Interrupter chamber

The arcing grid was invented by the outstanding Russian pioneer-electrician M.O. Dolivo-Dobrovolsky ( German patents No. 266745 and No. 272742 dated May 4 and July 24, 1912, respectively) ^{[1] [2]} .

The simplest arcing lattice, used, for example, in sectional insulators , can be made in the form of two plates located at an angle. The arc, moving along the plates, stretches, cools and goes out.

The arcing switch circuit is a set of metal (usually steel) stamped rectangular plates with a V-shaped neck, galvanically coated with copper or chrome to improve electrical conductivity and corrosion protection, mounted parallel or fan-shaped at some distance from each other between two holders made of dielectric (typically pressboard), or in large switching power devices, in the holder of asbestos, with the arcing plates are electrically isolated from each other. The arcing chambers of powerful switching devices include permanent magnets or electromagnets that repel the plasma arc of an electric arc from metal contacts into the arcing chamber (the so-called "magnetic blast").

The principle of operation of the arcing grid is based on the fact that near the electrodes there is a significant voltage drop (the total drop in the near-cathode and anode voltages at one contact is 15-30 V) in the arc shaft. Under the influence of the intrinsic magnetic field , the arc plasma begins to move along the arcing horns of the switching contacts (the movement of the arc under its own magnetic field is the movement of a current conductor interacting with a self-generated magnetic field, since the gas in the arc is strongly ionized and, in a first approximation, can be considered as elastic conductor with current. The movement of the conductor with current when interacting with a magnetic field is described by Ampere's law ). In this case, the plasma of the arc is drawn into the arcing chamber and is divided into a number of small arcs between the plates, which is equivalent to a series of consecutive contacts, each of which causes a near-electrode voltage drop ^[3] . Since the highly ionized plasma has a very high thermal conductivity due to the high concentration of free electrons , it cools down, transferring part of the heat to the plates of the lattice, which entails deionization due to ion recombination and subsequent arc quenching. The manufacture of arcing plate plates from a ferromagnetic material (usually steel ) is mainly caused not by considerations of saving non-ferrous metals , but by facilitating the entry of the arc cable into the lattice: the magnetic field of the arc tends to close in the ferromagnetic mass, as a result of which forces are drawn that draw the plasma of the arc into the arcing grid. An additional advantage of ferromagnetic arcing plates is that electromagnetic forces not only draw the arc into the lattice, but also exclude the exit of plasma from the other side of the arcing system.

The arcing chamber is designed in such a way that the electric arc formed by opening the contacts of switching devices is drawn into the arcing grid, since such a plasma motion is energetically favorable. Having drawn itself into the gaps of the chamber plates, the electric arc lengthens, breaks up by the chamber plates into several smaller arcs in length, and at the same time it quickly deionizes, cools and goes out. In arcing chambers with magnetic blasting, carried out using an additional magnetic field created with the help of permanent magnets or electromagnets , the plasma of the arc is more effectively drawn into the arcing chamber by the action of the magnetic field generated by these magnets on it, since the plasma tends to push out from the high electrical conductivity magnetic field, keeping the magnetic flux inside itself unchanged. A favorable additional factor of interaction with a ferromagnetic lattice, which affects the movement of a number of small arcs (obtained by splitting a large arc), is the alignment of their velocities: the arcs that are pulled forward will slow down, and the lagging ones will accelerate, excluding them from the outside of the lattice and retracting the arc at low currents in an arc.

The plasma of the electric arc when opening the switching contacts accelerates to supersonic speeds . Therefore, the arc entering the lattice is strongly inhibited due to aerodynamic drag . The reduction of this resistance is due to the proper design of the arcing device. For example, a grid is used in the form of plates covering power contacts on three sides, and the plates themselves have a V-shaped cut for moving movable switching contacts in this cut-out and better coverage of the plasma arc cord (in addition, the V-shaped cut in the plates gives accelerated movement arcs when moving deeper into the lattice due to the increasing interaction with the arc ^[4] ). Sometimes the plates in the grid are staggered. The aerodynamic drag for a moving plasma can be reduced by reducing the number of plates inside the grating, but at the same time, to maintain the efficiency of arc extinction, it is necessary to increase the length of the grating, which increases the size of the switching device as a whole. Therefore, the distance between the plates is selected for compromise reasons, usually not more than 2 mm. At shorter distances between the plates, it is possible to weld the plates by spraying drops of molten metal with an electric arc and form metal bridges between the plates.

Arcing chambers are used in automatic air circuit breakers , magnetic starters (starting from the second value), contactors , electromagnetic switches , sectional isolators of the contact network , load breakers and circuit breakers , some of them have arc suppression devices.

• Rodshtein L.A. Electric devices, L 1981
• Interrupter device // Great Soviet Encyclopedia : [in 30 vol.] / Ch. ed. A.M. Prokhorov . - 3rd ed. - M .: Soviet Encyclopedia, 1969-1978.