JP2013242977A - Switch - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a switch in which the arc voltage is increased with a small number of components, the current limit effect for limiting the interrupting current is enhanced, and the arc-extinguishing performance is enhanced while reducing the cost.SOLUTION: The switch includes a movable contactor 6 provided detachably for a contactor 4 disposed oppositely, an arc-extinguishing grid 7 provided in an arc-extinguishing chamber formed to include an arc generated when opening the movable contactor, an exhaust port 8 provided in the back surface of the arc-extinguishing grid and exhausting hot gas during interruption, and a permanent magnet 11 provided at a position where magnetic lines of force can interlink a current element in the arc, on the reverse side of the contact 3 of a contactor disposed oppositely to the movable contact 5 with respect to the movable contact 5 at the open end of the movable contactor, and directing the magnetic pole face of N pole or S pole toward an arbitrary direction between the arc-extinguishing grid and the exhaust port.

Description

  TECHNICAL FIELD The present invention relates to a power switch such as a distribution line, and more particularly to a switch excellent in the breaking performance of a DC circuit.

Due to the recent increase in capacity and space saving of low-voltage wiring equipment, power switches and the like are required to have smaller external dimensions. One of the issues in miniaturization is the improvement of current limiting performance that suppresses overcurrent. For this reason, the resistance is increased by increasing the arc length by arc extension, the arc is drawn into the arc extinguishing plate as an arc extinguishing device, and the arc voltage is increased by generating an electrode drop voltage and cooling the arc. It is important to limit the current by such a method. By improving the current limiting performance, it is possible to reduce the arc energy processed in the arc extinguishing chamber of the switch, and it is possible to reduce the size by reducing the thermal and electromagnetic load on the components constituting the switch.
The technique for improving the arc voltage is effective for both AC and DC circuits, but the effect is particularly great for DC circuits that must generate a current zero point by raising the arc voltage above the power supply voltage. is there. In the conventional power switch, as described above, the arc voltage is increased by extending the arc or dividing the arc in the grid, but a driving force is applied to the arc generated between the contacts at the time of opening, It is necessary to move from the space near the contact. Therefore, in particular, in a switch applied to a DC circuit, a permanent magnet is generally arranged in an arc extinguishing chamber, a magnetic driving force is generated in the arc by interlinking magnetic flux with the arc, and its behavior is controlled, The extension of the arc and the incorporation of the arc into the grid are realized. For example, when two permanent magnets are arranged at the upper and lower positions of an arc extinguishing device in which a plurality of grids are stacked to generate a magnetic driving force in the arc, strengthen the arc capture into the grid, and the energization direction is reversed There is one that realizes the generation of a high arc voltage (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2011-3378 (pages 12-17, FIG. 6)

  In the conventional switch as described above, the arc extinguishing function part has no moving part, the structure of the arc extinguishing function is simple, and a high-voltage AC or DC current arc can be controlled and cut off by a forced magnetic field. However, in order to cope with the polarity reversal of the breaking current, it is necessary to arrange two permanent magnets on the movable side and the fixed side, and further, it is necessary to specify the polarity direction of the permanent magnet. Since it is necessary to manage the polarity direction during assembly, there is a problem of high cost.

  The present invention has been made in order to solve the above-described problems of the prior art, and the arc current is increased with a small number of parts, and the current limiting effect of limiting the breaking current is increased. The purpose is to obtain a switch that is improved and can be reduced in cost.

  The switch according to the present invention includes a movable contact provided so as to be able to contact and separate from an opposed contact and an arc extinguishing chamber formed so as to include an arc generated when the movable contact is opened. The arc-extinguishing grid provided, the exhaust port for discharging the hot gas at the time of interruption provided on the back of the arc-extinguishing grid, and the movable contact of the movable contact at the open end are opposed to each other On the opposite side of the contact point of the contactor, the magnetic field lines are provided at positions where the magnetic field lines can be linked to the current element in the arc, and the magnetic pole surface of the N pole or the S pole extends from the arc extinguishing grid to the exhaust port. Permanent magnets oriented in any direction were provided.

