Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Patent
1989-02-23
1992-02-25
Deboer, Todd E.
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
361130, 313306, 31323111, H02H 904
Patent
active
050918192
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a gas-electronic switch (pseudospark switch) having a gas discharge chamber, which contains two metal electrodes, namely, a cathode and an anode, which are spaced a distance (d) apart and are separated from each other by an electrically insulating wall made of ceramic material or glass, the cathode has a hole and the electrodes are joined to the insulating wall by a tight metal-ceramic joint or fused joint, wherein the gas discharge chamber is filled with an ionizable low-pressure gas under such a pressure p that the product p.times.d has such a value that a gas discharge between the electrodes will be fired in response to a voltage applied thereto which is disposed in that branch of the firing voltage-pressure characteristic in which the firing voltage decreases as the pressure rises.
PRIOR ART
Such a switch has been disclosed in DE-28 04 393 C2. In that switch, electrons and/or ions are generated in a discharge vessel which contains spaced apart metal electrodes, which are held by a surrounding insulating wall and have a gas discharge passage, which is constituted by aligned openings in said electrodes. Said discharge vessel is filled with an ionizable gas, which in accordance with the teaching of DE-28 04 393 C2 is present in such a quantity that the product of the electrode spacing (d) and the gas pressure (p) is of an order of 130 pascals or less. The sparklike fast gas discharge which will result when such switch is triggered or which takes place spontaneously as soon as the breakdown voltage is exceeded is known in the literature as the pseudospark voltage. In an extension of the p.times.d range explained in DE-28 04 393 C2 that pseudospark voltage will occur at p.times.d values which have a decreasing firing voltage-pressure characteristic as the pressure rises. In the language which is conventional for planoparallel electrodes that pressure range corresponds to the "disruptive gas discharge at the left-hand branch of the Paschen curve". That left-hand branch succeeds the minimum in he characteristic curve in which the breakdown voltage is plotted against p.times.d. In this patent specification we describe as pseudosparks all gas discharges which are spontaneously fired under pressures which in a given switch are lower than the pressure which defines the minimum of the gas pressure - firing voltage characteristics of the system. The plate spacing (d) is defined as that distance between the cathode and anode near their hole which determines the pseudospark character of the gas discharge and which must be provided in the cathode and may be provided in the anode.
The literature contains numerous papers on the properties and the operation of pseudospark chambers and pseudospark switches. Their insulating wall is usually arranged to extend at right angles to the electrodes (FIG. 1) and to have a length that is equal to the electrode spacing. Almost all published investigations have been made for scientific purposes so that the life and the existence of a permanently gas-filled switch were not significant.
It is an object of the invention to provide a pseudospark switch which has a life that is sufficiently long for industrial use and is capable of numerous switching operations and in which undesired spontaneous breakdowns will be avoided as far as possible.
SUMMARY OF THE INVENTION
That object is accomplished by a switch having the features recited in the claims. Additional desirable features of the invention are recited in the dependent claims.
Glass or a ceramic material is used for the insulating wall of the switch in accordance with the invention and is so joined to the electrodes that there can be no appreciable delivery of gas to the system during the operation of the switch. The invention ensures that a diffusion of metal vapor, which may originate substantially at the electrodes close to the holes formed in the cathode and possibly in the anode, to the insulator wall and a deposition of such metal vapor on said wall will be hindered. That hindranc
REFERENCES:
patent: 4433354 (1984-02-01), Lange et al.
patent: 4628399 (1986-12-01), Shigemori et al.
Journal of Physics EiScientific Instruments, Jun. 1986, pp. 466-470.
Christiansen Jens
Frank Klaus
Hartmann Werner
Kozlik Claudius
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