra bucks will need to be spent in the region above 20KV just to 
insulate and avoid corona flashover and bleed.

Richard Hull, TCBOR
From: bin
To: Tesla-list-subscribers
Subject: Re: Primary spacing on large coil.
Date: Monday, April 29, 1996 9:25PM

>From rwstephens-at-ptbo.igs-dot-netMon Apr 29 21:09:29 1996
Date: Mon, 29 Apr 1996 13:07:38 -0500
From: "Robert W. Stephens" <rwstephens-at-ptbo.igs-dot-net>
To: tesla-at-pupman-dot-com
Subject: Re: Primary spacing on large coil.

>>From larrycg-at-intele-dot-netSun Apr 28 22:06:15 1996
>Date: Sun, 28 Apr 1996 10:17:51 -0600
>From: "Larry C. Gardner" <larrycg-at-intele-dot-net>
>To: tesla-at-pupman-dot-com
>Subject: Primary spacing on large coil.

Larry Gardner wrote,

>I am currently in the process of building a large Tesla coil.
>It will have an input of 50KV at 100mA.  The primary capacitance is
>12.5nF, and will resonate at 120kHz. The secondary has a diameter of 15
>       The problem here is how far apart do the primary winding need to
>be in a large coil?  In the smaller coils built I know that primary
>sapcing was recommended to be from 3/8 to 1/2 of and inch.

>       Any help would be greatly appreciated.

>Larry Gardner

>"The present is theirs, the future, for which I really worked, is
>mine"-Nikola Tesla


Break timing  jitter and dwell start to deviate wildly  and
become increasingly hard to control with conventional rotary breaks at
such voltages.  The only reason I can figure that you must wish to
try this is to get higher power from a very high voltage, small value
capacitor that you must have lucked upon and that you also have a
100mA, 50 kilovolt transformer.  I think the extra problems that you
will have with  your break merely to achieve 5 kilowatts, commonly
achieved by simpler means, will diminish the value of this exercize.
However,... if you want to go to that trouble to charge a LARGE value
capacitor at 50 kilovolts with say 1 amp or more,  I'd say go for it before 
do so and maybe I can learn from your mistakes!

Happy coiling!, rwstephens