A multi-stage arc-extinguishing protection device for high breaking fuses

Abstract

The application discloses a multi-stage arc extinguishing protection device of high-breaking fuse, and relates to the technical field of high-breaking fuses, which comprises a base and an end cover, and a side wall is fixedly arranged on the base and comprises: a conductor which is detachably arranged on the base, current input ends and current output ends are respectively connected to two ends of the conductor, the conductor has a wave-shaped structure, and a section of a fuse link which is connected in series with adjacent parts of the conductor is arranged in the wave-shaped structure. After the fuse link is vaporized and disconnected, the current is forced to completely transfer to the wave-shaped conductor. Since the full length of the wave line of the conductor is far greater than the linear distance of the two ends of the conductor, and the main cross-sectional area of the conductor is smaller than the cross-sectional area of the fuse link, the whole loop resistance suddenly increases at the moment when the fuse link is vaporized. The resistance mutation immediately produces a strong limiting effect on the short-circuit current which is rapidly rising, and the arc peak value is reduced in the stage when the arc has not been formed or has just been formed.

Description

Technical Field

[0001] This invention relates to the field of high breaking capacity fuse technology, and more specifically to a multi-stage arc extinguishing protection device for high breaking capacity fuses. Background Technology

[0002] As one of the most widely used and lowest-cost short-circuit protection devices in power systems, the core working principle of a fuse is to utilize the fusible metal conductor (fusible element) connected in series in the circuit to heat up and melt when an overload or short-circuit current passes through, thereby cutting off the faulty circuit. Due to its simple structure, reliable operation, and strong breaking capacity, fuses hold an irreplaceable position in low-voltage power distribution, power electronic protection, new energy systems, and industrial control.

[0003] Traditional fuses primarily fall into two categories regarding arc extinguishing mechanisms: filled and unfilled. Among these, filled fuses (such as the NT and RT series) are currently the most widely used high-breaking-capacity fuses. These fuses encapsulate the fusible element within an insulating tube, and granular silica sand is tightly packed around the fusible element as the arc-extinguishing medium. When a fault current causes the fusible element to melt and vaporize, the silica sand extinguishes the arc through the following mechanism.

[0004] However, this passive arc-extinguishing method, which relies entirely on quartz sand, has several inherent drawbacks that are difficult to overcome: First, the arc-extinguishing performance is not adjustable. The filling density, particle size distribution, and purity of the quartz sand are fixed during manufacturing, thus locking the arc-extinguishing characteristics. Regardless of the fault current, the cooling and breaking capacity provided by the arc-extinguishing medium is constant. This leads to a fundamental contradiction: if the arc-extinguishing chamber is designed based on the maximum short-circuit current, the arc extinguishing will be too "violent" under small current faults, potentially generating excessively high operating overvoltages; if small current arc extinguishing is also considered, the arc extinguishing may be insufficient under large currents, leading to breaking failure. Existing technology struggles to achieve the function of adaptively adjusting the arc-extinguishing force according to the fault current magnitude.

[0005] Secondly, in traditional filled fuses, the combustion, movement, and extinguishing of the electric arc within the quartz sand gaps are completely uncontrollable random physical processes. The arc path, the location of the arc root, and the rate of rise of the arc voltage cannot be actively intervened. This results in significant dispersion in the fuse's I²t (allowed energy), making it difficult to accurately predict and control the protection effect on downstream equipment. Summary of the Invention

[0006] The purpose of this invention is to provide a multi-stage arc-extinguishing protection device for high-breaking capacity fuses, which solves the problems of non-adjustable arc-extinguishing performance, difficulty in handling both small and large current faults, severe arc extinguishing under small arcs, and insufficient arc extinguishing under large currents, leading to breaking failure.

[0007] To achieve the above objectives, the present invention provides the following technical solution: a multi-stage arc-extinguishing protection device for a high breaking capacity fuse, comprising a base and an end cap, wherein a side wall is fixedly disposed on the base, comprising: A conductor detachably mounted on the base has a current input terminal and a current output terminal connected to its two ends respectively. The conductor has a corrugated structure and contains a fuse piece that connects adjacent parts in series. The conductor has a fuse joint near the current output terminal, and the mechanical strength of the fuse joint is lower than that of the rest of the conductor. The sensing circuit is located inside the end cap, between the second end of the conductor and the current output end; An insulating sleeve is fixedly mounted on the base and used to accommodate the induction circuit. A guide rod is hinged to the outer side of the insulating sleeve, and the first end of the guide rod is connected to the outer side of the insulating sleeve by a pre-tension spring, so that the guide rod remains horizontal. The end of the guide rod is provided with an arc-inducing structure, which is oriented toward the fusible connector and maintains an air insulation gap with the conductor. It also includes an inverted pyramid grid located above the arc-leading structure. The inverted pyramid grid is formed by multiple rectangular structures stacked together and fixed inside the base. The bottom grid (a) has the largest spacing and the fewest number of grids. The number of grids increases and the spacing between grids decreases as you go up. It also includes a power transmission structure for driving the guide rod to swing upward against the tension of the pre-tension spring, which enables the arc-initiating structure to guide the arc toward the inverted pyramid grid. Preferably, the conductor and the fuse form a through horizontal current channel. Before the fuse melts, the initial resistance is determined by the cross-sectional area of ​​the fuse and the length of the conductor. After the fuse melts, the current-limiting resistance is determined by the total length of the wavy line of the conductor and its cross-sectional area, and the cross-sectional area of ​​the conductor is smaller than the cross-sectional area of ​​the fuse.

