RU2144716C1 - Method and device for turning-on plasma- coupled thyristor - Google Patents

Abstract

FIELD: thyristors. SUBSTANCE: setting voltage applied between anode and cathode of gas-filled device is chosen to be lower than self-maintained arc discharge firing voltage. Working gas is heated in Aston glow region of glow-discharge pubic layer at negative electrode. Gate electrode is arranged within gas-filled device at cathode so that it is spaced through several lengths of working gas ion recharge, its circuit being electrically isolated from anode-cathode circuit. EFFECT: improved design. 5 cl, 4 dwg

Description

 The invention relates to the field of gas-discharge equipment, and more particularly to controlled gas-discharge devices of power electronics.

 In practice, a method for controlling the current of a gas-discharge device is quite widely known and applied, namely, a voltage is applied between the positive and negative electrodes of the device that exceeds the ignition voltage of an independent arc discharge (Kalganov I. L. Ionic devices. M.: Energy, 1970 )

 The disadvantages of this method are the increased cost of energy (power) and reduced reliability due to the significant difference between the ignition voltage of the discharge (hundreds of volts) and its burning (several volts - tens of volts), which requires the use of special measures and schemes to reduce peak loads at the time of ignition of the discharge . All this limits the capabilities of plasma valves, especially in the range of increased power and voltage when working on a load.

 This method is implemented in practice in two-electrode (diode) devices containing an anode and a cathode in a dielectric housing, separated by an interelectrode gap filled with a working fluid (gas or metal vapor). Control is achieved by applying an external voltage to the electrodes in magnitude greater than the ignition voltage of an independent arc discharge. The process is accompanied by current fluctuations, which negatively affects the resource of the device and its reliability due to overvoltages acting on the dielectric body (Kaganov I.L. Ionic devices. M.: Energy, 1970).

 Closest to the claimed one is a method for controlling the current of a gas discharge valve, which consists in creating an independent arc discharge from a smoldering working fluid at constant pressure by applying a voltage between the anode and cathode, as well as a positive potential relative to the cathode on the valve control electrode (grid) (Kaganov I. L. Ionic devices. M.: Energy, 1970). The method is used in tacitrons, thyratrons, excitrons and other types of valves. It is characterized by a rather high efficiency associated with the pulsed nature of the effect on the discharge gap, which reduces the energy costs of controlling the device (in relation to the power along the anode-cathode circuit, the control value is two to three orders of magnitude less). However, the presence of an electrical connection between the control and power circuits imposes certain restrictions on the controls, determines the use of protective elements along its control circuit, etc. The current control process is associated with the creation of a conductive plasma (i.e., gas ionization in the interelectrode gap by a pulse control in which energy is transferred to cold gas atoms from the electronic component through collisions). The costs consist of the costs of increasing the internal energy of atoms and their ionization.

 This method is implemented in a gas discharge valve containing a cathode, anode and a control electrode in a dielectric housing, separated by an interelectrode gap filled with a working fluid, in which the control electrode is located closer to the cathode. The control is carried out by applying a voltage to the anode and cathode (not less than the burning voltage of an independent arc discharge) and a voltage pulse is applied between the control electrode and the cathode (exceeding the ignition voltage of an independent arc discharge). The result is the ionization of a part of the gas in the gap between the cathode and the control electrode, which is picked up by an external field between the anode and cathode and contributes to the development and ignition of an independent arc discharge (Kaganov I. L. Ionic devices. M .: Energy, 1970).

 The disadvantage of this method of current control is to increase energy costs due to heating and ionization of cold gas in the interelectrode gap, as well as the presence of electrical connection between the main discharge circuit and the control circuit, which reduces reliability.

 The disadvantage of these devices is the low reliability of the control electrode circuit associated with the leakage of the main current at the time of ignition of the arc discharge, as well as the cost of control energy for heating and ionizing a cold working fluid in the cathode region.

 The technical result of the invention is to increase the reliability of control and reduce energy costs, which leads to an increase in the efficiency of the plasma valve.

 The specified technical result is achieved by the fact that in the known method for controlling the current of a gas-filled device, which consists in creating in the interelectrode gap an independent arc discharge from a working fluid glowing at constant pressure by applying a voltage between the anode and cathode, the magnitude of the applied voltage is set less than the magnitude of the ignition voltage arc discharge, while the working fluid is heated in the region of the "Aston glow" of the ion layer of a glow discharge in the negative on the electrode.

