Fuse having higher medium-rate overcurrent fusing speed

Abstract

The present application discloses a fuse having a higher medium-rate overcurrent fusing speed. The fuse having a higher medium-rate overcurrent fusing speed comprises a first terminal, a second terminal, and a first current-carrying device and a second current-carrying device that are connected in parallel between the first terminal and the second terminal; the first current-carrying device comprises at least one first fuse body connected to the first terminal and the second terminal; the second current-carrying device comprises at least one medium-rate fast-fusing branch connected to the first terminal and the second terminal; the medium-rate fast-fusing branch comprises second fuse bodies and a disconnecting device that are connected in series, the disconnecting device disconnecting before the first fuse body and the second fuse bodies when medium-rate overcurrent occurs. According to the fuse of the present application, the first current-carrying breaking device and the second current-carrying breaking device are combined, ensuring the maximum breaking capacity of the fuse while implementing fast fusing when medium-rate overcurrent occurs, and preventing damage to a rear-end facility caused by continuous overcurrent.

Description

A fuse with accelerated medium-rate overcurrent fusing speed

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This disclosure claims priority to a Chinese patent application filed with the Patent Office of China on August 31, 2023, with application number 202311115423.3 and titled “A Fuse with Accelerated Medium-Rate Overcurrent Fusing Speed,” the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of fuses, and in particular to a fuse with an accelerated medium-rate overcurrent fusing speed. Background Art

[0004] Currently, the lithium battery industry primarily uses a combination of relays and fuses for protection. In the event of a high-current short circuit, the fuse provides overcurrent protection. Non-current anomalies are primarily handled by detection signals, which, after being identified by the battery management system, trigger a relay to disconnect the abnormal circuit. However, when selecting fuses for existing lithium battery systems, consideration must be given to the temperature rise required for high-current charging and discharging, as well as the pulse current associated with high-capacity output. Consequently, fuse specifications are typically oversized. For example, a short-circuit protection current greater than 3kA is selected. This means that when currents less than five times the rated current are encountered, the fuse will not operate in a timely manner, potentially damaging the back-end circuit board or lithium battery.

[0005] Existing fuses often blow prematurely due to abnormal overcurrent, mainly because the selected specifications are too small. However, if the specifications are large, the fuse cannot provide timely protection under medium-rate overcurrent conditions.

[0006] Summary of the Invention

[0007] In view of the above-mentioned defects of the prior art, the purpose of this application is to provide a fuse that accelerates the melting speed of medium-rate overcurrent, so that under the medium-rate overcurrent state, the fuse can melt in time to provide circuit breaker protection.

[0008] To achieve the above-mentioned object, the present application provides a fuse with a faster medium-rate overcurrent fusing speed, comprising a first terminal, a second terminal, and a first current-carrying device and a second current-carrying device connected in parallel between the first terminal and the second terminal;

[0009] The first current carrying device includes at least one first fuse connecting the first terminal and the second terminal;

[0010] The second current-carrying device includes at least one medium-rate fast-fuse branch connecting the first terminal and the second terminal;

[0011] The medium-rate fast-melting branch includes a second fuse and a disconnecting device connected in series. The disconnecting device disconnects before the first fuse and the second fuse when a medium-rate overcurrent occurs.

[0012] In some embodiments of the present application, the first melt and the second melt are fuse wires or fuse sheets with narrow diameters.

[0013] In some embodiments of the present application, the first melt and the second melt are copper, silver, aluminum, or one of a copper-based alloy, a silver-based alloy, an aluminum-based alloy, or a copper-silver composite material.

[0014] In some embodiments of the present application, the first melt is copper, silver, aluminum, or one of copper-based alloys, silver-based alloys, aluminum-based alloys, or copper-silver composite materials; and the second melt is nickel.

[0015] In some embodiments of the present application, the disconnecting device comprises a low melting point metal.

[0016] In some embodiments of the present application, the disconnect device further includes a flux, which is coated on the surface of the low-melting-point metal.