[0008] Preferably, the power transmission structure further includes: A limiting seat fitted onto the second end of the conductor; The return springs at both ends abut against the side wall and the limiting seat, respectively; An insulating cavity for accommodating a return spring and formed on the base; The end of the limiting seat is provided with a lever, which is used to actuate the arc-initiating structure of the guide rod when the conductor contracts.

[0009] Preferably, the arc-initiating structure is an integral conductive component disposed at the end of the guide rod, and the side of the arc-initiating structure facing the fusible connector is an arc surface or a slope surface.

[0010] Preferably, an excitation coil is connected in series on the induction line, and a magnet is sleeved inside the excitation coil; a one-way ratchet sleeve is fixedly provided at the tail end of the pretension spring, and an annular armature is fixedly provided at the tail end of the one-way ratchet sleeve, and the armature is coaxial with and opposite to the excitation coil. The excitation coil is configured to generate a magnetic field when a fault current flows through it, attracting the armature to drive the one-way ratchet sleeve to further stretch the pretension spring.

[0011] Preferably, a fixing seat is provided inside the end cap via an elastic element, and the fixing seat engages with the one-way ratchet sleeve.

[0012] Preferably, the grids in the same layer of the inverted pyramid grid are connected by a fixed rod; it also includes a transmission seat located between two adjacent fixed rods and used to drive the fixed rods to slide vertically, the transmission seat being hinged to the adjacent fixed rod with an inclined rod; the fixed rod is vertically slidably disposed on the side wall, and the transmission seat is horizontally slidably disposed on the side wall.

[0013] Preferably, a transmission rod is fixedly connected between the transmission seat and the one-way ratchet sleeve.

[0014] Preferably, the grid spacing of the inverted pyramid grid decreases by half from bottom to top, which is half the ratio of the previous spacing.

[0015] In the above technical solution, the multi-stage arc-extinguishing protection device for high breaking capacity fuses provided by the present invention has the following beneficial effects: 1. After the fuse breaks by vaporization, the current is forced to transfer completely to the corrugated conductor. Because the total length of the conductor's corrugation is much greater than the straight-line distance between its two ends, and its main cross-sectional area is smaller than that of the fuse, the resistance of the entire circuit increases abruptly at the moment the fuse vaporizes. This sudden change in resistance immediately exerts a strong limiting effect on the rapidly rising short-circuit current, reducing the peak value of the arc before or just as it forms. 2. The bottom layer has the largest grid spacing and the fewest grid plates, resulting in minimal segmentation resistance. This allows the arc to be smoothly introduced into the grid during the initial stage, preventing it from being deflected due to excessive resistance. As the arc-initiating structure continues to rise, the arc is gradually delivered to an increasingly dense array of grid plates, with the segmentation depth increasing and the arc voltage rising steadily from low to high. This avoids the risk of sudden arc voltage changes and reignition caused by direct contact between fixed-spacing grid plates and the arc, significantly improving the stability of the arc extinguishing process. 3. Under small fault currents, the excitation coil has weak magnetic force, the unidirectional ratchet sleeve has small displacement, the pawl is locked in a shallow tooth groove position, the pretension spring tension increase is limited, and the guide rod swings at a moderate speed and force, suitable for interrupting small current arcs. Under large fault currents, the excitation coil has strong magnetic force, the unidirectional ratchet sleeve has large displacement, the pawl is locked in a deeper tooth groove position, the pretension spring is stretched significantly, and the guide rod obtains extremely strong driving force, swinging upwards at a speed and force far exceeding the norm, ensuring that the arc can be quickly and forcefully introduced into the arc-extinguishing chamber and reliably extinguished under large currents. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0017] Figure 1 This is an overall three-dimensional schematic diagram provided for an embodiment of the present invention; Figure 2 This is a schematic diagram of the inner sectional view of the end cap provided in an embodiment of the present invention; Figure 3 This is a schematic cross-sectional view provided for an embodiment of the present invention; Figure 4 A side view provided for an embodiment of the present invention; Figure 5 This is another side view schematic diagram provided for an embodiment of the present invention; Figure 6 This is a schematic diagram of the conductor and induction circuit structure provided in an embodiment of the present invention; Figure 7 A schematic diagram of the guide rod and one-way ratchet sleeve structure provided in an embodiment of the present invention; Figure 8 This is a schematic diagram of the excitation coil and magnet structure provided in an embodiment of the present invention; Figure 9 This is a schematic diagram of an inverted pyramid grid structure provided in an embodiment of the present invention; Figure 10 This is a schematic diagram of the inverted pyramid grille and transmission seat structure provided in an embodiment of the present invention.

