CN212648167U - 5G hydraulic electromagnetic circuit breaker with large arc extinguish chamber - Google Patents

Abstract

The utility model provides a 5G hydraulic electromagnetic circuit breaker with a large arc extinguish chamber, which comprises a shell, a tripping mechanism, a moving contact, a static contact and an arc extinguish chamber, wherein the tripping mechanism, the moving contact, the static contact and the arc extinguish chamber are arranged in the shell; one end of a static contact is connected with an incoming line terminal, the static contact is of a sheet structure, the front end of the middle part of the static contact extends to one side far away from the incoming line terminal and then is twisted to one side to form a U-shaped structure, the lower end part of the U-shaped structure is bent downwards to form a bearing part, and the static contact is arranged on the bearing part; one side of the bearing part, which is far away from the U-shaped structure, extends towards the inner direction of the arc extinguish chamber to form a lower arc angle; the arc extinguishing chamber is adjacent to the static contact, and the arc extinguishing chamber sets up a plurality of arc extinguishing bars pieces including two bars piece supports that the symmetry set up in between the bars piece, and each arc extinguishing bars piece interval and range upon range of setting, arc extinguishing bars piece and arc angle parallel arrangement down. The circuit breaker can realize the quick separation of the moving contact and the static contact, rarely has breaking delay, and is more suitable for 5G application scenes.

Description

5G hydraulic electromagnetic circuit breaker with large arc extinguish chamber

Technical Field

The utility model relates to a circuit breaker, specifically speaking relates to a can divide hydraulic pressure electromagnetic circuit breaker for 5G of disconnected arc extinguishing fast who divides with big explosion chamber.

Background

The circuit breaker is a switching device capable of closing, carrying, and opening/closing a current under a normal circuit condition and a current under an abnormal circuit condition within a prescribed time. The circuit breaker generally includes contact, tripping device and explosion chamber etc. and current explosion chamber structure generally comprises the arc extinguishing bars piece that the multi-disc is parallel and the interval sets up and the insulation board that two are parallel and the interval sets up, and two insulation boards are fixed with the parallel state of the range upon range of arc extinguishing bars piece of multi-disc. Generally, an avoiding groove is formed on one side of each arc-extinguishing grid plate close to the contact, and thus when a plurality of arc-extinguishing grid plates are stacked, an avoiding space for the moving contact to pass through is formed in the middle of the stacked arc-extinguishing grid plates. When the movable contact and the static contact are separated, the electric arc generated between the movable contact and the static contact enters the arc extinguishing grid plate under the action of electric power, the arc extinguishing grid plate is divided into a plurality of sections of short arcs connected in series by the stacked arc extinguishing grid plate, and when the power supply voltage is lower than the arc voltage, the electric arc is naturally extinguished. Because the space structure of the circuit breaker is limited, the number of arc extinguishing grids is limited, and therefore, how to improve the arc extinguishing capability of the arc extinguishing chamber in the limited space is one of the technical difficulties in the prior art.

SUMMERY OF THE UTILITY MODEL

In order to solve the technical problem, the utility model provides a can divide hydraulic pressure electromagnetic circuit breaker for 5G of disconnected arc extinguishing fast with big explosion chamber, this circuit breaker can realize the quick separation of sound contact, and the disconnected characteristic of delaying of branch appears very few, more is applicable to in the 5G applied scene.

Based on the above purpose, the utility model provides a 5G hydraulic electromagnetic circuit breaker with a large arc extinguish chamber, which comprises a shell, a tripping mechanism, a moving contact, a static contact and an arc extinguish chamber, wherein the tripping mechanism, the moving contact, the static contact and the arc extinguish chamber are arranged in the shell; one end of the static contact is connected with the incoming line terminal, the static contact is of a sheet structure, the front end of the middle part of the static contact extends to one side far away from the incoming line terminal and then is twisted to one side to form a U-shaped structure, the lower end part of the U-shaped structure is bent downwards to form a bearing part, and the static contact is arranged on the bearing part; one side of the bearing part, which is far away from the U-shaped structure, extends towards the inner direction of the arc extinguish chamber to form a lower arc angle for guiding the electric arc to rapidly enter the arc extinguish chamber;

the arc extinguishing chamber with the static contact is adjacent to be set up, and the arc extinguishing chamber sets up a plurality of arc extinguishing bars piece including two bars piece supports that the symmetry set up between the bars piece, each arc extinguishing bars piece interval and range upon range of setting, the arc extinguishing bars piece with arc angle parallel arrangement down.

