Contact arc extinguishing system and circuit breaker

Abstract

The invention relates to the technical field of low-voltage electric appliance manufacturing, in particular to a contact arc extinguishing system and a circuit breaker, which comprises an arc extinguishing assembly, a static contact is arranged in the arc extinguishing assembly, a movable contact capable of rotating is arranged in the arc extinguishing assembly, and the static contact and the movable contact can be in contact or separated operation. The arc extinguishing assembly comprises an arc extinguishing chamber and a protective cover; arc-isolating walls are arranged on two sides of the arc-extinguishing chamber; a first arc-extinguishing grid sheet, a second arc-extinguishing grid sheet, a third arc-extinguishing grid sheet and a fourth arc-extinguishing grid sheet are arranged between the two arc-isolating walls; each second arc-extinguishing grid sheet is provided with a first inclined plane and a second inclined plane, a first gap is arranged at the joint of the first inclined plane and the second inclined plane, the first gap is deviated to one side of the second arc-extinguishing grid sheet, and the second arc-extinguishing grid sheets are sequentially arranged in a staggered manner according to the position of the first gap. The projection of the first gap on the plane where the first arc extinguishing grid sheet is located is located in the first arc extinguishing grid sheet.

Description

Technical Field

[0001] The invention relates to the technical field of low-voltage electrical appliance manufacturing, in particular to a contact arc extinguishing system and a circuit breaker. Background Art

[0002] A circuit breaker is an electrical product that can automatically cut off power supply protection in the event of overload and short circuit. With the continuous development of the power system, higher requirements are placed on the breaking capacity of circuit breakers. Low-voltage circuit breakers mainly use the deionization effect of arc extinguishing grids to improve the dielectric recovery strength, extinguish the arc and prevent the arc from reigniting. In order to obtain better arc extinguishing ability, common methods are: 1. Increase the opening distance between the moving and static contacts to lengthen the arc; 2. Increase the number of arc extinguishing grids. These methods will inevitably lead to an increase in the size of the circuit breaker, which is not conducive to the development of circuit breakers in the direction of miniaturization. Summary of the invention

[0003] 1. Technical issues to be resolved

[0004] In view of the deficiencies in the prior art, the present invention provides a contact arc extinguishing system and a circuit breaker, which have the characteristics of small size and good arc extinguishing performance.

[0005] (II) Technical solution

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: a contact arc extinguishing system, comprising an arc extinguishing assembly, wherein a static contact is provided in the arc extinguishing assembly, a rotatable moving contact is provided in the arc extinguishing assembly, the static contact and the moving contact can be in contact or separated operation, and the arc extinguishing assembly comprises an arc extinguishing chamber and a protective cover;

[0007] Arc-isolating walls are provided on both sides of the arc-extinguishing chamber, and a first arc-extinguishing grid, a second arc-extinguishing grid, a third arc-extinguishing grid and a fourth arc-extinguishing grid are provided between the two arc-extinguishing walls;

[0008] The second arc-extinguishing grid is provided with a first inclined surface and a second inclined surface, a first notch is provided at the connection between the first inclined surface and the second inclined surface, the first notch is biased toward one side of the second arc-extinguishing grid, the second arc-extinguishing grids are arranged alternately in sequence according to the positions of the first notches, and a projection of the first notch on the plane where the first arc-extinguishing grid is located is located inside the first arc-extinguishing grid;

[0009] The third arc-extinguishing grid is provided with a second notch at a lateral middle position;

[0010] The fourth arc-extinguishing grid has a movable arc-striking piece extending outwardly at a lateral middle position, and when the moving contact is in the open position, one end of the movable arc-striking piece is close to the moving contact;

[0011] The protective cover includes a first partition plate arranged on the static contact, the first partition plate is arranged in a horizontal direction, second partition plates are arranged on both sides of the first partition plate, the second partition plate is arranged in a vertical direction, a third partition plate is arranged on one side of the second partition plate, and the third partition plate is fixed to the upper surface of the first partition plate.

