An overload protector

Abstract

The application is suitable for the technical field of lightning protection, and provides an overload protector which is used for being connected between two poles of a power supply circuit, comprising: a pressure sensitive resistor, an AC / DC heating unit and an over-temperature tripping mechanism which are connected in series in the power supply circuit, and a high-voltage pulse bypass unit which is connected in parallel with the AC / DC heating unit, wherein the AC / DC heating unit is connected in thermal coupling with the pressure sensitive resistor, and the over-temperature tripping mechanism is connected in direct or interval thermal coupling with at least one of the thermistor and the pressure sensitive resistor; the AC / DC heating unit is used for triggering the over-temperature tripping mechanism to act separately and to be separated from the power supply circuit at a predetermined temperature; by inserting an AC / DC heating unit with a certain resistance in an AC loop of the pressure sensitive resistor, the total impedance of the AC loop is actively increased greatly, the power grid filling current level of the pressure sensitive resistor is reduced significantly, the time of uniform heating of the pressure sensitive resistor is prolonged, and enough time is obtained for the heat conduction of the over-temperature tripping mechanism and the melting of tin and the action tripping.

Description

Technical Field

[0001] This application relates to the field of lightning protection technology, and in particular to an overload protector. Background Technology

[0002] The industry standard for surge protectors, "IEC 61643-11_2011 Low Voltage Surge Protectors," clearly stipulates in Clause 5.12, "Failure Modes of SPDs," that surge protectors must be capable of operating in two failure modes: "open circuit" and "short circuit." Open-circuit failure SPDs must be equipped with an over-temperature tripping mechanism, while short-circuit failure SPDs must be equipped with a thermal short-circuit mechanism. Currently, commercially available TMOVs (Thermally Protected Metal Oxide Varistors) or SPDs (Surge Protective Devices) lack surge protector products with built-in current-limiting elements and over-temperature tripping capabilities, thus lacking reliable protection for the circuit. Utility Model Content

[0003] The purpose of this application is to provide an overload protector, which aims to provide a safe and reliable lightning protection solution.

[0004] This application provides an overload protector for connection between two poles of a power supply circuit. The overload protector includes: a varistor, an AC / DC heating unit, and an over-temperature tripping mechanism connected in series in the power supply circuit, and a high-voltage pulse bypass unit connected in parallel with the AC / DC heating unit. The AC / DC heating unit is thermally coupled to the varistor, and the over-temperature tripping mechanism is directly or indirectly thermally coupled to at least one of the AC / DC heating unit and the varistor. The AC / DC heating unit is used to trigger the over-temperature tripping mechanism to disengage and disconnect from the circuit at a predetermined temperature.

[0005] In some embodiments, if the AC / DC heating unit uses a resistor, its resistance value should be between 500 ohms and 5,000 ohms in order to have a significant current-limiting effect on overload voltage; if the AC / DC heating unit uses a positive temperature coefficient thermistor, its resistance value at room temperature should be between 50 ohms and 5,000 ohms in order to have a significant current-limiting effect on overload voltage.

[0006] In some embodiments, the AC / DC heating unit is preferably a positive temperature coefficient thermistor, and the Curie temperature of the positive temperature coefficient thermistor is 20°C to 40°C higher than the operating temperature of the over-temperature tripping mechanism, so that the over-temperature tripping mechanism operates below the Curie temperature, thereby limiting the maximum temperature of the entire overload protector.

[0007] In some embodiments, the AC / DC heating unit includes a positive temperature coefficient thermistor with a Curie temperature not exceeding 180°C, so that in the extreme case where the over-temperature tripping mechanism fails to spring back normally due to mechanical reasons, the maximum temperature of the entire overload protector is limited to below 210°C, preventing the welded components from collapsing and disintegrating due to the melting of solder.

[0008] In some embodiments, the varistor and the AC / DC heating unit are stacked back-to-back via a common flat metal electrode, so that the varistor and the AC / DC heating unit have direct thermal coupling characteristics.

