RU2608825C2 - Spark discharger - Google Patents

Abstract

FIELD: electronic equipment.

SUBSTANCE: invention relates to electronic equipment, in particular, to uncontrolled spark switching dischargers, intended for switching of different pulse devices high-current high-voltage circuits, including aircraft engines ignition system. For this purpose, spark discharger comprises insulator, fixing high-voltage electrodes (HVE) separated by discharge gap, as well as arranged in, at least, one of HVE on its surface, in groove facing opposite HVE, breakdown initiation element (BIE) is separated from HVE by intermediate layer, embedded into HVE for not less than 10 nm and with thickness of not less than 10 nm, consisting of high-temperature semiconductor or dielectric material with porous structure and/or powdered or resilient metal filler, providing multi-point contact of these elements.

EFFECT: technical result consists in creation of uncontrolled spark switching discharger with high electric strength and longevity, operating frequency of up to 1–3 kHz, low variation of breakdown voltage amplitude in different moments of switching time.

5 cl, 3 dwg

Description

(i) Technical Field

The invention relates to electronic equipment, and more particularly to vacuum and gas-discharge devices, in particular uncontrolled switching arresters, designed for switching high-current high-voltage circuits of various pulse devices in a wide range of operating temperatures, including ignition systems of aircraft engines, as well as protective arresters, designed to protect equipment from lightning impulses and other electromagnetic interference.

(ii) Prior Art

Temporary breakdown stability of the discharge gap, statistical breakdown delay time, its spread, static and dynamic breakdown voltage are the main parameters of the spark gap. They are determined by the presence of irradiation of the electrodes and the volume of gas by charged particles, light photons, x-ray, gamma and cosmic rays, the value of the electric field strength, the state of the surface of the electrodes and a number of other factors. Almost all of these processes, their intensity, are random, probabilistic in nature, which leads to a spread in the time parameters of the arresters, as well as such a parameter as the voltage of the first breakdown (the effect of the first pulse), which exceeds the average value of the breakdown voltage by 50 percent or more. For the normal operation of the equipment, this requires an increase in the supply of voltage of power sources, and, accordingly, of the operating voltages of capacitors, and an increase in their overall dimensions. In this regard, such arresters are unacceptable for switching capacitive storage in many applications, especially in aircraft engine ignition systems.

To reduce the voltage of the first breakdown and increase the stability of the arresters, they create artificial preionization, for example, by introducing radioactive isotopes into the device (Kiselev Yu.V., Cherepanov V.P. "Spark Dischargers", M .: "Soviet Radio", 1976, and also Kiselev Yu.V., "Spark arresters", Ryazan RRTI, study guide, 1989). Thus, after a dose of the Ni ⁶³ isotope with an activity of 185 × 10 ⁴ 1 / s (50 μCi) is introduced, the standard deviation of the voltage of the first breakdown σ decreases by a factor of 2. However, the Ni ⁶³ isotope is introduced in the form of solid or liquid salts, is environmentally hazardous and requires very strict handling measures, special disposal, endangers the environment, which complicates and increases the cost of production of arresters,

Known spark gap (Zorin A.M., Mitrokhina IA GAS-FILLED DISCHARGE, Application: 2003107187/09 of 03/18/2003. Published: 08/20/2004), which contains a cylindrical body with electrode holders and a gas filling, consisting of argon and hydrogen. The tritium additive was added to the filling to a value of 0.74 ± 0.186 MBq (2 ± 0.5 μCi), which ensures stabilization of the first breakdown of the device. Tritium at first glance is not as dangerous as other radioactive substances, evaporating in the event of depressurization or destruction of the arrester, relatively quickly reduces the level of radiation in the room to the maximum permissible level. However, this isotope has a high cost, the conditions for its handling and disposal also increase the cost of production and operation of devices, since when it enters the body (by inhalation) it replaces hydrogen in the molecules containing it and irradiates human tissue, which even at low doses provides high the likelihood of cancer.

For this purpose, a spark gap has been proposed (Arefyev A.S., Anisimov V.F., Kiselev Yu.V., DISTRIBUTION, RU 2227951 C2, dated June 15, 2001) containing at least two electrodes that form a vacuum tight with an insulating casing a shell and at least one breakdown initiator, which together with resistance elements forms an electric circuit connected in parallel with the main electrodes of the spark gap, characterized in that the breakdown initiator is made on an additional insert located in the zone of the main discharge gap and passing through a recess or The neutral hole in at least one of the main electrodes uses active and / or reactive elements as resistance elements, and the gap between the insert and the main electrode does not exceed the interelectrode distance.