 In addition, the achievement of the technical result is ensured by the fact that in the known gas-discharge device containing a cathode, an anode and a control electrode separated by an interelectrode gap filled with a working fluid, the control electrode is located at the cathode at a distance of several charge exchange ion lengths of the working fluid, and the circuit is electrically isolated from the anode-cathode circuit.

 Since the proposed method can only be implemented in the proposed device, characterized by certain structural features claimed in the FI, therefore, both objects are combined into a group of inventions, which makes it possible to achieve the specified technical result during implementation.

 The claimed technical solution meets the criterion of "novelty." It is distinguished by a new set of essential features in the distinguishing part of the patent formula: the magnitude of the applied voltage is set less than the ignition voltage of an independent arc discharge, while the working fluid is heated in the region of the "Aston glow" of the ion layer of the glow discharge at the negative electrode.

 Moreover, a new set of features in the inventive device is expressed in the fact that the control electrode is located at the cathode at a distance of several recharging ions of the working fluid, which ensures heating of the working fluid in the "Aston glow" when implementing the method. In this case, the voltage at the electrodes of the device is set less than the ignition voltage of an independent arc discharge. A new set of features of the device is complemented by the fact that the control electrode does not have direct electrical connection with the cathode and anode circuit, and the electrode itself is electrically isolated from discharge in the interelectrode gap. In the inventive device, the control electrode acquires a new quality - it becomes a source of energy for the "Aston glow", that is, it can be made of a dielectric transparent to electromagnetic radiation (visible, infrared or other ranges); allows you to transport the energy flow in the area of "Aston's glow."

 The claimed technical solution meets the criterion of "inventive step". A new set of essential features: namely, the magnitude of the applied voltage is set less than the ignition voltage of an independent arc discharge, while the working fluid is heated in the region of the "Aston glow" of the ion layer of the glow discharge at the negative electrode, it gives a new previously unknown effect - control is carried out non-electric way (there is no direct electrical connection between the main discharge and the control action, which significantly increases the reliability of control of the device by a large in capacities where breakdowns along the control circuit are possible in well-known technical solutions), and the effect is rather thin and selective - the “Aston glow” region is heated, where the temperature of the atoms of the working fluid already reaches several thousand degrees (as evidenced by the radiation yield), which increases the efficiency discharge control (device).

 A new set of essential features of the device allows you to implement the proposed method of current control: the location of the control electrode (source of heating of the working fluid) at a specified distance from the cathode allows ignition of an independent arc discharge at a voltage lower than the breakdown voltage (ignition voltage of an independent arc discharge) due to energy exposure to a small part of the working fluid in the interelectrode gap (which is in a state of glow discharge due to the applied voltage).

 The proposed technical solution meets the criterion of "industrial applicability". This method can be used in gas discharge technology in the development of powerful (power) valves, in automation elements (transforming a sensor signal into an electric one for actuators), etc., is especially effective in stand-alone devices.

 The application materials contain a sufficient and necessary amount of information that fully disclose the possibility of implementing the invention.

 At present, the design of a plasma thyristor sample has been developed and tested, which confirms the control efficiency.

 In FIG. 1 shows the distribution of the potential, the temperature of the atoms of the working fluid in the interelectrode gap for the glow discharge state, explaining the physical essence of the proposed method. In FIG. 2 shows a diagram of the interelectrode gap for a glow discharge. In FIG. 3 shows the test results.

или

которые преобразуются с учетом уравнения Пуассона к виду:

или

С учетом (5^*) решение принимает вид:

(8)
где E_A - напряженность поля на отрицательном электроде, d_k - протяженность ионного слоя, n_a - концентрация атомов рабочего тела в зазоре, Q_ia - сечение перезарядки, m_a - масса атома, κ_a - теплопроводность рабочего вещества, к - постоянная Больцмана, e - заряд электрона, ε_o - диэлектрическая постоянная, T_a - температура атомов. Вид распределения дан на фиг. 1.The physical nature of the proposed technical solution is as follows. The ionic layer at the negative electrode in a glow discharge has a fairly high resistance - up to 10 ⁵ ... 10 ⁶ Ohms, that is, it can be considered as a dielectric in a strong electric field in the drift approximation and is described by the following equations:

or

which are transformed taking into account the Poisson equation to the form:

or

Given (5 ^* ), the decision takes the form:

(8)
where E _A is the field strength at the negative electrode, d _k is the length of the ion layer, n _a is the concentration of atoms of the working fluid in the gap, Q _ia is the charge exchange cross section, m _a is the atomic mass, κ _a is the thermal conductivity of the working substance, and k is the Boltzmann constant , e is the electron charge, ε _o is the dielectric constant, and T _a is the temperature of the atoms. The distribution type is given in FIG. 1.