Preferably, the upper end of the arc extinguishing chamber extends to a side close to the U-shaped structure, so that a gap above the gas generating piece is filled, and arc leakage is avoided.

Preferably, the angle of the downward bending of the bearing part is 30-40 degrees.

Preferably, the inner side of the U-shaped structure is symmetrically provided with air sheet brackets, and the air sheet brackets are provided with air generating sheets; therefore, the static contact is arranged on the outer side of the gas production support, the current carrying and the electric conduction of the static contact are not influenced, the heat dissipation is facilitated, and the temperature rise of a product is ensured.

Preferably, the lower edge of the gas generating piece is parallel to the lower arc angle, so that the gas generating piece above the lower arc angle is arranged in a parallelogram.

Preferably, the gas generating piece is made of a Nomi silk paper material.

Preferably, an arc isolating block is further arranged in the U-shaped structure.

Compared with the prior art, the beneficial effects of the utility model are that:

the utility model discloses cooperation structure to static contact and explosion chamber is improved, like this, has not only effectively increased the explosion chamber, improves the arc extinguishing ability of circuit breaker, also is favorable to the quick separation of sound contact simultaneously, avoids or reduces electric arc to produce the scaling loss to sound contact and near related device, based on the utility model discloses quick arc extinguishing appears dividing the characteristic of breaking time delay very few, the utility model discloses the product is more applicable to in the 5G applied scene.

Drawings

The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.

Fig. 1 is a first schematic diagram of an internal structure of a hydraulic electromagnetic circuit breaker for 5G in an embodiment of the present invention;

fig. 2 is a schematic diagram of an internal structure of a 5G hydraulic electromagnetic circuit breaker according to an embodiment of the present invention;

fig. 3 is an appearance structure diagram of a hydraulic electromagnetic circuit breaker for 5G in the embodiment of the present invention;

fig. 4 is a schematic diagram of a pre-assembly structure of a 5G hydraulic electromagnetic circuit breaker and a panel according to an embodiment of the present invention;

fig. 5 is a schematic view of an assembly structure of a hydraulic electromagnetic circuit breaker and a panel for 5G in the embodiment of the present invention;

fig. 6 is a schematic structural view of a stationary contact connection inlet terminal according to an embodiment of the present invention;

fig. 7 is a side view structural diagram of a stationary contact connection inlet terminal according to an embodiment of the present invention;

fig. 8 is an assembly structure diagram of a static contact and a gas generating component in an embodiment of the present invention;

fig. 9 is an exploded view of a static contact and a gas generating component according to an embodiment of the present invention;

fig. 10 is a schematic view of the internal structure of the circuit breaker of the embodiment shown in fig. 6-9;

fig. 11 is a schematic structural diagram of a static contact according to another embodiment of the present invention;

fig. 12 is a structural view of an assembly of a static contact and an arc extinguish chamber in another embodiment of the invention;

fig. 13 is a structural diagram of an internal assembly of a static contact and an arc extinguish chamber in another embodiment of the invention;

fig. 14 is a top view of an arc chute according to another embodiment of the present invention;

fig. 15 is a schematic view of the internal structure of the circuit breaker having the embodiment of fig. 11-14;

fig. 16 is a schematic view of the airflow and arc conduction directions of the hydraulic electromagnetic circuit breaker for 5G in the embodiment of the present invention.

Wherein, 1, a shell; 2. a tripping mechanism; 3. a moving contact; 4. static contact; 5. an arc extinguishing chamber;

11. a through hole; 21. an armature; 22. an electromagnetic coil; 31. a movable contact; 32. an arc extinguishing block;

41. a stationary contact; 42. a receiving part; 43. a lower arc angle; 44. an arc-isolating sheet;

51. a grid support; 52. arc extinguishing grid pieces;

61. a push rod; 62. a positioning member; 63. a linkage member; 64. a first elastic member; 65. a second elastic member; 66; a third elastic member;

71. a gas production support; 72. a gas generating sheet;

81. an incoming terminal; 82. an outlet terminal;

a. a panel; b. and (4) an arc.