Such a spark gap is designed for circuits with low discharge currents and low breakdown voltages, since when the breakdown initiator is connected to the main electrodes in parallel, due to the rapid deposition of conductive films from the discharge on the surface of the initiator and resistance elements, a short circuit of high-voltage electrodes occurs, its characteristics are low, short service life. The disadvantage is the large size of the passage capacitance formed by a conductive (or semi-conductive) insert and the main electrodes.

Also known is a spark gap (Patent for a utility model of the Russian Federation No. 108224) containing an insulator fixing high-voltage electrodes (VE) separated by a discharge gap, as well as an additional element connected to the main VE, characterized in that the additional element is located at least in one of the CEs and is an insert (B) adjacent to the surface of the CEs facing the opposite CE and made of a material having physical properties, for example, the nature of the dielectric constant or conductivity, o different from the properties of the main material of REs, in particular, from a semiconductor or dielectric.

This design gives an effect only with reliable contact between the RE and B and therefore requires very precise fitting of the sizes of the RE and the insert to ensure the stability of the parameters of the devices, which is difficult and expensive to perform in the process of mass production. In addition, it is practically impossible to ensure the equality of the expansion coefficients of the insert and the HE so that between the insert and the HE in the manufacture, for example, after soldering the device (heating from room temperature to 800-1000 ° C), a tight contact would remain. In addition, during the cyclic operation of the spark gap, which determines the temperature fluctuations from the ambient temperature of minus 60 ° С to the heating of the electrodes due to losses in the discharge reaching + 600 ° С, mechanical stresses arise due to the difference in the linear expansion coefficients of the mating elements, leading to destruction insertion.

The closest technical solution to the proposed invention is a spark gap with a breakdown initiation element, which is an insert made of a solid dielectric, in particular polyethylene, located at the end of one of the high-voltage electrodes (VE) facing the opposite VE (SU 738021 A1, NIIVN at Tomsk Polytechnic Institute, 05/30/1980), and the dielectric constant of the insert is chosen different from the dielectric constant of the liquid medium in which the high-voltage electrodes are placed.

The choice of an elastic material (polyethylene) provides an accurate fit without gaps and reliable contact between the insert and the CE in a patented design that does not require vacuum high-temperature processing of the device. This arrester is designed to operate at operating temperatures of no higher than 80 ° C and placing renewable energy in a liquid dielectric, which provides cooling and constant change of the dielectric medium when pumping the liquid through the working interval and its cleaning on external filters.

The design drawback is its complexity, cumbersomeness, low temporal stability, low switching frequency (less than 1 Hz), short service life. This design cannot be used in the manufacture of vacuum sealed compact devices designed for long-term switching of large charge values (more than 0.01 C) in a gaseous medium or in a vacuum, which are chosen in most applications of arresters. Vacuum technology assumes to achieve the purity of the gas working medium and to ensure stable pressure of this medium during the service life of the devices (up to 850-1080 ° С when soldering the device and up to 500 ° С when degassing at the pumping station) before filling with working gases. All known plastics cannot withstand such temperatures without melting.

In this regard, sealed devices use not an organic, but a mineral dielectric, for example, high-alumina ceramics, which have greater heat resistance and allow its high-temperature processing to produce a stable gas composition.

(iii) Disclosure of the invention

The objective of the invention is the creation of uncontrolled, sealed and small-sized spark switching spark gap with high electric strength, durability, small variation in the amplitude of the breakdown voltage at various times of switching time (including the voltage of the first breakdown), with high temporal stability of switched current pulses, and also with a technologically simple, environmentally friendly design without the use of radioactive isotopes.

This is achieved by the fact that in the spark gap containing an insulator fixing high-voltage electrodes (VE) separated by a discharge gap, and also located in at least one of the VE on its surface, for example, in a groove facing the opposite VE, a breakdown initiation element (EIT), made in the form of an insert made of a solid material having physical properties, for example, the nature of the dielectric constant or conductivity, different from the properties of the main material of the SE, while the element of breakdown initiation flax from CEs intermediate layer, a RE recessed not less than 10 nm and not thicker than 10 nm, consisting of high-temperature semiconductor or dielectric having a porous structure and / or particulate filler or a resilient metal, providing multipoint contact these elements.