  In the present invention, the magnetic flux of the permanent magnet is linked to the current element parallel to the power source-load direction of the switch in the arc near the movable contact at the open extreme, and the electromagnetic driving force based on the vector product of the magnetic flux and the current element is Occur. As a result, the arc is curved in the direction of the side of the arc extinguishing chamber and extends upward from the arc extinguishing chamber, thereby increasing the arc length, increasing the arc resistance and increasing the arc voltage. Furthermore, as the arc length increases, the number of arc extinguishing plates of the arc extinguishing grid facing the arc increases. For this reason, the arc voltage increases due to the effect of arc extension, the arc division by the arc extinguishing grid, and the increase of the cooling effect, and the interruption performance is improved. In addition, since only one permanent magnet is required, the manufacturing cost can be reduced.

It is a principal part side view which shows the arc-extinguishing chamber vicinity in the closing state of the switch concerning Embodiment 1 of this invention. It is a principal part side view which shows the arc extinguishing chamber vicinity in the open state of the switch shown in FIG. It is a perspective view which expands and shows the stationary contact of the switch shown in FIG. It is a perspective view which shows the positional relationship of the stationary contact of the switch shown in FIG. 1, and an arc-extinguishing grid. In Embodiment 1 of this invention, it is operation | movement explanatory drawing which looked at the state which the magnetic flux from a permanent magnet links with an arc, and the driving force generate | occur | produced from the exhaust port side. It is a principal part side view which shows the arc extinguishing chamber vicinity in the open state of the switch concerning Embodiment 2 of this invention. In Embodiment 2 of this invention, it is operation | movement explanatory drawing which looked at the state which the magnetic flux from a permanent magnet links with an arc, and the drive force generate | occur | produced from the exhaust port side. It is a principal part side view which shows the arc-extinguishing chamber vicinity in the open state of the switch concerning Embodiment 3 of this invention. It is a principal part side view which shows the arc extinguishing chamber vicinity in the open state of the switch concerning Embodiment 4 of this invention. In Embodiment 4 of this invention, it is operation | movement explanatory drawing which looked at the state which the magnetic flux from a permanent magnet links with an arc, and the driving force generate | occur | produced from the exhaust port side. It is a principal part side view which shows the arc extinguishing chamber vicinity in the open state of the switch concerning Embodiment 5 of this invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that the same reference numerals denote the same or corresponding parts throughout the drawings.
Embodiment 1 FIG.
1-5 is a figure for demonstrating the switch which concerns on Embodiment 1, More specifically, FIG. 1 is a principal part side view which shows the arc extinguishing chamber vicinity in the closing state of a switch, 2 is a side view of the main part showing the vicinity of the arc extinguishing chamber in the open state, FIG. 3 is an enlarged perspective view showing the fixed contact in FIG. 1, and FIG. 4 shows the positional relationship between the fixed contact and the arc extinguishing grid. FIG. 5 is an operation explanatory view of the state in which the magnetic flux from the permanent magnet is linked to the arc and the driving force is generated from the exhaust port side in the first embodiment.

  In the figure, when the switch is configured so that the interior of the housing formed by the base 1 made of a resin insulator and the cover 2 can be applied to, for example, a three-phase AC circuit, the switch is arranged in a space partitioned in three phases. , Each arc extinguishing chamber portion is formed. As shown in FIGS. 1 and 2, a stationary contact 4 having a fixed contact 3 fixed thereto and a movable contact 6 having a movable contact 5 fixed to one end thereof are disposed in the arc extinguishing chamber of each phase. The other end side of the movable contact 6 is supported by a rotating shaft 6a as a support portion so as to be able to rotate. Although not shown, a cross bar made of an insulating portion is provided so as to surround the movable contact 6 in the vicinity of the rotating shaft 6a, and is linked to a drive mechanism portion that performs the ON / OFF operation of the contact point. The movable contact 6 is configured to open and close around the rotation shaft 6a.

  As shown in FIG. 3, the fixed contact 4 is provided with a terminal portion 4a for connecting to an external conductor at one end (upper right side in the figure), and the other end where the fixed contact 3 is provided from the terminal 4a. The conductors branched in two in the direction of the part extend in parallel, are integrated in front of the rotating shaft 6a of the movable contact 6, and pass through the central part in the direction of the terminal part 4a between the conductors extending in parallel. The fixed contact 3 is fixed in the vicinity of the folded portion, and the folded piece is further extended in the direction of the terminal portion 4a to form an arc runner 4b. In the first embodiment, the fixed contact having the shape as shown in FIG. 3 is used. However, the shape and the like of the fixed contact are not particularly limited in the implementation of the present invention, and the fixed contacts having other configurations are used. It can be a contact.

