Hi David,
About the time this mishap came about, esteemed and much appreciated Terry
gave me and arrester that looks great.
I am not sure what advantage can be had by these other than their high
speed. ( and they look very menacing :-^) I would think a horn topped pig
would survive just as well as they do on the pole tops with proven miles
of
conductors picking up electrical disturbance like a lightning strikes.
Most
of this part of California is 3 P Delta. No ground on the I believe 16KV 3
wire. We don't have a lot of lightning but do from time to time. There are
delta shaped triangles on many of our poles (point up). I thought, "hey
safety spark gaps"! Not so said a New Mexico line man (wye I believe),
"they
protect the critters". This I found not at all believable, since a squirle
actively connected to two phases is going to be very much carbon or maybe
just some calcium.
Horn gaps look way cool too and evidently are used here too. I have a
tendency to look up along the road more than I should :-^)
Jim Mora
Anyone who knows about these: I'll called delta gaps, may want to comment
as
they would work too I would think.
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of David Rieben
Sent: Tuesday, August 26, 2008 11:12 AM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Terry Filter Caps
Hi Phil,
My big coil once used an 18 kV rated distriubution arrester
acorss the 14.4 kV pole transformer for the "safety gap". Upon
firing the coil on a windy day a few years ago, some of the stream-
ers were "blown back" into the lower end of the secondary
coil and the primary circuit. This resulted in the arrester failing
as a dead short. I eventually replaced the defunct 18 kV
arrester with a 36 kV rated arrester. This one is nearly 30" long
but I have had not more problems like this since. Of course I
also now tend to avoid runs when the weather conditions are
marginal. It goes without saying that all runs with the Green
Monster, which throws 12 to 15 ft. sparks, are done out-
doors, since my "shop" is nothing more than a double car
garage with 8 ft. overhead ceilings!
David
----- Original Message -----
From: <FIFTYGUY@xxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Monday, August 25, 2008 8:40 PM
Subject: Re: [TCML] Terry Filter Caps
In a message dated 8/24/08 11:39:19 P.M. Eastern Daylight Time,
bartb@xxxxxxxxxxxxxxxx writes:
Hi Adam,
Where was "Adam" in this part of the discussion?
Did I get this right? Are you running a Terry Filter with a pig?
Just curious about that. I personally don't use such a filter with a pig
transformer. Only for NST's. Not that it hurts, but I'm not sure it's
necessary. NST's are voltage fragile. Transients are part of that. The
filter helps some in that department.
Bart, I just sent this post out:
_http://www.pupman.com/listarchives/2008/Aug/msg00413.html_
(http://www.pupman.com/listarchives/2008/Aug/msg00413.html)
I was surprised nobody commented at the time... but it's in the
archives, so I know ya'll got it!
Regardless, in this discussion, people should remember the MOV's across
each cap/resistor circuit within the Terry filter. As long as the cap is
of adequate voltage and the MOV's are designed for the "transformer",
then there is plenty of protection across each individual RC section
(beyond the cap or resistor ratings). But with a good design, those are
last resort.
Yeah, and the MOV's are slow to respond to transients at 1 MHz. But
they
certainly are nice to have!
Some distribution arrestors use "combined technology" with a spark
gap
in series with the MOV element, just to complicate things. I think the
big one
I've got sitting around is like that, since the last time I tried it
across
my pig on an untuned coil, hot metal sparks actually shot out of it and
rolled on the ground.... The two arrestors on my pig have done just fine
at
15+kVA, even when the safety gap has been firing. I feel I've got that
safety gap
set pretty tight, but my arrestors are as tight on the MCOV specs as I
dare go
(even tighter than the specs for the "usual NST" Terry Filter).
-Phil LaBudde
Center for the Advanced Study of Ballistic Improbabilities
**************It's only a deal if it's where you want to go. Find your
travel
deal here.
(http://information.travel.aol.com/deals?ncid=aoltrv00050000000047)
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