Circuit breaker

Abstract

To improve the driving force to extend an arc and the ability to cool the arc and improve the shut-off performance in a circuit breaker.SOLUTION: A circuit breaker 11 includes stators 21, 22, a mover 23, multiple arc-extinguishing grids 24, a pair of permanent magnets 25, and a pair of arc-extinguishing insulators 26. The multiple arc-extinguishing grids 24 are provided on the outer radial side of the mover 23 when it rotates. The multiple arc-extinguishing grids 24 attract an arc A generated between a fixed contact 31 and a movable contact 32. The pair of permanent magnets 25 opposes each other across the mover 23 and provides an external magnetic field φe to the arc A. The pair of arc-quenching insulators 26 opposes each other across the track of the movable contact 32 and cools the arc A by thermal decomposition due to the heat of the arc A.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a circuit breaker.

Background Art

[0002] A circuit breaker, also called a non-fuse breaker, automatically shuts off the circuit when it detects an abnormal overcurrent due to overload or short circuit to protect against damage caused by the overcurrent. As a technique for improving the breaking performance, for example, as shown in Patent Document 1, it is known to drive an arc by its self-magnetic field and cool the arc by thermal decomposition when the surface of the arc extinguishing insulator evaporates.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When driving an arc only by its self-magnetic field, the driving force may be insufficient in the small current region, and the arc may not be stretched sufficiently. Also, if the arc extinguishing insulator is not provided in the direction of stretching the arc, it cannot be cooled sufficiently. An object of the present invention is to enhance the driving force for stretching an arc and the ability to cool the arc in a circuit breaker, thereby improving the breaking performance.

Means for Solving the Problems

[0005] A circuit breaker according to one aspect of the present invention includes a stator having a fixed contact, a rotor having a movable contact that contacts and separates from the fixed contact by rotation, a plurality of arc extinguishing grids provided on the outer side in the radial direction when the rotor rotates, for drawing in an arc generated between the fixed contact and the movable contact, a pair of permanent magnets facing each other with the rotor therebetween, for applying an external magnetic field to the arc, and a pair of arc extinguishing insulators facing each other with the orbit of the movable contact therebetween, for cooling the arc by thermal decomposition due to the heat of the arc.

Advantages of the Invention

[0006] According to the present invention, the arc is drawn into the arc extinguishing grid by its self-magnetic field and is driven toward the arc extinguishing insulator by the external magnetic field generated by the permanent magnet. Therefore, compared with the case where the arc is driven only by its self-magnetic field, the driving force for stretching the arc and the ability to cool the arc can be enhanced, and the interruption performance can be improved.

Brief Description of the Drawings

[0007]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Embodiments for Carrying Out the Invention

[0008] Hereinafter, embodiments of the present invention will be described with reference to the drawings. Note that each drawing is schematic and may differ from the actual one. Further, the following embodiments illustrate devices and methods for embodying the technical idea of the present invention, and do not specify the configuration to the following ones. That is, the technical idea of the present invention can be variously modified within the technical scope described in the claims.

[0009] 《One Embodiment》 《Configuration》 In the following description, for convenience, three mutually orthogonal directions are defined as the longitudinal direction, the width direction, and the depth direction. FIG. 1 is a diagram showing the interruption cylinder of the circuit breaker. The circuit breaker 11, also called a non-fuse breaker, houses an opening / closing mechanism, an overcurrent tripping device, an interruption cylinder 12 which is a current interruption part, etc. (not shown) in a main body case, and automatically interrupts the circuit when an abnormal overcurrent is detected due to overload or short circuit to protect against damage caused by the overcurrent. The circuit breaker 11 includes a resin-made interruption cylinder 12 for each pole, and here only the interruption cylinder 12 for one pole is shown. The housing of the interruption cylinder 12 is configured by combining a pair of cases 13 that can be divided in the width direction.

