Voltage/Length (fwd)

From:  John H. Couture [SMTP:couturejh-at-worldnet.att-dot-net]
Sent:  Saturday, January 24, 1998 11:34 AM
To:  Tesla List
Subject:  Re: Voltage/Length (fwd)

  Bill, All -

  The Tuve et al 5 million volt TC "pick up ball" method for measuring the
secondary voltage is unique in that it offers infinite impedance. This meant
no loading on the secondary circuit. Because the sec wiring was so small any
loading would have made it impossible to measure the sec voltage.

  Borrowing on this idea I made some tests on some of my coils a few years
ago. The setup is shown in the Tesla Coil Construction Guide. As there is no
loading on the sec circuit this is a good test for small coils. However, the
system requires calibration which I never got around to do. I used the test
only as a comparison of coil output when I made changes to the coil.

  John Couture


At 05:15 AM 1/23/98 +0000, you wrote:
>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?

>Tesla Technology Research