Detailed Description

The present invention will be further explained with reference to the accompanying drawings and examples.

It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.

It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.

The embodiment provides a hydraulic electromagnetic circuit breaker for 5G, as shown in fig. 1-3, the circuit breaker includes a housing 1, and an unlocking mechanism, a tripping mechanism 2, a moving contact 3, a static contact 4 and an arc extinguish chamber 5 which are arranged in the housing 1, wherein the moving contact 3 is provided with a moving contact 31, and the static contact 4 is provided with a static contact 41; wherein,

the unlocking mechanism is arranged adjacent to the tripping mechanism 2 and can drive the tripping mechanism 2 to rotate; the tripping mechanism 2 is hinged with the moving contact 3, and when the tripping mechanism 2 rotates, the moving contact 3 rotates along with the tripping mechanism, so that the moving contact 31 is driven to contact or be far away from the static contact 41, and the on-off of the circuit breaker is realized;

one end of the static contact 4 is connected with the incoming line terminal 81, the middle part of the static contact 4 is bent towards one side far away from the incoming line terminal 81 to form a U-shaped structure, and the arc extinguish chamber 5 is arranged adjacent to the U-shaped structure; the other end of static contact 4 sets up stationary contact 41, and one side of stationary contact 41 is provided with and extends to the inside direction of explosion chamber 5 and is used for guiding the quick lower arc angle 43 that gets into explosion chamber 5 of electric arc. When the load is overloaded, when the current of the electromagnetic coil 22 in the tripping mechanism 2 is increased and exceeds a rated value, the magnetic field intensity of the electromagnetic coil 22 is enhanced, the movable iron core in the delay tube moves towards the pole shoe, the electromagnetic force reaches the maximum value, the armature 21 is attracted to the pole shoe, the tripping device acts to drive the movable contact 3 to rotate, and therefore the movable contact 31 is separated from the fixed contact 41. It should be noted that, under the condition of short circuit, short circuit instantaneous tripping is very easy to occur, and the short circuit instantaneous tripping can cause the moving contact 3 and the static contact 4 to be separated to generate electric arc instantly; the current passing through the electromagnetic coil 22 is large, the electromagnetic force is rapidly increased, the armature 21 is attracted to the pole shoe before the movable iron core moves, the release does not have delay action, and the contact is opened, namely short-circuit instantaneous release is realized.

As a preferred embodiment, as shown in fig. 1-3, the unlocking mechanism includes a push rod 61, a positioning member 62, a linkage member 63, a first elastic member 64, a second elastic member 65, and a third elastic member 66, wherein a through hole 11 is formed at the top of the circuit breaker housing 1, the positioning member 62 is embedded in the through hole 11, and the positioning member 62 is connected to the second elastic member 65; one end of the first elastic member 64 is connected with the operation end of the push rod 61, and the other end is connected with the positioning member 62 through a second elastic member 65; when the push rod 61 slides into the housing 1 under an external force, the first elastic member 64 is squeezed to apply an elastic force to the second elastic member 65, so that the second elastic member 65 drives the positioning member 62 to rotate, and the positioning member 62 is contracted in the housing 1, and when the external force disappears, the positioning member 62 drives a lower part to extend out of the housing 1 under the resilience force of the first elastic member 64 and the second elastic member 65;

