CN115472473A - Circuit breaker - Google Patents

Abstract

The invention discloses a circuit breaker, which comprises a contact system, an insulating device and an arc extinguishing device, wherein the contact system comprises a rotating shaft, a moving contact and a static contact; the arc extinguishing device comprises a connecting plate, an equipotential connecting line, an upper arc striking plate, a lower arc striking plate and an arc extinguishing grid group; the upper arc striking sheet is connected with the connecting plate through an equipotential connecting line, the connecting plate is connected with the moving contact through flexible connection, and the upper arc striking sheet and the moving contact are equipotential; one end of the lower arc striking piece is fixedly connected with the fixed contact, and the other end of the lower arc striking piece is fixedly connected with the insulating device; the arc-extinguishing grid group is fixedly installed on the insulating device, and the upper arc striking plate and the lower arc striking plate are embedded in the middle concave part of the arc-extinguishing grid group. This scheme can shift the electric arc that the separating brake produced, concentrates the arc extinguishing again, and the arc extinguishing ability obtains very big promotion.

Description

Circuit breaker

Technical Field

The invention relates to a circuit breaker, in particular to a circuit breaker.

Background

When fault current occurs in an electric power system, a tripping system of the circuit breaker unlocks an original mechanism, drives a rotating shaft system to rotate, and finally separates a movable contact from a fixed contact, when the voltage in the system exceeds 12-20V, the cut-off current exceeds 0.25-1A, and an air medium between the movable contact and the fixed contact is broken down to form electric arcs. If the arc can not be extinguished quickly, the contact surface can be burnt and high-temperature ionic gas is generated to damage the shell of the circuit breaker, and the internal pressure of the arc extinguish chamber is increased to cause the high-temperature gas to flow out of the shell of the circuit breaker, so that the health of equipment around the circuit breaker and workers around the circuit breaker is affected. In particular, the arc contains metal ions, which easily causes short-circuiting of electrical equipment or conductive parts around the circuit breaker. Based on the condition of above circuit breaker, for increasing the arc extinguishing performance of circuit breaker, current circuit breaker generally goes out electric arc through the arc extinguishing bars group, and the concrete mode is that guide electric arc gets into the arc extinguishing bars group, cuts into several short arcs with electric arc through the arc extinguishing bars piece to this improves electric arc voltage, reaches the purpose of extinguishing electric arc, but this scheme has the difficult problem of electric arc transfer, in addition, still has the arc extinguishing bars piece quantity few and arc extinguishing bars piece group utilization inefficiency.

Therefore, how to improve the arc extinguishing performance of the circuit breaker is very important, and the quality of the arc extinguishing performance of the circuit breaker can directly influence the breaking capacity of the circuit breaker on fault current, the electric service life of the circuit breaker and the electric performance characteristics of the circuit breaker. In order to improve the breaking capacity and breaking reliability of the circuit breaker, the invention carries out optimization design on the arc extinguishing system.

Disclosure of Invention

The invention aims to: the invention aims to provide a circuit breaker, which can transfer electric arcs generated by opening and then carry out centralized arc extinguishing, and greatly improves the arc extinguishing capability.

The technical scheme is as follows: the arc extinguishing device comprises a contact system, an insulating device and an arc extinguishing device, wherein the contact system comprises a rotating shaft, a moving contact and a static contact, the moving contact is fixedly arranged in the rotating shaft and is driven by the rotating shaft to move so as to realize the contact and separation of the moving contact and the static contact; the arc extinguishing device comprises a connecting plate, an equipotential connecting line, an upper arc striking plate, a lower arc striking plate and an arc extinguishing grid group; the upper arc striking sheet is connected with the connecting plate through an equipotential connecting line, the connecting plate is connected with the moving contact through flexible connection, and the upper arc striking sheet and the moving contact are equipotential; one end of the lower arc striking piece is fixedly connected with the fixed contact, and the other end of the lower arc striking piece is fixedly connected with the insulating device; the arc extinguishing grid group is fixedly arranged on the insulating device, and the upper arc striking plate and the lower arc striking plate are embedded in the middle concave part of the arc extinguishing grid group.

An arc striking groove is formed in the middle of each of the upper arc striking plate and the lower arc striking plate, and the width of each arc striking groove is 1-2 times of the thickness of the corresponding arc striking plate, so that electric arcs can fully enter the arc extinguishing grid group, and the arc extinguishing capacity of the arc extinguishing grid group is improved.