Another difference is that the intermediate element (layer) providing multipoint contact with the RE is made in the form of a composite material consisting of a metal (polycrystalline), semiconducting or dielectric base with a porosity of at least 20% mixed with a foreign material, for example, with made of sintered metal powder, the pores between the powder particles are filled with a dielectric or semiconducting substance, and, conversely, with a base made of dielectric powder, the pores between it is filled with metal or a semiconducting substance.

The third difference is that the intermediate element (layer) uses fibrous material either in the form of short segments as a filler in the main material or an intermediate layer wrapped around the insert in one or several layers, for example, of quartz or carbon fibers, fullerenes or graphenes .

The fourth difference is the performance of renewable energy in its groove with a non-metallic surface (for example, by oxidation, anodizing, nitriding, phosphating), which is filled with the material of the intermediate element.

The fifth difference is the implementation of the intermediate element in the form of an elastic, spring element inserted in the gap between the CE and the insert.

(iv) Preferred Embodiments and Brief Description of the Drawings

Possible embodiments of the invention are illustrated by drawings.

The figure 1 shows a General view of the design of the spark gap, figure 2 is an enlarged drawing of the electrode 2 with an insert and an intermediate layer.

The spark gap contains high-voltage electrodes of the CE (1 and 2), separated by an insulator 3 and a discharge gap 4, as well as a breakdown initiation element (EIT) - an insert (B) 5 in the groove (recess) of the CE 2 on the surface facing the opposite CE 1. Between the insert 5 and the electrode 2, the groove space is filled with an intermediate element (PE) 6. High-voltage electrodes are made of conductive material with high resistance to erosion, for example, tungsten or tungsten-copper composition, tungsten-nickel with the addition of emission-active elements products (barium, lanthanum) of their oxides or salts, and the insert is made of a material having physical properties, dielectric constant, and / or conductivity that are different from the properties of the main CE material, in particular, from a semiconductor or dielectric. Pumping and filling is carried out through the plug 7, which after vacuum processing (and, if required, filling with working gas) is snacked, while the device is sealed by cold welding.

When voltage is applied to high-voltage electrodes at the contact points of dissimilar materials (Figure 3A), effects arise that contribute to the development of breakdown between CE 1 and CE 2. So, in the case of insulator insertion, an increase in the electric field intensity occurs at the points of contact with the CE, the magnitude of which depends on the value of the dielectric constant ε of the insert and the shape factor of the surface layer of the SE β. The coefficient β, for example, in the presence of micropoints (microprotrusions) on the SE 2, is approximately determined by the ratio of the length to the average diameter of the micropoint. On the tip located in the zone of action of the electric field, depending on the value of β, the field strength can increase from units to tens of times. In the absence of contact between the conductor and the insulator with a gap or a gap filled with gas (dielectric constant of the gas ε _g ≈ ε _vacuum = 1), the electric field between the CE and the insert, for example, near the micro tip 8 will be proportional to ε _g β, and in the contact between the protrusions 9 and insert 5 - will increase in proportion to the product εβ, which is several orders of magnitude more (ε is the dielectric constant of the insert, which can reach tens of thousands of units) and breakdown occurs at lower operating voltages. However, when located far from the surface, the field can be significantly reduced down to zero, and therefore such a contact should be close to the surface.

Thus, to ensure the effective operation of the insert when performing the electrodes of the arrester without PE, it is necessary to make close contact with the cell or to use the material of the insert from an elastic substance as in the prototype. In real production conditions, it is almost impossible to provide. Indeed, in order to maintain tight contact, it is necessary to ensure the equality of the expansion coefficients of the insert and the CE, which is unrealistic, and during manufacture, for example, after soldering the device (heating from room temperature to 800-1100 ° C), either mechanical stress arises between the insert and the CE, destroying the insert, or the clearance increases. This is exacerbated by the cyclic operation of the arrester, which determines the temperature fluctuations from the ambient temperature of minus 60 ° С to heating due to losses in the discharge reaching + 600 ° С, due to the difference in the linear expansion coefficients of the mating elements, mechanical stresses arise, leading to destruction of the insert .

