Re: whats the largest VTTC?

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "David Sharpe by way of Terry Fritz <teslalist-at-qwest-dot-net>" <sccr4us-at-erols-dot-com>

Hi Steven

Tesla list wrote:

 > Original poster: "Steven Ward by way of Terry Fritz 
<teslalist-at-qwest-dot-net>" <srward16-at-hotmail-dot-com>
 >
 > Hi,
 >
 > anyone know what the largest VTTC is out there?  I havent seen anything
 > larger than John Freau's 4x 833A setup that makes some 38" arcs.  If anyone
 > knows of anything larger, i would like to know about it, just curious.
 >
 > Steve Ward.

Robert Stephens out of Ontario built a very large VTTC using DC power supply
and 3 air cooled 5kW plate dissipation class tubes out of AM or MF short-wave
transmitters, if up to full capability would be able to deliver nearly 50kW 
(short duty)
to tank circuit.

Bill Wysock I believe posted a while back about tests performed in Hawaii 
using a LF
communication system for testing insulators (<50kHz), notable in that power
was very large VT transmitter in the 100-200kW input range feeding a helix 
/ resonator
through a matching line, length of arcs measured for breakdown alludes me 
but was
certainly in the feet.

Recently Ross Overstreet built a large VTTC using an induction heating VT
(3CX2500H3), tube is capable of up to 4kW short duty overload (2.5kW
continuous), and comfortably 10kW to tank, 20" of spark running arguably
1/10 of tubes capability.  Induction Heating VT's are ideal for VTTC service.
They are designed for severe overloads, ion back bombardment,
and overvoltage/overcurrent sins that would detonate or melt down glass tubes.

David Sloan in 1934 used two hand built triodes running push pull at 15kV
AC to deliver 100-200kW into a resonator for development 1MV for
generation of intense X-rays for early cancer treatment (predecessor to
modern linac radiation sources).  This work may be available on hotstreamer
or on the Web somewhere (Review of Scientific Instruments).

I've heard from several sources that an extremely large bipolar VTTC was
built capable of several 100kW input, may be Internet / Folk / Technology
Legend, never saw any pictures, experimental composition, creators or
other technical details.

Largest VTTC I've personally witnessed was John Freau's (HI!) triple and
quadruple 833 coil, fed by a 7.2kV PDT, capable of measured sparks in
the 38" range,  input power was in the 5-7kVA range.  Ed Wingate has
a similar VTTC using graphite 833C's, capable of nearly 30" discharges
at ~ 4 - 5kVA input.

Realize, just having the tubes is not enough, you have to in no particular
order:
    1. Cool them.
    2. Power them
    3. Find _very_ high voltage - high power capacitors capable of continuous
        RMS tank currents in the 10's or hundreds of RF amps
    4. Start worrying about primaries catching on fire from thermal rise from
        RF currents
    5. Watch for fires caused by collateral induction heating effects around
        energized primaries and secondaries.
    6. Prevent primary to secondary breakdowns due to HV used in tank

Building a really large VTTC would be a much more challenging exercise IMO
then building an equivalent power SG driven TC.

Regards
Dave Sharpe, TCBOR
Chesterfield, VA. USA