[0010] FIG. 2 is a diagram showing the inside of the interruption cylinder (interrupted state). Here, the interrupted state with the contacts open is shown. The interruption cylinder 12 is a high interruption capacity product with increased arc voltage by providing two contacts for each pole, and can also be energized in the reverse direction. The interruption cylinder 12 includes stators 21 and 22, a rotor 23, an arc extinguishing grid 24, a permanent magnet 25, and an arc extinguishing insulator 26. The stator 21 is provided on one side in the longitudinal direction and the front side in the depth direction, and is a strip-shaped conductor that turns back from the other side in the longitudinal direction and heads toward one side in the longitudinal direction on the back side in the depth direction. One end side of the stator 21 is plate-shaped along the longitudinal and width directions protruding to one side in the longitudinal direction, and a terminal is connected from the front side in the depth direction. The other end side of the stator 21 is plate-shaped along the longitudinal and width directions protruding to one side in the longitudinal direction on the back side in the depth direction compared to the one end side, and a fixed contact 31 is formed on the surface on the back side in the depth direction.

[0011] The stator 22 is provided on the other side in the longitudinal direction and the back side in the depth direction, and is a strip-shaped conductor that turns back from the one side in the longitudinal direction and heads toward the other side in the longitudinal direction on the front side in the depth direction. One end side of the stator 22 is plate-shaped along the longitudinal and width directions protruding to the other side in the longitudinal direction, and a terminal is connected from the front side in the depth direction. The other end side of the stator 22 has the same position in the depth direction as the one end side, is plate-shaped along the longitudinal and width directions protruding to the other side in the longitudinal direction, and a fixed contact 31 is formed on the surface on the front side in the depth direction. The mover 23 is a rod-shaped conductor extending substantially in the longitudinal direction, and movable contacts 32 are formed at both ends. The movable contacts 32 are brought into contact with and separated from the respective fixed contacts 31 by rotation.

[0012] The arc extinguishing grid 24 is a magnetic body formed in a thin flat plate shape. Here, as an example, seven arc extinguishing grids 24 are arranged at equal intervals in the direction perpendicular to the surface, and are respectively supported by the case 13. The arc extinguishing grid 24 is provided outside the radial direction when the mover 23 rotates within the movable range of the movable contact 32, and a set is provided on each of the stator 21 side and the stator 22 side. Exhaust ports 33 are formed in the case 13 on the back side in the depth direction on one side in the longitudinal direction and on the front side in the depth direction on the other side in the longitudinal direction. The ionized gas generated during interruption is discharged from the interruption cylinder 12 through the exhaust ports 33. The pair of permanent magnets 25 are formed in a disc shape along the longitudinal direction and the depth direction, and are opposed to each other with the mover 23 interposed therebetween in the axial direction. The pair of permanent magnets 25 are provided such that the same magnetic pole faces face each other, thereby applying an external magnetic field orthogonal to the axial direction of the mover 23 with respect to the arc when viewed from the direction in which the fixed contact 31 and the movable contact 32 are separated, that is, the depth direction. Here, the inner side in the width direction is the N pole, and the outer side is the S pole.

[0013] The arc extinguishing insulator 26 cools the arc by thermal decomposition when the surface evaporates due to the heat of the arc, and increases the arc voltage by such ablation action. Specifically, a polymer compound having excellent heat resistance is used, and polyamide 66 (PA66), polyamide 6 (PA6), etc. which are particularly likely to generate polymer vapor are preferable. The arc extinguishing insulator 26 is formed in a piece shape having end faces along the longitudinal direction and the depth direction, and is fitted and fixed to the case 13 so as to sandwich the range centered on the position where the movable contact 32 contacts the fixed contact 31 in particular among the orbits of the movable contact 32 from both sides in the width direction. A pair of arc extinguishing insulators 26 are provided on each of the stator 21 side and the stator 22 side.

[0014] FIG. 3 is a diagram showing the disassembled case. In each of the pair of cases 13, a boss-shaped holder accommodating portion 16 having the width direction as the axial direction is formed at the center in the longitudinal direction. FIG. 4 is a diagram showing the rotating holder. The rotating holder 34 is a substantially cylindrical insulating member with both ends closed, and is rotatably supported by fitting both ends in the axial direction into the holder accommodating portion 16 of the case 13. The mover 23 is inserted through the rotating holder 34 in the diameter direction, and is held so as to protrude from both ends of the cylindrical surface of the rotating holder 34. The rotating holder 34 is connected to the rotating holders 34 of the other adjacent poles via a connecting shaft (not shown) extending in the width direction, so that the rotating operations are interlocked. The pair of permanent magnets 25 are provided on both end faces in the axial direction of the rotating holder 34.