[0018] Explanation of reference numerals in the attached figures: 1. Base; 2. End cap; 3. Side wall; 4. Current input terminal; 5. Current output terminal; 100. Conductor; 110. Fuse; 120. Fuse connector; 130. Limit seat; 131. Toggle block; 140. Return spring; 150. Insulating chamber; 200. Induction circuit; 210. Excitation coil; 220. Magnet; 300. Guide rod; 310. Insulating sleeve; 320. Pre-tension spring; 330. Arc ignition structure; 340. One-way ratchet sleeve; 350. Armature; 360. Elastic element; 370. Fixing seat; 400. Inverted pyramid grid; 410a. Bottom grid; 420. Fixing rod; 430. Transmission seat; 440. Diagonal bar; 450. Transmission rod. Detailed Implementation

[0019] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0020] like Figure 1-3 As shown, a multi-stage arc-extinguishing protection device for a high-breaking capacity fuse includes a base 1 and an end cap 2. A side wall 3 is fixedly installed on the base 1, comprising: A conductor 100 is detachably mounted on the base 1. Both ends of the conductor 100 are connected to a current input terminal 4 and a current output terminal 5, respectively. Both the current input terminal 4 and the current output terminal 5 are made of copper or copper alloy, using knife-shaped contacts or bolt terminals for series connection to the protected main circuit. They are respectively mounted on end caps 2 for easy connection to external busbars or cables. The conductor 100 has a corrugated structure, and its interior contains a fuse 110 that connects adjacent sections in series. The conductor 100 includes a fuse 110 that connects and separates adjacent corrugated structures in series. The cross-sectional area of ​​the fuse 110 is much smaller than the cross-sectional area of ​​other parts of the conductor 100, forming the first-stage fuse point. Under normal operating conditions, because the resistance of the fuse 110 is much smaller than the resistance of the corrugated conductor 100 connected in parallel, most of the load current flows through the fuse 110, and the conductor 100 exists only as a bypass. Conductor 100 has a fusible connector 120 near the current output terminal 5. The mechanical strength of the fusible connector 120 is lower than that of the rest of conductor 100. The fusible connector 120 can be formed by locally reducing the cross-sectional area of ​​the conductor at that location or by using a low-melting-point alloy for welding in a local area, thus forming a second-stage fusion point. Conductor 100 and fuse 110 form a through horizontal current channel. Before fuse 110 melts, the initial resistance is determined by the cross-sectional area of ​​fuse 110 and the length of conductor 100. After fuse 110 melts, the current-limiting resistance is determined by the total length of the wavy line of conductor 100 and its cross-sectional area. The cross-sectional area of ​​conductor 100 is smaller than that of fuse 110. Conductor 100 itself is made of an alloy material with a positive temperature coefficient. It has extremely low resistance at room temperature, but can heat up rapidly and exhibit current-limiting resistance characteristics when overcurrent occurs.

[0021] After fuse 110 vaporizes and breaks, the current is forced to transfer completely to the corrugated conductor 100. Since the total length of the corrugated line of conductor 100 is much greater than the straight-line distance between its two ends, and its main cross-sectional area is smaller than that of fuse 110, the resistance of the entire circuit increases abruptly at the moment fuse 100 vaporizes. This sudden change in resistance immediately exerts a strong limiting effect on the rapidly rising short-circuit current, reducing the peak value of the arc before or just as it forms.

[0022] The two ends of conductor 100 can be connected in series in the circuit by means of bolts, etc. After the fuse protection is completed, the operator can perform maintenance by opening the end cover 2 to replace conductor 100.

[0023] like Figure 4 As shown, the sensing line 200 is located inside the end cover 2 between the second end of the conductor 100 and the current output terminal 5. The sensing line 200 is used to detect the magnitude of the current passing through it. It can be set up using existing technologies such as current sensors, which will not be described in detail.

