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Voltage/Length (fwd)
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From: Greg Leyh [SMTP:lod-at-pacbell-dot-net]
Sent: Tuesday, February 03, 1998 8:10 AM
To: Tesla List
Subject: Re: Voltage/Length (fwd)
D.C. Cox wrote:
> One could strike an arc with a super powerful welder or a 10 kV arc at
> perhaps 1000 amperes and surely draw an arc 9-10 feet long so there are
> many parameters. We used three different "standard" Tesla coil to take our
> measurements and used a measured calibrated x-radiation system to determine
> the potential. The coil, when operated in free air, and running at the
> power levels I specified produced a striking arc at 9 ft in length. In the
> pulsed mode it generated 1 MEV x-rays. Measurements were taken at various
> potentials and spark lengths with 3 different systems and the 500 kV and
> 1000 kV free air sparks measured 5 ft and 9 ft respectively in continuous
> 400 pps mode. Primary cap value on the 9 ft spark primary was .05 MFD and
> .03 MFD on the 500 kV system.
I appreciate the efforts that you and your friend at the
Univ. of Wis. plasma physics dept went through to develop
and calibrate the 1MeV x-ray detector -- a very novel way
of measuring HV! It is a bit of a mystery, however, as to
how the coil could have generated 1MV in the first place.
Assuming 100pF for the total secondary output capacitance
and given 0.05uF for the primary capacitance, the transfer
ratio (at 100% efficiency) is 22.4, requiring a primary
voltage of 45,000V. If the coil efficiency is only 75%,
then the required minimum primary voltage to get 1MV out is
well over 50,000V!
Clearly I am missing something somewhere, or perhaps my
assumption of the secondary C is way off. I had estimated
about 50pF for a single 3ft toroid, and 40 to 90pF of
coil self-capacitance. Does this seem right?
-GL