  The arc-extinguishing grid 7 shown in FIGS. 1 and 2 has an interval between horseshoe-shaped arc-extinguishing plates provided with notches for preventing the rotating operation of the movable contact 6 as shown in FIG. It is made of a plurality of stacked layers, held by an insulator (not shown), and disposed above the stationary contact 4. The back part (right direction in the figure) of the arc extinguishing grid 7 made of the above laminate is provided with a base 1 and a cover 2 for exhausting hot gas from the arc generated in the arc extinguishing chamber when the current is interrupted to the outside of the arc extinguishing chamber. The formed exhaust port 8 is configured. The exhaust port 8 has a plate-like barrier 9 having a vent hole, and the exhaust port 8 and the barrier 9 are overlapped and closed when not shut off, and an arc is generated. When the pressure in the arc extinguishing chamber rises, a barrier 10 is disposed so that the upper portion is inclined to the side opposite to the arc extinguishing chamber (right direction in the figure), and the arc extinguishing space is opened to the space outside the switch.

  As shown in FIG. 2, the movable contact 5 is located above the arc-extinguishing chamber from the movable contact 5 when the movable contact 6 is in the extreme open state (maximum open state), that is, when the movable contact 6 is completely opened. On the other hand, the permanent magnet 11 which is insulated and held at the position on the opposite side of the opposed fixed contact 4 to the fixed contact 3 and on the exhaust port 8 side is a magnetic pole surface of either the N pole or the S pole. (N pole here) is arranged in a state of facing the arc extinguishing grid 7 side. The permanent magnet 11 is provided on the extended portion of the surface including the rotation locus of the movable contact 6. Further, although the permanent magnet 11 is illustrated as having a structure enclosed in a resin insulator constituting the cover 2, a structure in which the permanent magnet 11 is insulated and held using a member different from the cover 2 may be used. Since other configurations are the same as those of the conventional switch, illustration and description are omitted.

  Next, the operation of the switch configured as described above will be described. In the arc extinguishing chamber, the stationary contact 4 and the movable contact 6 in the state of FIG. 1 are energized. For example, when the switch is turned off by manual operation, the movable contact 6 opens and the fixed contact 3 The movable contact 5 leaves and an arc is generated between the fixed contact 3 and the movable contact 5. As the opening distance of the movable contact 6 becomes longer, the arc on the fixed contact 3 moves to the arc runner 4b due to the magnetic driving force from the current flowing through the fixed contact 4, and further to the arc facing the arc extinguishing grid 7. On the other hand, the arc 12 expands greatly as shown in FIG. 2 due to the magnetic attractive force of the arc extinguishing grid 7 which is a ferromagnetic material, the flow of hot gas generated by the arc to the exhaust port 8, and the like. Become. The degree of contribution of the factors that drive these arcs differs depending on the breaking current. At the same time, the arc 12 is divided by the arc extinguishing grid 7, the arc 12 is cooled, and the arc voltage rises.

  Here, the direction in which the current flows is the anode side on the stationary contact 4 side and the cathode side on the movable contact. When the movable contact 6 reaches the maximum open state and the arc 12 expands greatly, the magnetic flux 13 of the permanent magnet 11 disposed above the movable contact 6 is linked to the arc 12 as shown in FIG. It becomes like this. FIG. 5 shows a case where the peripheral structure of the movable contact 5 and the permanent magnet 11 is viewed from the exhaust port 8 side as described above, and there is a component from the front side to the back side in FIG. As a result, a Lorentz force is generated in the arc 12 in the vicinity of the movable contact 5, and a magnetic driving force in a direction perpendicular to the magnetic flux acts, and the arc extinguishing chamber in which the permanent magnet 11 is arranged while curving in the arc extinguishing chamber side surface direction. It is possible to obtain the state of the arc 14 which has moved further upward and is further extended from the arc 12 as indicated by a broken line in FIG.