[0017] In some embodiments of the present application, the disconnecting device further includes a heating device, which is activated when the medium-rate overcurrent occurs, thereby actively heating the low-melting-point metal to accelerate the melting of the low-melting-point metal.

[0018] In some embodiments of the present application, the melting point of the low-melting-point metal ranges from 70°C to 450°C.

[0019] In some embodiments of the present application, the disconnecting device further includes a mechanical breaking device, which is disposed adjacent to the low-melting-point metal and is activated when a medium-rate overcurrent occurs, thereby actively cutting off the low-melting-point metal.

[0020] In some embodiments of the present application, the mechanical breaking device is an elastic breaking mechanism, the movable end of the elastic breaking mechanism is in contact with the low-melting-point metal and is in an energy storage state, and is used to cut off the low-melting-point metal in an overcurrent softening state.

[0021] In some embodiments of the present application, the mechanical breaking device is a pyrotechnic explosion cutting mechanism, the cutter of the pyrotechnic explosion cutting mechanism is set on one side of the low-melting-point metal, and the pyrotechnic explosion cutting mechanism is activated when there is a medium-rate overcurrent, thereby actively cutting off the low-melting-point metal.

[0022] In some embodiments of the present application, the disconnecting device includes a conductor and a mechanical breaking device; the conductor and the second fuse are connected in series and provided with a structural weakening point for mechanical breaking.

[0023] In some embodiments of the present application, the mechanical breaking device is a pyrotechnic explosion cutting mechanism, the cutter of the pyrotechnic explosion cutting mechanism contacts the conductor, and the control circuit of the pyrotechnic explosion cutting mechanism is activated when there is a medium-rate overcurrent, thereby actively cutting off the conductor.

[0024] In some embodiments of the present application, a current carrying ratio of the first melt of the first current-carrying device to the medium-rate fast-melting branch of the second current-carrying device is in a range of 5:1 to 1:5.

[0025] In some embodiments of the present application, the fuse further includes a first housing, a first end cover, a second end cover, a first soldering pad, and a second soldering pad;

[0026] The second current-carrying device and the first current-carrying device are installed in the first housing;

[0027] Two ends of the second current-carrying device and the first current-carrying device are welded to the first welding pad and the second welding pad respectively;

[0028] The first end cover and the second end cover are lead-out electrodes of the fuse. The first end cover and the second end cover are fixed to two ends of the first shell and are fixedly electrically connected to the first welding pad and the second welding pad respectively.

[0029] In some embodiments of the present application, the first shell is provided with a T-shaped cavity, and the disconnecting device extends to a raised portion in the middle of the T-shaped cavity.

[0030] This application achieves the following technical effects:

[0031] The fuse of the present application adopts a combination of a first current-carrying breaking device and a second current-carrying breaking device to ensure that the maximum breaking capacity of the fuse is consistent with the breaking capacity of the structure when there is no breaking device in the second current-carrying device; a fuse with a larger nominal current can be selected to bear the ability of a larger temporary high current when the whole machine is working, while achieving rapid melting during medium-rate overcurrent, to prevent damage to the back-end facilities caused by continuous overcurrent.

[0032] The terminal voltage of the disconnecting device in the second current-carrying device at the time of disconnection is only the impedance voltage drop of the first current-carrying device, and basically no arc is generated. Therefore, there is no need or difficulty in designing the structure to extinguish the arc. It is only necessary to consider whether the withstand voltage meets the standard, and the disconnecting device can be minimized in design.

[0033] The above description is only an overview of the technical solution of the present disclosure. In order to more clearly understand the technical means of the present disclosure, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present disclosure more obvious and easy to understand, the specific implementation methods of the present disclosure are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure or related technologies, the following is a brief introduction to the drawings required for use in the embodiments or related technical descriptions. Obviously, the drawings described below are some embodiments of the present disclosure. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0035] FIG1 is a block diagram of the fuse of the present application;

[0036] FIG2 is a circuit diagram of the first embodiment of the present application;

[0037] FIG3 is a product structure diagram of the first embodiment of the present application;

[0038] FIG4 is a cross-sectional view of the product structure of the first embodiment of the present application;