[0012] Furthermore, the arc extinguishing assembly also includes an arc isolation plate, the arc isolation plate is provided with a plurality of long holes, gaps are provided between the first arc extinguishing grid, the second arc extinguishing grid, the third arc extinguishing grid and the fourth arc extinguishing grid, and the gaps correspond to the long holes one by one.

[0013] Furthermore, the overlapping area between the projection of the cross section of the gap close to the arc isolation plate on the arc isolation plate and the long hole increases from bottom to top.

[0014] Furthermore, a static arc-striking piece is also provided on the static contact, and one end of the static arc-striking piece is arranged below the first arc-extinguishing grid piece.

[0015] Furthermore, a number of magnetic conductive sheets are provided below the static contact.

[0016] Furthermore, a first arc-extinguishing grid, a plurality of second arc-extinguishing grids, a plurality of third arc-extinguishing grids and a fourth arc-extinguishing grid are sequentially arranged between the two arc-isolating walls from bottom to top; two second partitions are symmetrically distributed in the first partition, a groove for rotating the moving contact is provided in the third partition, and the first partition, the second partition and the third partition are perpendicular to each other.

[0017] Furthermore, the number of the second arc-extinguishing grids is four, and the number of the third arc-extinguishing grids is five.

[0018] A circuit breaker comprises a contact arc extinguishing system according to any one of claims 1 to 4.

[0019] Furthermore, when a short-circuit fault current flows through the circuit breaker, the static contact and the moving contact change from being in contact to being separated, and an arc is generated between the static contact and the moving contact. The arc goes through the following three steps from generation to extinction:

[0020] When the moving contact is just opened;

[0021] The currents of the stationary contact and the moving contact flow in opposite directions, and the arc moves toward the arc extinguishing chamber under the action of the Lorentz magnetic force; the heat generated by the arc causes the surrounding air to expand due to heat, and most of the expanded air moves toward the arc extinguishing chamber through the blocking of the first partition, the second partition and the third partition; the high temperature generated by the arc causes the protective cover to decompose molecular gas, which cools the arc and reduces the arc diameter;

[0022] When the moving contact rotates to the vicinity of the second arc-extinguishing grid;

[0023] The current flows of the static contact and the moving contact are still opposite, and the first partition, the second partition and the third partition continue to block the expanding air, and the protective cover continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc moves to the static arc-starting plate and flows through the first arc-extinguishing grid; due to the first notch set on the second arc-extinguishing grid, the upper arc flows from one first notch to another adjacent first notch, and the arc current flows in a broken line, the arc is greatly elongated, and the arc current is further suppressed; due to the obstruction of the arc isolation plate, the lower end of the arc isolation plate does not have enough air outlet, and the expanding air begins to move upward;

[0024] The moving contact is fully opened;

[0025] After the moving contact rotates to the vicinity of the moving arc-striking piece, the current flows of the static contact and the moving contact are still opposite, and the first partition, the second partition, the third partition and the arc-isolating plate continue to block the expanding air, and the protective cover continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower section of the arc flows through the first arc-extinguishing grid and the second arc-extinguishing grid; the upper section of the arc moves to the moving arc-striking piece; under the blowing of the expanding air, the middle section of the arc moves to the second gap and finally enters the third arc-extinguishing grid.

[0026] In this plan Figures 5 to 8 The dotted lines in the figure indicate the direction of current and arc.

[0027] A contact arc extinguishing system and an arc extinguishing method for a circuit breaker, the method comprising:

[0028] Step 1: When the short-circuit fault current flows through the circuit breaker, the circuit breaker operating mechanism or the electric repulsion force drives the moving contact to rotate, so that an arc is generated between the stationary contact and the moving contact;

[0029] Step 2: After the moving contact is just opened, the generated arc moves toward the arc extinguishing chamber under the action of the Lorentz magnetic force. The heat generated by the arc causes the surrounding air to expand due to the heat. Most of the expanded air moves toward the arc extinguishing chamber through the blocking of the first partition, the second partition and the third partition. The high temperature generated by the arc causes the protective cover to decompose molecular gas, thereby cooling the arc and reducing the arc diameter.

