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Re: The Magneon Porkchop
Tesla List skrev:
>
> Original Poster: Mark Finnis <mefinnis-at-medicine.adelaide.edu.au>
Snip
>
> Just one concern. If you have the "centre-tap" of the two secondaries
> innermost, you have maximal dV from the outside of the secondary windings,
> which appear VERY CLOSE !!!!
>
> With my TF there was about 1 cm between the secondaries and you could hear
> the corona at 13.5 kV with a total of 200kV insulation between the
> windings!!! (very pretty in the dark .. too) This was solved my adding
> another 12 sheets of pyrolam (8kV / layer) between the windings and putting
> it in oil.
>
> I would be VERY careful running that TF dry, especially in a coil circuit,
> as you are going to see a lot more than 20kV across the secondaries ......
This is also my observation, when I first turned the variac up, I heard
a faint sssssssss, then I turned it diwn immediately. Now, the gap
between the secondarys is 3 mm, and when I fill it out with mylar, which
should be good for 300 kV / mm, I feel that it should be enough.
This said, I can assure you, that I don`t dare to turn it up again,
unloaded, before it is submerged in oil. I have made a polypropylene
tank, and bought 25 litres of castrol insulating oil BS 147 for that,
and caps. The clearance btwn. the end of the turns and the core is 15
mm, and I am going to insert 2 mm of mylar here, too.
>
> Also not sure whay you went to 20kV. This makes making caps much harder /
> more expensive. I would have stayed at 14 kV and gone for more AMPS ;-))
>
I am glad you ask this question, because it gives me the opportunity to
write how i think the tank circuit works, and get corrected if i am
wrong.
My choice of the high voltage is based on what I have read in the
archives, where Richard Quick claims that a well developed system has a
primary that is about as large in diametre, as the length of the
secondary coil, _and tapped out beyond the 12 -13th turn_.
And the assumption, that the "matching capasitor" that wingate and tesla
coil cad predict, is the max. size cap that the transformer is able to
charge to full voltage in one cycle.(IE, use one that is a bit smaller
to avoid resonance) But not so small that it fires twice or more with
static gaps, or backfires on a rotary, when i get one built.
In other words: this matching capasitor is the size that will allow me
to load the transformer to the limit, and get the maximum energy into
the cap, so that the gap fires close to the top of the cycle, even if i
set it close to 20 kV.
With the resonant freq. that I am aiming at, around 120 KHz, and a
voltage of 14 kv, I would need a cap of 0.04 µF to match the
transformer, and this would force me to tap in to turn 8-9.
With 20 kV, the perfect cap would be 0.024 µF, I can use a cap of 0.02
µF and tap btwn. 12 and 13.
Somehow it seems to me, that this would make the better use of the
available power, and still honour the findings of Mr. Quick.
I am really poking around in the dark, here, so some input to this
explanation would be appreciated.
I will make a separate post with this explanation to try to get total
exposure, call it "tank circuit question"
As far as caps go: I have bought 200 meters of 0,05 mm ( 2mill) thick
allufoil, 500 mm wide, and ordered 30 Kg of 0,4 mm (16 mill) thick
virgin poly from italy. I will stack this plate cap under oil, to
visually confirm that there is absolutely no air inside, and make it a 4
in series configuration, clamped down tight, with a total of 3,6 mm (144
mill) ,-) of dielectric.
> Anyhow ...... very nice & keep us posted.
I will, Finn