I would love to see your transformer :)
On Fri, Jun 29, 2018, 3:08 PM Jan Ohlsson <jan@xxxxxxxx> wrote:
> HI, i am new on this list and in the early stages of designing a big coil.
> A few years ago I built a medium size coil, but want to go bigger now. I
> have access to at least 40 A at 400 V. Pigs are hard to come by in my
> country, so I am in the final stages of fabricating my own, 55 kg UI core,
> isolated with paper and in a tank under transformer oil, in the old
> fashioned way. It should be capable of delivering up to 16 kVA
> intermittently at 13 kV,I think.
>
> But now I would like to test a few ideas in this forum, before I commit.
> Please correct me if they seem crazy!
>
> 1. The ballast should have a low flux in the core at max current,
> otherwise the current limitation will be unstable due to the unlinearity of
> the iron cores permeability. I am thinking of a UI core weighing 110 kg
> with a good sized air gap, would that be excessive? I am planning on
> several taps to be able to change the current from 10 to 40 A.
> 2. The SRSG should have a high rotational speed for good quenching, I
> am planning 3000 rpm and 400 mm diameter, 4 electrodes.
> 3. The secondary should be wound on a tube with very low losses, I am
> thinking of polyethylene, and varnished as well with low loss material,
> epoxy resin. Nothing lossy inside the coil form, low dielectric loss is
> very important.
> 4. Secondary with large diameter, 315 mm, and not to long, 900 mm. Cu
> wire 1,2 mm, low losses are more important then many turns.
> 5. Very large thoroid, minor diameter 300 mm, major 1,5 m.
> 6. A small thoroid under the big, to be able to raise the main
> thoroid and still avoid downwards strikes.
> 7. No possibility for a normal earth, the site is a big underground
> bomb shelter with a very well reinforced concrete floor. I plan on using
> several sheet metal plates on the floor to get a counterpoise type ground
> by coupling capacitively with the metal sheets to the rebar system in the
> concrete floor. The floor is very big, 1800 square meters, so it is a big
> electrical mass with more or less conductive rebar.
> 8. An isolating plastic sheet above the primary, to avoid strikes to
> the primary.
> 9. MMC capacitor bank, probably up to 200 nF, will have to be tested.
> What do you think? Please feel free to critizise!
>
> Jan, Stockholm, Sweden
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