[0039] FIG5 is a partial enlarged view of FIG4;

[0040] FIG6 is a current-time fusing curve of the first embodiment of the present application;

[0041] FIG7 is a circuit diagram of a second embodiment of the present application;

[0042] FIG8 is a product structure diagram of the second embodiment of the present application;

[0043] FIG9 is a current-time fusing curve of the second embodiment of the present application;

[0044] FIG10 is a circuit diagram of a third embodiment of the present application;

[0045] FIG11 is a product structure diagram of the third embodiment of the present application;

[0046] FIG12 is a cross-sectional view of the product structure of the third embodiment of the present application;

[0047] FIG13 is a schematic diagram of the structure of the present application using an elastic breaking mechanism for mechanical breaking;

[0048] FIG14 is a schematic diagram of the structure of the mechanical separation using a pyrotechnic explosion cutting mechanism of the present application;

[0049] FIG15 is a current-time melting curve of a fuse using a pyrotechnic explosion cut-off mechanism.

[0050] Wherein: 1 - shell; 2 - nickel strip; 3 - low-melting-point metal; 4 - soldering pad; 5 - end cover; 6 - silver strip; 7 - quartz sand; 8 - heating plate; 9 - T-shaped cavity; 10 - elastic breaking mechanism; 11 - pyrotechnic explosion cutting mechanism; 30 - thermal fuse; 32 - upper cover; 33 - lower cover; 34 - fuse; 80 - heating device; 82 - thermal fuse; 83 - upper cover; 84 - bracket; 85 - lower cover; 100 - first current-carrying device; 101 - first melt; 200 - second current-carrying device; 201 - second melt; 202 - disconnecting device; 2021 - low-melting-point metal; 2022 - elastic breaking mechanism; 2023 - conductor; 2024 - pyrotechnic explosion cutting mechanism. Specific embodiments

[0051] In the claims, any reference signs placed between parentheses shall not be construed as limiting the claim. The word "comprising" does not exclude the presence of elements or steps not listed in the claim. The word "a" or "an" preceding an element does not exclude the presence of a plurality of such elements. The present disclosure may be implemented by means of hardware comprising several different elements and by means of a suitably programmed computer. In a unit claim enumerating several means, several of these means may be embodied by the same item of hardware. The use of the words first, second, and third etc. does not indicate any order. These words may be interpreted as names.

[0052] To further illustrate various embodiments, this application includes accompanying drawings. These drawings form part of the disclosure and are primarily used to illustrate the embodiments and, in conjunction with the relevant description in the specification, to explain the operating principles of the embodiments. By referring to these drawings, those skilled in the art will understand other possible implementations and the advantages of this application. The components in the figures are not drawn to scale, and similar reference numerals are generally used to represent similar components.

[0053] The present application will now be further described with reference to the accompanying drawings and specific implementation methods.

[0054] As shown in Figure 1, the present application provides a fuse that accelerates the fusing speed of medium-rate overcurrent, including a first terminal P1, a second terminal P2, and a first current-carrying device 100 and a second current-carrying device 200 connected in parallel between the first terminal P1 and the second terminal P2; the first current-carrying device 100 includes at least one first fuse 101 connecting the first terminal and the second terminal; the second current-carrying device 200 includes at least one medium-rate fast-fuse branch connecting the first terminal P1 and the second terminal P2; the medium-rate fast-fuse branch includes a second fuse 201 and a disconnecting device 202 connected in series, and the disconnecting device 202 disconnects before the first fuse 101 and the second fuse 201 during medium-rate overcurrent.

[0055] In a specific implementation process, different disconnecting devices 202 may be provided to achieve rapid blowing of the fuse during a medium-rate overcurrent.

[0056] Example 1

[0057] As shown in Figures 2 to 6, the present application provides a fuse that accelerates the melting speed of medium-rate overcurrent. In this embodiment, the first melt 101 of the first current-carrying breaking device 100 is mainly made of copper, silver, aluminum or copper-based alloys, silver-based alloys, aluminum-based alloys or copper-silver composite materials. The disconnecting device 202 in the second current-carrying breaking device 200 is a low-melting-point metal. The second melt 201 can be made of copper, silver, aluminum or copper-based alloys, silver-based alloys, aluminum-based alloys or copper-silver composite materials. More preferably, the second melt 201 is made of a high-resistance temperature coefficient material such as nickel strip in series.

