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RE: X-Ray HT power supply
To Gavin,
In 1962, I also received a similar type power supply, although it
was A.C. output only, rated at 85 KV peak -at- 55 ma. I built a
nichrome wire resistance as a series input current limiter (had to
be air blown with a fan for cooling,) and used a 240 volt 30 amp
circuit. The coil I built, was long before I became experienced
(or knowledgable) in Tesla Coil design and construction.
The high voltage output leads (two,) were shielded cables, and
I simply insulated the filament leads from each other, and tied
one lead to its respective high voltage conductor. The coil was
built on a 30" square base, and I used a total of 40 "Glassmike"
capacitors (these were cylindrical glass sleeved units with
8-32 threaded end cap terminals, and were red in color.) Each
cap was rated at 0.1 mfd -at- 8 KVDC. With one string arranged in
two rows of 10, all connected in series, gave 0.005 mfd -at- 160 KVDCV.
Two such banks of twenty were connected in parallel, giving
0.01 mfd -at- 160 KVDC. The primary coil was a helical form, made
from wooden dowels and hard masonite top and bottom plates.
The primary winding was made from 20 turns of # 10 AWG solid copper
wire, with tap positions every turn from # 10 to # 19. I believe I used
about 17 turns, for resonance. The secondary was made from a
schedule 40 gray PVC tube, with a 1/8" wall thickness, and was 6 " o.d.
by 50" tall. I had wound about 1,000 turns of #26 AWG magnet wire
on the form, and used a small 2" o.d. brass ball as the output terminal
on top of a 4 1/2" tall porcelain feed through insulator.
The spark gap (cringe) was a pair of 20 penny nails positioned between
two 5" tall stand off insulators, and were space 1.5" apart, between the
nail tips. I found that I had to use a squirrel cage type fan, to direct an
air blast across this gap, to aid quenching. Believe it or not, this crude
arrangement actually worked fairly well!
The input power was limited to about 20 amps at 240 volts, and the
X-ray control panel was set at the 65 KV tap position. The coil would
put out about 75 inch long arcs. It was this coil, that was shown on an
ABC-TV news program, in Los Angeles, circa 1965, and I think I still
have some black and white photos of this arrangement somewhere.
Since your power supply is of a much higher power capability, you
will certainly be able to use it for a larger size coil. I would suggest
that
if you can limit the output voltage, and still obtain the 500 ma. current
rating, you will have a power supply that can be adapted to many
different size Tesla Coils. A great find! Good luck and _be careful_!
Best Regards,
Bill Wysock
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Tesla Technology Research
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From: Tesla List
To: Tesla List
Subject: X-Ray HT power supply
Date: Wednesday, November 25, 1998 3:41AM
Original Poster: Gavin Hubbard <ghub005-at-xtra.co.nz>
Hello all.
This morning a local radiology technician (who knows of my HV interests)
'gifted' me a 150kV, 500mA (peak) x-ray HT power supply. The power supply
is operational and comes from a decommissioned installation. The output is
full wave rectified (approx 2-3% ripple at peak current) and the only fault
with the unit is that the tube filament heater output (6V above 150kV) is
not functional.
I would be interested if anyone on this list has designed or built a TC
which is powered by such an extremely high DC tank voltage. I have been
playing with the numbers today, and am aware that such a coil will require
a physically huge primary capacitor (approx 130 litres of oil dielectric)
and that the whole tank circuit and secondary would have to be run under
oil (except the spark gap of course). I would also be interested to know
what other inherent problems are to be expected with these designs.
Thanks in advance for your help,
Gavin Hubbard