RU2158459C2 - Electric circuit current limiting and disconnecting device - Google Patents

Abstract

FIELD: protection of electric circuits. SUBSTANCE: device has two parallel electrodes connected to power supply and interconnected through electrical discharge initiator. Novelty is that device electrodes are, essentially, parallel rails made of resistive material and that electric arc initiator is connected at ends of rails designed for their connection to electric circuit. Rails are coiled into spiral to reduce size of device. EFFECT: improved efficiency of current limiting and reduced voltage surges in electric circuit. 7 cl, 6 dwg

Description

 This invention relates to the protection of electrical networks and is intended to limit and disable the current of the electrical circuit. Advantageously, this invention can be used in devices for protecting electric networks and sources of electric energy from overloads during switching of an electric circuit, for example, as a result of short circuits.

 A known field suppression machine, designed to turn off a circuit with an inductance, comprising electrical contacts, a limiting resistance, and an arcing chamber consisting of a housing, a radial field coil, a magnetic blast coil, a magnetic circuit, arcing plate plates, shunted by active resistances. In such a device, when the circuit is switched off by electric contacts, the electric arc arising under the influence of the self-induction EMF of the switched circuit, under the influence of the magnetic field of the above coils, moves to the arcing plate plates and collapses. In this case, the energy accumulated in the inductance of the circuit is dissipated by the active resistance of the arc [1].

 The disadvantage of this device is the complexity of its design.

 The closest in design and principle of operation, the device selected as a prototype is a device for limiting and turning off the current of an electric circuit, containing two parallel electrodes interconnected by a device for initiating an electric discharge, and rails located parallel to each other are used as electrodes and the device for initiating an electric arc is connected from the side of the ends of the rails intended for their inclusion in the protected electric w chain [2].

 This device has a relatively low efficiency when limiting and turning off the electric current of an electric circuit, since almost all the energy is released in an electric arc having a low resistance to electric current, and when the arc is extinguished, an overvoltage in the protected circuit inevitably occurs.

 The technical result of the present invention is to increase the efficiency of limiting electric current and reducing overvoltage in the protected circuit.

 To achieve the technical result, it is proposed to improve a device for limiting and turning off the current of an electric circuit, containing two parallel electrodes interconnected by a device for initiating an electric discharge, moreover, rails arranged in parallel to each other are used as electrodes, and the device for initiating an electric arc is connected to the sides of the ends of the rails intended for their connection in a protected electrical circuit. The improvement is that the rails are made of resistive material, such as nichrome.

 In another embodiment of the proposed device, the free ends of the rails are connected by a shorting jumper.

 In the third embodiment of the proposed device in order to reduce the size, the rails are coiled in a spiral, both rails being located in the same plane.

 In a fourth embodiment, the rails are coiled into spirals, with the spirals arranged in parallel planes.

 In the fifth embodiment, the rails are twisted in a helical spiral, forming alternating turns located on one cylindrical surface.

 In a sixth embodiment, the rails are coiled in a helical spiral, with the coils of the coils of each rail located on different coaxial cylindrical surfaces.

 In the seventh embodiment, one rail is folded in a helical spiral, and the second is made in the form of a rod and is located along the axis of this helical spiral.

 The essence of the proposed invention is illustrated by the accompanying drawings. In FIG. 1 shows an electrical diagram of the proposed device. In FIG. 2 shows a diagram in the on state, explaining the principle of operation. In FIG. 3 - FIG. 8 shows the design features of the rails in various embodiments of the proposed device.

 In Fig. 1, a device for limiting and turning off the current of an electric circuit comprises a channel formed by a pair of parallel conductive rails 1 and 2 made of resistive material with a high electrical resistivity, the input ends of which are connected in series to an external circuit containing an electric energy source 3 and load 4, the current of which must be limited and disconnected. In addition, the input of the railgun is shunted by a device for initiating an electric arc 5, for example, a safety fusible insert or an opening contact of the switch. The housing and electrical insulators are not shown.

 In FIG. 2 shows the proposed device in the on state. In this case, the arrows indicate the path of the flow of electric current I and the direction of the speed V of the movement of the electric arc 6.

 In another embodiment, the implementation of the proposed device, shown in figure 3, shows a channel formed by a pair of parallel rails 1 and 2, made of a material with high electrical resistance, the input ends of which are connected in series to an external circuit containing an electric energy source 3 and a load 4. The input of the rails is shunted by a device for initiating an electric arc 5, and the free ends are short-circuited by a jumper 7.