  As a result, the arc voltage is increased by the extension of the arc length, and a switch having excellent current limiting performance can be obtained. Furthermore, by extending like the arc 14, the number of arc extinguishing plates facing the arc on the movable contact 5 side is increased, and the arc voltage is improved accordingly, and the arc can be effectively extinguished and the current can be interrupted. It should be noted that one or both of the energization direction of the current and the polarity direction of the permanent magnet 11 may be opposite to the above description, but also in these cases, when one of the energization direction and the polarity direction is opposite, the side of the arc extinguishing chamber In any case, the arc is driven in the same manner above the arc extinguishing chamber in which the permanent magnet 11 is disposed, and the effect of improving the arc voltage can be obtained. . Moreover, although the interruption | blocking of direct current was demonstrated, it cannot be overemphasized that it can interrupt | block also in the case of alternating current.

  As described above, in the first embodiment, the exhaust port 8 side discharges the hot gas generated above the movable contact 5 of the movable contact 6 at the open extreme and when the current is interrupted to the outside of the arc extinguishing chamber. In this example, the permanent magnet 11 is arranged at a position where the lines of magnetic force intersect with the current element of the arc, and in this example, the N pole or S pole magnetic pole surface of the permanent magnet 11 is subjected to arc partial cooling. By facing the arc extinguishing grid 7 side, the magnetic flux of the permanent magnet 11 is chained to the current element of the arc parallel to the power source-load direction of the switch with respect to the arc 12 near the movable contact 5 in the open state. When crossed, an electromagnetic driving force based on the vector product of the magnetic flux and the current element acts on the arc 12, and a driving force that causes the arc 12 to move upward in the arc extinguishing chamber is generated.

  As a result, the arc in the vicinity of the movable contact 5 is bent upward in the arc extinguishing chamber so as to bend in the side direction of the arc extinguishing chamber, the arc length becomes longer like the arc 14, and the arc resistance increases. Excellent current limiting performance can be obtained by increasing the arc voltage. In particular, it is effective for interrupting current in a DC circuit where generation of a high arc voltage is important. Further, as the arc length becomes longer, the number of touching the arc extinguishing plates of the arc extinguishing grid 7 facing the arc increases. The arc voltage increases due to the effect of the arc extension, the arc division by the arc extinguishing grid 7, and the effect of increasing the cooling effect, and the interruption performance is improved. Furthermore, regardless of the polarity of the permanent magnet 11 and the energization direction, the arc is extended above the arc extinguishing chamber, and excellent current limiting performance can be obtained. Moreover, the number of permanent magnets 11 may be one, and since it is not necessary to consider the polarity direction of the permanent magnet 11, manufacture is easy and cost can be reduced. As a result, the switch can be downsized and the durability can be improved.

Embodiment 2. FIG.
FIG. 6 is a side view of the main part showing the vicinity of the arc extinguishing chamber in the open state of the switch according to the second embodiment of the present invention, and FIG. 7 is a diagram showing the magnetic flux from the permanent magnet in the arc in the second embodiment of the present invention. It is operation | movement explanatory drawing which looked at the state which linked with respect to and the driving force generate | occur | produced from the exhaust-port side. In the figure, the permanent magnet 11A has magnetic lines of force linked to the current element in the arc above the arc-extinguishing chamber from the movable contact 5 when the movable contact 6 is in the open extreme and on the exhaust port 8 side. It is placed in a position where it is insulated and protected by the resin insulator that constitutes the cover 2, and is further installed with the N pole or S pole pole face (here, the N pole) facing the exhaust port 8 side. Has been. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  In Embodiment 2 configured as described above, the case where the stationary contact 4 side is the anode and the movable contact is the cathode side will be described as the direction of current flow. When the movable contact 6 reaches the maximum open state and the arc 12 expands greatly, the magnetic flux 13 emitted from the N-pole surface of the permanent magnet 11A disposed above the movable contact 6 is as shown in the operation explanatory diagram of FIG. In addition, since they are distributed almost radially, they are interlinked with the arc 12. When the vicinity of the movable contact 5 and the permanent magnet 11A is viewed from the exhaust port 8 side, there is a component from the front side to the back side in FIG.