The arc extinguishing grid group comprises a first arc extinguishing grid group, a second arc extinguishing grid group, a third arc extinguishing grid group, a fourth arc extinguishing grid group, a left arc barrier wall and a right arc barrier wall; first arc extinguishing grid piece group, second arc extinguishing grid piece group, third arc extinguishing grid piece group, fourth arc extinguishing grid piece group transversely arrange in proper order, at the whole both sides installation left arc wall and the right arc wall that a plurality of grid piece groups are constituteed, arc extinguishing grid piece group transversely places, can be in limited circuit breaker volume, increase arc extinguishing grid piece quantity as much as possible, arc extinguishing grid piece quantity increase will be cut apart into more short arcs into to the electric arc that breaking fault current produced, can improve arc voltage, increase arc extinguishing device extinguishes electric arc's ability.

The arc-extinguishing grid group also comprises a left gas-generating piece and a right gas-generating piece, and a first partition rib of the left gas-generating piece is inserted into a gap of the arc-extinguishing grid group; and the second barrier rib of the right gas generating piece is inserted into the gap of the arc extinguishing grid group. When electric arcs are generated, the left gas generating piece and the right gas generating piece are eroded by the electric arcs to generate gas, so that the gas pressure in the cavity of the arc extinguish chamber is increased to form gas blowing, the electric arcs can enter the arc extinguish grating group conveniently, and meanwhile, the electric arc plasma beams are blown by high-speed gas flow, and the electric arcs can be cooled conveniently.

The movable contact is provided with a movable silver point at the position contacted with the fixed contact, and the fixed contact is provided with a fixed silver point corresponding to the movable silver point, so that the conductive capacity of the loop can be improved, the use frequency of the conductor is increased, and the contact effect is improved.

The insulation device comprises a first insulation piece and a second insulation piece; the first insulating part is provided with a groove and a first boss, the first insulating part is arranged in a groove between the left gas generating part and the right gas generating part through the groove, and the first boss is inserted into the corresponding groove of the base for splicing; and a second boss is arranged on the second insulating part, and the second insulating part is inserted into the corresponding groove of the base through the second boss for splicing. The first insulating part is mainly used for providing insulation between the static contact and the arc extinguishing device, and the second insulating part is mainly used for providing insulation between the connecting plate screw and the arc extinguishing device.

The insulation device comprises a third insulation piece, a fourth insulation piece and a fifth insulation piece; the third insulating part is fixed on the base through a plurality of holes and is used for providing insulation between the rotating shaft and the arc extinguishing device; the fourth insulating part is arranged on a hole of the moving contact through a rivet and used for providing insulation between the rotating shaft and the arc extinguishing device when the moving contact is repelled; and the fifth insulating part is fixed in the groove of the base through a screw and is used for providing insulation between the rotating shaft and the arc extinguishing device.

Has the beneficial effects that: compared with the prior art, the technical scheme of the invention has the beneficial effects that:

(1) By adding an equipotential connecting line between the connecting plate and the upper arc striking plate, the moving contact, the connecting plate and the upper arc striking plate have the same potential, and the fixed contact and the lower arc striking plate have the other potential, so that the transfer time of the electric arc from the contact to the arc striking plate can be shortened, the arc extinguishing capability can be improved, the arc striking effect of the arc striking plate can be improved, and the arc extinguishing performance is more beneficial;

(2) Compared with most of the existing arc extinguishing devices which are longitudinally arranged, the arc extinguishing device is transversely arranged in the arrangement mode, the number of the arc extinguishing grid pieces can be increased as much as possible in the limited volume of the circuit breaker, the increased number of the arc extinguishing grid pieces can divide the electric arc generated by the disjunction fault current into more short arcs, the electric arc voltage can be improved, and the electric arc extinguishing capability of the arc extinguishing device is increased. And the high-temperature gas generated in the breaking process of the circuit breaker can be prevented from being sprayed out, the adverse effect on the external environment can be eliminated, and the flashover distance can be reduced.

