Current limiting contact unit

Abstract

In a current-limiting contact unit added to a circuit breaker, contact welding is suppressed when the device returns from current-limiting interruption. [Solution] The air damper 25 delays the operation of the movable contact 23, which has been opened by flow limiting and blocking, when it is closed again by a compression spring 24, and comprises a cylinder 31 and a piston 32. The cylinder 31 extends in the direction in which the movable contact 23 moves linearly, and is formed in a cylindrical shape with one end closed and the other end open. The piston 32 extends in the direction in which the movable contact 23 moves linearly, is fixed to the movable contact 23, has its tip side fitted into the cylinder 31, and its base end side is biased in the forward direction by a compression spring 24.

Description

Technical Field

[0001] The present invention relates to a current-limiting contact unit.

Background Art

[0002] Patent Document 1 shows a circuit breaker that interrupts a circuit when an overcurrent flows due to an overload or a short circuit.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] As an accessory that can be added to a circuit breaker, a current-limiting contact unit with higher breaking performance has been developed. The current-limiting contact unit constitutes a normally-closed contact that brings a movable contact into contact with a fixed contact by a compression spring. When performing current-limiting interruption due to a short circuit, it opens due to electromagnetic repulsive force, and after the current-limiting interruption, it closes again by the compression spring. If the contact becomes hot due to the current-limiting interruption, there is a possibility that the contact will weld when it closes again. An object of the present invention is to suppress welding of the contact when returning from current-limiting interruption in a current-limiting contact unit added to a circuit breaker.

Means for Solving the Problems

[0005] A current-limiting contact unit according to one aspect of the present invention is added to a circuit breaker. The current-limiting contact unit comprises a pair of fixed contacts, a movable contact, a compression spring, and an air damper. The movable contact moves linearly between a closed position in contact with the fixed contact and an open position separated from the fixed contact. The compression spring biases the movable contact in the closed direction. The air damper delays the operation of the movable contact when it is closed again by the compression spring after being opened by current-limiting interruption. The air damper comprises a cylinder and a piston. The cylinder extends in the direction in which the movable contact moves linearly and is formed in a cylindrical shape with one end closed and the other end open. The piston extends in the direction in which the movable contact moves linearly and is fixed to the movable contact, with its tip fitted into the cylinder and its base biased in the forward direction by the compression spring. [Effects of the Invention]

[0006] According to the present invention, the air damper delays the operation of the movable contact when it closes again after current limiting and interruption, thereby suppressing contact welding. [Brief explanation of the drawing]

[0007] [Figure 1] This diagram shows an electromagnetic contactor and a current-limiting contact unit. [Figure 2] This is a diagram showing a current-limiting contact unit. [Figure 3] This diagram shows a closed-pole current-limiting contact unit. [Figure 4] This figure shows a pair of fixed contactors and fixed contactors. [Figure 5] This is a diagram showing a movable contact. [Figure 6] This is a diagram of a cylinder. [Figure 7] This is a diagram showing the tip. [Figure 8] This is a diagram showing the base end. [Figure 9] This figure shows a movable contact, a compression spring, and a piston. [Figure 10] This figure shows a movable lid. [Figure 11]This diagram shows an open current-limiting contact unit. [Modes for carrying out the invention]

[0008] Embodiments of the present invention will be described below with reference to the drawings. Note that the drawings are schematic and may differ from actual examples. Furthermore, the following embodiments are illustrative examples of devices and methods for realizing the technical concept of the present invention, and do not limit the configuration to those described below. In other words, the technical concept of the present invention can be modified in various ways within the technical scope described in the claims.

[0009] 《Embodiment》 "composition" In the following explanation, the three mutually orthogonal directions will be referred to as the vertical direction, the width direction, and the depth direction for convenience. Figure 1 shows a circuit breaker 11 and a current limiting contact unit 12. Here, the circuit breaker 11 and the current-limiting contact unit 12 are shown as viewed from one side in the vertical direction, one side in the width direction, and from the front in the depth direction. The circuit breaker 11, also called a no-fuse breaker, automatically shuts off the circuit to protect against damage from overcurrent when it detects an abnormal overcurrent due to overload or short circuit. One side in the vertical direction is the power supply side, and the other side is the load side. The current-limiting contact unit 12 is attached to the power supply side of the circuit breaker 11. In this diagram, the current-limiting contact unit 12 is attached only to the third pole located on one side in the width direction of the circuit breaker 11, but in reality, the current-limiting contact unit 12 is attached to all three poles.

