From: FutureT@aol.com
Date: Sat, 18 May 2002 12:50:50 EDT
Subject: Re: [TSSP] Racing arcs
--part1_2f.277d96a7.2a17e06a_boundary Content-Type: text/plain; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 5/18/02 10:25:10 AM Eastern Daylight Time, paul@abelian.demon.co.uk writes: > Bart, John, > > Intriguing that you can turn the racing arcs on/off by quite modest > adjustments to topload height, primary coupling, and tuning. And > your coils each demonstrate a different type of racing arcs - > the full length from Bart's, and the ones that gather round the > top and bottom of the coil from John's. Paul, Bart, all, There were two or three times that I saw the full length types of racing sparks on my coils. One time I had coupled up extra tight using a so-called fast quenching series rotary gap. It didn't really quench much faster, but it also didn't permit me to couple any closer at all. In another case, I built a very short secondary which was only 9" long. I wanted to see how long of a spark I could obtain at 120 bps from the coil. I had to load up a bunch of stacked toroids on top, and eventually got 26" sparks I think, but the secondary was plagued by full length (and shorter) racing sparks. I'd say the coil was overpowered. I forget what the coupling value was. In some cases of the full length racing sparks, they seemed to be triggered by roughness, or small ROC on the lowest smallest toroid which was directly above the secondary winding. Bart, do you have any sort of corona ring type object directly above the secondary winding which could be promoting the full length racing sparks? I may be interesting if Bart detunes his primary to a higher frequency to see if he gets the racing sparks only at the bottom and/or top. I don't think he did that test? > > I think we can get this by calculating the Cexternal for the > secondary with the primary in/not in place, and taking the > difference to get the pri-sec cap per unit area, and thus the > extra charge per unit area, and from that to the surface field > radial to the coil. Hmm, some stuff to think about there. > The 'hottest' spot may not be directly between the primary > and secondary, but may be a little way above. Sounds like a good idea to me. In the close-coupled test I mentioned above, I used a cylinder primary instead of a flat primary. I think the racing sparks tended to occur directly between the primary and secondary in that case. But it so happens that the primary diameter was such that the primary had to be an inch or so above the bottom the the secondary to get the proper coupling that I wanted, so that may have caused it to be a coincidence that the racing sparks occured between the two coils. Maybe if the primary was of a smaller diameter, (in which case it would have been positioned lower for the same coupling), then the racing sparks may have still occured at the same spot on the secondary, and would have been above the the primary. > > If the best tuning for a coil's streamer performance is a > few percent -ve, and the primary is wound in such a way that > in -ve tuning the primary volts is the opposite sign to the > secondary volts, then whenever the unfortunate coiler > approaches a good tuning, the racing arcs start to break out. > Lowering the primary sharply reduces the radial field and we > wrongly blame overcoupling? I guess that's a possibility. > > Other coils, identical but for an opposite primary sense, > would be free of racing arcs. Is the cure simply to flip > the primary? It would be great if that is the solution :) That'll take a bit of careful thought over the > > relative signs, phases, etc, hmmm... > > > I should mention too that the various cases I saw in my > > coils where the notches didn't look well defined were all > > cases where the coils were actually tuned reasonably well. > > That makes sense if by 'tuned reasonably well' you mean > that Fpri was close to Fsec. Because then the secondary would > be detuned by the streamers and the primary would be unable > to transfer all its energy. > > But then I've a nasty feeling that you meant the coil was > tuned reasonably well for streamers, in which case that's > hard to understand. Your nasty feeling is correct. My observations may have been incorrect. The problem is that back when I did those tests, I knew less than now. The problem of blurry scope traces, and interference from the primary waveforms, may have bamboozed my results. I find myself constantly going back and re-doing old tests, to root out possible error. Cheers, John > -- > Paul Nicholson, > -- > --part1_2f.277d96a7.2a17e06a_boundary Content-Type: text/html; charset="US-ASCII" Content-Transfer-Encoding: 7bit In a message dated 5/18/02 10:25:10 AM Eastern Daylight Time, paul@abelian.demon.co.uk writes:
Bart, John,
Intriguing that you can turn the racing arcs on/off by quite modest
adjustments to topload height, primary coupling, and tuning. And
your coils each demonstrate a different type of racing arcs -
the full length from Bart's, and the ones that gather round the
top and bottom of the coil from John's.