[0030] Step 3: When the moving contact continues to rotate to the vicinity of the second arc-extinguishing grid, the first partition, the second partition and the third partition continue to block the expanding air, and the protective cover continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc moves to the static arc-starting plate and flows through the first arc-extinguishing grid; the upper arc flows from one first gap to another adjacent first gap, and the arc current flows in a broken line, the arc is greatly elongated, and the arc current is further suppressed;

[0031] Step 4: When the moving contact is fully opened, after the moving contact rotates to the vicinity of the moving arc-striking plate, the first partition, the second partition, the third partition and the arc-striking plate continue to block the expanding air, and the protective cover continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower section of the arc flows through the first arc-extinguishing grid and the second arc-extinguishing grid; the upper section of the arc moves to the moving arc-striking plate; under the blowing of the expanding air, the middle section of the arc moves to the second gap and finally enters the third arc-extinguishing grid, so that the arc is extinguished.

[0032] Compared with the prior art, the contact arc extinguishing system and circuit breaker have the following advantages: 1. The protective cover and arc isolation plate are well arranged, which has a better air blowing effect; 2. The arc extinguishing grid is well arranged, so that the arc is better pulled in the early stage of breaking, and the arc enters the arc extinguishing chamber better in the later stage of breaking; 3. The protective cover is well arranged to prevent the arc from reigniting due to the short circuit between the moving and static contacts; 4. The structure is compact and will not increase the volume of the conventional circuit breaker. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the external structure of the contact arc extinguishing system of the present invention;

[0034] Figure 2 For the present invention Figure 1 Schematic diagram of the split structure;

[0035] Figure 3 For the present invention Figure 1 Schematic diagram of the cross-sectional structure in;

[0036] Figure 4 It is a structural schematic diagram of the arc extinguishing chamber of the present invention;

[0037] Figure 5 It is a schematic structural diagram of the first arc-extinguishing grid of the present invention;

[0038] Figure 6 is a schematic structural diagram of a second arc-extinguishing grid of the present invention;

[0039] Figure 7 is a schematic structural diagram of a third arc-extinguishing grid of the present invention;

[0040] Figure 8 is a schematic structural diagram of a fourth arc-extinguishing grid of the present invention;

[0041] Fig. 9 It is a schematic diagram of the structure of the circuit breaker of the present invention when it is closed;

[0042] Fig.10 It is a structural schematic diagram of the circuit breaker of the present invention when the moving contact is just opened;

[0043] Fig.11 It is a schematic diagram of the structure of the circuit breaker of the present invention when the moving contact rotates to the vicinity of the second arc-extinguishing grid;

[0044] Fig.12 It is a schematic diagram of the arc extinguishing chamber current and arc direction when the moving contact of the circuit breaker of the present invention rotates to the vicinity of the second arc extinguishing grid;

[0045] Fig.13 It is a schematic diagram of the structure of the circuit breaker of the present invention when the moving contact is fully opened.

[0046] In the figure: 1, arc extinguishing assembly; 2, static contact; 3, moving contact; 4, arc extinguishing chamber; 41, arc isolation wall; 42, first arc extinguishing grid; 43, second arc extinguishing grid; 431, first inclined plane; 432, second inclined plane; 433, first notch; 44, third arc extinguishing grid; 441, second notch; 45, fourth arc extinguishing grid; 451, moving arc-starting plate; 46, gap; 5, protective cover; 51, first partition; 52, second partition; 53, third partition; 54, groove; 6, arc isolation plate; 61, long strip hole; 7, static arc-starting plate; 8, magnetic conductive sheet. DETAILED DESCRIPTION

[0047] The technical solutions in the embodiments of the present invention will be described clearly and completely below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments.