[0010] Figure 2 shows the current limiting contact unit 12. Here, the current-limiting contact unit 12 is shown viewed from one side in the vertical direction, one side in the width direction, and from the front in the depth direction. The current-limiting contact unit 12 is an accessory that can be added to the circuit breaker 11 and has higher interruption performance than the circuit breaker 11. The current-limiting contact unit 12 has a resin housing comprising a case 13 and a cover 14. FIG. 3 is a diagram showing the closed-limit current-limiting contact unit 12. Here, in the closed-limit current-limiting contact unit 12, a cross-section along the longitudinal direction and the depth direction passing through the center in the width direction is shown as viewed from one side in the width direction. The current-limiting contact unit 12 includes a pair of fixed contacts 21 and 22, a movable contact 23, a compression spring 24, an air damper 25, and an arc extinguishing device 26.

[0011] The pair of fixed contacts 21 and 22 are made of a conductive metal. The movable contact 23 is made of a conductive metal and linearly moves along the depth direction between a closed position where it contacts the pair of fixed contacts 21 and 22 and an open position where it is separated from the pair of fixed contacts 21 and 22. The compression spring 24 is a compression coil spring and biases the movable contact 23 in the closing direction. The air damper 25 delays the operation when the movable contact 23 opened by current-limiting interruption closes again by the compression spring 24. The air damper 25 is made of an insulating resin and includes a cylinder 31, a piston 32, and a movable lid 33.

[0012] The cylinder 31 extends in the depth direction and is formed in a cylindrical shape with the front in the depth direction blocked and the back open. The piston 32 extends in the depth direction and is fixed to the movable contact 23, and includes a tip end portion 36 and a base end portion 37. The piston 32 advances when moving forward in the depth direction and retreats when moving backward in the depth direction. The tip end portion 36 fits into the cylinder 31, and the base end portion 37 is biased in the forward direction by the compression spring 24. The movable lid 33 fits in front of the cylinder 31 and is displaced in the depth direction according to the forward and backward movement of the piston 32. The arc extinguishing device 26 is composed of a plurality of magnetic plates formed with V-shaped cutouts called grids, and extinguishes the arc at the time of opening by cooling, dividing, and stretching.

[0013] FIG. 4 is a diagram showing the pair of fixed contacts 21 and 22. In the figure, (a) shows a state where a pair of fixed contacts 21 and 22 are viewed from one side in the longitudinal direction, one side in the width direction, and the front in the depth direction. (b) in the figure shows a state where a pair of fixed contacts 21 and 22 are viewed from one side in the longitudinal direction, one side in the width direction, and the back in the depth direction. One fixed contact 21 is the primary side, and the other fixed contact 22 is the secondary side. The fixed contact 21 and the fixed contact 22 are isolated by a resin insulating frame not shown in the figure.

[0014] The fixed contact 21 extends in the longitudinal direction, is flat along the longitudinal and width directions, and a fixed contact point 41 is formed on the other side in the longitudinal direction of the surface facing the back in the depth direction. An opening 42 is formed at the center in the longitudinal direction of the fixed contact 21. The opening 42 penetrates the fixed contact 21 in the depth direction. A terminal plate 43 is formed on one side in the longitudinal direction of the fixed contact 21. The terminal plate 43 is connected to the circuit on the power supply side. The fixed contact 22 is arranged inside the opening 42, extends in the longitudinal direction, is flat along the longitudinal and width directions, and a fixed contact point 44 is formed on the other side in the longitudinal direction of the surface facing the back in the depth direction. The fixed contact 22 has a connecting portion 45 extending from one end in the longitudinal direction toward the front in the depth direction, and a terminal plate 46 extending from the front in the depth direction of the connecting portion 45 toward the other side in the longitudinal direction. The terminal plate 46 is connected to the terminal on the power supply side of the circuit breaker 11.