one end of the linkage member 63 is hinged to the side wall of the housing 1 through a third elastic member 66, and the other end extends to one side of the armature 21 of the tripping mechanism 2; the operating end of the push rod 61 abuts against the third elastic member 66, when the push rod 61 slides towards the housing 1 by an external force, the third elastic member 66 drives the linkage member 63 to rotate clockwise, so as to toggle the armature 21 to pull in, and enable the tripping mechanism 2 to drive the moving contact 3 to rotate and separate from the static contact 4, and when the external force disappears, the linkage member 63 returns by virtue of the resilience of the third elastic member 66. Thus, as shown in fig. 4-5, when the circuit breaker is installed, the push rod 61 can be pushed to the bottom by a tool, the push rod 61 pushes the linkage member 63, the linkage member 63 pushes the armature 21, so that the armature 21 is closed, and meanwhile, the armature 21 unlocks the tripping mechanism 2, so that the moving contact and the static contact 4 are separated; in the process, the positioning member 62 is rotated and contracted in the housing 1 due to the second elastic member 65, so that the circuit breaker is freely moved into or away from the panel a; after the push rod 61 is released, the resilience force of the second elastic member 65 drives the positioning member 62 to rotate and return, and the top of the positioning member 62 extends out of the panel a, so that the circuit breaker is installed in the panel a and then is clamped in the panel a through the positioning member 62.

Preferably, the first elastic member 64 includes a compression spring, and the second elastic member 65 both employ torsion springs.

Preferably, the positioning element 62 is of an inverted T shape, and one side of the upper end of the positioning element, which is far away from the push rod 61, is a slope surface, so that when the positioning element 62 is forced to rotate, the positioning element does not rub against the side wall of the through hole 11; meanwhile, when the pressing force of the push rod 61 is insufficient, the positioning member 62 is not completely retracted into the housing 1, and the panel can press the slope surface of the positioning member 62 downwards along with the pushing of the circuit breaker to the panel a side in the process of assembling the circuit breaker into the panel a, so that the contraction of the positioning member 62 is promoted or assisted.

As a preferred embodiment, the stationary contact 4 is a sheet-shaped structure, as shown in fig. 6 and 7, a front end of a middle portion of the stationary contact 4 extends to a side away from the incoming line terminal 81 and then twists to a side to form a U-shaped structure, so as to provide a sufficient arc extinguishing space for the arc extinguishing chamber 5, a lower end portion of the U-shaped structure is bent downward to form a receiving portion 42, and the stationary contact 41 is disposed on the receiving portion 42; one side of the bearing part 42, which is far away from the U-shaped structure, extends towards the inside of the arc extinguish chamber 5 to form a lower arc angle 43 for guiding the arc to rapidly enter the arc extinguish chamber 5. When the moving contact 3 and the static contact 4 are disconnected, the arc leg of the electric arc is on the moving contact 41, the material of the arc extinguishing block 32 releases gas due to the huge heat generated by the electric arc, the electric arc is pushed to enter the arc extinguishing chamber 5, and when the electric arc is pushed to be elongated to enter the arc extinguishing chamber 5, the arc leg on the static contact 41 is guided to the lower arc corner 43, so that the burning loss of the static contact 41 is reduced; then, when the feeler lever returns to the end position, the upper arc angle and the feeler lever are always in the same electric potential, and the arc foot on the movable contact 31 jumps to the upper arc angle, thus being beneficial to the electric arc to enter the arc extinguish chamber 5 and reducing the burning loss of the movable contact 31.

Preferably, the angle of the downward bending of the bearing part 42 is 30-40 °.

Preferably, as shown in fig. 8-9, the inner side of the U-shaped structure is further symmetrically provided with an air sheet bracket, and the air sheet bracket is provided with an air generating sheet 72; therefore, the static contact 4 is placed at the outer side of the gas generating bracket 71, so that the current carrying and the electric conduction of the static contact 4 are not influenced, the heat dissipation is facilitated, and the temperature rise of a product is ensured.

Preferably, the lower edge of the gas generating piece 72 is parallel to the lower arc angle 43, so that the gas generating piece 72 above the lower arc angle 43 is in a parallelogram arrangement.

Preferably, the gas generating plate 72 is made of a nomex paper material, and two gas generating plates are symmetrically arranged, so that at the moment of short circuit and breaking, as shown in fig. 16, the gas generating plate 72 can generate gas under high heat, and the arc is rapidly pushed into the arc extinguishing grid plate 52 of the arc extinguishing chamber 5 in a gas flow manner, so as to rapidly extinguish the arc b.

Preferably, an arc isolation block is further arranged in the U-shaped structure, so that arc leakage is avoided, and other parts in the circuit breaker are protected from being damaged by the arc.

