used in the early 1960s. It consisted of a wide strip of acrylic sheet,
0.250" thick, and, then on each side I affixed a wide flat copper
ribbon,
thus forming a capacitive "transmission line" allowing me to transfer
power
to the coil base. It had an extremely low inductance (less than 2 uH)
at
distances up to 30 feet. Over a 10 ft. distance the inductance would be
very low. One drawback was an occassional flashover from sec HV
terminal
to
the transmission line. We were using very robust capacitors in our
oscillator so no damage was ever sustained by the transmission line
strikes. My acrylic was 8 inches wide and each copper strip was 5
inches
wide to allow a very long creepage distance. All sharp edges on the
copper
strip were deburred and the edges coated with G.E. Red Glyptal.
This was later abandoned when "common sense" dictated I place all the
components directly under the coil. I began using this design around
1971
and have used it ever since. It ended the flashover problems except to
the
HV feed lines. Metal raingutter( lay out inverted) is cheap and
prevents
this problem in large coils.
Dr. Resonance
2009/8/2 Peter Terren <pterren@xxxxxxxxxxxx>
Thanks for all the suggestions. I did switch to a coax setup for primary
lead wires with heavy wire inside about 50cm copper pipe to each
primary
and
I think that it improved output over the parallel conductors.
Interesting about the coupling because using a single secondary, I
could
induce racing arcs before if I tried to max coupling.. Not as twins,
however, although the 6-7 turns required probably puts the coupling
range
back to "normal". I also have plastic wrap on the coils as well.
My application does not permit separate electronics at present and the
leads need to be almost 80 cm.
I am aware of the V-twin at Palais. I already had the boards and
components for a standard SISG though but a triggered SISG sounds
attractive, particularly if I could use some of my IGBT bricks. The low
turns and high current would require the electronics to be separate and
local which is not suitable here.
So at present I have 80cm sparks between 50cm secondaries. Certainly
nothing to write home about but is probably adequate. I am awaiting
better
SIDACs as half were 200V rated and plastic packed so starts firing at
about
180V on the variac (out of expected 250V) Had to source them from
China
as
the usual suppliers were out of them. Hopefully that will take sparks
up
to
100cm.
I did flame a MOT today with this arrangement so some voltages are
appearing when they shouldn't. Plenty more where that one came from.
Peter www.tesladownunder.com