Paul, Bart, all,
There were two or three times that I saw the full length types
of racing sparks on my coils. One time I had coupled up
extra tight using a so-called fast quenching series rotary gap.
It didn't really quench much faster, but it also didn't permit
me to couple any closer at all. In another case, I built a
very short secondary which was only 9" long. I wanted to
see how long of a spark I could obtain at 120 bps from the
coil. I had to load up a bunch of stacked toroids on top,
and eventually got 26" sparks I think, but the secondary
was plagued by full length (and shorter) racing sparks.
I'd say the coil was overpowered. I forget what the coupling
value was. In some cases of the full length racing sparks,
they seemed to be triggered by roughness, or small ROC
on the lowest smallest toroid which was directly above the
secondary winding. Bart, do you have any sort of corona
ring type object directly above the secondary winding which
could be promoting the full length racing sparks?
I may be interesting if Bart detunes his primary to a higher
frequency to see if he gets the racing sparks only at the
bottom and/or top. I don't think he did that test?
I think we can get this by calculating the Cexternal for the
secondary with the primary in/not in place, and taking the
difference to get the pri-sec cap per unit area, and thus the
extra charge per unit area, and from that to the surface field
radial to the coil. Hmm, some stuff to think about there.
The 'hottest' spot may not be directly between the primary
and secondary, but may be a little way above.
Sounds like a good idea to me. In the close-coupled test
I mentioned above, I used a cylinder primary instead of a
flat primary. I think the racing sparks tended to occur directly
between the primary and secondary in that case. But it so
happens that the primary diameter was such that the primary
had to be an inch or so above the bottom the the secondary to
get the proper coupling that I wanted, so that may have caused
it to be a coincidence that the racing sparks occured between
the two coils. Maybe if the primary was of a smaller diameter,
(in which case it would have been positioned lower for the same
coupling), then the racing sparks may have still occured at the
same spot on the secondary, and would have been above the
the primary.
If the best tuning for a coil's streamer performance is a
few percent -ve, and the primary is wound in such a way that
in -ve tuning the primary volts is the opposite sign to the
secondary volts, then whenever the unfortunate coiler
approaches a good tuning, the racing arcs start to break out.
Lowering the primary sharply reduces the radial field and we
wrongly blame overcoupling?
I guess that's a possibility.
Other coils, identical but for an opposite primary sense,
would be free of racing arcs. Is the cure simply to flip
the primary?
It would be great if that is the solution :)
That'll take a bit of careful thought over the
relative signs, phases, etc, hmmm...
> I should mention too that the various cases I saw in my
> coils where the notches didn't look well defined were all
> cases where the coils were actually tuned reasonably well.
That makes sense if by 'tuned reasonably well' you mean
that Fpri was close to Fsec. Because then the secondary would
be detuned by the streamers and the primary would be unable
to transfer all its energy.
But then I've a nasty feeling that you meant the coil was
tuned reasonably well for streamers, in which case that's
hard to understand.
Your nasty feeling is correct. My observations may have been
incorrect. The problem is that back when I did those tests,
I knew less than now. The problem of blurry scope traces,
and interference from the primary waveforms, may have
bamboozed my results. I find myself constantly going back
and re-doing old tests, to root out possible error.
Cheers,
John
--
Paul Nicholson,
--
--part1_2f.277d96a7.2a17e06a_boundary--
Maintainer Paul Nicholson, paul@abelian.demon.co.uk.