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Coronatron update
All,
I have mentioned previously that I am building a 15 kilowatt, vacuum
tube Tesla coil as a prototype part of some development work for a
commercial client. As part of the arrangement I retain possession and ownership
of this nifty toy.
The good news is the unit is now completed, minus only
the secondary resonator, and has undergone successful preliminary
testing into a lamp load!!!! : ) On first power-up I promptly let the smoke
out of the actuator coil on the plate transformer contactor, and
after an hour of testing one of the cooling blowers failed, both
victims of years of damp cold storage, but these defective used parts
are now replaced with good working extra spare used parts. Nothing
serious. Heck, even all of the 6 panel meters moved the correct
direction the first time!
The RF section contains three, forced air cooled BR1160 transmitting triodes
with a plate dissipation of 5 kW each. Provision is made to connect an outboard
plate transformer to buzz this unit up to full power, which is expected to yield
15 kW RMS RF output (for short runs to maybe 30 seconds as the cooling
blowers capacity are the limiting factor) with a DC input to the plates of some
22 kilowatts.
The unit has an internal, on-board 4.4 kVa plate transformer. Tests
using this transformer have achieved a power input to the plates of
6240 watts (3900 VDC-at-1.6 Amps). At this power level the oscillator
idles smoothly, happily driving a lamp load consisting of five, 1000 watt, 230
volt incandescent lamps connected in parallel and coupled to the
oscillator tank with a two turn pickup coil, to nearly full brilliance.
The plate tank consists of 31 turns of RG-214 coaxial cable with the
insulation left on, wound to a length of 16 inches and a diameter of
22 inches with a 1/8th inch air space between turns. Only the outer, double
layered, silvered copper braid is employed electrically. A number of taps are
provided which allow some tuning flexibility. Operation is possible between
75 kHz and 100 kHz with tap changes. The tank resonates with a pair
of 0.0039 mfd -at- 20 kVDC , type G3 micas in parallel. A small
'cheese slicer' type variable aluminum finned tuning capacitor is
also included to raise the knob count on the control panel. The
oscillator is a self-excited, tuned-plate, untuned grid configuration. The grid coil
resides immediately below the plate tank and consists of 25 turns of #10 AWG,
PVC insulated, stranded copper wire. This grid 'tickler' coil is
wound to the same diameter and center-to-center spacing as the plate
coil. The form is a phenolic tube 20 inches O.D and 41.5 inches long
which was obtained surplus and is provided with eight, micalex
(sindanyo) standoff formers with molded depressions for the wire to
seat into, equally spaced around its circumference. Nice piece!
It's a darned shame that the 3/8 inch O.D. litz wire originally on it had been
damaged beyond use by some genius with big wire cutters. : (
This unit will now be moved to my new Shelburne facility which I have
just acquired and am now in the process of moving into. At the new lab
a high voltage secondary resonator will be fabricated and dropped into the tank
coil and final development work and testing done.
This unit is proposed to function as the BBQ for my upcoming
Teslathon and St. Elmo Dog weeinie roast. I can smell those dogs
already! : )
rwstephens