  As a result, a Lorentz force is generated in the arc 12 in the vicinity of the movable contact 5, and a magnetic driving force in a direction perpendicular to the magnetic flux acts, and the arc extinguishing chamber in which the permanent magnet 11A is arranged while curving in the arc extinguishing chamber side surface direction. It becomes possible to obtain the state of the arc 14 that has been moved upward and further extended from the arc 12. As a result, the arc voltage can be improved by extending the arc length, and a switch excellent in current limiting performance can be obtained. Further, as an effect of extending like the arc 14, the number of arc extinguishing plates facing the arc on the movable contact 5 side is increased, and an effect that the arc voltage is improved correspondingly is obtained. Even when one or both of the current application direction and the polarity direction of the permanent magnet 11A are opposite to each other, as in the case of the first embodiment, the arc 12 is similarly directed above the arc extinguishing chamber in which the permanent magnet 11A is disposed. It is driven and the arc voltage improvement effect can be obtained similarly.

Embodiment 3 FIG.
FIG. 8: is a principal part side view which shows the arc extinguishing chamber vicinity in the open state of the switch concerning Embodiment 3 of this invention. In the figure, the permanent magnet 11 is similar to the first embodiment in that the arc on the exhaust port 8 side opposite to the fixed contact 3 of the fixed contact 4 with respect to the movable contact 5 at the open extreme of the movable contact 6. A resin insulator that is insulated and held at a position where the magnetic lines of force cross with respect to the current element, and is arranged with the N pole face facing the arc extinguishing grid 7 and covers the outside of the permanent magnet 11 A portion forming the inner wall of the arc extinguishing chamber further outside is covered with a protective cover 15 made of a nonmagnetic metal. Since other configurations are the same as those of the first embodiment, description thereof is omitted.

  In the third embodiment configured as described above, when the movable contact 6 reaches the maximum open state when the current is interrupted and the arc 12 is greatly expanded, the arc 12 is in the side direction of the arc extinguishing chamber as in the first embodiment. It is possible to obtain a state of the arc 14 that is further extended than the arc 12 by moving to the upper part of the arc extinguishing chamber in which the permanent magnet 11 is arranged while being bent in a straight line. When the protective cover 15 is not provided, the cover 2 becomes high temperature when the arc 14 approaches, and an insulating vapor is ejected from the surface to become a pressure generation source. For this reason, the force which pushes back the arc 14 downward is generated, and it becomes difficult to stably maintain the arc 14 in the arc extinguishing chamber 14. On the other hand, since the protective cover 15 suppresses the ejection of insulating vapor from the cover 2 made of a resin insulator, there is no force to push the arc downward to the arc extinguishing chamber, and the arc is stably stabilized above the arc extinguishing chamber. The arc voltage can be improved by stretching the Moreover, the effect that the arc voltage can be raised by the protective cover 15 made of a non-magnetic metal cooling the arc 14 similarly to the arc extinguishing plate is obtained.

Embodiment 4 FIG.
FIG. 9 is a side view of the main part showing the vicinity of the arc extinguishing chamber in the open state of the switch according to the fourth embodiment of the present invention, and FIG. 10 shows the magnetic flux from the permanent magnet in the arc in the fourth embodiment of the present invention. It is operation | movement explanatory drawing which looked at the state which linked with respect to and the driving force generate | occur | produced from the exhaust-port side. In the figure, the surface portion forming the inner wall of the arc extinguishing chamber on the outer surface of the resin insulator that covers the outside of the permanent magnet 11 is divided into a plurality of portions in the left-right direction of FIG. It is covered with a protective cover 15A made of a plurality of nonmagnetic metals. Other configurations are the same as those of the first embodiment.

  In the fourth embodiment configured as described above, when the movable contact 6 reaches the maximum open state when the current is interrupted and the arc 12 expands greatly, as shown in FIG. 10, as in the first embodiment. By the action of the magnetic lines 13 of the permanent magnet 11, the arc 12 moves to the upper side of the arc extinguishing chamber where the permanent magnet 11 is arranged while curving in the side direction of the arc extinguishing chamber, and the state of the arc 14 further extended from the arc 12 is obtained. Is possible. The divided protective cover 15A suppresses the ejection of insulating gas vapor from a part of the cover 2 made of a resin insulator, and further contacts with the arc 14 so that the arc is similar to the arc extinguishing plate. Therefore, the arc 14 can be stably maintained above the arc extinguishing chamber and the arc voltage can be further increased.