[0015] Figure 5 is a diagram showing the movable contact 23. In the figure, (a) shows a state where the movable contact 23 is viewed from one side in the longitudinal direction, one side in the width direction, and the front in the depth direction. (b) in the figure shows a state where the movable contact 23 is viewed from the front in the depth direction. The movable contact 23 extends in the longitudinal direction, is flat along the longitudinal and width directions, and movable contact points 51 are formed on both sides in the longitudinal direction of the surface facing the front in the depth direction. An annular portion 52 is formed at the center in the longitudinal direction of the movable contact 23. Inside the annular portion 52, protruding portions 53 protruding from both sides in the longitudinal direction toward the inside in the radial direction are formed.

[0016] Figure 6 shows the cylinder 31. Figure (a) shows the cylinder 31 as viewed from one side in the vertical direction, one side in the width direction, and the front in the depth direction. Figure (b) shows the cylinder 31 as viewed from one side in the vertical direction, one side in the width direction, and the back in the depth direction. Figure (c) shows the cylinder 31 as viewed from one side in the vertical direction, with a cross section passing through the center in the width direction and along the depth and width directions. The cylinder 31 has a cylindrical shape with the front in the depth direction closed and the back in the depth direction open, and a through hole 56 is formed in the end plate that closes the front in the depth direction. The through hole 56 is a round hole that penetrates in the depth direction. The inner circumferential surface of the cylinder 31 has a uniform inner diameter, but the outer circumferential surface has a step, and the outer diameter at the back in the depth direction is smaller than the outer diameter at the front. The outer diameter at the back in the depth direction of the cylinder 31 corresponds to the inner diameter of the annular portion 52 of the movable contact 23. The cylinder 31 has a notch 57 formed in the region where the outer diameter is reduced. The notches 57 are formed one on each of the vertical sides of the cylinder 31, extending along the depth direction, and the protruding portion 53 fits into them to guide the linear motion of the movable contact 23.

[0017] Figure 7 shows the tip portion 36. Figure (a) shows the tip portion 36 viewed from one side in the vertical direction, one side in the width direction, and the front in the depth direction. Figure (b) shows the tip portion 36 viewed from one side in the vertical direction, one side in the width direction, and the back in the depth direction. The tip portion 36 has an outer diameter that allows it to slide into the cylinder 31, and its tip is formed in a spherical shape. A connecting shaft 61 is formed on the tip portion 36, protruding toward the back in the depth direction. The connecting shaft 61 is cylindrical and has a smaller diameter than the tip portion 36.

[0018] Figure 8 shows the base portion 37. Figure (a) shows the base end portion 37 as viewed from one side in the vertical direction, one side in the width direction, and the front in the depth direction. Figure (b) shows the base end portion 37 as viewed from one side in the vertical direction, one side in the width direction, and the back in the depth direction. Figure (c) shows a cross-section of the base end portion 37 passing through the center in the width direction and along the depth and vertical directions, as viewed from one side in the width direction. The base end portion 37 is cylindrical in shape that slidably fits into the cylinder 31, and a connecting hole 66 is formed in its center. The connecting hole 66 is a round hole that penetrates in the axial direction, into which the connecting shaft 61 of the tip portion 36 fits. The base end portion 37 has one recess 67 on each side of its outer circumferential surface in the vertical direction. The recess 67 is formed at the corners between the cylindrical surface of the base end portion 37 and the end face facing the front in the depth direction, into which the protruding portion 53 of the movable contact 23 fits. A groove 68 is formed on the base end 37, facing inward in the depth direction. The groove 68 is an annular groove that is concave toward the front in the depth direction, into which the compression spring 24 fits.

