RE: Tesla Coil - Internal Arcing on Secondary

["Tesla list" <tesla@xxxxxxxxxx>]

Original poster: "Malcolm Watts" <m.j.watts@xxxxxxxxxxxx>

Hi Dan,
        I used a 2-stage modified Marx to double the voltage of a
beefy 7.5kV transformer once to run a Tesla coil. The Marx caps
doubled as the primary caps and the circuit effectively had three
gaps in series. The Marx bit used chokes as charging elements rather
than resistors. There is no reason why I couldn't have used more
stages. The primary PRF was 2Fmains.

Malcolm

On 15 Aug 2005, at 13:10, Tesla list wrote:

> Original poster: "Mccauley, Daniel H" <daniel.h.mccauley@xxxxxxxx>
>
>
> I'm confused to what the 7 stage marx generator is doing???
>
> ********************
>
> I've just finished a 1 kw 1/4 wave tesla coil, off a 7 stage marx
> generator off of a microwave oven transformer. 3J pulses in PP snubber
> caps. Far too much work - I removed the secondary on some signal
> transformers for inductive separation between stages, and it took a
> couple tries to figure out a workable spark gap system. I ended up
> using concrete bolts with wire wrapped around the threading and vise-d
> together. Problem is, now the secondary is arcing. The secondary is
> ~700 turns of 22 awg wire on a 6 in diameter acrylic tube, spacewound
> at the top and the bottom, with 3 spray coats and 1 brush coat of
> polyurethane on it after winding. The topload is 25.75 pf (calculated)
> and the secondary is 21.3mh (experimental) for resonance at ~215kHz.
> The winding is about 19 inches, spacewound above and below that.The
> primary is inside the secondary, on a 3 inch diameter tube. The arcing
> seems to happen at a consistent place. The arcing is clearly between
> the secondary's wire and the acrylic form; it is so bright it shines
> through the enamel clearly, making a cool looking lightning pattern
> just under the wire. Any ideas on how to stop the arcing? I can draw
> off maybe 6 inches of spark, but I should get 6-8 times that according
> to my figuring.
>
>
>