Embodiment 5 FIG.
FIG. 11: is a principal part side view which shows the arc extinguishing chamber vicinity in the open state of the switch concerning Embodiment 5 of this invention. In the figure, the outer surface portion of the resin insulator constituting the cover 2 that covers the outside of the permanent magnet 11 and forms the inner wall of the arc extinguishing chamber, in particular, the exhaust port 8, the arc extinguishing grid 7, and the movable contactor. 6 is a commutation plate as a commutation member made of a magnetic material or a non-magnetic material electrically connected by a flexible conductor 16 so as to have the same potential as the movable contact 6. 17 is provided. The commutation plate 17 is integrally bent from the surface facing the exhaust port 8 to the surface facing the movable contact 6. Other configurations are the same as those of the first embodiment.

  In the fifth embodiment configured as described above, when the movable contact 6 reaches the maximum open state when the current is interrupted and the arc 12 is greatly expanded, the arc 12 is in the direction of the arc extinguishing chamber side as in the first embodiment. It moves to the upper part of the arc extinguishing chamber in which the permanent magnet 11 is arranged while being curved, and comes into contact with the commutation plate 17. As a result, the current path passing through the movable contact 6 is changed to a path passing through the commutation plate 17, and an arc 18 is generated between the commutation plate 17 and the fixed contact 4. Since the commutation plate 17 extends from the movable contact 6 in the direction of the exhaust port 8 and reaches the upper part of the arc extinguishing device, the arc is maintained in the movable contact 6 that needs to extend the arc in the direction of the arc extinguishing grid 7. Compared to the above, arc division and cooling performance in the arc extinguishing grid 7 are excellent. In this way, by providing the commutation plate 17, the ejection of the insulating gas vapor from the cover 2 is eliminated, and furthermore, the arc extinguishing plate constituting the arc extinguishing grid 7 can be effectively used. Can be further increased.

  It should be noted that within the scope of the present invention, a part or all of each embodiment can be freely combined, or each embodiment can be appropriately modified or omitted. For example, both the fixed contact 4 and the movable contact 6 in the above description may be configured to move together. In that case, the permanent magnet 11 is one of the pair of movable contacts facing each other. Should be provided. In addition, the permanent magnet 11 (11A) has been described in which the direction of the N-pole or S-curved magnetic pole face is opposed to the arc-extinguishing grid 7 and that opposed to the exhaust port 8, but the present invention is not limited to this. It is attached obliquely at an arbitrary angle within the range of 90 ° from the direction of the arc grid 7 (downward direction in the figure) to the direction of the exhaust port 8 (lateral direction or rearward direction) or slightly beyond it. However, the same effect can be expected.

  DESCRIPTION OF SYMBOLS 1 Base, 2 Cover, 3 Fixed contact, 4 Fixed contact, 4a Terminal part, 4b Arkrunner, 5 Movable contact, 6 Movable contact, 6a Rotating shaft, 7 Arc extinguishing grid, 8 Exhaust port, 9, 10 Barrier, 11 11A permanent magnet, 12 arc, 13 magnetic flux, 14 arc, 15, 15A protective cover, 16 flexible conductor, 17 commutation plate, 18 arc.

Claims (5)

  A movable contact provided so as to be able to contact and separate with respect to the opposed contact; an arc extinguishing grid provided in an arc extinguishing chamber formed so as to include an arc generated when the movable contact is opened; An exhaust port provided on the back surface of the arc extinguishing grid that discharges hot gas at the time of interruption to the outside, and a contact point opposite to the contact point of the contact point opposed to the movable contact point of the movable contact point at the open end The permanent magnet is provided at a position where magnetic field lines can be linked to the current element in the arc, and the pole surface of the N pole or S pole is directed in an arbitrary direction from the arc extinguishing grid to the exhaust port. A switch characterized by comprising.   2. The switch according to claim 1, wherein only one permanent magnet is used for one of the movable contacts.   The permanent magnet is surrounded by a resin insulator, and a surface of the resin insulator facing the arc extinguishing grid and the exhaust port is covered with a nonmagnetic metal. The switch according to claim 2.   The switch according to claim 3, wherein the nonmagnetic metal is divided into a plurality of parts.   The permanent magnet is surrounded by a resin insulator, and the surface of the resin insulator facing the arc extinguishing grid and the exhaust port is a magnetic or nonmagnetic material provided at the same potential as the movable contact. The switch according to claim 1 or 2, wherein the switch is covered with a commutation member made of a metal.

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