[0048] See also Figure 1 The present invention provides a technical solution: a contact arc extinguishing system, including an arc extinguishing component 1, a static contact 2 is provided in the arc extinguishing component 1, a rotatable moving contact 3 is provided in the arc extinguishing component 1, the static contact 2 and the moving contact 3 can perform contact or separation operations, and the arc extinguishing component 1 includes an arc extinguishing chamber 4 and a protective cover 5.

[0049] like Figure 1 When the circuit breaker is closed, the moving contact 3 and the static contact 2 are in contact; when the circuit breaker is opened, the moving contact 3 and the static contact 2 are separated.

[0050] Arc-extinguishing walls 41 are provided on both sides of the arc-extinguishing chamber 4, and a first arc-extinguishing grid 42, a second arc-extinguishing grid 43, a third arc-extinguishing grid 44 and a fourth arc-extinguishing grid 45 are provided between the two arc-extinguishing walls 41. The first arc-extinguishing grid 42, a plurality of second arc-extinguishing grids 43, a plurality of third arc-extinguishing grids 44 and a fourth arc-extinguishing grid 45 are provided in sequence from bottom to top between the two arc-extinguishing walls 41, the number of the second arc-extinguishing grids 43 is four, and the number of the third arc-extinguishing grids 44 is five;

[0051] The second arc-extinguishing grid 43 is provided with a first inclined surface 431 and a second inclined surface 432. A first notch 433 is provided at the connection between the first inclined surface 431 and the second inclined surface 432. The first notch 433 is biased toward one side of the second arc-extinguishing grid 43. The second arc-extinguishing grids 43 are arranged alternately in sequence according to the positions of the first notches 433. The projection of the first notches 433 on the plane where the first arc-extinguishing grid 42 is located is located in the first arc-extinguishing grid 42.

[0052] like Figure 2-Figure 3 The arc extinguishing chamber 4 includes arc-isolating walls 41 on both sides for fixing and insulating purposes. The first arc-extinguishing grid 42, a number of second arc-extinguishing grids 43, a number of third arc-extinguishing grids 44 and a fourth arc-extinguishing grid 45 are evenly arranged from bottom to top between the arc-isolating walls 41 on both sides. There is no notch on the first arc-extinguishing grid 42. The second arc-extinguishing grid 43 is provided with a first inclined surface 431 and a second inclined surface 432. A first notch 433 is provided between the first inclined surface 431 and the second inclined surface 432. The first notch 433 is biased to one side of the second arc-extinguishing grid 43. The second arc-extinguishing grid 43 is arranged in a staggered manner according to the position of the first notch 433. In this way, when the circuit breaker is opened, the arc will not directly enter the arc-extinguishing chamber 4 in a straight line, but will connect between the first notches 433 and enter the arc-extinguishing chamber 4 in a broken line manner, which will lengthen the arc, limit the current, and facilitate the extinguishing of the arc. The projection of the first notches 433 on the plane where the first arc-extinguishing grid 42 is located is located inside the first arc-extinguishing grid 42 , which ensures that the arc first flows through the first arc-extinguishing grid 42 , which is conducive to the arc flowing through each first notch 433 .

[0053] The third arc-extinguishing grid 44 is provided with a second notch 441 at a transverse middle position.

[0054] The second notch 441 is arranged in the middle position, which is beneficial for the arc to smoothly enter the arc extinguishing grids on the arc extinguishing chamber 4 in the later stage of breaking, thereby ensuring the effective utilization rate of the arc extinguishing grids.

[0055] A movable arc-striking piece 451 extends outwardly from a lateral middle position of the fourth arc-extinguishing grid 45 . When the moving contact 3 is in the opening position, one end of the movable arc-striking piece 451 is close to the moving contact 3 .

