Gary,
I am also new to this group.
And also building a TC like Jan.
I have a 10 kva transformer and have 40 amp varics to control input
voltage and have built an air gap primary ballast to limit current.
I have test this configuration with a 10 foot tall travelling arc and
it works very well.
With the varics at full setting the air gap was set to limit current to 42 amps.
I am trying to get to the next step with the capacitor and spark gap.
I am very interested in your comments on the SRSG.
I have read Richie Burnetts web page and find his comments on
synchronous spark gaps informative.
I readily admit that it is very much over my head but it does appear
to make sense.
Can you respond with your comments on his page on rotary spark gap overview?
I would very much appreciate it sir.
Teddy
On 6/29/18, Gary Lau <glau1024@xxxxxxxxx> wrote:
> Hi Jan,
>
> First, a disclaimer - I have not attempted a TC as powerful as what you're
> considering - only NST-powered coils.
>
> But, I think most similarly-powered coils use a variable-speed ARSG. Is
> there a reason to use a SRSG? I calculate that with a 200 BPS SRSG,
> charging voltage of 18.4kV, 200nF cap, the maximum power than can be
> processed is 1/2 C V**2 * 200bps or 6.7kW. Serious juice but no way to
> turn it up.
>
> I can't comment on ballast considerations. I think you know more than me
> on this topic.
>
> I think the concern for low-loss secondary form is unwarranted. Dielectric
> losses occur in capacitor dielectrics, but the e-fields in a coil form are
> not significant. Polyethylene is fine but uncommon and not easy to glue.
> PVC or sonotube won't disappoint as far as losses are concerned.
>
> Good luck winding that transformer, I think that's going to be your biggest
> challenge. Coil on!
>
> Regards, Gary Lau
> MA, USA
>
>
>
> On Fri, Jun 29, 2018 at 3:49 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
>> _______________________________________________
>> Tesla mailing list
>> Tesla@xxxxxxxxxxxxxxxxxx
>> https://www.pupman.com/mailman/listinfo/tesla
>>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxxxxxx
> https://www.pupman.com/mailman/listinfo/tesla
>
_______________________________________________
Tesla mailing list
Tesla@xxxxxxxxxxxxxxxxxx
https://www.pupman.com/mailman/listinfo/tesla