[0058] In Figure 2, ATCO1 and ATCO2 are low-melting-point metals, and second melt 201 is a nickel strip. ATCO1 and melt 201, and ATCO2 and melt 201, form the two branches of the second current-carrying disconnecting device; the two first melts 101 form the two branches of the first current-carrying disconnecting device. P1 and P2 are the lead terminals of the fuse.

[0059] Silver / copper / silver-copper composite materials, used as the melt in conventional fuses, have high melting points (copper is 1083°C, silver is 960°C) and high electrical conductivity. Compared to other lower-melting-point materials of the same size, the resulting melt offers higher rated currents, lower resistance, and lower power consumption, making it easier to meet high interrupting current requirements. Different numbers of melts are connected in parallel, depending on the current carrying capacity, to form the primary current-carrying interrupting device.

[0060] The second melt of the second current-carrying disconnect device is preferably nickel strip, primarily utilizing the temperature rise characteristics of nickel's high resistance temperature coefficient during overcurrent, combined with the low-temperature melting characteristics of low-melting-point metals, to form a fast-fusing device for medium-rate overcurrent. This device accelerates the response time during medium-rate overcurrent while ensuring the melting requirements for both low-rate and high-rate overcurrents. The resistance temperature coefficient of nickel is approximately 6900ppm / °C, while that of silver / copper is approximately 4000ppm / °C. Under overcurrent conditions, nickel generates heat due to its own resistivity, and as the temperature rises, its own resistance also increases, with a greater magnitude of change than silver / copper. Low-melting-point metals are metals and their alloys with a melting point of 70°C to 450°C, typically composed of low-melting-point metal elements such as Bi, Sn, Pb, and In. At low-rate overcurrent, the nickel strip's temperature rise is minimal, so the nickel strip's temperature rise is not noticeable, and its melting time is comparable to that of a conventional fuse. At medium-rate overcurrent, the nickel strip's temperature rise enters the transition zone, rapidly heating the strip and transferring heat to the low-melting-point metal. This causes the low-melting-point metal to melt, and the current is then applied to the first current-carrying disconnecting device at a multiplier rate. This disconnecting device quickly melts, achieving overall safety disconnection. At high-rate overcurrent, the nickel strip's temperature rise response rate is too slow to act on the low-melting-point metal, and the low melting point and internal resistance of the low-melting-point metal contribute more to the disconnection. As the current rises, the low-melting-point metal heats up due to its internal resistance. Due to its low melting point, the low-melting-point metal quickly disconnects, resulting in a response time comparable to that of the first current-carrying disconnecting device. In this application, the preferred low-melting-point metal has a melting point range of 100°C to 250°C.

[0061] By combining a high-TCR material with a low-melting-point metal, the temperature rise of the high-TCR material during medium-rate overcurrent is used as the melting heat for the low-melting-point metal, causing the medium-rate fast-blow branch to melt. This in turn converts the current-carrying current into a multiplier current, shortening the melting response time. This allows for early response during medium-rate overcurrent, preventing damage to downstream facilities caused by sustained overcurrent.

[0062] In this embodiment, the first current-breaking device is equipped with two sets of current-breaking branches. Silver ribbon 6 serves as the first melt of the first current-breaking device (first melt 101 in Figure 2) and is connected between the two end caps 5. In specific applications, first melts of varying numbers or cross-sectional areas can be connected in parallel to form the first current-breaking device, depending on the current carrying requirements.

[0063] In this embodiment, the second current-carrying interrupter device is provided with two sets of medium-rate fast-acting branches, each consisting of a nickel strip 2 (corresponding to the second melt 201 in FIG. 2 ) and a low-melting-point metal 3 (corresponding to ATCO1 and ATCO2 in FIG. 2 ) connected in series.