[0056] When the moving contact 3 is in the opening position, one end of the moving arc-striking piece 451 is close to the moving contact 3 , so that the arc can smoothly jump to the top of the arc extinguishing chamber 4 .

[0057] The protective cover 5 includes a first partition plate 51 arranged on the static contact 2, the first partition plate 51 is arranged in the horizontal direction, second partition plates 52 are arranged on both sides of the first partition plate 51, two second partition plates 52 are symmetrically distributed in the first partition plate 51, the second partition plate 52 is arranged in the vertical direction, a third partition plate 53 is arranged on one side of the second partition plate 52, the third partition plate 53 is fixed to the upper surface of the first partition plate 51, the third partition plate 53 is provided with a groove 54 for rotating the moving contact 3, and the first partition plate 51, the second partition plate 52 and the third partition plate 53 are perpendicular to each other.

[0058] like Figure 1 The protective cover 5 includes a first baffle 51 in the horizontal direction, a second baffle 52 and a third baffle 53 in the vertical direction, and the three are perpendicular to each other. The third baffle 53 is provided with a groove 54 for the moving contact 3 to rotate. The first baffle 51 prevents the moving contact 3 and the static contact 2 from breaking down and short-circuiting from behind, and the second baffle 52 prevents the arc from burning on the side. At the same time, the three cooperate with each other to form a semi-enclosed cavity, allowing the expanded air to blow forward and upward.

[0059] like Figure 1 The arc extinguishing assembly 1 also includes an arc isolation plate 6, which is provided with a plurality of elongated holes 61. Gaps 46 are provided between the first arc extinguishing grid 42, the second arc extinguishing grid 43, the third arc extinguishing grid 44 and the fourth arc extinguishing grid 45. The gaps 46 correspond to the elongated holes 61 one by one, and the overlapping areas of the projections of the cross sections of the gaps 46 close to the arc isolation plate 6 on the arc isolation plate 6 and the elongated holes 61 increase from bottom to top.

[0060] This ensures that the air outlet at the lower side of the arc extinguishing chamber 4 is resisted, so that the expanded air maintains a certain pressure in the arc extinguishing chamber and the air is discharged upward.

[0061] A static arc-striking piece 7 is also provided on the static contact 2 , and one end of the static arc-striking piece 7 is arranged below the first arc-extinguishing grid piece 42 .

[0062] This allows the arc to move to the static arc-striking piece 7, reducing the burning of the static contact by the arc.

[0063] A number of magnetic conductive sheets 8 are also provided under the static contact 2 .

[0064] This increases the magnetic induction intensity in the arc extinguishing chamber, allowing the arc to move to the arc extinguishing chamber 4 more quickly.

[0065] A circuit breaker comprises a contact arc extinguishing system according to any one of claims 1 to 4.

[0066] When a short-circuit fault current flows through the circuit breaker, the static contact 2 and the moving contact 3 change from being in contact to being separated, and an arc is generated between the static contact 2 and the moving contact 3. The arc goes through the following three steps from generation to extinction:

[0067] When the moving contact 3 is just opened;

[0068] like Figure 1 and Figure 5 As shown, the currents of the stationary contact 2 and the moving contact 3 flow in opposite directions, and the arc moves toward the arc extinguishing chamber 4 under the action of the Lorentz magnetic force; the heat generated by the arc causes the surrounding air to expand due to the heat, and most of the expanded air moves toward the arc extinguishing chamber 4 through the obstruction of the first partition 51, the second partition 52 and the third partition 53; the high temperature generated by the arc causes the protective cover 5 to decompose molecular gas, so that the arc is cooled and the arc diameter is reduced;

[0069] When the moving contact 3 rotates to the vicinity of the second arc-extinguishing grid 43;