[0019] Figure 9 shows the movable contact 23, the compression spring 24, and the piston 32. Figure (a) shows the movable contact 23, compression spring 24, and piston 32 fitted together, viewed from one side in the vertical direction, one side in the width direction, and the front in the depth direction. Figure (b) shows the movable contact 23, compression spring 24, and piston 32 fitted together, viewed from one side in the vertical direction, one side in the width direction, and the back in the depth direction. First, the movable contact 23 is fitted to the base end 37 by fitting the protruding part 53 into the recess 67. Next, the tip part 36 is fitted to the base end 37 by inserting the connecting shaft 61 into the connecting hole 66. The connecting shaft 61 and the connecting hole 66 can be fixed by fitting their threads together, press-fitting, or adhesive. As a result, the movable contact 23 is supported by being sandwiched between the tip part 36 and the base end 37. Then, the compression spring 24 is fitted into the groove 68. In this way, the movable contact 23, the compression spring 24, and the piston 32 are assembled.

[0020] Figure 10 shows the movable cover 33. Figure (a) shows the movable lid 33 as viewed from one side in the vertical direction, one side in the width direction, and from the front in the depth direction. Figure (b) shows the movable lid 33 as viewed from one side in the width direction. Figure (c) shows the movable lid 33 as viewed from the front in the depth direction. The movable lid 33 comprises a lid plate 71, a neck portion 72, and a head portion 73. The lid plate 71 is oriented axially in the depth direction and is formed in a disc shape with a diameter larger than the through hole 56 of the cylinder 31. The neck portion 72 is cylindrical and protrudes from the lid plate 71 towards the front in the depth direction, and is longer in the axial direction than the through hole 56 and has a smaller diameter than the through hole 56. The head portion 73 is roughly conical in shape, becoming smaller in diameter towards the front in the depth direction, and is provided at the tip of the neck portion 72. The bottom surface, which is at the innermost part in the depth direction, has a larger diameter than the through hole 56. The head portion 73 and the neck portion 72 have a slit 74 cut out along the diameter from the tip of the head portion 73 to the base end of the neck portion 72. The movable cover 33 is inserted into the through hole 56 from the inside of the cylinder 31 with the head portion 73 inside. At this time, the head portion 73 and the neck portion 72, which are separated by the slit 74, elastically deform so that they move closer to each other, allowing the head portion 73 to pass through the through hole 56. As a result, the movable cover 33 is able to move axially with the neck portion 72 fitted into the through hole 56 (see Figure 3).

[0021] 《Operation》 Next, the main operation of the embodiment will be described. Under normal conditions, as shown in Figure 3, the piston 32 is in the position advanced by the compression spring 24, so the movable contact 23 is in contact with the pair of fixed contacts 21 and 22, resulting in a closed state. In the event of a short circuit, before the circuit breaker 11 trips, the electromagnetic repulsion force pushes the movable contact 23 back, opening the contacts and causing a current-limiting interruption. The principle of generating the electromagnetic repulsion force is that at each contact point between the fixed contacts 41 and 44 and the movable contact 51, current concentration and diffusion occur, and the currents flowing in opposite directions generate an electromagnetic repulsion force that tries to move them apart.

[0022] Figure 11 shows the open current limiting contact unit 12. Here, the cross-section of the open current-limiting contact unit 12, passing through the center in the width direction and along the vertical and depth directions, is shown as viewed from one side in the width direction. When the piston 32 retracts against the repulsive force of the compression spring 24, negative pressure is created inside the cylinder 31, causing the movable cover 33 to be pulled inward in the depth direction, and the head 73 to contact the outer surface of the cylinder 31. At this time, the movable cover 33 is in an open position, connecting the inside and outside of the cylinder 31 through the slit 74 and opening the through hole 56. The slit 74 serves as an air passage when the piston 32 retracts. Therefore, the retraction of the piston 32 is not hindered.

[0023] Subsequently, when the electromagnetic repulsive force due to the short circuit disappears, the compression spring 24 closes the polarity again, but the air damper 25 delays the closing operation. That is, when the piston 32 moves forward, the inside of the cylinder 31 becomes positive pressure, pushing the movable cover 33 forward in the depth direction, and as shown in Figure 3, the cover plate 71 comes into contact with the inner circumferential surface of the cylinder 31. At this time, the movable cover 33 is in the closed position that closes the through hole 56. Therefore, the air inside the cylinder 31 is compressed, slowing down the forward movement of the piston 32. In this way, the air damper 25 delays the operation when the movable contact 23 closes the polarity again after the current limiting interruption.