As a preferred embodiment, as shown in fig. 10, the arc extinguishing chamber 5 is disposed adjacent to the stationary contact 4, the arc extinguishing chamber 5 includes two symmetrically disposed grid supports 51, a plurality of arc extinguishing grids 52 are disposed in the grid supports 51, and the arc extinguishing grids 52 are spaced and stacked, and in particular, the arc extinguishing grids 52 are disposed parallel to the lower arc angle 43, so that the arc can rapidly enter the arc extinguishing grids 52 from the stationary contact 41.

Preferably, the upper end of the arc extinguishing chamber 5 extends to a side close to the U-shaped structure, so as to fill up the gap above the gas generating piece 72 and avoid the leakage of the arc.

As a preferred embodiment, the static contact 4 is a sheet-shaped structure, as shown in fig. 11, one end of the static contact 4 connected to the wire inlet terminal 81 extends forward and backward to form a two-sheet structure symmetrically arranged forward and backward, the middle portion of the static contact 4 is arranged in a step shape, the bottoms of the two-sheet structure are folded and extend toward one side close to the arc extinguish chamber 5 to form a horizontally arranged receiving portion 42, the static contact 41 of the static contact 4 is arranged on the receiving portion 42, and one side of the receiving portion 42 close to the arc extinguish chamber 5 extends toward the inside of the arc extinguish chamber 5 to form a lower arc angle 43 for guiding the arc to rapidly enter the arc extinguish chamber 5.

Preferably, as shown in fig. 12, the two-piece structure is symmetrically provided with air-piece brackets at inner sides thereof, the air-piece brackets are provided with air-generating pieces 72, and the static contact 4 is placed at an outer side of the air-generating bracket 71, so that current-carrying, electric conduction and generated electromagnetic repulsion of the static contact 4 are not affected, heat dissipation is facilitated, and temperature rise of a product is ensured. Preferably, the gas generating pieces 72 are symmetrically provided with two pieces, and at the moment of short circuit and breaking, the gas generating pieces 72 can generate gas under high heat, and the arc is rapidly pushed into the arc extinguishing grid pieces 52 of the arc extinguishing chamber 5 in a gas flow manner to rapidly extinguish the arc.

Preferably, the gas generating sheet 72 is made of a nomex paper material.

As a preferred embodiment, as shown in fig. 13 to 14, the arc extinguish chamber 5 is disposed adjacent to the fixed contact 4, the arc extinguish chamber 5 includes two grid supports 51 symmetrically disposed, a plurality of arc extinguish grids 52 are disposed in the grid supports 51, and the arc extinguish grids 52 are spaced and stacked.

Preferably, the outlet terminal 82 of the circuit breaker is arranged on the same side as the inlet terminal 81, the outlet terminal 82 is arranged below the fixed contact 41, the moving contact 31 is arranged above the fixed contact 41, and the current flows into the fixed contact 4 from the inlet terminal 81, flows into the moving contact 31 from the fixed contact 41, and finally flows out from the outlet terminal 82, so that when a short circuit occurs in the line, the current direction at the fixed contact 41 is opposite to the current direction at the upper and lower sides, so that the fixed contact 41 and the moving contact 31 generate an electric repulsive force, and the separation of the moving contact 31 and the fixed contact 41 is accelerated. Specifically, as shown in fig. 15, when the static contact 4 with such a structure is disconnected with an ultra-large current, the current enters from the end I and then flows to the end I2 and the end I3 in sequence along the direction I1, and since the current directions of the end I2 and the end I3 are opposite, an electric repulsive force is inevitably generated, so that the moving contact 3 and the static contact 4 can be rapidly disconnected; meanwhile, because the current directions of the I1 and the I3 are the same, attraction force to the static contact 4 is generated, and the disconnection of the movable contact 3 and the static contact 4 is further accelerated.

Preferably, the distance between two adjacent arc-extinguishing grid plates 52 gradually increases from the contact end to the contact end, so that the plurality of arc-extinguishing grid plates 52 are distributed in a fan shape from top to bottom, and the arc-extinguishing space between the adjacent arc-extinguishing grid plates 52 gradually increases, thereby lengthening the arc in the arc breaking process.

An avoiding groove is formed in the middle of one side, close to the contact, of the arc extinguishing grid piece 52, and the width of the avoiding groove gradually narrows from the contact end to the direction away from the contact.