[0064] As shown in FIG3 and FIG5 , the surface of the low-melting-point metal 3 is coated with a fuse 34 and is packaged together by an upper cover 32 and a lower cover 33 to form a thermal fuse 30 .

[0065] In this embodiment, both ends of the low-melting-point metal 3 are connected to two sections of nickel ribbon 2, and the other ends of the two sections of nickel ribbon 2 are connected to two pads 4. In specific applications, the low-melting-point metal 3 can also be connected to a section of nickel ribbon 2.

[0066] In specific applications, nickel strips 2 and temperature fuses 30 of different numbers or cross-sectional areas can be provided as the second current-carrying disconnecting device according to current carrying requirements.

[0067] The first and second current-carrying disconnect devices are spot-welded to pads 4, forming a parallel, integrated unit. The unit is then housed within housing 1. Housing 1 is constructed of high-strength, voltage-resistant insulating materials such as ceramic. End caps 5 are located at each end of housing 1. These caps 5 and pads 4 are fixedly connected by screws, spot welding, or other means, thereby allowing the fuse electrodes to be extracted.

[0068] In order to ensure that the first current-carrying breaking device and the second current-carrying breaking device are fused normally and to prevent abnormal arcing, quartz sand 7 is further filled around the first melt and the second melt in the housing 1 .

[0069] Nickel has a temperature coefficient of resistance of approximately 6900ppm / °C, while silver and copper have a temperature coefficient of resistance of approximately 4000ppm / °C. Under overcurrent conditions, nickel's inherent resistivity generates heat, and as the temperature rises, its resistance also increases, with a greater magnitude of change than silver and copper. Low-melting-point metals are metals and their alloys with a melting point between 70°C and 450°C, typically composed of low-melting-point metal elements such as Bi, Sn, Pb, and In.

[0070] The current-time fusing curve of this embodiment is shown in FIG6 . Curve 1 is the fusing curve of a conventional silver ribbon as the melt. After the specification is selected to be large, the current carrying requirement of low-rate overcurrent is met. For medium-rate overcurrent, the pre-arcing response time will also be delayed as a whole, which will cause damage to the back-end facilities due to continuous overcurrent. Curve 2 is an example of a 400A current-time fusing curve of this embodiment. At low-rate overcurrent, less than 1.2kA, due to the small temperature rise, the temperature rise of the nickel strip is not significantly superimposed, and its fusing time is comparable to that of a conventional fuse. At medium-rate overcurrent, between 1kA and 10kA, the temperature rise of the nickel strip enters the transition zone, the nickel strip rapidly heats up, and the heat is transferred to the low-melting-point metal, causing the low-melting-point metal to melt. The current is then multiplied and loaded onto the first current-carrying disconnecting device, which quickly fuses, achieving overall safe disconnection. At high-rate overcurrent, above 10kA, the temperature rise response rate of the nickel strip is too slow to act on the low-melting-point metal. Instead, it is more due to the low melting point characteristics and internal resistance of the low-melting-point metal. As the current rises, the low-melting-point metal heats up due to the internal resistance. Due to its low melting point, the low-melting-point metal can be quickly disconnected, and its response time is comparable to that of the first current-carrying disconnecting device.

[0071] In summary, the fuse in this embodiment combines the first current-carrying breaking device and the second current-carrying breaking device, which has the following technical effects:

[0072] 1. The terminal voltage of the disconnecting device in the second current-carrying device at the time of disconnection is only the impedance voltage drop of the first current-carrying device, and basically no arc is generated. Therefore, there is no need for arc extinguishing and no difficulty in designing the structure. It is only necessary to consider whether the withstand voltage meets the standard, and the disconnecting device can be minimized in design.

[0073] 2. Ensure that the maximum breaking capacity of the fuse is consistent with the breaking capacity of the structure when there is no disconnect device in the second current carrier.

[0074] 3. A fuse with a larger nominal current can be selected to bear the large temporary high current when the whole machine is working, while achieving fast melting when the medium-rate overcurrent occurs, to prevent damage to the back-end facilities caused by continuous overcurrent.

