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Re: [TCML] Hazards of Asynchronious arc gaps?
Hi Jim,
I run my Green Monster coil at similar "parameters" to your proposed
coil. My rotary gap is async and consist of a 2.5 HP DC treadmill mo-
tor that is fed with rectified variable voltage through a small variac and
a FWB rectifier block. The G-10 rotary disc is 11 1/2" x 1/2" thick with
(8) 1/2" x 1 3/4" long tungsten flying electrode slugs. The (4) tungsten
stationary electrodes are each 1/2" x 3" long and are each set in 1 1/4"
square
x 2 1/2" long brass blocks. Each of the 4 brass blocks are now also mounted
against a 4" x 4" piece of 1/4" thick aluminum flat bar for further heat
dissipa-
tion. I also recently ended up adding appropriately sized aluminum shaft
collars on the flying electrode slugs (one on each side of the rotary disc
for each flying electrode for a total of 16) because of trouble with the
flying electrodes getting hot enough to blister the G-10 rotary disc!
(discussed in the fairly recent "G-10 blistering" thread). ~ 20 kVA
firing twice on each flying electrode during each disc rotation obvious-
ly makes for pretty heavy thermal loading!
The secondary coil is wound on a 12" ID gray PVC duct pipe that is
about 54" long and is wound with 49.5" worth of close wound # 19
GREEN enameled magnet wire (hince the coil's name). The actual
outside diameter of the PVC form is 12.5". That windings count
comes out to approximately 1260 turns, IIRC.
The primary coil is the classic Archemedian spiral made of 1/2" ID
copper tubing (that's actually about 5/8" OD) and consist of 12 turns
with about 1/2" spacing. It's tapped around 10.5 turns and the outer-
most (12th) turn has about a 40" diameter.
The toroid is a "homemade" 12 x 56" "donut" fabricated from the
heavy duty 12" aluminum flex tubing from McMaster-Carr and tho-
roughly wrapped in heavy duty 3" aluminum duct tape for added rigidity.
The primary cap is a .1 uF, 50 kV rated Hipotronics pulse cap unit that I
got from Jeff Parisse (KVA Effects) becuase it was one of his spares. I
drive
this coil through a 14,400 volt, 10 kVA rated pig with a 4-stack 1256D
variac (that's a 112 amp rating!) and use the input winding of a huge
240 volt / 120-208-240 volt Toshiba isolation transformer seriesed with
the 240 volt input to the pig for ballasting. I also short several of its
paralleled 120 volt output taps. This allows me to drive the Green
Monster with up to ~90 amps at >240 volts input for very bright and
fat 12 to 15 ft. discharges!
As far as the ARSG's BPS rate, I find that my coil likes around 350
BPS (about 75 to 80 on the speed control variac dial), although the BPS
adjustment is nearly infinitely variable due to the variac speed control of
the permanent magnet DC treadmill motor.
Hope this info can help you out a bit.
David
----- Original Message -----
From: "Jim Mora" <wavetuner@xxxxxxxxx>
To: "'Tesla Coil Mailing List'" <tesla@xxxxxxxxxx>
Sent: Tuesday, August 12, 2008 9:17 PM
Subject: RE: [TCML] Hazards of Asynchronious arc gaps?
Hello friends,
It seems that I remember 400 BPS ASRG is a healthy break rate. I have a
nice
duty cycle speed controller. If I ever get my rotary gap back from my
machinist, the big coil will come to life. (we have been caught in the on
going physical geometry/heat of the gap dilemma). He is often doing
aerospace quality machining, a hell of a nice guy, and a lurker on our
list.
It is 18" g10 with 3/8 tungsten 2" long slugs. The "towers" x2 are holding
9/16 diameter heat sinked electrodes and can be series/parallel
SO, what is the optimum rotation speed? I bought all the copper before it
went ballistic in price (.5" x 100 feet primary). Of course this is
directly
proportional to the power and the caps. I have a 5kva 14,400V potential
transformer and (2) .1uf serious, new, general atomics capacitors.
Let's have some feedback from the people that have worked with these
parameters. The coil form is 5:1 1/8" pvc x12" but can easily scaled to
larger sonotube. I have lots of 16 and 18 awg high quality magnet wire.
This has been back burner as I have making my own bio-fuel for awhile with
a
drill press and 5 gallon stirrer. Off topic, but my 250 diesel loves it!
Please check in with your experience with these parameters!
Credit goes out to Salt Lake Jack for the GE PT which can be wired for
16KV@5KVA. I wish I could find another one!
Jim Mora
-----Original Message-----
From: tesla-bounces@xxxxxxxxxx [mailto:tesla-bounces@xxxxxxxxxx] On Behalf
Of bartb
Sent: Tuesday, August 12, 2008 6:51 PM
To: Tesla Coil Mailing List
Subject: Re: [TCML] Hazards of Asynchronious arc gaps?
Not only sync rotary's for NST's, but also ensure bps is at least 100.
Low bps can really cause some unexpected problems.
The em fields are intensified as are the nasty transients, so other
components around the house can be killed as well when running low bps
on a rotary or even async. I've mentioned this in the past. I killed an
xbox-360 and a sound card in the pc simply by slowing down the rotary
for only a moment (maybe 10 seconds). The firing during that time was
very erratic and I immediately increased speed (I just wanted to see how
the coil would react at low bps). It was later that I realized the
damage incurred. The damage and the out-of-the-ordinary low bps is no
coincidence.
By running async and/or low bps, all kinds of high voltage damage can
occur to your components. This is not like single shot mode where the
single shot is a one time event. Low bps is like many single shot
situations without voltage control. The voltages "will" climb to values
which the NST and cap may not handle. And as mentioned, other things in
the house can be affected as well.
It's really good learning experience however.
Bart
Harold Weiss wrote:
Hi Harvey,
With NST drive, you want to be running with a syncronous gap.
Otherwise you may kill the NST by overvolting when the gap fails to
fire on the peak, and the voltage rings up extremely high. That's
probably what's happening to the caps as well. I have seen it go 7X
on one coil, but generally, it's between 2-4X for most coils.
David Weiss
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