[0024] An insulating sleeve 310 is fixedly mounted on the base 1 and is used to accommodate the induction circuit 200. A guide rod 300 is hinged to the outer side of the insulating sleeve 310, and the first end of the guide rod 300 is connected to the outside of the insulating sleeve 310 through a pre-tension spring 320, so that the guide rod 300 is kept horizontal. In this way, the tension axis of the pre-tension spring 320 just passes through the first end of the guide rod 300 and the hinge point, so that the guide rod 300 is kept horizontal and in a balanced position under normal conditions.

[0025] The end of the guide rod 300 is provided with an arc-initiating structure 330, which is positioned towards the fusible connector 120 and maintains an air insulation gap of 3-5 mm between itself and the conductor 100. The guide rod 300 itself does not bear the bending moment that would cause it to swing upwards or downwards, and the initial force required to break this balance and drive the guide rod 300 to swing upwards is very small. Any upward thrust from the direction of the lower fusible point (such as the impact force of the arc or the air expansion caused by the arc, or the mechanical structure described later) can trigger this balancing system. Once the tip of the guide rod 300 is slightly pushed upwards, the tip of the guide rod 300 will be pulled upwards by the elastic force of the pre-tension spring 320.

[0026] It also includes an inverted pyramid grid 400 located above the arc-leading structure 330. The inverted pyramid grid 400 is formed by multiple rectangular structures stacked together and fixed in the base 1. The bottom grid 410a has the largest spacing and the fewest number of grids. The number of grids increases and the spacing between grids decreases as you go up.

[0027] Specifically, the bottom layer grid 410a is composed of multiple layers of rectangular metal frames with relatively large spacing, forming a relatively sparse grid structure for initial contact and arc segmentation. Overall, the number of grids increases sequentially from bottom to top, forming a stepped grid array resembling an inverted pyramid. The metal frames of each grid layer are made of highly conductive and high-temperature resistant metal plates (such as stamped copper or steel plates, with silver plating to reduce contact resistance).

[0028] The workflow is as follows: At the instant the electric arc is generated, the surrounding gas is rapidly heated and expands, producing an initial upward shock wave and hot airflow. Although this force is insufficient to complete the entire arc extinguishing process, it is enough to cause the guide rod 300, which is in a critical equilibrium state, to begin to tilt slightly upward.

[0029] Because the arc plasma is conductive, it will find the path of lowest impedance in a very short time and break down the aforementioned air gap. At this point, the original 3-5mm air insulation gap is heated by the high temperature of the arc and transforms from an insulator into a conductor or semi-conductive channel. Due to the short distance between the arc-initiating structure 330 and the arc, and its own conductivity, the electric field intensity at its tip is sharply concentrated, quickly becoming the attachment point for a new cathode (or anode) of the arc.

[0030] The arc-initiating structure 330 is an integral conductive component located at the end of the guide rod 300. The side of the arc-initiating structure 330 facing the fusible connector 120 is an arc surface or a slope. When an arc root jumps to the tip of the arc-initiating structure 330, under the combined action of the arc's own electromagnetic force and thermal buoyancy force, the arc root will be forced to slide upward along this smooth arc surface, successfully guiding the originally horizontal or uncertain arc to a vertically upward direction.

[0031] The guide rod 300 drives the arc-initiating structure 330 and the captured arc to continue swinging upwards. Along the swing path, the arc-initiating structure 330 first contacts the bottom grid 410a of the inverted pyramid grid 400, and then successively contacts the middle and top grids of the inverted pyramid grid 400. The grid spacing of the inverted pyramid grid 400 decreases by half from bottom to top. Under normal conditions without intersecting, the bottom spacing is the largest (e.g., 8mm), the middle spacing is halved (4mm), and the top spacing is halved again (2mm). This equal-decreasing structure allows the arc to overcome only minimal segmentation resistance upon initial entry, making it easy to be introduced into the grid; as the guide rod 300 continues to swing upwards, the segmentation intensifies exponentially, and the arc voltage rises steadily.

[0032] By default, when adjacent grid layers intersect, the grid plates of the middle layer grid are embedded in the gaps of the bottom layer grid 410a, and the grid plates of the top layer grid are embedded in the gaps of the middle layer grid. After intersectation, the original planar division formed by a single layer of grid becomes a three-dimensional division formed by the alternation of upper and lower grid plates.

[0033] At this point, the electric arc no longer flows along the planar gaps of a certain layer, but is forced to travel in a zigzag or spiral path between the staggered grid plates. Its equivalent spacing (i.e., the effective gap width that the electric arc actually needs to cross) is much smaller than the originally designed layer spacing, and this reduction has a non-linear characteristic—the deeper the penetration, the more drastically the equivalent spacing decreases.

