High Voltage Direct Current Generators Research Articles

Optimization of a Triggered Vacuum Switch With Multirod Electrodes System

The breakdown and triggering characteristics of triggered vacuum switch (TVS) are very important features, and they affect the operation reliability of TVS. Both of them mainly depend on the electrode material, electrode shape, gap distance, and surface condition. For an optimized electrode's geometry, finite-element method electrostatic field simulations were conducted to evaluate the effect of geometric parameters on the electrostatic field strength and distribution. The distribution of electrostatic field of the TVS with multirod system (MTVS) is calculated by the finite method. The simulation results show that the geometric enhancement factor (GEF) is decreased with the increase of the fillet radius of the edge of the rod. In case of the fillet radius for the side face of rod 3 mm and the fillet radius of the top face of the rod is 5 mm, the GEF is decrease to a minimum value of 3. The breakdown voltage of MTVS was measured by the high-voltage direct current generator after switch currents with amplitude of 63 kA and width of 13 ms with the interval time of 10–15 min. The influences of electrode materials and operation times on the breakdown voltage and trigger characteristics are also studied. The experimental results show that the breakdown voltage of the optimized MTVS is higher than that of the non-optimized MTVS. The breakdown voltage of CuCr30 is higher than that of oxygen-free copper. In addition to, the trigger characteristics of MTVS are influenced mainly by the electrode materials, the fillet radius of electrode has a little effect on the triggering characteristics of MTVS.

FLAT-FILM PROCESSING IN ELECTROSTATIC FIELD

A high density polyethylene was subjected to the flat-film casting through a 20cm coathanger die coupled to a 25mm single screw extruder. A specially designed electrode, consisting of 26 needles vertically aligned on a surface of a thin aluminum strip at intervals of 2mm, was placed several centimeters apart under the coathanger die and connected to a high voltage direct current generator, while the chill-roller of the film processor being grounded so as to act as the counterelectrode. The molten running film emerged through the die at the linear velocity of 0.75m/min. was drawn down in the electrostatic field generated between these electrodes and immediately frozen on the chill-roller rotating at the surface velocity of 15m/min. The variation of the film width was measured as a function of the applied voltage and the film-to-electrode distance. When the applied voltage exceeded 4kV, the running film began to spread in width and to retract in thickness. The width increased drastically at the voltages ranging from 6kV to 18kV. Above 20kV it gradually levelled off to the value 1.4 times as wide as that at 0kV. On the other hand, the film width was almost independent of the film-to-electrode distance. The mechanism for spreading width was considered as follows: The corona shower from the electrode put the sufficient quantity of the electric charge on one side of the film surface and subsequently induced the corresponding charge of opposite sign on the surface of the chill-roller contacting to the other side of the film. The coulombic attractive force between these positive and negative charges might press the film in the direction of the film thickness and it consequently resulted in the spreading of the film in both longitudinal and transverse directions. The longitudinal contribution, however, probably reduced the draw-down tension because of the large draw-down ratio, whereas the transverse one might make the neck-down smaller. Finally it must be noted that the film thus prepared was very transparent and had a very clear surface.

A 300 KV Direct Current Generator using Continuously Evacuated Rectifiers

With the advent of the continuously evacuated X-ray tube, the question of the development of high voltage direct current generators reappears, since, in general, the anticathode of such an X-ray tube will be at earth potential, and the generator will therefore be required to develop the full voltage to ground. Alternating current generators for voltages in excess of one million volts are fairly common, and in high voltage testing and research laboratories these transformers generally have one pole of the secondary winding grounded, so that the full A. C. voltage to ground appears at the other end of the winding. Likewise, impulse voltage generators have been constructed for five million volts with one pole grounded, so that there is a large amount of data now available on the behavious of dielectrics under these very high voltages. Direct current generators, however, have most frequently been designed to operate with both poles insulated from ground, i.e. with the centre point grounded, so that the proble...

A High Voltage Direct Current Generator

When powdered materials are blown through metal tubes by means of compressed air considerable quantities of electricity are produced by contact electrification. It was found that 6\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ coulombs could be produced per gram of diatomaceous earth, a form of silica, blown through a short length of copper tube. A generator of extremely high voltage is proposed, and a small scale model of such a generator is described, by means of which currents of 8\ifmmode\times\else\texttimes\fi{}${10}^{\ensuremath{-}5}$ amperes at 260 kilovolts were generated.

A High Voltage Direct Current Generator

This high-voltage direct-current generator supplied with alternating current utilizes a so-called ''''Villard''s chain'''' i.e. a voltage-adding and current-rectifying chain of capacitors and diodes. The capacitor plates are disposed in two parallel spaced rows and the capacitor plates of any pair of successive adjacent capacitors in each line of capacitors are closely adjacent, the diodes being housed in the gap left between the two rows of capacitor plates, the diode and capacitor assembly being embedded in a mass of dielectric material in order to constitute a compact, three-terminal block. Thus, a high-power generator can be constructed will very reduced overall dimensions and weight.

On the Use of Constant Potential Generators for Charging Radio Telegraphic Condensers and the New Radio Telegraphic Installations of the Postal and Telegraph Department of France

The charging of condensers by high voltage direct current generators is discussed theoretically and practically. The stationary and rotary gaps are compared as dischargers, and the evolution of the system used by the French Department of Posts and Telegraphs is given.