Drawings

FIG. 1 is a perspective view of the present invention;

FIG. 2 is a general assembly view of the present invention;

FIG. 3 is an exploded view of an arc extinguishing device and contact system;

FIG. 4 is a schematic view of an assembled arc extinguishing device and contact system;

fig. 5 is a schematic structural view of an arc extinguishing grid group;

FIG. 6 is a schematic view showing a state in which the insulator is mounted in FIG. 5;

FIG. 7 is a schematic structural view of a left gas generating member;

FIG. 8 is a schematic structural view of a right gas generating member;

FIG. 9 is an assembled view of the first insulator and the base;

FIG. 10 is an assembly view of the second insulating member, the fifth insulating member and the base;

FIG. 11 is an assembly view of the connection plate and the equipotential bonding wire with the base;

FIG. 12 is an assembly view of the third insulator and base;

fig. 13 is an assembly view of a stationary contact and a base;

FIG. 14 is an assembly view of the upper and lower tab and the base;

FIG. 15 is a general assembly view of the insulator assembly;

figure 16 is a distribution diagram of the internal cavity of the circuit breaker housing;

FIG. 17 is a current profile of arc extinguishing system operation when fault current is not present;

FIG. 18 is a current profile for the arc suppression system just beginning to operate when a fault current occurs;

FIG. 19 is a current direction diagram showing the state that the movable contact moves to the maximum distance and the arc is not transferred when the fault current occurs;

fig. 20 is a current-flow diagram of a state in which the movable contact acts to the maximum distance and the arc transfer is completed when a fault current occurs.

Detailed Description

The technical scheme of the invention is described in detail in the following with the combination of the specific embodiments and the attached drawings.

As shown in fig. 1-4, the arc extinguishing system of the circuit breaker of the invention includes three parts, namely a contact system, an insulating device and an arc extinguishing device, wherein the contact system includes a rotating shaft 1, a moving contact 3 and a static contact 10, the moving contact 3 is fixedly installed in the rotating shaft 1, the rotating shaft 1 is driven by a mechanism to move, so that the moving contact 3 rotates in the rotating shaft 1, the moving contact 3 and the static contact 10 are contacted and separated, and the circuit is connected or disconnected. In the scheme, a movable silver point 2 is arranged at the position where a movable contact 3 is contacted with a static contact 10, the movable silver point 2 is fixed on the movable contact 3 in a welding mode, and the material of the movable silver point is generally silver alloy; the static contact 10 is provided with a static silver point 8 corresponding to the dynamic silver point 2, the static silver point 8 is fixed on the static contact 10 in a welding mode, the static silver point is generally made of silver alloy, and the dynamic silver point 2 and the static silver point 8 are arranged to improve the conductive capacity of a loop, increase the use frequency of a conductor and increase the contact effect. .

The arc-extinguishing device comprises a connecting plate 5, an equipotential connecting wire 6, an upper arc striking plate 7, a lower arc striking plate 9 and an arc-extinguishing grid group. The upper arc striking plate 7 is connected with the connecting plate 5 through an equipotential connecting wire 6, and the connecting plate 5 is connected with the moving contact 3 through the flexible connection 4, so that the upper arc striking plate 7 and the moving contact 3 are equipotential, the transfer time of electric arcs from the contact to the arc striking plate is shortened, and the arc extinguishing capacity is improved. As shown in fig. 13, one end of the static contact 10 is connected and fixed to the base 21 of the insulating device through screws on the first through hole 101 and the second through hole 102, and the other end of the static contact 10 is fixedly connected to the static silver point 8 by welding. One end of the upper arc striking plate 7 is connected with the fourth through hole 63 at one end of the equipotential connecting line 6 at the third through hole 71 by a screw, and the other end of the upper arc striking plate 7 is fixed on the base 21 at the fifth through hole 72 by a screw. As shown in fig. 11, the other end of the equipotential connecting line 6 is fixedly connected to the eighth through hole 51 and the ninth through hole 52 of the bonding plate 5 at the sixth through hole 61 and the seventh through hole 62 by screws. One end of the lower arc striking piece 9 is welded on the static contact 10, the lower arc striking piece 9 is positioned below the static silver point 8, and the other end of the lower arc striking piece 9 is fixed on the base 21 at the tenth through hole 91 by a screw. Two ends of the flexible connection 4 are respectively fixed on the movable contact 3 and the connecting plate 5 in a welding way. The upper arc striking plate 7 and the lower arc striking plate 9 are arranged, so that electric arcs can be guided into the arc extinguishing device more completely, more arc extinguishing grid plates are enabled to act, and the arc extinguishing performance is improved. In this embodiment, an arc striking groove is formed in the middle of each of the upper arc striking plate 7 and the lower arc striking plate 9, and the width of the arc striking groove is 1 to 2 times the thickness of the corresponding arc striking plate, as shown in fig. 14.