[0070] like Figure 1 , Figure 6 and Figure 7 As shown, the current flows of the static contact 2 and the moving contact 3 are still opposite, wherein the first partition 51, the second partition 52 and the third partition 53 continue to block the expanding air, and the protective cover 5 continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc moves to the static arc-starting plate 7 and flows through the first arc-extinguishing grid 42; due to the first notch 433 provided on the second arc-extinguishing grid 43, the upper arc flows from one first notch 433 to another adjacent first notch 433, the arc current flows in a broken line, the arc is greatly elongated, and the arc current is further suppressed; due to the obstruction of the arc-isolating plate 6, the lower end of the arc-isolating plate 6 does not have sufficient air outlet, and the expanding air begins to move upward;

[0071] The moving contact 3 is fully opened;

[0072] like Figure 1 and Figure 8 As shown, after the moving contact 3 rotates to the vicinity of the moving arc-striking piece 451, the current flows of the stationary contact 2 and the moving contact 3 are still opposite, and the first partition 51, the second partition 52, the third partition 53 and the arc-isolating plate 6 continue to block the expanding air, and the protective cover 5 continues to decompose the molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower section of the arc flows through the first arc-extinguishing grid 42 and the second arc-extinguishing grid 43; the upper section of the arc moves to the moving arc-striking piece 451; under the blowing of the expanding air, the middle section of the arc moves to the second notch 441 and finally enters the third arc-extinguishing grid 44.

[0073] A contact arc extinguishing system and an arc extinguishing method for a circuit breaker, characterized in that the method comprises:

[0074] Step 1: When the short-circuit fault current flows through the circuit breaker, the circuit breaker operating mechanism or the electric repulsion force drives the moving contact 3 to rotate, so that an arc is generated between the stationary contact 2 and the moving contact 3;

[0075] Step 2: After the moving contact 3 is just opened, the generated arc moves toward the arc extinguishing chamber 4 under the action of the Lorentz magnetic force. The heat generated by the arc causes the surrounding air to expand due to the heat. Most of the expanded air moves toward the arc extinguishing chamber 4 through the obstruction of the first partition 51, the second partition 52 and the third partition 53. The high temperature generated by the arc causes the protective cover 5 to decompose molecular gas, thereby cooling the arc and reducing the arc diameter.

[0076] Step 3: When the moving contact 3 continues to rotate to the vicinity of the second arc-extinguishing grid 43, the first partition 51, the second partition 52 and the third partition 53 therein continue to block the expanding air, and the protective cover 5 continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc moves to the static arc-starting plate 7 and flows through the first arc-extinguishing grid 42; the upper arc flows from one first notch 433 to another adjacent first notch 433, and the arc current flows in a broken line, the arc is greatly elongated, and the arc current is further suppressed;

[0077] Step 4: When the moving contact is fully opened, after the moving contact 3 rotates to the vicinity of the moving arc-striking plate 451, the first partition 51, the second partition 52, the third partition 53 and the arc-striking plate 6 continue to block the expanding air, and the protective cover 5 continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower section of the arc flows through the first arc-extinguishing grid 42 and the second arc-extinguishing grid 43; the upper section of the arc moves to the moving arc-striking plate 451; under the blowing of the expanding air, the middle section of the arc moves to the second notch 441 and finally enters the third arc-extinguishing grid 44, so that the arc is extinguished.

[0078] The electrical components mentioned in this article are all connected to an external main controller and 380V commercial power, and the main controller can be a conventional known device for control such as a computer.

[0079] In the description of this specification, the terms "connect", "install", "fix", "set", etc. are understood in a broad sense. For example, "connection" can be a fixed connection or an indirect connection through an intermediate component without affecting the relationship between components and the technical effect. It can also be an integral connection or a partial connection. As in this example, for ordinary technicians in this field, the specific meanings of the above terms in the present invention or invention can be understood according to the specific circumstances.