[0075] Example 2

[0076] As shown in Figure 7, based on Example 1, the fuse can also be equipped with a self-thermal protection heater PTC, which, in conjunction with overcurrent and overvoltage detection signals, implements a controlled function. When the system detects an overcurrent signal, it triggers the heater circuit to conduct, and the heater PTC begins to operate and generate heat, providing heat to ATCO1 and ATCO2. ATCO1 and ATCO2 are heated and melted, disconnecting the second current-carrying disconnecting device. The current is then applied to the first current-carrying disconnecting device 100 at a multiplier rate, causing the temperature rise of the first fuse 101 to increase, quickly breaking the circuit. Simultaneously, the heater PTC continues to operate, and ATCO3 is heated and melted, disconnecting the heater circuit and ceasing operation.

[0077] FIG8 shows a product embodiment corresponding to FIG7 , wherein the PTC heater corresponds to the heating plate 8 ; the first melt 101 corresponds to the silver ribbon 6 ; ATCO1 and ATCO2 correspond to the low-melting-point metal 3 ; and ATCO3 corresponds to the temperature fuse 82 .

[0078] In this embodiment, the heating device 80 comprises a series-connected heater plate 8 and a thermal fuse 82, encapsulated together with the low-melting-point metal 3 of the two branches by an upper cover 83, a lower cover 85, and a bracket 84. The thermal fuse 82 heats up and melts when operating continuously at a medium-rate current, preventing the heating device 80 from continuing to operate after the fuse has blown.

[0079] Specifically, the heating plate 8 is arranged between the two low-melting-point metals 3 of the second current-carrying disconnecting device and is fixed by a bracket 84. At the same time, the low-melting-point metals 3 of the two branches are fixed on both sides of the heating plate 8 by the upper cover 83, the lower cover 85 and the bracket 84, thereby ensuring that the heating plate 8 uniformly heats the low-melting-point metals 3 of the two branches in a controlled manner, causing the low-melting-point metals 3 of the two branches to melt, and then the current is loaded on the first current-carrying disconnecting device at a multiple rate, causing the first current-carrying disconnecting device to melt quickly, and achieving safe cutting off as a whole.

[0080] The current-time fusing curve of this embodiment is shown in FIG9 , wherein curve 1 is the fusing curve of a conventional silver ribbon as a melt; curve 2 is an example of a 400A current-time fusing curve of this embodiment. The first inflection point (the inflection point on the left) indicates that the heating device is started at a lower current, and the protection response time is shortened due to the passive fusing of the low-melting-point metal; the second inflection point (the inflection point on the right) indicates that the protection response time is further shortened when the heating device is started at a larger current; the two inflection points of the dotted line indicate that the starting current of the disconnection is different. The larger the starting current, the faster the response disconnection speed and the shorter the response disconnection time. At low-rate overcurrent, less than 1.2kA, due to the small temperature rise, the temperature rise of the nickel strip is not obvious, and its melting time is equivalent to that of a conventional fuse; at medium-rate overcurrent, between 1kA and 10kA, it is directly heated by the heater to melt the low-melting-point metal, and the current is loaded on the first current-carrying disconnecting device at a multiple rate. The first current-carrying disconnecting device quickly melts and the overall safe cutoff is achieved; at high-rate overcurrent, above 10kA, the temperature rise response rate of the nickel strip and the heating of the heater do not have time to act on the low-melting-point metal. It is more achieved by the low melting point characteristics and internal resistance of the low-melting-point metal. The current rises, and the low-melting-point metal heats up due to the internal resistance. Due to its low melting point, the low-melting-point metal can be quickly cut off, and its response time is equivalent to that of the first current-carrying disconnecting device.

[0081] In specific implementations, the current distribution of each current-carrying disconnecting branch can be adjusted by adjusting the number of branches or the wire diameter of the fuse. Preferably, the current-carrying disconnecting branch of the first current-carrying disconnecting device and the medium-rate fast-acting branch of the second current-carrying disconnecting device are generally set to a ratio between 5:1 and 1:5. Preferred values ​​include 3:1, 2:1, 1:1, 1:2, and 1:3.