As shown in fig. 4, 5, 7 and 8, the arc-extinguishing grid set includes a left arc-isolating wall 11, a left gas-generating component 12, a first arc-extinguishing grid set 13, a second arc-extinguishing grid set 14, a third arc-extinguishing grid set 15, a fourth arc-extinguishing grid set 16, a right gas-generating component 17 and a right arc-isolating wall 18. The first arc-extinguishing grid piece group 13, the second arc-extinguishing grid piece group 14, the third arc-extinguishing grid piece group 15 and the fourth arc-extinguishing grid piece group 16 are sequentially and transversely arranged, and the number of the arc-extinguishing grid pieces can be increased as much as possible in the limited volume of the circuit breaker. The left arc-insulating wall 11 and the right arc-insulating wall 18 are arranged on two sides of the whole body formed by the first arc-insulating grid group 13, the second arc-insulating grid group 14, the third arc-insulating grid group 15 and the fourth arc-insulating grid group 16, a plurality of arc-insulating grid plates are sequentially riveted on square holes of the left arc-insulating wall 11 and the right arc-insulating wall 18, the arc-insulating grid plates are vertically arranged relative to the left arc-insulating wall 11 and the right arc-insulating wall 18, and the left arc-insulating wall 11 and the right arc-insulating wall 18 are utilized to separate a plurality of arc-insulating grid plates contained by the first arc-insulating grid group 13, the second arc-insulating grid group 14, the third arc-insulating grid group 15 and the fourth arc-insulating grid group 16. The interval all exists between two adjacent arc extinguishing bars piece, and the several arc extinguishing bars piece can be cut apart into more short arcs with the electric arc that divides disconnected fault current produced, can improve arc voltage, increases arc extinguishing device's ability of extinguishing electric arc. When an electric arc is generated, the left and right gas generation parts are eroded by the electric arc to generate gas, so that the air pressure in the chamber of the arc extinguishing chamber is increased to form air blowing, the electric arc is favorably enabled to enter the arc extinguishing grid set, and meanwhile, the high-speed air flow blows an electric arc plasma beam, so that the electric arc is also favorably cooled.

As shown in fig. 15 and 16, the insulating device includes a base 21, a bottom sealing plate 25, a small cover 26, a middle cover 27, and a plurality of insulating members, wherein the base 21, the bottom sealing plate 25, the small cover 26, and the middle cover 27 form a housing of the circuit breaker. The inside of circuit breaker is divided into different cavities to the casing, when the combination concatenation between different cavities, combines together through the mode that increases rectangular recess and rectangular boss on the casing to increase the insulating properties of circuit breaker. Specifically, the small lid 26 and the middle lid 27 form a first chamber 28, the middle lid 27 and the base 21 form a second chamber 29, and the base 21 and the bottom closure panel 25 form a third chamber 30. The first chamber 28 is used to store the accessories of the circuit breaker. The rotating shaft 1, the moving contact 3, the flexible connection 4, the connecting plate 5 and the equipotential connecting line 6 are arranged in the second cavity 29, specifically, a groove is formed in the base 21 and used for storing the equipotential connecting line 6, and an insulating part is arranged above the equipotential connecting line 6, so that the equipotential connecting line 6 is completely sealed in the groove; in addition, the insulating element cooperates with the moving contact 3, the rotating shaft 1 and the base 21 to form a closed area, which isolates the second chamber 29 from the third chamber 30. The static contact 10, the arc extinguishing grid group, the upper arc striking plate 7 and the lower arc striking plate 9 are arranged in the third chamber 30. The arc-extinguishing grid plate group is installed at the bottom of the third chamber 30, specifically, the arc-extinguishing grid plate group is fixedly installed above the sealing bottom plate 25, and the upper arc striking plate 7 and the lower arc striking plate 9 are embedded in the middle concave part of the arc-extinguishing grid plate group. The base 21 and the cover plate 25 provide a mounting and fixing space for the entire arc extinguishing system, and a plurality of insulating members are used to provide insulation between different components. The insulating part provides reliable insulating properties for whole arc extinguishing system, and insulating properties of whole arc extinguishing device cavity has been guaranteed in insulating device's setting. The method specifically comprises the following steps: the plurality of insulating members includes a first insulating member 19 and a second insulating member 20, a third insulating member 22, a fourth insulating member 23, a fifth insulating member 24. As shown in fig. 6 and 9, a groove 191 and a first boss 192 are formed on the first insulating member 19, the first insulating member 19 is installed in the groove between the left gas generating member 12 and the right gas generating member 17 through the groove 191, and the first boss 192 is inserted into the corresponding groove of the base 21 for splicing; the first insulating member 19 mainly serves to insulate the stationary contact 10 from the arc extinguishing device. As shown in fig. 10, a second boss 201 is disposed on the second insulating member 20, and the second insulating member 20 is inserted into a corresponding groove of the base 21 through the second boss 201 for splicing. The second insulating member 20 mainly serves to provide insulation between the bolt of the linking plate 5 and the arc extinguishing device, and to prevent the mechanism above the arc extinguishing device from being ablated. As shown in fig. 12, the third insulating member 22 is fixed on the base 21 through the holes 221, 222, 223, 224, and mainly functions to insulate the arc extinguishing device below the base 21 from the mechanism above, and insulate the equipotential connection lines 6 below the base 21. As shown in fig. 15, a fourth insulating member 23 is mounted on the hole 31 of the movable contact 3 by a rivet, and is used for providing insulation between the rotating shaft 1 and the arc extinguishing device when the movable contact 3 is repelled; the fifth insulating member 24 is fixed in the recess 211 of the base 21 by a screw for providing insulation between the rotating shaft 1 and the arc extinguishing device.

