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Re: Secondary coil arcing to itself
From: DR.RESONANCE[SMTP:DR.RESONANCE-at-next-wave-dot-net]
Sent: Saturday, June 28, 1997 2:25 AM
To: Tesla List
Subject: Re: Secondary coil arcing to itself
To: Kevin
It appears you inadvertently tuned your secondary inductor with too large a
capacitive tophat. This large torus is too large for a .005 MFD drive on
the primary and as a result the secondary inductor is reaching resonant
peaks at several points along its length. No amount of insulation will
cure this problem. It appears you may be operating at 5/4 or 7/4
wavelength instead of 1/4 wavelength.
You have a few choices -- either reduce your large top capacitance to a 3-4
inch ball or go to a .01 MFD cap and increase the primary drive current to
60 ma (12 KV, 60 ma as an example). Experiment with a wide range of
primary taps running a variac on the primary side of the neon xmfr to keep
it to around 40% or less until you get the tuning where it should be.
Hope this helps out.
DR.RESONANCE-at-next-wave-dot-net
----------
> From: Tesla List <tesla-at-pupman-dot-com>
> To: 'Tesla List' <tesla-at-poodle.pupman-dot-com>
> Subject: Secondary coil arcing to itself
> Date: Friday,June 27,1997 1:28 PM
>
>
> From: Kevin Christiansen[SMTP:kevin+-at-cs.cmu.edu]
> Sent: Thursday, June 26, 1997 7:25 PM
> To: tesla-at-pupman-dot-com
> Subject: Secondary coil arcing to itself
>
>
>
> Hello everybody!
>
>
> I just put togeather a small Tesla Coil that is exibiting
>
> a behavior that I have never seen before: the secondary
>
> coil arcs to itself at various points along its length.
>
> Basically, an arc will break out somewhere along the length
>
> of the secondary, streak up (or down) the secondary for 2 to
>
> 4 inches, and then re-enter the secondary. While these little
>
> arcs playing all over the surface of the secondary are certainly
>
> neat-looking, I am sure that they are murduring the insulation on
>
> the wire and are robbing me of power. (Note that these are NOT
>
> torroid-secondary, primary-secondary, etc. arcs - these arcs just
>
> streak from here to there along the surface of the secondary.)
>
>
> Any suggestions on how to stop them?
>
>
> (I have a can of that 2 part Devcon Flexane Urethane rubber
>
> stuff, which claims a dielectric strength of 350 volts/mil.
>
> Should I glop a thick layer of that over the top of the
>
> windings?)
>
>
> Here are the specs on the coil, for those that are interested:
>
>
> Power supply
>
> 7.5 A variac
>
> 15 Kv 30 mA neon
>
> misc RF protect chokes, protect gaps, etc.
>
>
> Primary tank
>
> .005 uF, 60 Kv energy storage cap by High Voltage Components, inc.
>
> 12.75 turns of .08" house wiring: 5" tall and 10.5" diameter
>
> Wound on a plastic bucket
>
> .25" static gap, in 10 to 40 equally sized "mini-gaps".
>
> Tungsten carbide electrodes
>
>
> Secondary
>
> #24 magnet wire: 17.75" tall and 4" diameter, close-wound
>
> Wound on a PVC pipe that was sanded, heated, and painted
>
> with several layers of oil-based polyurethane varnish.
>
> Coil was varnished after winding as well.
>
> Torroid is 3" Al dryer duct, 12.5" wide
>
>
> Ground
>
> About 30' of Belden 8213 heavy 0.5" coax, using both the shield
>
> and the center conductor, clamped to the plumbing system of my
>
> appartment in 2 different places.
>
>
> Currently, I am getting 14" arcs from a small wire taped to the side
>
> of the torroid, to ground. How long of arcs should I be able to
>
> get out of a 15 Kv 30 mA neon?
>
>
> Thanks for any suggestions/comments that you can give me!
>
>
>
> <bigger>-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>
> Kevin D Christiansen
>
> Human Computer Interaction Institute - Carnegie Mellon University
>
> kevin-at-cs.cmu.edu http://www.cs.cmu.edu/~kevin/
>
>
> "The universe is composed of space, galaxies, and intergalactic
>
> dust. Galaxies themselves are composed of space, stars, and
>
> interstellar dust. From the omnipresence of dust, we conclude
>
> that nature abhors a vacuum and won't pick up a broom, either."
>
> -=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-
>
> </bigger>
>
>