Electricity: electrical systems and devices – Safety and protection of systems and devices – High voltage dissipation
Patent
1995-11-27
1997-09-23
Gaffin, Jeffrey A.
Electricity: electrical systems and devices
Safety and protection of systems and devices
High voltage dissipation
361117, 31323111, 313609, H02H 322
Patent
active
056711140
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention is in the field of electronic components. More specifically, the invention is used in the construction of gas-filled overvoltage diverters. To ensure the ignition properties, the electrodes of the gas-filled overvoltage diverters are coated with an activation compound, and at least one axially running ignition strip and an additional ionization source are applied on the wall of the insulating body.
BACKGROUND OF INVENTION
Overvoltage diverters filled with inert gas have a number of desired performance characteristics including: igniting voltage, response time, static response voltage, dynamic response voltage, extinction voltage and glow operating voltage. To achieve each of these desired performance characteristics, different measures like the constructive design of the electrodes, the type and pressure of the gas filling, and the selection of the activation compound arranged on the active surfaces of the electrodes must be adjusted to one another. Furthermore, to produce definitive ignition conditions, one or more ignition strips are customarily arranged on the inside wall of the glass or ceramic insulator and a special ionization source may also be provided. For example, a known overvoltage diverter has two electrodes inserted into the two front ends of a ceramic insulator; the electrode surfaces face each other and are coated with an activation compound in depressions in the electrode surface. A plurality of ignition strips running in the axial direction of the ceramic insulator are arranged on the inside wall. The ignition strips are called middle ignition strips because they do not directly interface with the electrodes as described in U.S. Pat. No. 4,266,260 and German Patent 28 28 650.
Furthermore, where gas-filled overvoltage diverters are arranged in a space shut off from outside light influence during their operation, an additional ionization source in the form of a point-shaped deposit of a radioactive material is customarily arranged on the inside wall of the insulator. Alternatively, the gas filling of the overvoltage diverter can consist of a radioactive gas as shown in U.S. Pat. No. 3,755,715.
SUMMARY OF THE INVENTION
The invention seeks to develop an overvoltage diverter that exhibits very slight ignition delay in the dark space, even without the use of a radioactive preparation.
The invention achieves this objective by another ionization source, in addition to the two electrodes, which comprises a coating connecting the two electrodes. The coating is made of an electroluminescent material based on alkali halides and/or alkaline-earth halides where the coating has a thickness of approximately 50 to 500 .mu.m.
For example, potassium bromide and sodium bromide, potassium chloride and sodium chloride, and sodium fluoride and barium chloride can be used for the coating as described in (Opt. Spectrosc. (USSR) 51 (2), Aug., 1981, Pages 165-168). As parent substances, alkali-fluorides and alkali-bromides are to be particularly considered because they additionally contain alkaline-earth chloride. The additional alkaline-earth halide should be in a quantity of 5%-30% atomic percentage. Because of this additional alkaline-earth halide, the melting process necessary to apply the coating can be specifically controlled with regard to the melting temperature.
Because the coating contacts the two electrodes of the overvoltage diverter, the coating places an increased number of primary charge carriers at disposal in the overvoltage diverter so that, upon reaching the igniting voltage, the start of the gas discharge is initiated without time delay. Additionally, to strengthen this effect, the coating material can contain dielectric crystals (e.g., titanium oxide or aluminum oxide) or ferro-electric crystals (e.g., barium titanate, lithium niobate or lithium tantalate). Because such crystals have a particle size of approximately 10-30 .mu.m, an increased charge density is produced at their interface resulting in a higher current flow in the electroluminescent coat
REFERENCES:
patent: 3755715 (1973-08-01), Klayum et al.
patent: 4266260 (1981-05-01), Lange et al.
patent: 4287548 (1981-09-01), Hahndorff
Effect Of a Strong Electric Field On Recombination And Intracenter Process In Alkali-Halide Crystals, A.P. Druszhinin and N.S. Nesmelov: Opt. Spectrosc. (USSR) 51(2), Aug. 1981, pp. 165-168.
Boy Jurgen
Daumer Wolfgang
Gaffin Jeffrey A.
Medley Sally C.
Siemens Aktiengesellschaft
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