[0015] FIG. 5 is a diagram showing the arc extinguishing grid. (a) in the figure shows a state of viewing seven arc extinguishing grids 24 provided on the side of the stator 21 from the inner side in the longitudinal direction, the other side in the width direction, and the front side in the depth direction. Each arc extinguishing grid 24 is formed with a groove portion 35 that is concave toward the outer side in the longitudinal direction. The groove portion 35 is formed in a substantially V shape that opens to the inner side in the longitudinal direction when viewing the arc extinguishing grid 24 in a direction perpendicular to the surface. When the movable contact 32 is separated from the fixed contact 31, an arc A is generated between the fixed contact 31 and the movable contact 32. (b) in the figure is a view of the arc A at the time of interruption as seen from the back side in the depth direction, and the arc A flows from the back side to the front side in the depth direction. When viewed from the back side in the depth direction, a self-magnetic field φs in the counterclockwise direction is generated around the arc A, and the self-magnetic field φs is drawn into the groove portion 35 toward the outer side in the longitudinal direction by the groove portion 35 when passing through the arc extinguishing grid 24, as shown by the dotted line. Due to this bias of the magnetic flux density, a Lorentz force Fs acting toward the outer side in the longitudinal direction as shown by the block arrow is applied, and the arc A is drawn into the groove portion 35 of the arc extinguishing grid 24. In this way, the arc extinguishing grid 24 has a deion type arc extinguishing structure that increases the arc voltage by drawing the arc A to the outer side in the longitudinal direction by the self-magnetic field φs and dividing it into each gap.

[0016] Figure 6 is a view showing the inside of the interruption cylinder (in the input state). Here, an input state with the contacts closed is shown. When viewed from the other side in the width direction, when the rotation holder 34 rotates clockwise together with the mover 23, the movable contact 32 of the mover 23 comes into contact with each of the fixed contacts 31, resulting in an input state where the power supply side is connected to the load side. When viewed from the other side in the width direction, the mover 23 is biased clockwise by a contact spring (not shown) with respect to the rotation holder 34, thereby maintaining a constant contact pressure of the movable contact 32 against the fixed contact 31.

[0017] 《Operation》 Next, the main operation of one embodiment will be described. The circuit breaker 11 of one embodiment includes stators 21 and 22, a rotor 23, a plurality of arc extinguishing grids 24, a pair of permanent magnets 25, and a pair of arc extinguishing insulators 26. The stators 21 and 22 are formed with fixed contacts 31. The rotor 23 is formed with a movable contact 32, and the movable contact 32 is brought into contact with and separated from the fixed contact 31 by rotation. The plurality of arc extinguishing grids 24 are provided on the outer side in the radial direction when the rotor 23 rotates, and draw in an arc A generated between the fixed contact 31 and the movable contact 32. The pair of permanent magnets 25 face each other with the rotor 23 interposed therebetween in the axial direction, and apply an external magnetic field φe to the arc A. The pair of arc extinguishing insulators 26 face each other with the orbit of the movable contact 32 sandwiched in parallel with the axial direction, and cool the arc A by thermal decomposition when the surface evaporates due to the heat of the arc A.

[0018] As a result, the arc A is drawn into the arc extinguishing grid 24 by the self-magnetic field φs and is driven toward the arc extinguishing insulator 26 by the external magnetic field φe generated by the permanent magnet 25. Therefore, even in a small current region where the self-magnetic field φs weakens, the arc A can be quickly and sufficiently stretched by the external magnetic field φe. Further, since the arc extinguishing insulator 26 is provided in the direction in which the arc A is stretched by the external magnetic field φe, the surface of the arc extinguishing insulator 26 is likely to evaporate due to the heat of the arc A, and the cooling effect by thermal decomposition can be efficiently enhanced. In this way, compared with the case of driving the arc A only by the self-magnetic field φs, the driving force for stretching the arc A and the ability to cool the arc A can be enhanced, the interruption performance can be improved, the rated current can be increased in capacity, and the circuit breaker 11 can be miniaturized.