[0034] Taking a design with decreasing spacing as an example: if the bottom layer spacing is 8mm and the middle layer spacing is 4mm, when the middle layer grid extends downwards to intersect with the bottom layer grid 410a, the effective channel of the electric arc between the two layers is no longer 4mm or 8mm, but is squeezed and narrowed by the intersecting grids to a tortuous gap that may only be 1-2mm.

[0035] During this process, the arc is continuously lengthened and divided into more and more short arcs in series. Each additional short arc means an increase in near-electrode voltage drop (approximately 150-250V), causing the total arc voltage to rise sharply. When the total arc voltage exceeds the system voltage, the fault current is forced to drop to zero, and the arc is eventually extinguished. The grid spacing of the inverted pyramid grid 400 decreases proportionally from bottom to top, while the number of grids increases. This structure allows the arc to overcome only a small segmentation resistance upon initial entry, making it easy to be introduced into the grid. In contrast, in existing technologies, fixed-gap arc-extinguishing grids result in poor segmentation if the spacing is too large, and high resistance if the spacing is too small, causing the arc to easily bypass the grid and burn on the outside, or generate violent arc voltage oscillations at the entrance.

[0036] The inverted pyramid grid 400 in this solution solves this problem. Its bottom grid 410a has the largest spacing and the fewest grid plates, resulting in minimal segmentation resistance. This allows the arc to be smoothly introduced into the grid in the initial stage, without being deflected due to excessive resistance. As the arc-initiating structure 330 continues to swing upwards, the arc is gradually delivered to an increasingly dense array of grid plates, with the segmentation depth increasing and the arc voltage rising steadily from low to high. This avoids the risk of sudden arc voltage changes and reignition caused by direct contact between fixed-spacing grid plates and the arc, significantly improving the stability of the arc extinguishing process.

[0037] The larger opening of the bottom grille 410a provides ample tolerance for the initial entry of the guide rod 300, reducing manufacturing and assembly precision requirements. As the grille becomes denser upwards, the arc-guiding structure 330 of the guide rod 300, in conjunction with the pre-tension spring 320, pulls the guide rod 300 upwards, causing it to abut against the inner surface of the end cap 2 (e.g., Figure 5 As shown, flexible pads for cushioning can be set at corresponding positions to reduce the impact force of the guide rod 300 on the end cap 2.

[0038] like Figure 3 As shown, in a further embodiment of the present invention, a power transmission structure is also included for driving the tip of the guide rod 300 to swing upward against the tension of the pre-tension spring 320, which causes the arc-inducing structure 330 to guide the electric arc toward the inverted pyramid grid 400. The power transmission structure further includes: A limiting seat 130 is sleeved on the second end of conductor 100; The return springs 140 are respectively abutted against the side wall 3 and the limiting seat 130 at both ends; An insulating cavity 150 for accommodating the return spring 140 and formed on the base 1; The end of the limiting seat 130 is provided with a toggle block 131, which is used to actuate the arc-initiating structure 330 of the guide rod 300 when the conductor 100 contracts.

[0039] Specifically, under normal operating conditions, the load current flows through the fuse element 110 and conductor 100, and then through the induction circuit 200 to the current output terminal 5. At this time, conductor 100 remains stationary due to forces from two directions: First, the conductor 100 remains intact at the fuse joint 120, forming an axial constraint on the limiting seat 130. The end of the sensing line 200 is connected to the fuse joint 120 of the conductor 100 and forms a pulling force toward the fuse joint 120.

[0040] Secondly, the two ends of the return spring 140 abut against the side wall 3 and the limiting seat 130 respectively, and are in a pre-tensioned state, continuously applying a pulling force to the limiting seat 130 in the direction opposite to the fusible connector 120.

[0041] Meanwhile, the limit seat 130 is firmly fixed in its original position, and the elastic potential energy of the return spring 140 is stored and cannot be released. The entire return spring 140 is completely encapsulated in the insulating chamber 150, which physically isolates it from the main circuit and possible arc areas, ensuring that its mechanical properties are not corroded by the high temperature of the arc and ionized gas.

[0042] Meanwhile, the toggle block 131 at the end of the limiting seat 130 remains stationary below the arc-starting structure 330, maintaining a small gap or slight contact with the lower surface of the arc-starting structure 330. When a short-circuit fault occurs, after the first stage of melting of the fuse 110 and the current-limiting stage of the conductor 100, heat concentrates at the fuse joint 120, causing its temperature to rise rapidly to the melting point and melt.

