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Re: [TCML] tcml primary self c

David, all,
Another small factor to take into account is the primary may ionize the air around it if there is no air flow though the primary coil. After a while the breakdown voltage of the air around the primary will become less, then this will promote break out from the sharp edges of the primary. I also think that low resistance of the primary will prevent losses into air. Maybe not a good analogy, but pass a 400PSI water pump down a 6mm pipe and then drill holes in the pipe.. water escapes, progress to 100mm pipe, water will flow in the pipe regardless of holes (but will still leek just not be under pressure). Corona will lower the resistance of the air helping break out from the sharp edges.
The solution to me, use a good 2" wide strip for less resistance, space the turns like 1inch apart, vent the primary with some airflow.. I do not see much of a problem with that...
I suppose you could argue eddy currents, though with this being a damped wave rather than a constant AC source, I am not sure even if eddy currents are even an issue. Even if the strap has more eddy current, then the surface area is a lot larger lowing AC resistance, so overall maybe it would just balance out anyway ?
From what I have read so far, nobody seems to have a problem with strap vs.
tube other than the corona issues ? maybe 6mm pipe vs. 0.5inch strap , maybe the pipe would work better, but a 2inch wide strap maybe will work better than 6mm pipe.. Skin depth for the strap isn't going to leave much room for eddy currents anyway. If we were talking about a solid metal pipe then maybe things would be different there.. but not for copper strap which isn't thick enough anyway. I think the lower resistance and larger surface area should work out much better than pipe as long as you don't have corona issues.... 

Chris
----- Original Message ----- From: "David Rieben" <drieben@xxxxxxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Tuesday, July 29, 2008 3:48 PM
Subject: Re: [TCML] tcml primary self c



Hi all,


Since I have not built a fully successful coil with a ribbon primary
coil, I'm probably jumping in out of line line here, but it seems to
me that a multiple turn ribbon primary coil wouldn't have as much
of a corona issue as would a SINGLE sharp ribbon edge, as the
neighboring ribbon windings should sort of electrostatically shield
each other, shouldn't they? Just like a rough surfaced large toroid
can still hold off breakput until some decent high potentials are
reached because of this effect.

I know for a fact that Cameron Prince runs his big coil with
a ribbon primary and he has had no issues, that I know of, with
excessive primary/ secondary corona. The only issue he had
with this original primary coil is that the ribbon would get really
hot during operation. This was due to the fact that it was that
bronze weather stripping. It was not very robust for pig power,
plus bronze is relatively poor conductor compared to pure cop-
per. Once he changed over to 3" wide pure copper ribbon, the
output improved and the new primary stayed much cooler during
operation.

David Rieben
----- Original Message ----- From: "DC Cox" <resonance@xxxxxxxxxxxx> 
To: "Tesla Coil Mailing List" <tesla@xxxxxxxxxx>
Sent: Monday, July 28, 2008 8:44 PM
Subject: Re: [TCML] tcml primary self c



No myth here --- I am sticking to the facts. Physics is physics and it
doesn't change.
If you look at some photos of Wysock's earlier coils using copper ribbon you 
see a generous amount of corona off the sharp edges.

I also experienced this in photos I shot.
My advise is: if you are running a coil with ribbon shoot your own photos 
and check for corona.  Make your own determination.  But, if you are
designing from scratch, why not use good engineering practice in the first 
place?
Anytime you run a coil at 200-400 kV (or more) and put a sharp edge near the 
secondary (12-24" away), it will definitely produce corona.  Just do the
physics or look at some electrostatic plots of ribbon coils and you will see 
what I mean.
I urge future coil builders to use copper tubing --- it's rounded edges help 
retard corona.  A better solution than burying your head in the sand and
pretend the corona doesn't exist.

Dr. Resonance

On Mon, Jul 28, 2008 at 6:39 PM, <dr.hankenstein@xxxxxxxxxxxxx> wrote:
I agree with Finn. Here is a long time exposure taken at 1600ASA of a small 
coil with a flat ribbon primary:
http://www.audiotesla.org/images/Corona%20Experiment/DSC_0155.JPG I don't 
see any evidence of the ribbon causing corona worth worrying about. I am
using "high voltage buss" on my larger coil. The difference between high
voltage buss and low voltage buss is that the corners are rounded on the HV 
buss to help reduce the effects of corona when the buss is in close
proximity of each other. Over 69kv the buss is usually round and the edges 
are all smoothed down.

Woo


> [Original Message]
> From: Finn Hammer <f-h@xxxx>
> To: Tesla Coil Mailing List <tesla@xxxxxxxxxx>
> Date: 7/28/2008 5:23:25 AM
> Subject: Re: [TCML] tcml primary self c
>
> DC Cox skrev:
> > After I saw all the corona in B&W asa 400 photos I shot with 4-8 sec
> > exposure time,
> Even posting this picture would not add much credit to your point of
> view. Pictures taken with the same film, and exposure times, of > similar 
> sized tubular coils excited by the same primary bang energy would have
> to be produced.
> Then a long term study of the effects on the secondary (Which I have
> already done) would also have to be produced
> >  I realized the sec coil would be slowly degraded using sharp
> > edged copper ribbon and quit this procedure.
> >
> Oh, so you _assumed_, in the stead of actually _observed_, that a
> degradation would take place.
>
> A lot of newbies are listening. Let`s stick to facts instead of adding
> to the list of coiling myths, shall we? Doc?
>
> Cheers, Finn Hammer
>
>
> _______________________________________________
> Tesla mailing list
> Tesla@xxxxxxxxxxxxxx
> http://www.pupman.com/mailman/listinfo/tesla
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