Re Richie Burnetts web site - I just took a look at his rotary gap page -
https://www.richieburnett.co.uk/rotary.html. I've been on his site
previously but there seems to be some problem now with images not loading
and painfully low contrast fonts.
I don't think I disagree with anything cited there, but I think one
important takeaway that was not mentioned is that SRSG's shine in that they
are able to process the maximum amount of power from a given transformer.
In the pole pig league, that's not really important, so much as with lower
power NST's.
On Sat, Jun 30, 2018 at 5:12 PM, Tedd Dillard <tedd.dillard@xxxxxxxxx>
wrote:
> 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
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