[0043] At the instant the fusible connector 120 melts, the conductor 100 breaks at that point, and its axial constraint force on the limiting seat 130 disappears instantly. At this time, the limiting seat 130 is only subjected to the unidirectional tension of the return spring 140. Under the push of the return spring 140, the limiting seat 130 moves at high speed, and the top of the toggle block 131 at its end quickly approaches and violently impacts the lower surface of the arc-inducing structure 330, causing the balance of the guide rod 300 to be broken and swing upward.

[0044] Simultaneously, conductor 100 is folded by the return spring 140 due to its wavy structure, resulting in controllable folding along the bends of its wavy structure. This increases the port distance between the second end of conductor 100 and the induction line 200, forming a stable isolation break. Conductor 100 can be made of copper-clad steel or copper-coated steel composite strip, with high-strength spring steel (such as 301 stainless steel or beryllium copper) as the core material and a high-conductivity oxygen-free copper outer layer. The core material provides a high elastic modulus (approximately 200 GPa) and high yield strength, ensuring the elastic folding capability and fatigue resistance of the wavy structure, while the outer copper layer provides a low-resistance path, bearing the main conductive and current-limiting heating properties.

[0045] like Figure 6As shown, in a further embodiment of the present invention, an excitation coil 210 is connected in series on the induction circuit 200, and a magnet 220 is sleeved inside the excitation coil 210; a one-way ratchet sleeve 340 is fixedly provided at the tail end of the pretension spring 320, and an annular armature 350 is fixedly provided at the tail end of the one-way ratchet sleeve 340, and the armature 350 is coaxial with and opposite to the excitation coil 210; The excitation coil 210 is configured to generate a magnetic field when a fault current flows through it, attracting the armature 350 to drive the one-way ratchet sleeve 340 to further stretch the pretension spring 320.

[0046] Specifically, a fixing seat 370 is provided inside the end cap 2 via an elastic element 360, and the fixing seat 370 is engaged with a one-way ratchet sleeve 340.

[0047] Under normal operating conditions, the load current is small, and the magnetic field generated by the current flowing through the induction line 200 and the excitation coil 210 is negligible. The attraction force on the armature 350 is far from sufficient to overcome the initial tension of the pretension spring 320. The one-way ratchet sleeve 340 remains in the initial position, and the pawl of the fixed seat 370 engages with the first tooth groove or initial positioning groove of the ratchet sleeve under the push of the elastic element 360. The pretension spring 320 only bears the basic pretension force.

[0048] When a short-circuit fault occurs, a huge fault current flows through the induction line 200 and the excitation coil 210 connected in series with it. Under the reinforcement of the magnet 220, the excitation coil 210 instantaneously generates a strong axial magnetic field. This magnetic field acts on the coaxially opposite annular armature 350, generating an electromagnetic attraction force in the direction of the coil (i.e., in the direction of stretching the pre-tension spring 320).

[0049] When the suction force exceeds the sum of the initial tension of the pretension spring 320 and the slight resistance of the elastic element 360, the armature 350 begins to drive the one-way ratchet sleeve 340 to move outward. The greater the fault current, the stronger the magnetic force generated by the excitation coil 210, the greater the displacement of the armature 350 and the one-way ratchet sleeve 340, the longer the pretension spring 320 is stretched, and the higher the elastic potential energy stored inside it.

[0050] After the fuse 110 or fuse connector 120 blows, the fault current is cut off, the current in the induction circuit 200 and the excitation coil 210 disappears, and the magnetic field disappears accordingly. At this time, the armature 350 is no longer subject to electromagnetic attraction, and the huge tension of the pretension spring 320 attempts to pull the one-way ratchet sleeve 340 back to its initial position.

[0051] However, because the pawl of the fixed seat 370 is always pressed against the tooth surface of the one-way ratchet sleeve 340 under the thrust of the elastic element 360, when the one-way ratchet sleeve 340 tends to retract, the pawl immediately engages in the nearest tooth groove, firmly locking the one-way ratchet sleeve 340 in its current position. The pre-tension spring 320 cannot retract. When the fuse of the fuse connector 120 causes the conductor 100 to contract and the pry block 131 to strike the arc-igniting structure 330, the moment the head of the guide rod 300 is pushed upward, the pre-enhanced spring tension immediately transforms into a powerful driving force, causing the guide rod 300 to swing upward at a speed and force far exceeding the norm, performing the aforementioned arc-ignition and arc-extinguishing actions. That is, at small fault currents, the magnetic force of the excitation coil 210 is weak, the displacement of the one-way ratchet sleeve 340 is small, the pawl is locked in a shallow tooth groove position, the increase in tension of the pre-tension spring 320 is limited, and the guide rod 300 swings at a moderate speed and force, which is suitable for interrupting small current arcs.