[0080] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A contact arc extinguishing system, characterized in that: The arc extinguishing assembly (1) comprises a stationary contact (2) provided in the arc extinguishing assembly (1), a rotatable moving contact (3) provided in the arc extinguishing assembly (1), the stationary contact (2) and the moving contact (3) being capable of contacting or separating, and the arc extinguishing assembly (1) comprising an arc extinguishing chamber (4) and a protective cover (5); Arc-isolating walls (41) are provided on both sides of the arc-extinguishing chamber (4), and a first arc-extinguishing grid (42), a second arc-extinguishing grid (43), a third arc-extinguishing grid (44) and a fourth arc-extinguishing grid (45) are provided between the two arc-extinguishing walls (41); The second arc-extinguishing grid (43) is provided with a first inclined surface (431) and a second inclined surface (432); a first notch (433) is provided at the connection between the first inclined surface (431) and the second inclined surface (432); the first notch (433) is biased toward one side of the second arc-extinguishing grid (43); the second arc-extinguishing grids (43) are arranged in sequence in an interlaced manner according to the positions of the first notches (433); and a projection of the first notch (433) on the plane where the first arc-extinguishing grid (42) is located is located within the first arc-extinguishing grid (42); The third arc-extinguishing grid (44) is provided with a second notch (441) at a transverse middle position; The fourth arc-extinguishing grid (45) has a movable arc-striking piece (451) extending outwardly at a lateral middle position, and when the moving contact (3) is in an open position, one end of the movable arc-striking piece (451) is close to the moving contact (3); The protective cover (5) comprises a first partition (51) arranged on the static contact (2), the first partition (51) being arranged in a horizontal direction, second partitions (52) being arranged on both sides of the first partition (51), the second partition (52) being arranged in a vertical direction, a third partition (53) being arranged on one side of the second partition (52), and the third partition (53) being fixed to the upper surface of the first partition (51).

2. A contact arc extinguishing system according to claim 1, characterized in that: The arc extinguishing assembly (1) further comprises an arc isolation plate (6), the arc isolation plate (6) being provided with a plurality of elongated holes (61), gaps (46) being provided between the first arc extinguishing grid (42), the second arc extinguishing grid (43), the third arc extinguishing grid (44) and the fourth arc extinguishing grid (45), the gaps (46) corresponding one to one with the elongated holes (61).

3. A contact arc extinguishing system according to claim 2, characterized in that: The overlapping area between the projection of the cross section of the gap (46) close to the arc isolation plate (6) on the arc isolation plate (6) and the long hole (61) increases from bottom to top.

4. A contact arc extinguishing system according to claim 1, characterized in that: A static arc-striking piece (7) is also provided on the static contact (2), and one end of the static arc-striking piece (7) is arranged below the first arc-extinguishing grid piece (42).

5. A contact arc extinguishing system according to claim 1, characterized in that: A number of magnetic conductive sheets (8) are also provided below the static contact (2).

6. A contact arc extinguishing system according to claim 1, characterized in that: A first arc-extinguishing grid (42), a plurality of second arc-extinguishing grids (43), a plurality of third arc-extinguishing grids (44) and a fourth arc-extinguishing grid (45) are sequentially arranged between the two arc-isolating walls (41) from bottom to top; two second partitions (52) are symmetrically arranged in the first partition (51); a groove (54) capable of being used for the movable contact (3) to rotate is provided in the third partition (53); and the first partition (51), the second partition (52) and the third partition (53) are perpendicular to each other.

7. A contact arc extinguishing system according to claim 6, characterized in that: The number of the second arc-extinguishing grid pieces (43) is four, and the number of the third arc-extinguishing grid pieces (44) is five.

8. A circuit breaker, characterized in that: It comprises a contact arc extinguishing system according to any one of claims 1 to 4.