[0082] Example 3

[0083] As shown in Figures 10 to 12, the fuse housing 1 can be provided with a T-shaped cavity 9, thereby extending the thermal fuse 30 or low-melting-point metal 3 of the second current-carrying disconnect device to the raised portion in the center of the T-shaped cavity. In this structure, the thermal fuse 30 is kept at a certain distance from the other melts, and its melting is not or is less affected by the temperature rise of the other melts. Sufficient structural space is also provided for the installation of a mechanical breaking device.

[0084] In order to achieve rapid disconnection of the second current-carrying disconnecting device, a mechanical breaking device can be used to perform mechanical breaking.

[0085] Example 4

[0086] In this embodiment, the disconnecting device includes a low-melting-point metal 2021 and an elastic disconnecting mechanism 2022 as a mechanical breaking device, as shown in FIG13 . In this embodiment, one end of the elastic disconnecting mechanism 2022 is fixed (such as fixed to the shell), and the other end is in contact with the low-melting-point metal 2021, so that the entire elastic disconnecting mechanism is in an energy storage state. When the low-melting-point metal is softened by heat and its structural strength decreases, its structural strength cannot withstand the elastic force applied by the elastic disconnecting mechanism. Therefore, the elastic disconnecting mechanism releases the stored energy and disconnects the low-melting-point metal. After disconnection, sufficient safety distance and electrical insulation strength are formed at the breaking point.

[0087] Example 5

[0088] In this embodiment, the disconnect device includes a conductor 2023 and a pyrotechnic explosion disconnect mechanism 2024, which serves as a mechanical breaking device, as shown in Figure 14. Pyrotechnic explosion disconnect mechanisms are commonly used in circuit breakers. The circuit breaker's main circuit electrode is provided with a structurally weakened point, such as a narrow diameter. Upon receiving a command, the pyrotechnic explosion disconnect mechanism actuates to disconnect the weakened point. The pyrotechnic explosion disconnect mechanism includes components such as a piston and an ignition device. When the pyrotechnic explosion disconnect mechanism is activated, the piston, propelled by the explosive airflow, acts on the narrow diameter to disconnect the main circuit electrode, ensuring a sufficient safety distance and electrical insulation strength at the breakpoint. Because the pyrotechnic explosion disconnect mechanism 2024 has a high impact and strong breaking capacity, conductor 223 can be made of copper or aluminum strip with a narrow diameter (which will not melt under medium-rate overcurrent) or a low-melting-point metal (which will melt under medium-rate overcurrent). Similarly, the low-melting-point metal is also a structural weakness in the circuit. When the structural strength of the low-melting-point metal decreases, it can be disconnected when the pyrotechnic explosion cutoff mechanism 2024 is activated, ensuring sufficient safety spacing and electrical insulation strength at the disconnection point. The current-time fusing curve of this embodiment is shown in Figure 15, where Curve 1 is the fusing curve of a conventional silver ribbon as the melt, and Curve 2 is an example of the current-time fusing curve using the pyrotechnic explosion cutoff mechanism. The first inflection point (the inflection point on the left) indicates that the pyrotechnic explosion cutoff mechanism is activated at a lower current, and the protection response time is shortened compared to the passive fusing of the low-melting-point metal. The second inflection point (the inflection point on the right) indicates that the protection response time is further shortened when it is activated at a higher current. Compared with the technical solution using a heating device in Example 2, the technical solution using the pyrotechnic explosion cutoff mechanism has a faster fusing speed and a shorter protection response time. The two inflection points of the dotted line indicate different starting currents for disconnection. The larger the starting current, the faster the response disconnection speed and the shorter the response disconnection time.

[0089] In summary, the fuse in the above embodiment also has the following technical effects:

[0090] 1. When the disconnect device in the second current-carrying device is added with a pyrotechnic explosion cut-off mechanism or a heating device, the function of rated overcurrent protection can be realized.

