[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: Power factor correction
Original poster: "David Rieben" <drieben@xxxxxxxxxxxxxxx>
Aaron,
I hope the moderator will allow a little bit of latitude here since
we are talking about Jacob's ladders but this post will also ad-
dress Tesla coils and many coilers build JLs as well during the
"learning curve" toward building a coil. That flickr.com JL photo is from
Clint Dickey, who was a list member at one time, but not sure he
still subscribes. He resides about 55 miles from me here in the
Memphis area and I helped him put a lot of his stuff together. I
assume his "15 kVA" nomenclature is referring to the rating of that
pole pig, which it was, and not to what he was actually pul-
ling from the wall socket.
BTW, I've never experienced any of the "voltage spike" problems
caused by the arc "snapping" at the bottom of the rails when it
starts its "climb" that you mention, although I'm sure that under the
right or wrong circumstances, actually, this could be a problem.
I wouldn't agree that it could be more of a problem than
with a large Tesla coil that draws similar power levels, though. I've done
quite a bit of damage to other sensitive electrical components in
my house in the past from firing a large Tesla coil but have never
damaged anything from firing a JL, even a very large and powerful
one. Maybe the control panel ballasting that I use to control the
input to my 125 kVp, 500 mA x-ray transformer helps to suppress
any of the transient nasties that could try to feed back into the house
wiring by the snap of the arc starting? However, the ballasting didn't stop
damaging kickbacks from the large coil when I did something wrong,
as I use the same ballasting control panel for my large Tesla coil that
I use for the x-ray transformer powered JL.
David Rieben
----- Original Message ----- From: "Tesla list" <tesla@xxxxxxxxxx>
To: <tesla@xxxxxxxxxx>
Sent: Friday, June 23, 2006 1:35 PM
Subject: RE: Power factor correction
Original poster: "J. Aaron Holmes" <jaholmes@xxxxxxxxxxxxxxxxxx>
(gettin' a bit OT here, but...)
Jacob's ladders are mostly about current, not voltage.
You need current to generate plasma/heat, and heat to
make the plasma/arc rise. More current will permit
the arc to "stretch" longer. If you have mega-high
voltage but virtually no current, then the legs of
your Jacob's ladder will be far apart and nearly
parallel, since there will be little "stretching"
involved, and this in turn will probably yield
inconsistent performance (arc frequently giving up and
restarting at the bottom before it reaches the top,
etc.)
NSTs make ok Jacob's ladders. A 15/30 can produce an
arc that self-starts at under an inch but may stretch
to a couple of inches before breaking and restarting
at the bottom of the ladder. Fun, easy to build, and
(relatively) safe. Still, the lack of current in the
NST case can make ladder peformance inconsistent, and
placing the ladder in some kind of enclosure may be
necessary to allow convection (and thereby the arc) to
be more consistent.
A typical 14.4kV pig is about like a 15/30 for
voltage, but can deliver several amps! This has an
enormous influence on ladder performance; the arc can
easily be made to stretch to a foot or more! Here's a
picture of what that might look like (from some
Googling--not sure whose this is, really):
http://www.flickr.com/photos/tesla1000/page3/
The picture has "15kVA" above it, and "14,400 volts, 2
amps" below it, which doesn't quite add up!! The
latter would be about 30kVA, not 15kVA, but
whatever... Note, too, that the arc is a totally
opaque white flame. There is a big difference between
a Jacob's ladder running ~15kV at 30ma and 2A!!!
BUT (!!!): Beware the Voltage Spikes of Doom! Running
big Jacob's ladders is a good way to kill stuff in
your house just as surely as a lot of RF from a TC,
maybe worse! Put some caps across the LV side of the
tranny to eat these up or you could really have a mess
on your hands.
Regards,
Aaron, N7OE