9. A circuit breaker according to claim 5, characterized in that: When a short-circuit fault current flows through the circuit breaker, the static contact (2) and the moving contact (3) change from being in contact to being separated, and an arc is generated between the static contact (2) and the moving contact (3). The arc is generated and extinguished as follows: When the moving contact (3) is just opened; The currents of the stationary contact (2) and the moving contact (3) flow in opposite directions, and the arc moves toward the arc extinguishing chamber (4) under the action of the Lorentz magnetic force; the heat generated by the arc causes the surrounding air to expand due to the heat, and most of the expanded air moves toward the arc extinguishing chamber (4) through the obstruction of the first partition (51), the second partition (52) and the third partition (53); the high temperature generated by the arc causes the protective cover (5) to decompose molecular gas, thereby cooling the arc and reducing the arc diameter; When the moving contact (3) rotates to the vicinity of the second arc-extinguishing grid (43); The current flows of the stationary contact (2) and the moving contact (3) are still opposite, and the first partition (51), the second partition (52) and the third partition (53) therein continue to block the expanding air, and the protective cover (5) continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc moves to the stationary arc-starting plate (7) and flows through the first arc-extinguishing grid (42); due to the first notch (433) provided on the second arc-extinguishing grid (43), the upper arc flows from one first notch (433) to another adjacent first notch (433), and the arc current flows in a broken line, the arc is greatly elongated, and the arc current is further suppressed; due to the obstruction of the arc-isolating plate (6), the lower end of the arc-isolating plate (6) does not have sufficient air outlet, and the expanding air begins to move upward; The moving contact (3) is fully opened; After the moving contact (3) rotates to the vicinity of the moving arc-striking plate (451), the current flows of the stationary contact (2) and the moving contact (3) remain opposite, the first partition (51), the second partition (52), the third partition (53) and the arc-isolating plate (6) continue to block the expanding air, and the protective cover (5) continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc flows through the first arc-extinguishing grid (42) and the second arc-extinguishing grid (43); the upper arc moves to the moving arc-striking plate (451); under the blowing of the expanding air, the middle arc moves to the second notch (441) and finally enters the third arc-extinguishing grid (44).

10. The contact arc extinguishing system and the arc extinguishing method of the circuit breaker according to claim 1, characterized in that: The method includes: Step 1: When a short-circuit fault current flows through the circuit breaker, the circuit breaker operating mechanism or the electric repulsive force drives the moving contact (3) to rotate, so that an arc is generated between the stationary contact (2) and the moving contact (3); Step 2: After the moving contact (3) is just opened, the generated arc moves toward the arc extinguishing chamber (4) under the action of the Lorentz magnetic force, and the heat generated by the arc causes the surrounding air to expand due to the heat. Most of the expanded air moves toward the arc extinguishing chamber (4) through the obstruction of the first partition (51), the second partition (52) and the third partition (53), and the high temperature generated by the arc causes the protective cover (5) to decompose molecular gas, thereby cooling the arc and reducing the arc diameter; Step 3: When the moving contact (3) continues to rotate to the vicinity of the second arc extinguishing grid (43), the first baffle (51), the second baffle (52) and the third baffle (53) therein continue to block the expanding air, and the protective cover (5) continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc moves to the static arc-starting plate (7) and flows through the first arc extinguishing grid (42); the upper arc flows from one first notch (433) to another adjacent first notch (433), and the arc current flows in a broken line, the arc is greatly elongated, and the arc current is further suppressed; Step 4: When the moving contact is fully opened, after the moving contact (3) rotates to the vicinity of the moving arc-striking plate (451), the first partition (51), the second partition (52), the third partition (53) and the arc-striking plate (6) therein continue to block the expanding air, and the protective cover (5) continues to decompose molecular gas; under the action of the Lorentz magnetic force and the blowing of the expanding air, the lower arc flows through the first arc-extinguishing grid (42) and the second arc-extinguishing grid (43); the upper arc moves to the moving arc-striking plate (451); under the blowing of the expanding air, the middle arc moves to the second notch (441) and finally enters the third arc-extinguishing grid (44), so that the arc is extinguished.

Images