[0024] Effects and Benefits Next, the main effects and advantages of the embodiment will be described. The current-limiting contact unit 12 is added to the circuit breaker 11 and comprises a pair of fixed contacts 21 and 22, a movable contact 23, a compression spring 24, and an air damper 25. The movable contact 23 moves linearly between a closed position in contact with the fixed contacts 21 and 22 and an open position separated from the fixed contacts 21 and 22. The compression spring 24 biases the movable contact 23 in the closed direction. The air damper 25 delays the operation of the movable contact 23 when it is opened by current-limiting interruption and then closed again by the compression spring 24, and comprises a cylinder 31 and a piston 32. The cylinder 31 extends in the direction in which the movable contact 23 moves linearly and is formed in a cylindrical shape with one end closed and the other end open. The piston 32 extends in the direction of linear motion of the movable contact 23, is fixed to the movable contact 23, has its tip fitted into the cylinder 31, and its base is biased in the forward direction by a compression spring 24. As a result, the air damper 25 delays the operation when the movable contact 23 closes again after the current limiting cutoff, thereby suppressing contact welding.

[0025] The air damper 25 decelerates the forward movement of the piston 32 by compressing the air inside the cylinder 31. This ensures that the operation of the movable contact 23 when it closes again after the current limiting cutoff is reliably delayed. A through-hole 56 is formed at one end of the cylinder 31. The air damper 25 is equipped with a movable cover 33. The movable cover 33 fits into the through-hole 56, opening the through-hole 56 when the piston 32 retracts and closing the through-hole 56 as the pressure in the cylinder 31 increases when the piston 32 moves forward. This ensures that the forward movement of the piston 32 is reliably decelerated.

[0026] The movable cover 33 comprises a cover plate 71, a neck portion 72, and a head portion 73. The cover plate 71 has a larger diameter than the through hole 56. The neck portion 72 protrudes from the cover plate 71, is longer in the axial direction than the through hole 56, and has a smaller diameter than the through hole 56, and is inserted into the through hole 56. The head portion 73 is provided at the tip of the neck portion 72 and has a larger diameter than the through hole 56. The head portion 73 and the neck portion 72 have a slit 74 cut out along the diametrical direction from the tip of the head portion 73 to the base end of the neck portion 72. This allows the movable cover 33 to be easily fitted into the through hole 56. When the head portion 73 of the movable cover 33 contacts the outer circumferential surface of the cylinder 31, the slit 74 connects the inside and outside of the cylinder 31, opening the through hole 56. When the cover plate 71 contacts the inner circumferential surface of the cylinder 31, it enters a closed position, closing the through hole 56. This allows the opening and closing of the through hole 56 to be easily switched by the axial displacement of the movable cover 33.

[0027] The movable cover 33 is displaced to the open position when the piston 32 retracts, creating negative pressure inside the cylinder 31, and displaced to the closed position when the piston 32 advances, creating positive pressure inside the cylinder 31. This allows for easy switching between opening and closing the through hole 56 in accordance with the movement of the piston 32. The piston 32 comprises a tip portion 36 and a base portion 37. The tip portion 36 fits into the cylinder 31. The base portion 37 is connected to the tip portion 36, and a groove 68 is formed on its base end surface into which a compression spring 24 fits. The movable contact 23 is supported by being sandwiched between the tip portion 36 and the base portion 37. This allows the movable contact 23 and the piston 32 to be integrated. A notch 57 is formed on the other end of the cylinder 31, extending axially and guiding the linear motion of the movable contact 23. This allows for stabilization of the posture and movement of the movable contact 23.