[0052] During a large fault current, the excitation coil 210 has a strong magnetic force, the unidirectional ratchet sleeve 340 has a large displacement, the pawl is locked in a deeper tooth groove position, the pre-tension spring 320 is stretched significantly, and the guide rod 300 obtains extremely strong driving force, swinging upward at a speed and force far exceeding the norm, ensuring that the arc can be quickly and powerfully introduced into the arc extinguishing chamber and reliably extinguished under high current.

[0053] like Figure 9 and 10 As shown, the grids in the same layer of the inverted pyramid grid 400 are connected by fixed rods 420. It also includes a transmission seat 430 located between two adjacent fixed rods 420 and used to drive the fixed rods 420 to slide vertically. The transmission seat 430 is hinged to the adjacent fixed rod 420 by a diagonal rod 440. The fixed rods 420 are vertically slidably mounted on the side wall 3, and the transmission seat 430 is horizontally slidably mounted on the side wall 3. Multiple rectangular metal frames of each grid layer are connected and fixed by the fixed rods 420, forming an integral movable grid layer. The two ends of the fixed rods 420 are slidably mounted in vertical grooves opened on the side wall 3, allowing the entire grid layer to move vertically up and down. A transmission rod 450 is fixedly connected between the transmission seat 430 and the one-way ratchet sleeve 340. The transmission seat 430 is located between two fixed rods 420. Its upper and lower ends are respectively hinged to the upper fixed rod 420 and the lower fixed rod 420 through a diagonal rod 440. When the transmission seat 430 is driven to move horizontally, the upper and lower fixed rods 420 are driven to move towards or away from each other in the vertical groove by pushing or pulling through the two diagonal rods 440, thereby changing the height difference between the two adjacent grid layers.

[0054] The larger the fault current, the stronger the attraction of the excitation coil 210 to the armature 350, and the greater the displacement of the unidirectional ratchet sleeve 340. This displacement is proportionally transmitted to the transmission seat 430 through the transmission rod 450. The horizontal movement of the transmission seat 430 is converted into the vertical opposing movement of the upper and lower fixed rods 420 through the inclined rod 440, which increases the spacing between adjacent inverted pyramid grid layers 400. Under extremely large fault currents, the energy carried by the arc is enormous. If the layers of the inverted pyramid grid 400 are still tightly interlocked at this time, the arc extinguishing channel will be squeezed into an extremely narrow tortuous gap (such as the aforementioned 1-2mm equivalent spacing). In this extremely narrow channel, the arc root is forcibly constrained within a very small grid surface area, resulting in extremely high local current density and extremely concentrated thermal shock.

[0055] This highly concentrated energy impact can cause the local temperature of the grid to soar above the material's melting point in a very short time, resulting in severe ablation, surface melting, or even welding of adjacent grids together.

[0056] The greater the tensile displacement of the unidirectional ratchet sleeve 340, the greater the horizontal movement of the transmission rod 450 driving the transmission seat 430, and the more pronounced the vertical opposing movement of the inclined rod 440 driving the fixed rod 420—the more actively the grid layer spacing is increased. The electric arc is released to burn in a wider space, the adhesion area of ​​the arc root on the grid plate is significantly increased, the local current density is greatly reduced, and the degree of grid plate ablation is effectively mitigated.

[0057] Furthermore, as the layers of the grid are stretched apart and the interlayer spacing increases, the electric arc needs to traverse longer air gaps in the transition regions between layers when passing through each grid layer. This axial elongation effect, combined with the radial arc-inducing effect brought about by the swing of the guide rod 300, causes the arc surface of the arc-inducing structure 330 to lift the electric arc from the horizontal direction and guide it towards the vertical direction. At the same time, the increased interlayer spacing forces the electric arc to take a longer axial transition path between the grid layers.

[0058] The displacement of the unidirectional ratchet sleeve 340 is coupled with the adjustment of the grid spacing via the transmission rod 450, naturally forming a differentiated arc extinguishing mechanism that automatically switches according to the fault energy level. At low fault currents, the adaptive adjustment mechanism operates weakly or not at all, and the grid layer maintains a relatively compact initial state. At this time, the guide rod 300 swings slowly with moderate driving force, and the compact grid provides high segmentation density and long contact time, ensuring reliable arc segmentation and cooling even at low currents, achieving gentle yet thorough arc extinguishing.

[0059] During a large fault current, the grid layers are stretched apart, and the channels expand. At this time, the guide rod 300 swings at an extremely high speed. The wide channels ensure unobstructed movement, while the axial elongation effect of the interlayer spacing and the large-area contact of the grid plates are used to dissipate energy rapidly, completing arc extinguishing in a violent manner in a very short time.