As shown in fig. 17, when the fault current does not occur, the arc extinguishing device operates normally in a current profile. The normal working current enters from the inlet terminal connecting plate 5 and flows out sequentially through the flexible connection 4, the moving contact 3, the moving silver point 2, the static silver point 8 and finally the static contact 10.

As shown in fig. 18, when a fault current occurs, the movable contact 3 starts to operate, and the current flow diagram is shown. The fault current enters from the inlet terminal connecting plate 5, after passing through the flexible connection 4 and the moving contact 3, because the moving contact 3 acts rapidly between the moving silver point 2 and the static silver point 8, a metal phase arc 11 is generated, and then the fault current flows to the static silver point 8 and the static contact 10 through the arc 11.

As shown in fig. 19, when a fault current occurs, the movable contact 3 moves to the maximum open distance and the arc 11 still flows between the movable contact 3 and the stationary contact 10. The electric arc 11 will move downward continuously due to the action of air blowing and magnetic blowing until entering the arc extinguishing device completely and then is extinguished by the arc extinguishing device, and this state is a critical state that the electric arc 11 will move to the arc striking piece, because the electric arc 11 is still located between the moving silver point and the static silver point, the current trend of the whole conductive loop is consistent with that of the moving contact 3 when just moving, and still is the connecting plate 5-flexible connection 4-moving contact 3-moving silver point 2-electric arc 11-static silver point 8-static contact 10.

As shown in fig. 20, when the fault current occurs, the movable contact 3 acts to the maximum opening distance and the arc 11 has completely entered the arc extinguishing device. The current profile for this state differs from the previous arc 11 between the moving and stationary silver points by: because the upper arc striking sheet 7 is connected with the connecting plate 5 through the equipotential connecting wire 6, the upper arc striking sheet 7 and the connecting plate 5 are at the same high potential, and the lower arc striking sheet 9 and the static contact 10 are connected together, the lower arc striking sheet 9 and the static contact 10 are at the same low potential, and because of the potential difference between the upper arc striking sheet and the static contact, the loop current moves from the connecting plate 5 to the equipotential connecting wire 6 and then onto the upper arc striking sheet 7, and when the current moves to the tail end of the upper arc striking sheet 7, the current moves to the right through the electric arc 11 until reaching the tail end of the lower arc striking sheet 9, and then flows out from the lower arc striking sheet 9 to the static contact 10.

