US3558908A - High-voltage impulse generator - Google Patents

Abstract

A liquid dielectric capacitor comprises three metal cylinders coaxially nested within one another so that the bottoms of the outer and inner cylinders are connected to each other while the middle cylinder has its bottom facing in the opposite direction and is mounted on the outer cylinder by means of an insulator. The firing electrode of a three-electrode controlled spark gap is immersed in the liquid filling the space between the bottom of the middle cylinder and the ends of the inner cylinder, the two cylinders serving as the working electrodes of the spark gap.

Description

United'States Patent 2 llll 3,558,908

Inventors Boris lvanovich Kulikov;

Viktor Mikhailovich Lagunov; Yury El'removich Nesterikhin; Vladimir Mikhailovich Fedorov, Novosibirsk, U.S.S.R.

Sept. 3, 1968 Jan. 26, 197 1 Institut Yadernoi Fiziki So AnSSSR Novofibirsk, U.S.S.R.

Appl. No Filed Patented Assignee HIGH-VOLTAGE IMPULSE GENERATOR 4Chims,lDnwingFig.

u.s.c|. 307/109, 317/242 1111.- c1 ..1102m 3/06, H01f3/04 FieldofSeareh 320/1;

307/lO6l09; 333/12, 73C, 96, 13; 317/242, 258, 244; 174/28; 315/39 [56] References Cited UNITED STATES PATENTS 71 1,130 10/1902 Shoemaker 317/242 1,610,980 12/ 1926 Silberman 317/242 2,3 39,663 1/1944 Teare 317/244X 2,41 1,140 11/1946 Lindenblad 307/ 1 06X 2,947,926 8/1960 Murch 317/25 8' Primary Examiner-Terrell W. Fears Attorney-Waters, Roditi, Schwartz, & Nissen ABSTRACT: A liquid dielectric capacitor comprises threemetal cylinders ooa cially nested within one another so that the bottoms of the outer and inner cylinders are connected to each other while the middle cylinder has its bottom facing in the opposite direction and is mounted on the outer cylinder by means of an insulator. The firing electrode of a three-electrode controlled spark gap is immersed in the liquid filling the space between the bottom of the middle cylinder and the ends of the inner cylinder, the two cylinders serving as the working electrodes of the spark gap.

HIGH-VOLTAGE IMPULSE GENERATOR The present invention relates to high-voltage impulse generators and is intended for experimental research involving the use of very strong voltage and/or current pulses, such as in thermonuclear studies for heating plasma, in laser applications for optical pumping, etc.

There exist impulse generators which comprise a bank of paper oil capacitors and controlled spark gaps. The paper oil dielectric has a low specific capacitance, because of which the internal inductance of the generator increases out of proportion as the rate of rise and amplitude of the current impulse are increased. I

There also exist impulse generators using a capacitor with water as the dielectric which has a higher specific capacitance.

Such generators comprise a closed rectangular box which holds a flat plate insulated from the walls and serving as the potential plate of a plane-parallel capacitor.

Switching is accomplished by a two-electrode uncontrolled spark gap placed in water and destroyed after each use.

, Among the disadvantages of such a design are the impossibility of parallel operation of a great number of impulse generators, the generator is of a single-shot" type, and the load current cannot attain a maximum rate of rise.

An object of the present invention is to eliminate the above disadvantages and also to enhance the reliability of a highvoltage impulse generator.

This and other objects are accomplished by a high-voltage impulse generator comprising a liquid dielectric capacitor and a spark gap in which, according to the invention, the liquid dielectric capacitor is made in the form of three metal cylinderscoaxially nested within one another so that the bottoms of the outer and inner cylinders are connected to each other, while the middle cylinder has its bottom turned in the opposite direction and is mounted on the outer cylinder by means of an insulator, while the firing electrode of a three-electrode controlled spark gap is immersed in the liquid filling the space between the bottom of the middle cylinder and the ends of the inner cylinder, the two cylinders serving as the working electrodes of the spark gap.

The liquid dielectric may be water. For simplicity, the bottoms of the outer and inner cylinders are preferably made integral.

The type of high-voltage impulse generator disclosed herein offers the following advantages.

The nesting cylindrical plates of the capacitor reduce the size and increase the capacitance of the capacitor. The load is mechanically isolated from the generator and is not subject to the destructive action of the electrohydraulic shock produced by the spark gap in water, so that the generator can be used repeatedly. Since the spark gap is of a controlled type, the capacitor operates as a transmission line. Because of this, the rate of rise of the current can be readily increased, since the internal impedance of the transmission line is purely resistive. The negligible difference in the operate time between threeelectrode controlled spark gaps does not interfere with parallel simultaneous operation of a great number of impulse generators.