Preferably, the edge of the opening end of the avoiding groove is adducted in an arc shape, and the bottom of the avoiding groove is V-shaped.

Preferably, the evasion groove is V-shaped.

Preferably, the arc chute 52 is bent downward away from the contact end, thereby reducing the space occupied by the arc chute 52.

Preferably, the number of the arc extinguishing grid pieces 52 is 4-5.

Furthermore, the utility model discloses structure to the static contact is improved, like this, has not only effectively increased the explosion chamber, improves the arc extinguishing ability of circuit breaker, also is favorable to the quick separation of sound contact simultaneously, avoids or reduces electric arc to produce the scaling loss to sound contact and near related device, based on the utility model discloses quick arc extinguishing appears dividing the characteristic of breaking time delay very few, the utility model discloses the product is more applicable to in the 5G applied scene.

The utility model discloses the circuit breaker is provided with release mechanism, among this release mechanism, makes setting element, interlock spare and push rod linkage through the elastic component, like this, can guarantee under the condition of sound contact disconnection, the dismouting circuit breaker.

Although the embodiments of the present invention have been shown and described, it is to be understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that those skilled in the art can make changes, modifications, substitutions and alterations to the above embodiments without departing from the spirit and scope of the present invention, and that any simple modification, equivalent change and modification made to the above embodiments according to the technical spirit of the present invention still fall within the technical scope of the present invention.

Claims (7)

1. A5G hydraulic electromagnetic circuit breaker with a large arc extinguish chamber comprises a shell (1), and a tripping mechanism (2), a moving contact (3), a static contact (4) and the arc extinguish chamber (5) which are arranged in the shell (1), wherein the moving contact (3) is provided with a moving contact (31), and the static contact (4) is provided with a static contact (41); one end of the static contact (4) is connected with the incoming line terminal (81), and the static contact (4) is of a sheet structure, the front end of the middle part of the static contact (4) extends to one side far away from the incoming line terminal (81) and then is twisted to one side to form a U-shaped structure, the lower end part of the U-shaped structure is bent downwards to form a bearing part, and the static contact (41) is arranged on the bearing part; a lower arc angle (43) used for guiding electric arcs to rapidly enter the arc extinguish chamber (5) is formed by extending one side of the bearing part, which is far away from the U-shaped structure, towards the inner direction of the arc extinguish chamber (5);

the arc extinguishing chamber (5) with the static contact (4) is adjacent to be set up, and arc extinguishing chamber (5) sets up including two bars piece supports (51) of symmetry, set up a plurality of arc extinguishing bars piece (52) between the bars piece, each arc extinguishing bars piece (52) interval and range upon range of setting, arc extinguishing bars piece (52) with arc angle (43) parallel arrangement down.

2. The hydraulic electromagnetic circuit breaker for 5G with large arc-extinguishing chamber according to claim 1 is characterized in that the upper end of the arc-extinguishing chamber (5) extends to one side close to the U-shaped structure, so as to fill the gap above the gas-generating piece (72) and avoid the leakage of electric arc.

3. A hydraulic electromagnetic 5G disconnector according to claim 1, characterized in that the carrier part is bent downwards at an angle of 30 ° -40 °.

4. The hydraulic electromagnetic circuit breaker with a large arc extinguish chamber for 5G as claimed in claim 1, wherein the inside of the U-shaped structure is further symmetrically provided with a gas piece bracket, and the gas piece bracket is provided with a gas generating piece (72).

5. The hydraulic electromagnetic circuit breaker with a large arc-extinguishing chamber for 5G as recited in claim 4, characterized in that the lower edge of the gas generating piece (72) is disposed in parallel with the lower arc angle (43), so that the gas generating piece (72) above the lower arc angle (43) is disposed in a parallelogram.

6. The hydraulic electromagnetic circuit breaker for 5G with large arc-extinguishing chamber according to claim 4, characterized in that the gas generating sheet (72) is made of Nomick paper.

7. The hydraulic electromagnetic circuit breaker with a large arc extinguish chamber for 5G as claimed in claim 1, wherein an arc isolating block is further arranged in the U-shaped structure.

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