The contacting elements "dielectric-electrode" (insert-VE) should be located in the near-surface layer from the side of the high-voltage gap 4 mainly in the direction of the field, and not across it. In this case, the efficiency of the insert (its polarization) increases sharply. However, when the insert is paired with the electrode, even strictly in terms of generativity, the efficiency is low, because the case of the location of the "dielectric above the electrode" is unlikely, especially in microscale. The implementation of the dielectric element in the form of a film on the electrode is possible, but such a film during operation is quickly lost by discharge. The best option is to place (fill) the PE material in the gap between the electrode and the insert, when the probability of an effective arrangement increases. Some burial of the PE reduces the possibility of burning the main discharge from the gap, since after the initiation of the emission, taking into account the operation of the spark gap on the right branch of the Paschen curve, it is energetically more beneficial to burn the discharge along the short path of the VE 1-VE 2. , breakdown stability increases.

In FIG. 3 shows an enlarged view of the real picture of the mating surfaces in the gap between the CE 2 and the insert (B) 5 with the usual design of the insert (A) and with filling (B) with the mass of the intermediate element PE 6. The arrows indicate the direction of the electric field Ε between CE 1 and CE 2. In the known construction (Fig. 3A), without PE it is impossible (or unlikely) to achieve contact between the CE 2 and B near the surface (for example, protrusions 10 and 8), since it is more likely that somewhere at a depth among the many protrusions there is a protrusion 9 preventing the convergence of CE and B. In the design of FIG. ur 3B ledge 9 does not interfere, because pouring PE 6 near the surface of the CE and B is likely to provide contact with the effective location of the dielectric 11 above the protrusion 8 of the CE 2. Since the field strength decreases sharply when deepening from the surface of the CE and B, the contact points in the depth of the electrode (for example 9) do not will influence the initiation of breakdown. In this case, the near-surface layer will be working.

In the contact between PE 6 and the protrusion 8 located near the surface (Figure 3B), the electric field strength will increase in proportion to the product εβ, which is several orders of magnitude greater than without such a contact (ε is the dielectric constant of PE material, which can reach tens of thousands of units) and breakdown occurs at lower operating voltages.

In this design, in addition to the above field amplification, photo- and electron emission arise from the pn junction in the contact between the SE and PE, which also contributes to the initiation of the discharge.

In this solution, an intermediate element 6 (PE) is introduced between the CE and the insert. The most effective is pouring PE with a porous structure based on aluminum oxide Αl _{2 2 3} , magnesium oxide MgO, barium titanate, or mixtures thereof. The presence of PE and its selected thickness determines the absence of hard contact between the RE and the insert. An intermediate element in this design dampens mechanical stresses and, at the same time, provides emission phenomena that reliably ignite the discharge.

At the same time, it is possible not to achieve high accuracy in the manufacture of mating parts, and, moreover, it becomes possible to execute them with a developed (rough) surface, which increases the number of contacting points and involves not only the surface, but also some near-surface volume of these parts in the process of initiating the discharge. This reduces the cost of manufacturing and increases the resource of the device.

It is important that the insert 5 on the surface of the VE facing the opposite VE is performed in such a way that it is separated from the VE by an intermediate element 6 with a thickness of at least 10 nm with multipoint contacts of these elements. The size of the thickness of the PE provides a mitigation of mechanical stresses between the SE and the insert during temperature fluctuations, as well as the emission and exit of charge carriers or quanta into the interelectrode space. The value of 10 nm corresponds to the threshold wavelength of soft x-ray radiation, which actually takes place in discharge phenomena, providing for the preionization of the gas in the device.

The proposed design leads to stabilization of the breakdown voltage and the elimination of the effect of the first breakdown.

The intermediate layer, providing multi-point contact with the SE, can also be made in the form of a composite material consisting of a metal (polycrystalline), semiconducting or dielectric base with a porosity of at least 20% mixed with a foreign material. In a base made of sintered metal powder, the pores between the powder particles are filled with a dielectric or semiconducting substance or an emission-active substance with a small work function and, conversely, in a base made of dielectric powder, the pores between its particles are filled with a metal or semiconducting substance.

The roughness of the mating surfaces of CE and PE, which creates a developed contact surface, is ensured by the presence of their polycrystalline structure or sintering of powders from these materials with a given grain size.

