The Precise Measurement of Output Potentials in a Tesla Type Air Core Resonant Transformer System

(continued)

A small variac is attached to the primary side of the power transformer. The spark gap should be adjusted to a relatively close setting (1/8" or less). If a rotary gap is employed, it should not be rotating. Adjust the rotor so that the rotating electrodes are in their firing position at 1/8" spacing. The normal discharge electrode on top of the secondary coil of the Tesla coil is used, and a 4-8" diameter sphere is used for the grounded electrode.

The voltage is slowly raised with the variac until the secondary begins to discharge at a periodic rate. It is important that the grounded discharge ball be rigidly affixed in a suitable manner to insure accurate spark length measurements. These measurements can be checked against current published standards to determine the maximum output potential of your system to within 5% accuracy.

Due to the lack of long discharges which occur on 60 cycle operation, you will have to retune the primary coil slightly to achieve resonance. Pulsed D.C. operation usually takes 1/2-1 full turn less inductance than A.C. operation. This important fact can allow one to make initial adjustments on large resonance transformers without endangering capacitors by operating them in a non-resonant condition.

The exact measurement of the output potential of a resonance transformer system is only possible by two methods: (1) the acceleration of electrons within an evacuated tube, and then measuring the energy of these accelerated particles, and (2) the conversion of accelerated electrons into X-rays, and then precisely measuring the radiated energy. These two methods are accurate to within 100 electron volts because they do not load the resonant transformer, and hence, do not alter its operating resonant frequency point.

Warning!

Remember, unlike ac operation, this test procedure charges your capacitor bank with lethal 5 direct current, and must be discharged before making any adjustments on the oscillator. A small ground clip should be attached to allow convenient discharging of the capacitor bank before touching anything.

References

1. A Tesla Transformer High Voltage Generator; C.R.J. Hoffman; Atomic Energy Comm. of Canada Ltd. Chalk River, Ontario, Canada August 1974
2. Electrical Condensers: Their Construction, Design, and Industrial Uses; Phillip R. Coursey; Pitman & Sons, Ltd. 1927
3. Radiotron Designer's Handbook; F. Langford-Smith, Radio Corp. of America 1953
4. Ibid
5. Thomas Edison - take note!

Additional References

1. Dielectric Phenomena in High Voltage Engineering; F.W. Peek, Jr.; McGraw Hill Book Co., Inc. 1929
2. A Radiofrequency High Voltage Generator; David H. Sloan; Radiation Laboratory, Dept. of Physics, University of California, Physical Review Vol. 41, Jan. 1, 1935
3. Industrial High Frequency Electric Power; E. May; Chapman & Hall Ltd. 1949
4. Elements of Physics; G. Shortley & D. Williams; 5th Ed. 1 Prentice Hall, 1971 Chapter 33, pp 686-689