It should be noted that, if the equipotential connecting wire 6 is not added, when the movable contact 3 moves to the position with the maximum opening distance, the upper arc striking plate 7 also has a certain arc striking capability, and the arc 11 also moves downward along with the upper arc striking plate 7, but because there is no equipotential connecting wire 6, the upper arc striking plate 7 at this time will be at a low potential, and the movable contact 3 is at a high potential, such a potential difference will be unfavorable for the transfer of the arc 11, and a situation that the arc 11 does not move all the way to the end along the upper arc striking plate 7 will occur, and if the arc 11 does not move to the end of the arc striking plate, only a part of the arc extinguishing grid plate below will also play a role in dividing the arc 11, so that the arc extinguishing capability cannot be expected. The lower arc striking plate 9 is welded on the static contact 10, and belongs to direct electric connection, and the lower arc striking plate and the static contact always keep the same low potential, so that the electric arc 11 is transferred on the lower arc striking plate 9 quite easily, namely, the arc striking effect of the whole conductive loop mainly depends on the arc striking effect of the upper arc striking plate 7.

Claims (6)

1. A circuit breaker, characterized by: the arc extinguishing device comprises a contact system, an insulating device and an arc extinguishing device, wherein the contact system comprises a rotating shaft (1), a moving contact (3) and a static contact (10), the moving contact (3) is fixedly arranged in the rotating shaft (1), and the moving contact (3) is driven to rotate through the rotating shaft (1) so as to realize the contact and separation of the moving contact (3) and the static contact (10);

the arc extinguishing device comprises a connecting plate (5), an equipotential connecting wire (6), an upper arc striking plate (7), a lower arc striking plate (9) and an arc extinguishing grid group; the upper arc striking sheet (7) is connected with the connecting plate (5) through an equipotential connecting line (6), the connecting plate (5) is connected with the moving contact (3) through a flexible connection (4), and the upper arc striking sheet (7) and the moving contact (3) are equipotential; one end of the lower arc striking plate (9) is fixedly connected with the static contact (10), and the other end of the lower arc striking plate is fixedly connected with the insulating device; the arc extinguishing grid group is fixedly arranged on the insulating device, and the upper arc striking plate (7) and the lower arc striking plate (9) are embedded in the middle concave part of the arc extinguishing grid group.

2. The circuit breaker of claim 1, wherein: the middle parts of the upper arc striking piece (7) and the lower arc striking piece (9) are respectively provided with an arc striking groove, and the width of each arc striking groove is 1-2 times of the thickness of the corresponding arc striking piece.

3. The circuit breaker of claim 1, wherein: the arc extinguishing grid group comprises a first arc extinguishing grid group (13), a second arc extinguishing grid group (14), a third arc extinguishing grid group (15), a fourth arc extinguishing grid group (16), a left arc barrier wall (11) and a right arc barrier wall (18);

the first arc-extinguishing grid group (13), the second arc-extinguishing grid group (14), the third arc-extinguishing grid group (15) and the fourth arc-extinguishing grid group (16) are sequentially and transversely arranged, and a left arc-isolating wall (11) and a right arc-isolating wall (18) are arranged on two sides of the whole body formed by the plurality of grid groups.

4. The circuit breaker of claim 3, wherein: the arc-extinguishing grid group also comprises a left gas-generating piece (12) and a right gas-generating piece (17), and a first rib (122) of the left gas-generating piece (12) is inserted into a gap of the arc-extinguishing grid group; and the second spacing rib (172) of the right gas generating piece (17) is inserted into the gap of the arc extinguishing grid group.

5. The circuit breaker of claim 4, wherein: the insulation means comprises a first insulation (19) and a second insulation (20);

the first insulating part (19) is provided with a groove (191) and a first boss (192), the first insulating part (19) is arranged in a groove between the left gas generating part (12) and the right gas generating part (17) through the groove (191), and the first boss (192) is inserted into a base (21) of the insulating device for splicing;

and a second boss (201) is arranged on the second insulating part (20), and the second insulating part (20) is inserted into a corresponding groove of the base (21) through the second boss (201) for splicing.

6. The circuit breaker of claim 1, wherein: the insulation device comprises a third insulation piece (22), a fourth insulation piece (23) and a fifth insulation piece (24);

the third insulating piece (22) is fixed on a base (21) of the insulating device through a plurality of holes and is used for providing insulation between the rotating shaft (1) and the arc extinguishing device;

the fourth insulating part (23) is arranged on a hole (31) of the moving contact (3) through a rivet and is used for providing insulation between the rotating shaft (1) and the arc extinguishing device when the moving contact (3) is repelled;

the fifth insulating piece (24) is fixed in a groove (211) of the base (21) through a screw and is used for providing insulation between the rotating shaft (1) and the arc extinguishing device.

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