It is characteristic that the entire change in the field and potential falls on a narrow region of the ion layer — with a length of (5 ... 7) λ _ia , where the "Aston glow" is concentrated. In it, there is a sharp increase in the temperature of the working fluid in force.

 Thus, the balance of the thermal state of the working fluid in the "Aston glow" determines the stability of the glow discharge as a whole, and the impact on this area can lead to a transition to an arc discharge.

 The implementation of the proposed method and the operation of the device is as follows.

 Due to the application of external voltage to the electrodes, a glow discharge is realized in the thyristor. In this case, the interelectrode gap of the gas discharge thyristor, a section of which is shown in FIG. 2a, is an alternation of the "p" and "n" layers: the positive electrode is the anode (pos. 1) - the "p" layer, the negative space charge layer (pos. 2) - the "n" layer, the ionic layer (pos. .3) - "p" layer, negative electrode (pos. 4) - "n" layer, that is, similar to a semiconductor thyristor. The control electrode (pos. 5) is located near the surface of the cathode 4, in the region of the "Aston glow" of the ion layer 3. When a current pulse is passed through the control electrode 5, heat is released in it, which is transferred to the gas atoms by the thermal conductivity and increases their energy. Thus, with a certain amount of underwater heat to the "Aston glow" region, it is possible to carry out ionization and ignite an independent arc discharge in the device. The surface of the control electrode is coated with a dielectric to prevent electrical communication between it and the main electrodes of the device. The control in the proposed technical solution has a similar character (effect on the "p" layer), but unlike the known ones, the generation of current carriers is achieved by a non-electric effect and the effect itself can be dosed. The source of energy supply - the control electrode can be made in the form of a ring 5, transparent to infrared radiation (in another specific case, Fig. 2, b), which is fed into the area of "Aston glow". In this case, the heating of the working fluid occurs by radiation transported from the outside. When a voltage of a certain value is applied to the anode 1 and cathode 4, it is possible to ignite independently an arc discharge in a plasma thyristor.

This current control method was tested experimentally on a steam-filled device (with cesium filler). The test results are shown in FIG. 3. When regulating the current pulse passing through an electrically isolated, dielectric-coated ring electrode located near the cathode surface, the arc discharge was ignited in the device at different values of the applied voltage between the cathode and anode, which are less than the breakdown voltage (ignition of an independent arc discharge without additional impact). It is characteristic that in this way it is possible to lower the ignition voltage by almost an order of magnitude. The current pulse had a duration of 0.05 s, which makes it possible to maintain a constant pressure, the surface of the ring electrode is about 5% of the cathode surface, that is, there is almost no local change in vapor concentration. Since at small values of overheating of the ring electrode, ignition of an arc discharge occurs at voltages U _on = 200 ... 250 V, there is no emission character of breakdown.

 This method and device significantly expand the capabilities of plasma devices.

Claims (5)

 1. The method of turning on a gas-filled device, in which an independent discharge is created in the interelectrode gap from a working gas (steam) glowing at a constant pressure by applying a voltage between the anode and cathode, characterized in that the applied voltage is set less than the ignition voltage of an independent arc discharge while the working gas (steam) is heated in the region of the "Aston glow" of the ion layer of a glow discharge at the negative electrode.  2. The method according to claim 1, characterized in that the working gas (steam) is heated by long-wave radiation supplied to the "Aston glow" region, or by thermal conductivity from a body placed in it.  3. A gas-filled device for implementing the method according to claim 1, comprising a cathode, anode and a control electrode in a dielectric housing, separated by an interelectrode gap filled with a working gas (steam), characterized in that the control electrode is located at the cathode at a distance of several charge exchange lengths of the working ion gas (steam), and its circuit is electrically isolated from the anode-cathode circuit.  4. A gas-filled device according to claim 3, characterized in that the control electrode is coated with a dielectric.  5. A gas-filled device according to claim 3, characterized in that the control electrode is made in the form of a dielectric ring made of a material transparent to electromagnetic radiation.

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