[0019] FIG. 7 is a diagram for explaining the operation when energized in one direction. In the figure, (a) is a view of the arc A at the time of interruption as seen from the other side in the width direction. Here, as shown by the thick arrow, current is flowing in one direction from the stator 22, through the mover 23, and toward the stator 21. In the figure, (b) is a view of the arc A at the time of interruption as seen from the front side in the depth direction. The arc A is flowing from the back side to the front side in the depth direction, and an external magnetic field φe is applied to this arc A from a pair of permanent magnets 25 as shown by the dotted line. As a result, as shown by the block arrow, a Lorentz force Fe acting toward the other side in the width direction acts on the arc A on the stator 21 side, and a Lorentz force Fe acting toward one side in the width direction according to Fleming's left-hand rule acts on the arc A on the stator 22 side. Due to this Lorentz force Fe, the arc A can be stretched toward the arc extinguishing insulator 26, and the interruption performance can be improved.

[0020] FIG. 8 is a diagram for explaining the operation when energized in the reverse direction. In the figure, (a) is a view of the arc A at the time of interruption as seen from the other side in the width direction. Here, as shown by the thick arrow, current is flowing in the reverse direction from the stator 21, through the mover 23, and toward the stator 22. In the figure, (b) is a view of the arc A at the time of interruption as seen from the front side in the depth direction. The arc A is flowing from the front side to the back side in the depth direction, and an external magnetic field φe is applied to this arc A from a pair of permanent magnets 25 as shown by the dotted line. As a result, as shown by the block arrow, a Lorentz force Fe acting toward the other side in the width direction acts on the arc A on the stator 22 side, and a Lorentz force Fe acting toward one side in the width direction according to Fleming's left-hand rule acts on the arc A on the stator 21 side. Due to this Lorentz force Fe, the arc A can be stretched toward the arc extinguishing insulator 26, and the interruption performance can be improved. That is, a circuit breaker 11 corresponding to bidirectional current interruption can be provided.

[0021] The permanent magnet 25 applies an external magnetic field φe in the direction in which the mover 23 extends with respect to the arc A when viewed from the direction in which the fixed contact 31 and the movable contact 32 are separated. Thereby, a Lorentz force Fe acting in the width direction acts on the arc A, and the arc A can be stretched toward the arc-extinguishing insulator 26. The pair of permanent magnets 25 have the same magnetic pole faces facing each other. Thereby, an external magnetic field φe orthogonal to the axial direction of the mover 23 can be applied to the arc A when viewed from the direction in which the fixed contact 31 and the movable contact 32 are separated. The circuit breaker 11 includes a rotation holder 34 that can rotate while holding the mover 23. One fixed contact 31 is formed on one side of each of the pair of stators 21 and 22. Movable contacts 32 are formed one by one on both end sides protruding from the rotation holder 34, and each of the movable contacts 32 is brought into contact with and separated from the fixed contact 31 by the rotation of the rotation holder 34. By providing two contacts for each pole in this way, the arc voltage can be increased.

[0022] A plurality of arc-extinguishing grids 24 are formed with groove portions 35 that are concave toward the outside in the radial direction when the mover 23 rotates. Thereby, the arc A is drawn into the groove portion 35 of the arc-extinguishing grid 24 and divided into each gap of the arc-extinguishing grid 24, so that the arc voltage can be increased. The arc-extinguishing insulator 26 is a polymer compound. Thereby, the arc can be cooled by thermal decomposition when the surface evaporates due to the heat of the arc, and the arc voltage can be increased. The circuit breaker 11 includes a breaking cylinder 12. The breaking cylinder 12 is made of resin that houses the stator 21, the stator 22, the mover 23, a plurality of arc-extinguishing grids 24, a pair of permanent magnets 25, and a pair of arc-extinguishing insulators 26. Thereby, a breaking cylinder 12 unitized for each pole can be provided.

[0023] Next, a comparative example will be described. FIG. 9 is a diagram showing a comparative example. In the comparative example, a pair of permanent magnets 41 and a pair of arc extinguishing insulators 42 are provided so as to sandwich the arc A in the width direction. The pair of permanent magnets 41 have different magnetic pole faces facing each other. The arc extinguishing insulator 42 is provided so as to cover the inner side in the width direction and both sides in the longitudinal direction of the permanent magnet 41. (a) in the figure illustrates the operation when energized in one direction. The arc A flows from the back side to the front side in the depth direction, and an external magnetic field φc directed to one side in the width direction is applied to this arc A by a pair of permanent magnets 41 as shown by the dotted line. As a result, as shown by the block arrow, a Lorentz force Fc directed outward in the longitudinal direction acts on the arc A according to Fleming's left hand rule. By this Lorentz force Fc, the arc A can be stretched toward the arc extinguishing grid 24.

