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RE: [TCML] Primary Grounding was [Control Cabinet ...]
Hi Jim,
The blue and gray cable twisted together is a single x-ray
cable - the gray one - (with outer braid shield RF ground-
ed) and the low voltage supply cable for the ARSG motor
(14-3 AWG inside a blue flexible corregated plastic con-
duit). I was hoping that this conduit would help to repell
the strikes to the low voltage (120 VAC) line to the ARSG.
Obviously in that picture, I had changed over to a sinlge
HV transmission line with one side RF grounded and also
tied in to the center of the primary coil. It does make sense
to tie the inner primary and bottom secondary winding
to a common RF ground so that there is no potential
developed between the proximal areas of the primary
and secondary coils to cause possible primary/secondary
flashover problems. However, recent discussions have
me wondering if the RF grounding of the primary coil is
attracting excessive streamer hits to the primary coil
vicinity. Of course, as I was saying before, it would seem
that the RF grounded strike ring would also attract hits
toward the primary coil, regardless of whether the primary
coil was directly RF grounded or not.? Now that I think
about it, in the youtube video of my coil running, there
didn't appear to be many primary (or strike ring hits)
at all but I also don't think that my coil was running as
good at that time as it has in more recent runs. Note
that the output was not very "smooth" and there was
a single visible racing spark toward the end of the run. It
now runs much smoother with a more powerful output and
NO racing sparks. On the down side, there does seem
to be considerably more primary bound strikes than
there used to be (when it wasn't running as smoothly).
Incidently, most of the primary bound strikes are actu-
ally hitting the strike ring, not the primary coil itself, so
the strike ring is obviously doing what it was designed
to do - protect the primary coil from direct hits - for the
most part ;^)
In conclusion, I believe the big reason that I am seeing
more strikes toward the primary now is that I am really
pushing my coil toward its physical voltage standoff li-
mits with my power throughput. I can push over 15 kVA
into it and the secondary is only a 12.5" x 49" long. The
max output spark length is in the 15 ft. range, so that's
a spark length upwards of 3.5X the secondary coil length!
I noticed that Cameron Prince's coil, which has similar
performance to mine, is notably taller than mine. His se-
condary coil is also 12.5" in diameter, like mine, since we
both made our secondaries from the same 10 ft. piece of
PVC pipe that we split the cost on. However, Cameron uti-
lized the full 60" of his half of the piece to make his secon-
day coil (I believe his secondary total length is like 56").
Also, I believe his topload is a bit higher above his se-
condary coil than mine is. Cameron has about 2 more
feet of overhead clearnace under his garage door than I
do so he was able to make his taller. Both Cameron and
I have to "decapitate" our toploads to move our coils onto
our driveway to fire them off but I still have to be able to
get my "decpitated" coil under an 81" vertical clearance
to get it out the door ;^0 So I was forced to keep the vir-
tical height of my coil system short enough to store under
standard 8 ft. ceilings and to move out underneath an 81"
high garage door with the topload off. Anyway, it appears
that Cameron doesn't have as much trouble with primary
strikes as I do either.
Sorry for the lengthy post but others are strongly encou-
rafed to share their insight on this issue ;^)
David Rieben
----- Original Message -----
From: Jim Mora
To: 'Tesla Coil Mailing List'
Sent: Wed, 17 Dec 2008 23:27:20 +0000 (UTC)
Subject: RE: [TCML] Primary Grounding was [Control Cabinet ...]
Hi David,
I noticed the dual x-ray cable runs. Are they striped back on both ends? The
bad thing about that is the shield is floating...which makes an otherwise
very safe cable design dangerous. There was also a pic of a blue and a gray
cable twisted together. What's up with that? I may take DC's advise and put
the big PT in a separate cabinet and bring out dual cables. The isolated
primary seems like it may be the way to go assuming a large enough gap from
the primary to secondary windings. I wish there was some consensus here. The
pros seem to ground the inner turn of the primary.
Jim Mora
Did you have a safety gap across the Cap?
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of David%20Rieben
Sent: Wednesday, December 17, 2008 10:54 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Primary Grounding was [Control Cabinet ...]
Hi Phillip,
After reviewing my little youtube segment of my Green
Monster running, it appears me that you may indeed
be correct about the primary not drawing as many
strikes if it is not tied to RF ground:
http://www.youtube.com/watch?v=eWZD3M-nye8
At the time that I was running it here, I did have two se-
perate transmission lines running to the primary tank
circuit (you can see the 2 x-ray cables on the ground
in this video) and the primary was not tied to any
ground even though the RF grounded strike rail was
up at this time. If you review the video, you'll note that
there was only two noticable strike rail hits, so maybe
you're on to something here. I'll have to try running it
this way again and see if there is a notable decrease
in primary bound hits. I'm still not sure that the primary
strike that you saw just before the Hipo cap died was
the cause of the cap's death, though - maybe it was
just the "straw that broke the camel's back"!
BTW, I can still run my single eared pig in this fashion
as the tank sits on a dry plywood base inside the con-
trol panel and the pole mount brackets are fastened to
wooden 2x4's - the external tank of my pig has no con-
tact with any grounded metal.
David Rieben
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