Voltage/Length (fwd)

From:  wysock-at-ttr-dot-com [SMTP:wysock-at-ttr-dot-com]
Sent:  Thursday, January 22, 1998 11:24 AM
To:  Tesla List
Subject:  Re: Voltage/Length (fwd)

Jim, all,

I have this book, and I'm sure many others do as well:
High Voltage Laboratory Technique, J.D. Craggs &
J.M. Meek, 1954, Butterworths Scientific Publications,
London, p.p. 104-110.  The schematic diagram on pg. 109
shows the configuration of their "so-called" 5 MV Tesla
coil.  A futher discription is given in one of the old issues
of (I may be wrong on this, but I do have the article in my
library....somewhere!) "Physics Review" 35, (1930) pp 51.
Page 109 in Craggs & Meek report that Bret, Tuve, and Dahl,
constructed their Tesla coil "with 5,000 or 7,000 turns on a
Pyrex tube about 1 m. in length"  Supposedly, the oil tank
in which this coil was placed was under a pressure of 
500 lbs./in. sq.  Their reported results are to say the least,
very vague, when it comes to the "voltage 'pick-up' ball."
Whereas their work as served the high voltage engineering
community well over the years, I believe their reported results
were flawed in a number of significant ways; not the least of
which is how to contain (in the real world,) 5 MV across a
coil form that is only 1 m. in length...even at 500 lbs. oil
pressure.  The wire gauge they must have used to obtain such a
high turns count over 1 m. of Pyrex tube length must have been
on the order of 36-40 A.W.G.  They further reported a resonance
of about 100 Khz, which causes one to believe that the wiring
of this secondary (even if it did actually produce a bi-polar
potential difference of 5 MV,) must have only produced an
R.F. current on the order of no more then several tens of
milliamps.  The 'pick-up' ball referred to, could only approximate
the potential difference to one side of this bi-polar secondary
coil.  One would have to "assume" that the coil was "balanced"
and that they were only meausreing 1/2 of the total E.M.F. rise
of the system.  Moreover, if one was to "borrow" on the concept
of voltage measurement in oil under pressure, then perhaps
this approach could be adopted to one of the modern-day 1/4 Lambda
resonators that are out there.  Of course, a whole new set of
"headache" problems would have to be resolved: distributed
capacitance effects of the oil and the tank in which the coil was
placed, etc.  Maybe food for thought, since if these factors were
accounted accurately for, then the issue of loading the output of
the secondary might be more effectively delt with. 

Bill Wysock
> To:            "'Tesla List'" <tesla-at-pupman-dot-com>
> Subject:       Voltage/Length (fwd)
> Date:          Thu, 22 Jan 1998 17:22:50 -0600
> From:          Tesla List <tesla-at-pupman-dot-com>

> ----------
> From:  Jim Lux [SMTP:jimlux-at-earthlink-dot-net]
> Sent:  Thursday, January 22, 1998 10:31 AM
> To:  Tesla List
> Subject:  Re: ReVoltage/Length (fwd)
> Didn't Tuve, et.al. do some measurements on a 5 MV tesla coil in a oil tank
> using a capacitive divider and a calibrated sphere gap back in the 30's or
> 40's, before electrostatic generators became popular for accelerators?
> >   It should be noted that connecting a voltage divider to the secondary
> > terminal will reduce the sec voltage compared to a no load voltage. In
> order
> > not to have a voltage reduction the voltage divider would have to have an
> > infinite impedance. The reduction of the voltage can not be found
> indirectly
> > because the reduction is non linear. The TC sec voltage can only be
> > estimated and certainly cannot be a "hard reference or claim".
> > 
> >   However, if a voltage divider is connected to the sec terminal, a
> voltage
> > can be obtained. My guess is that a coil with a 60 inch spark at no load
> > would give a voltage of about 300 KV with the proper divider. This could
> > vary considerably depending on the total impedance of the divider.   
> >   We will all be looking foward for your report of the results of your HV
> > capacitive divider column. 
Tesla Technology Research