[0060] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A multi-stage arc-extinguishing protection device for a high breaking capacity fuse, comprising a base (1) and an end cap (2), wherein a side wall (3) is fixedly disposed on the base (1), characterized in that, include: A conductor (100) is detachably mounted on the base (1). The conductor (100) has a current input terminal (4) and a current output terminal (5) connected to its two ends respectively. The conductor (100) has a wave-shaped structure and a fuse (110) that connects its adjacent parts in series inside the conductor (100). The conductor (100) has a fuse connector (120) near the current output terminal (5). The mechanical strength of the fuse connector (120) is lower than that of the rest of the conductor (100). The sensing line (200) is located inside the end cap (2) between the second end of the conductor (100) and the current output terminal (5); An insulating sleeve (310) is fixedly mounted on a base (1) and is used to accommodate an induction circuit (200). A guide rod (300) is hinged to the outer side of the insulating sleeve (310), and the first end of the guide rod (300) is connected to the outer side of the insulating sleeve (310) through a pre-tension spring (320) so that the guide rod (300) remains horizontal. The end of the guide rod (300) is provided with an arc-inducing structure (330), which is positioned toward the fusible connector (120) and maintains an air-insulating gap with the conductor (100); It also includes an inverted pyramid grid (400) located above the arc-leading structure (330). The inverted pyramid grid (400) is formed by multiple rectangular structures stacked together and fixed inside the base (1). The bottom grid (410a) has the largest spacing and the fewest number of grids. The number of grids increases and the spacing between grids decreases as you go up. It also includes a power transmission structure for driving the tip of the guide rod (300) to swing upward against the tension of the pre-tension spring (320), which causes the arc-inducing structure (330) to guide the electric arc toward the inverted pyramid grid (400).

2. The multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 1, characterized in that, The conductor (100) and the fuse (110) form a through horizontal current channel. Before the fuse (110) melts, the initial resistance is determined by the cross-sectional area of ​​the fuse (110) and the length of the conductor (100). After the fuse (110) melts, the current-limiting resistance is determined by the full length of the wavy line of the conductor (100) and its cross-sectional area, and the cross-sectional area of ​​the conductor (100) is smaller than the cross-sectional area of ​​the fuse (110).

3. A multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 1, characterized in that, The power transmission structure also includes: A limiting seat (130) is sleeved on the second end of the conductor (100); The return springs (140) are respectively abutted against the side wall (3) and the limiting seat (130) at both ends. An insulating chamber (150) for accommodating a return spring (140) and formed on a base (1). The end of the limiting seat (130) is provided with a lever (131), which is used to actuate the arc-starting structure (330) of the guide rod (300) when the conductor (100) contracts.

4. A multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 1, characterized in that, The arc-inducing structure (330) is an integral conductive component disposed at the end of the guide rod (300), and the side of the arc-inducing structure (330) facing the fusible connector (120) is an arc surface or a slope surface.

5. A multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 1, characterized in that, An excitation coil (210) is connected in series on the induction circuit (200), and a magnet (220) is sleeved inside the excitation coil (210); a one-way ratchet sleeve (340) is fixedly provided at the tail end of the pretension spring (320), and an annular armature (350) is fixedly provided at the tail end of the one-way ratchet sleeve (340), and the armature (350) is coaxial with the excitation coil (210); The excitation coil (210) is configured to generate a magnetic field when a fault current flows through it, attracting the armature (350) to drive the one-way ratchet sleeve (340) to further stretch the pretension spring (320).

6. A multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 5, characterized in that, The end cap (2) is provided with a fixing seat (370) through an elastic element (360), and the fixing seat (370) is engaged with the one-way ratchet sleeve (340).

7. A multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 1, characterized in that, The inverted pyramid grid (400) has a grid of the same layer connected by a fixed rod (420); it also includes a transmission seat (430) located between two adjacent fixed rods (420) and used to drive the fixed rods (420) to slide vertically, the transmission seat (430) and the adjacent fixed rod (420) are hinged by a diagonal rod (440); the fixed rod (420) is vertically slidably disposed on the side wall (3), and the transmission seat (430) is horizontally slidably disposed on the side wall (3).

8. A multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 7, characterized in that, A transmission rod (450) is fixedly connected between the transmission seat (430) and the one-way ratchet sleeve (340).

9. A multi-stage arc-extinguishing protection device for a high-breaking capacity fuse according to claim 1, characterized in that, The grid spacing of the inverted pyramid grid (400) decreases by half from bottom to top, which is half the ratio of the previous spacing.

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