In the case of using a semiconductor PE material, a wide-gap semiconductor such as silicon carbide is recommended, which ensures the performance of the arrester due to its lower temperature dependence at significantly higher temperatures of the working medium (up to 500 ° C and more) and high pulse repetition rates. Its non-linear (varistor) current-voltage characteristic is ensured by an insert made in the form of a composite porous (polycrystalline) semiconductor base, the gaps (gaps between crystals) of which are filled with dielectric material. This design provides a sharpening of the front of the current pulse and greater erosion resistance than that of the dielectric insert.

In the intermediate layer 6, a fibrous material (for example, silica fiber) can be used either in the form of short segments as a filler in the main material, or wrapped around the insert 5 in one or more layers, but with a total thickness less than the inner diameter of the HE 2, in which insert. An option may be an intermediate layer of conductive carbon fibers (fullerenes), as well as graphenes. In the manufacture of REs, such an intermediate layer is pre-wound onto an insert lubricated with an organic binder or dielectric paste, and then inserted into the groove in the RE. After heat treatment, the fibers, when expanded, also form multipoint contacts.

One of the options of the proposed design is the implementation of grooves in the CE with a nonmetallic inner surface (for example, by oxidizing, anodizing, nitriding, phosphating), which is equivalent to the manufacture of a thin dielectric or semiconducting insert. The groove is filled with the material of the intermediate element. Such a process is necessary to ensure reliable adhesion of PE to VE, since VE with a purely metal surface does not create a strong connection with PE, which spills out of the groove. This design is especially suitable for miniature arresters.

The implementation of the intermediate element in the form of an elastic spring element inserted in the gap between the CE and the insert provides reliable contact between them. In this case, the PE material should not be subject to annealing at the processing temperatures of the device. High-temperature metals are suitable for this: molybdenum, tungsten, molybdenum-rhenium alloys, etc. in the form of strips, wires. To increase the contacting surface (increase the contact points), PE can be coated with a sintering layer of metal powder (for example, nickel or molybdenum) sintered with PE. This design eliminates the shortcomings of the compact HE material during temperature fluctuations, leaving constant contact with the insert.

The device can be vacuum or filled with gas (hydrogen, nitrogen, argon or carbon dioxide) at a pressure of more than 0.1 atm to ensure high breakdown voltages on the right branch of the Paschen curve.

The arrester of this design was tested in several modes - with an operating voltage of 2 kV, pulse currents of up to 1 kA, switched capacitance of 1 μF, with a repetition rate of up to 600 Hz, as well as 4 kV, 7 μF, current up to 10 kA. This eliminates the effect of the first breakdown in 98% of devices (in the case of a spark gap design without an intermediate layer, the effect of the first breakdown is observed in at least 45% of devices), the instability of the breakdown voltage is less than 5%, and the service life is about 10 million operations, in the second mode - up to 1 million pulses. This spark gap provides stable switching in a wide temperature range from -60 to + 300 ° С.

Claims (5)

1. A spark gap containing an insulator fixing high-voltage electrodes (VE) separated by a discharge gap, and also located in at least one of the VE in a recess on its surface facing the opposite VE, for example, in a groove, a breakdown initiation element (EIT) ), made in the form of an insert made of a solid material having physical properties, for example, the character of dielectric constant or conductivity, different from the properties of the main CE material, characterized in that the breakdown initiation element is Elena from CEs intermediate layer, a RE recessed not less than 10 nm and not thicker than 10 nm, consisting of high-temperature semiconductor or dielectric having a porous structure and / or particulate filler or a resilient metal, providing multipoint contact these elements. 2. The spark gap according to claim 1, characterized in that the intermediate layer providing multi-point contact with the SE is made in the form of a composite material consisting of a metal, semiconducting or dielectric base with a porosity of at least 20% mixed with a foreign material, for example, a base made of sintered metal powder, the pores between the powder particles are filled with a dielectric or semiconducting substance and, conversely, with a base made of dielectric powder, the pores between the particles are olnyayutsya metallic or semiconductive material. 3. The spark gap according to claim 1, characterized in that the intermediate layer uses fibrous material either in the form of short segments as a filler in the main material or wrapped around the insert in one or more layers, the intermediate layer, for example, of quartz or carbon fibers, fullerenes or graphenes. 4. The spark gap according to claim 1, characterized in that the renewable energy element is made with a groove having a non-metallic surface (for example, by oxidation, anodizing, nitriding, phosphating), which is filled with the material of the intermediate element. 5. The spark gap according to claim 1, characterized in that the intermediate element is made in the form of an elastic, spring element inserted in the gap between the CE and the insert.

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