[0091] 2. When the disconnect device in the second current-carrying device is added with a pyrotechnic explosion cut-off mechanism or a heating device, if the detection circuit fails or the ignition voltage input line or the heating current input line is accidentally disconnected, the fuse still has the basic functions of a fuse, such as overload protection disconnection and maximum capacity safe disconnection of short-circuit current.

[0092] Although the present application has been specifically shown and described in conjunction with preferred embodiments, it should be understood by those skilled in the art that various changes in form and details may be made to the present application without departing from the spirit and scope of the present application as defined by the appended claims, and all such changes are within the scope of protection of the present application.

Claims

1. A fuse that accelerates the fusing speed of medium-rate overcurrent, characterized in that: comprising a first terminal, a second terminal, and a first current-carrying device and a second current-carrying device connected in parallel between the first terminal and the second terminal; The first current-carrying device comprises at least one first fuse connecting the first terminal and the second terminal; The second current-carrying device comprises at least one medium-rate fast-fuse branch connecting the first terminal and the second terminal; The medium-rate fast-melting branch includes a second fuse and a disconnecting device connected in series. The disconnecting device disconnects before the first fuse and the second fuse when a medium-rate overcurrent occurs.

2. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 1, wherein: The first melt and the second melt are fuse wires or fuse sheets with narrow diameters.

3. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 2, wherein: The first melt and the second melt are one of copper, silver, aluminum or a copper-based alloy, a silver-based alloy, an aluminum-based alloy or a copper-silver composite material.

4. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 2, wherein: The first melt is one of copper, silver, aluminum or a copper-based alloy, a silver-based alloy, an aluminum-based alloy or a copper-silver composite material; the second melt is nickel.

5. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 1, wherein: The disconnect device comprises a low melting point metal.

6. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 5, wherein: The disconnect device further comprises a flux, and the flux is coated on the surface of the low melting point metal.

7. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 6, wherein: The disconnect device further comprises a heating device, which is activated when the medium-rate overcurrent occurs, thereby actively heating the low-melting-point metal to accelerate the melting of the low-melting-point metal.

8. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 5, wherein: The melting point of the low melting point metal ranges from 70°C to 450°C.

9. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 5, wherein: The disconnecting device also includes a mechanical breaking device, which is arranged adjacent to the low-melting-point metal and is activated when a medium-rate overcurrent occurs, thereby actively cutting off the low-melting-point metal.

10. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 9, wherein: The mechanical breaking device is an elastic breaking mechanism, the movable end of which contacts the low-melting-point metal and is in an energy storage state, and is used to cut off the low-melting-point metal in an overcurrent softening state.

11. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 9, wherein: The mechanical breaking device is a pyrotechnic explosion cutting mechanism, the cutter of which is arranged on one side of the low-melting-point metal. The pyrotechnic explosion cutting mechanism is activated when there is a medium-rate overcurrent, thereby actively cutting off the low-melting-point metal.

12. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 1, wherein: The disconnection device comprises a conductor and a mechanical breaking device; the conductor and the second fuse are connected in series and are provided with a structural weakening point for mechanical breaking.

13. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 12, wherein: The mechanical breaking device is a pyrotechnic explosion cutting mechanism, the cutter of which contacts the conductor, and the control circuit of which is activated when a medium-rate overcurrent occurs, thereby actively cutting off the conductor.

14. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 1, wherein: The current carrying ratio of the first melt of the first current carrying device and the medium-rate fast-melting branch of the second current carrying device is in the range of 5:1 to 1:

5.

15. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 1, wherein: The fuse also includes a first housing, a first end cover, a second end cover, a first soldering pad and a second soldering pad; The second current-carrying device and the first current-carrying device are installed in the first housing; Two ends of the second current-carrying device and the first current-carrying device are welded to the first welding pad and the second welding pad respectively; The first end cover and the second end cover are lead-out electrodes of the fuse. The first end cover and the second end cover are fixed at two ends of the first shell and are fixedly and electrically connected to the first welding pad and the second welding pad respectively.

16. The fuse with accelerated medium-rate overcurrent fusing speed as claimed in claim 15, wherein: The first shell is provided with a T-shaped cavity, and the disconnecting device extends to the middle convex part of the T-shaped cavity.

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