The invention will be better understood from the following description of a preferred embodiment when read in connection with the accompanying drawing which shows a high-voltage impulse generator, according to the invention.

Referring to the drawing, there is shown an impulse generator with a capacitor formed by three cylinders 1, 2 and 3, separated by water which serves as the dielectric.

The cylinders are made of metal about lcm. thick. The dielectric may be any liquid of high insulating and dielectric properties and, consequently, of high specific capacitance.

This capacitor, acting as a transmission line, has a wave impedance of 1 ohm and a capacitance of 0.1 microfarad. The cylinders l and 3 have a common bottom. The cylinder 2 is mounted on the cylinder 1 by means of an insulator 5. The controlled spark gap has three electrodes, the working electrodes being the bottom 6 of the cylinder 2 and the ends 8 of the cylinder 3, while the firing electrode 7 is anchored near the ends 8 of the cylinder 3 by means of an insulator 9.

The energy of the hydraulic shock is absorbed by a gas-filled bellows 10 the pressure inside which is atm. andwhich is attached to the bottom4 of the cylinder 1 inside the generator.

The impulse generator operates as follows. i

The middle cylinder 2 of the water capacitor is charged relative to the outer and inner cylinders 1 and 3 from an external source (not shown in the drawing) to a potential of +250 kilovolts during 2 microseconds. At the same time, one-half of this potential is applied to the firing electrode 7 of the spark gap. The controlled three-electrode spark gap operates after a negative trigger pulse of 250 kilovolts is applied to the firing electrode 7, producing an overvoltage across the spark gap. As a result, the Water capacitor produces a negative voltage pulse of 250 kilovolts at 250 kiloamperes with a rise time of 50 nanoseconds, which propagates away from the spark gap between the culinders 3 and '2 and then between the cylinders 1 and 2 in the direction of the load (not shown in the drawing) connected to the bottom 6.

Operating into an inductive load of about 10- henry, the impulse generator disclosed herein can produce impulses with an amplitude of 250 kilovolts and a rise time of 50 nanoseconds, following at a frequency of 4 megacycles.

In some applications it is preferable to use two impulse generators series connected to a load of about l00 nanohenrys. This connection produces a current pulse of 250 kiloamperes with a rise time of I00 and a fall time of 5 microseconds.

We claim:

l. A high-voltage impulse generator comprising a liquid dielectric capacitor made up of three metal cylinders nested coaxially within one another and constituting an outer, a mid- .dle and an inner cylinder with the bottoms of said outer and inner cylinders connected to each other, while the middle cylinder has its bottom facing in the opposite direction relative to the bottoms of said outer and inner cylinders; a liquid dielectric filling the space between said cylinders; an insulator fastening said middle cylinder to the outer cylinder; means for producing a controlled spark gap including a firing electrode, said inner cylinder and middle cylinder constituting working electrodes, the firing electrode being-immersed in the liquid dielectric between the ends of the inner cylinder and the bottom of the middle cylinder, and means at the bottom of the outer cylinder extending into the liquid dielectric between the inner and outer cylinders to absorb hydraulic shock produced in the generator.

2. A high'voltage impulse generator as claimed in claim 1 in which the dielectric is water.

3. A high-voltage impulse generator as claimed in claim] in which the bottoms of the outer and inner cylinders are integral.

4. A high-voltage impulse generator as claimed in claim 1 wherein said means for absorbing hydraulic shock comprises a bellows containing a pressure gas.

Claims (4)

1. A high-voltage impulse generator comprising a liquid dielectric capacitor made up of three metal cylinders nested coaxially within one another and constituting an outer, a middle and an inner cylinder with the bottoms of said outer and inner cylinders connected to each other, while the middle cylinder has its bottom facing in the opposite direction relative to the bottoms of said outer and inner cylinders; a liquid dielectric filling the space between said cylinders; an insulator fastening said middle cylinder to the outer cylinder; means for producing a controlled spark gap including a firing electrode, said inner cylinder and middle cylinder constituting working electrodes, the firing electrode being immersed in the liquid dieleCtric between the ends of the inner cylinder and the bottom of the middle cylinder, and means at the bottom of the outer cylinder extending into the liquid dielectric between the inner and outer cylinders to absorb hydraulic shock produced in the generator.

2. A high-voltage impulse generator as claimed in claim 1 in which the dielectric is water.

3. A high-voltage impulse generator as claimed in claim l in which the bottoms of the outer and inner cylinders are integral.

4. A high-voltage impulse generator as claimed in claim 1 wherein said means for absorbing hydraulic shock comprises a bellows containing a pressure gas.

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