 In FIG. 4 shows the construction of the rails in which the rails 1 and 2 are twisted into a spiral, both rails 1 and 2 being located in the same plane.

 In FIG. 5 shows the construction of the rails, in which the rails 1 and 2 are twisted into a spiral, and the rails 1 and 2 are located in parallel planes.

 In FIG. 6 shows the construction of the rails in which the rails 1 and 2 are twisted in a helical spiral, both rails being located on the same cylindrical surface.

 In FIG. 7 shows the construction of the rails in which the rails 1 and 2 are twisted in a helical spiral, wherein the rail 1 is located on one and the rail 2 is located on the other coaxial cylindrical surfaces.

 In FIG. 8 shows the construction of the rails in which the rail 1 is twisted in a helical spiral, and the rail 2 is located on the axis of this spiral.

 The operation of the proposed device (Fig. 1, Fig. 2) is as follows. In the initial state, the electric current from the source of electric energy 3 flows through the load 4 and through the conductor of the device for initiating an electric arc, in this example, through the fuse insert 5, shunting the input of the rails. When the fusible insert is destroyed, for example, melting as a result of current overload, an electric arc 6 arises at the rail input (Fig. 2), which, under the influence of the magnetic field of its own current, moves along the rails with speed V. As the arc moves, they are connected in series with the load sections of rails 1 and 2, made of resistive material with a high resistivity, from the points of connection of the external circuit to the arc. As a result of the voltage drop in these sections of the rails, the current of the external circuit is limited and reduced. The electric arc is extinguished as a result of a decrease in current or is destroyed upon reaching the free ends of the rails. As a result of this, the load current 4 is switched off. The relatively smooth inclusion of the increasing active resistance in series in the external circuit allows the energy stored in the inductance of the external circuit to be dissipated and the switching overvoltage reduced. The value of the total resistance of the rails is selected from the conditions of the required multiplicity of current limitation (decrease). For example, to protect against short circuit, the electrical resistance of the rails can be commensurate with the nominal load resistance.

 The device shown in FIG. 3 operates similarly to the device of FIG. 1, in addition, as the electric arc approaches the short-circuited ends of the rails, as a result of current shunting by jumper 7, the arc goes out without disconnecting the load current. In this case, the current of the external circuit is limited by the resistance of the rails, and switching off, if necessary, can be done by other known means, for example, an external circuit switch.

 Rails, the configuration of which is shown in FIG. 4. - FIG. 8 operate as part of the devices depicted in FIG. 1 and FIG. 3 similar to those described above and can reduce the size. However, in the devices of FIG. 5 and FIG. 7, after the arc passes through the first turn of the spiral, the total magnetic field of all the passed turns acts on the arc. Consequently, the electric arc will move more efficiently at lower currents. In addition, in such rails there is a higher value of the inductive component of the input resistance, which increases the efficiency of limiting the current of the external circuit.

 The invention allows to simplify the design of the device for limiting and turning off the current of the electric circuit and to increase the switching speed at low switching overvoltages, due to the dissipation of the energy of the inductances of the switched circuit on the input active resistance of the rails.

Literature
1. G. A. Lukyanov. Supersonic jets of plasma. L .: Engineering, 1985, p. 36, fig. 2-11.

 2. Copyright certificate of the USSR N 112017, cl. MKI G 01 R 31/02, H 01 T 1/02, dated 02/08/1958

Claims (7)

 1. A device for limiting and turning off the current of an electric circuit, comprising two parallel electrodes interconnected by a device for initiating an electric discharge, the rails being parallel to each other being used as electrodes, and a device for initiating an electric arc is connected from the ends of the rails intended for connecting them to an electric circuit, characterized in that the rails are made of resistive material.  2. The device according to p. 1, characterized in that the free ends of the rails are connected by a conductive jumper.  3. The device according to claim 1 or 2, characterized in that each of the rails is folded into a spiral, and both rails are located in the same plane.  4. The device according to claim 1 or 2, characterized in that each of the rails is folded into a spiral, while the spirals are located in parallel planes.  5. The device according to claim 1 or 2, characterized in that the rails are folded in helical spirals and form alternating turns located on one cylindrical surface.  6. The device according to claim 1 or 2, characterized in that the rails are folded in a helical spiral, the spiral coils of each rail being located on different coaxial cylindrical surfaces.  7. The device according to claim 1 or 2, characterized in that one rail is folded in a helical spiral, and the second is made in the form of a rod and is located along the axis of this helical spiral.

Images