[0028] Next, we will explain the comparative examples. Here, a configuration in which the air damper 25 is omitted will be described as a comparative example. Since the other components are the same as those in the previously described embodiment, common components are denoted by the same reference numerals, and detailed explanations are omitted. The current-limiting contact unit constitutes a normally closed contact in which the movable contact 23 is in contact with the fixed contacts 21 and 22 by a compression spring 24. When current limiting is interrupted due to a short circuit, the contact opens due to electromagnetic repulsion, and after current limiting is interrupted, it closes again by the compression spring 24. However, if the contact becomes hot due to current limiting interruption, there is a possibility that the contact may weld together when it is closed again.

[0029] Although the above description has been made with reference to a limited number of embodiments, the scope of the rights is not limited to those embodiments, and modifications of the embodiments based on the above disclosure will be obvious to those skilled in the art. [Explanation of Symbols]

[0030] 11...Circuit breaker, 12...Current limiting contact unit, 13...Case, 14...Cover, 21...Fixed contact, 22...Fixed contact, 23...Movable contact, 24...Compression spring, 25...Air damper, 31...Cylinder, 32...Piston, 33...Movable cover, 36...Tip, 37...Base, 41...Fixed contact, 42...Opening, 43...Terminal plate, 44...Fixed contact, 45...Connecting part, 46...Terminal plate, 51...Movable contact, 52...Ring part, 53...Protruding part, 56...Through hole, 57...Notch, 61...Connecting shaft, 66...Connecting hole, 67...Recess, 68...Groove, 71...Cover plate, 72...Neck part, 73...Head, 74...Slit

Claims

1. A current-limiting contact unit added to a circuit breaker, A pair of fixed contacts, A movable contact that moves linearly between a closed position in contact with the fixed contact and an open position separated from the fixed contact, A compression spring biases the movable contact in the closing direction, The system includes an air damper that delays the operation of the movable contact, which has been opened by current limiting and blocking, when it is closed again by the compression spring, The aforementioned air damper is The movable contact extends in the direction of linear motion, and is formed as a cylindrical cylinder with one end closed and the other end open, A current-limiting contact unit characterized by comprising: a piston that extends in a direction in which the movable contact moves linearly, is fixed to the movable contact, has its tip fitted into the cylinder, and has its base biased in the forward direction by the compression spring.

2. The flow limiting contact unit according to claim 1, characterized in that the air damper decelerates the forward movement of the piston by compressing the air inside the cylinder.

3. A through hole is formed at one end of the cylinder. The aforementioned air damper is The current limiting contact unit according to claim 1, characterized by having a movable cover that fits into the through hole, opens the through hole when the piston retracts, and closes the through hole in accordance with the increase in pressure in the cylinder when the piston advances.

4. The aforementioned movable cover is A cover plate having a larger diameter than the aforementioned through hole, A neck portion that protrudes from the cover plate, is longer in the axial direction than the through hole, has a smaller diameter than the through hole, and is inserted into the through hole, The neck portion is provided with a head that is larger in diameter than the through hole, The current limiting contact unit according to claim 3, characterized in that the head and neck portions have slits cut out along the diametrical direction from the tip of the head portion to the base end of the neck portion.

5. The current limiting contact unit according to claim 4, characterized in that when the head of the movable cover contacts the outer circumferential surface of the cylinder, the slit connects the inside and outside of the cylinder, opening the through hole, and when the cover plate contacts the inner circumferential surface of the cylinder, the cover plate contacts the inner circumferential surface of the cylinder, it enters a closed position, closing the through hole.

6. The flow-limiting contact unit according to claim 5, characterized in that the movable cover is displaced to the open position when the piston retracts, as negative pressure is created inside the cylinder, and displaced to the closed position when the piston advances, as positive pressure is created inside the cylinder.

7. The aforementioned piston is The tip portion that fits into the cylinder, It comprises a base end connected to the tip and having a recess formed on its base end face into which the compression spring fits, The current-limiting contact unit according to claim 1, characterized in that the movable contact is supported by being sandwiched between the tip and base portions.

8. The current limiting contact unit according to claim 1, characterized in that a notch extending along the axial direction is formed on the other end of the cylinder to guide the linear motion of the movable contactor.

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