[0024] However, the arc extinguishing insulator 42 is not arranged in the direction of stretching the arc A. Therefore, the effect of cooling the arc A by thermal decomposition when the surface of the arc extinguishing insulator 42 evaporates could not be sufficiently exerted. Furthermore, the comparative example cannot cope with bidirectional current interruption. (b) in the figure illustrates the operation when energized in the reverse direction. The arc A flows from the front side to the back side in the depth direction, and an external magnetic field φc directed to one side in the width direction is applied to this arc A from a pair of permanent magnets 41 as shown by the dotted line. In this case, as shown by the block arrow, a Lorentz force Fc directed inward in the longitudinal direction acts on the arc A, so the arc A could not be stretched toward the arc extinguishing grid 24.

[0025] <<Modification Example>> In one embodiment, the configuration in which two contacts are provided for each pole has been described, but the present invention is not limited to this, and it may be applied to a configuration in which one contact is provided for each pole. In one embodiment, a pair of permanent magnets 25 has been described with the inner side in the width direction being the N pole and the outer side being the S pole, but it is not limited thereto. That is, as long as an external magnetic field φe in the longitudinal direction can be applied to the arc A, the inner side in the width direction may be the S pole and the outer side may be the N pole.

[0026] Although the above has been described with reference to a limited number of embodiments, the scope of the rights is not limited thereto, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art.

Explanation of Reference Numerals

[0027] 11... Circuit breaker, 12... Interrupting cylinder, 13... Case, 16... Holder accommodating portion, 21... Stator, 22... Stator, 23... Rotor, 24... Arc extinguishing grid, 25... Permanent magnet, 26... Insulator for arc extinguishing, 31... Fixed contact, 32... Moving contact, 33... Exhaust port, 34... Rotating holder, 35... Groove portion, 41... Permanent magnet, 42... Insulator for arc extinguishing, A... Arc, Fc... Lorentz force, Fe... Lorentz force, Fs... Lorentz force, φc... External magnetic field, φe... External magnetic field, φs... Self magnetic field

Claims

1. A stator having fixed contacts formed thereon, A rotor having movable contacts formed thereon and configured to bring the movable contacts into contact with and separate them from the fixed contacts by rotation, A rotating holder that can rotate while holding the rotor, A plurality of arc extinguishing grids provided on the outer side in the radial direction when the rotor rotates, for drawing in the arc generated between the fixed contacts and the movable contacts, A pair of permanent magnets that oppose each other with the rotating holder sandwiched therebetween in the axial direction and apply an external magnetic field to the arc, A pair of arc extinguishing insulators that oppose each other with the orbit of the movable contact therebetween and cool the arc by thermal decomposition due to the heat of the arc, and comprising: The circuit breaker is characterized in that the pair of permanent magnets apply the external magnetic field in the direction in which the rotor extends with respect to the arc when viewed from the direction in which the fixed contacts and the movable contacts separate.

2. The circuit breaker according to claim 1, wherein the pair of permanent magnets have the same magnetic pole faces facing each other.

3. The pair of stators have the fixed contacts formed on one side thereof, respectively, The circuit breaker according to claim 1 or 2, wherein the rotor has the movable contacts formed on both end sides protruding from the rotating holder, and the rotation of the rotating holder brings each of the movable contacts into contact with and separates them from the fixed contacts.

4. The circuit breaker according to any one of claims 1 to 3, wherein the plurality of arc extinguishing grids are formed with groove portions that are recessed toward the outer side in the radial direction when the rotor rotates.

5. The circuit breaker according to any one of claims 1 to 4, wherein the arc extinguishing insulator is a polymer compound.

6. The circuit breaker according to any one of claims 1 to 5, further comprising a resin-made interruption cylinder that houses the stator, the rotor, the plurality of arc extinguishing grids, the pair of permanent magnets, and the pair of arc extinguishing insulators.

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