[0009] In some embodiments, the over-temperature tripping mechanism is welded to the surface electrode of the varistor, or to the surface electrode of the AC / DC heating unit.

[0010] In some embodiments, the over-temperature tripping mechanism includes an elastic electrode with a movable terminal at its end. The movable terminal is welded to the electrode surface of either side of the varistor or the surface electrode of the AC / DC heating unit by a low-temperature alloy. The melting point of the low-temperature alloy is the operating temperature of the over-temperature tripping mechanism. Alternatively, the over-temperature tripping mechanism includes a thermal fuse, which is welded to the electrode surface of either side of the varistor or the surface electrode of the AC / DC heating unit; the melting point temperature of the thermal fuse is the operating temperature of the over-temperature tripping mechanism.

[0011] In some embodiments, the welding position of the over-temperature tripping mechanism can be flexibly arranged; the over-temperature tripping mechanism can be arranged at the center of the surface electrode of the varistor, or the over-temperature tripping mechanism can be arranged at the edge of the surface electrode of the varistor, including the root position of the outer metal electrode of the varistor near the edge of the varistor, so as to simplify the processing and welding process of the over-temperature tripping mechanism.

[0012] In some embodiments, the high-voltage pulse bypass unit is electrically connected in parallel with the AC / DC heating unit. The high-voltage pulse bypass unit and the AC / DC heating unit are welded side by side to the surface metal electrode of the varistor. Alternatively, the high-voltage pulse bypass unit is placed independently outside the AC / DC heating unit in a thermally decoupled manner and is electrically connected to the AC / DC heating unit through conductive components.

[0013] In some embodiments, the high-voltage pulse bypass unit includes any one of a gas discharge tube, a solid-state discharge tube, a graphite discharge gap, and a spark gap; and / or, the DC operating voltage of the high-voltage pulse bypass unit is higher than the DC voltage withstand requirement designed for the overload protector. The overload protector provided in this application has the following advantages: The overload protector provided in this application embodiment actively and significantly increases the total impedance of the AC circuit by inserting an AC / DC heating unit with a certain resistance value into the AC circuit of the varistor. This significantly reduces the grid current level of the varistor, prolongs the continuous heating time of the varistor, and provides sufficient time for the over-temperature tripping mechanism to conduct heat, melt solder, and trip. Attached Figure Description

[0014] To more clearly illustrate the technical solutions in the embodiments of this application, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0015] Figure 1 This is a schematic diagram of the first circuit relationship of the overload protector provided in the embodiments of this application; Figure 2 This is a schematic diagram of the core module structure of the overload protector provided in the embodiments of this application. Figure 1 ; Figure 3 This corresponds to the overload protector provided in the embodiments of this application. Figure 2 A schematic diagram of a specific module structure; Figure 4 This corresponds to the overload protector provided in the embodiments of this application. Figure 2 Another specific module structure diagram; Figure 5 This is a schematic diagram of the core module structure of the overload protector provided in the embodiments of this application. Figure 2 ; Figure 6 This is a schematic diagram of the core module structure of the overload protector provided in the embodiments of this application. Figure 3 ; Figure 7 This corresponds to the overload protector provided in the embodiments of this application. Figure 6 A schematic diagram of a specific module structure; Figure 8 This corresponds to the overload protector provided in the embodiments of this application. Figure 6 Another specific module structure diagram; Figure 9 This corresponds to the overload protector provided in the embodiments of this application. Figure 6 Another specific module structure diagram; Figure 10 This is a schematic diagram of a second circuit relationship of the overload protector provided in the embodiments of this application; Figure 11 This is a schematic diagram of the core module structure of the overload protector provided in the embodiments of this application. Figure 4 ; Figure 12 This corresponds to the overload protector provided in the embodiments of this application. Figure 11 A schematic diagram of a specific module structure; Figure 13 This corresponds to the overload protector provided in the embodiments of this application. Figure 11 Another specific module structure diagram; Figure 14 This corresponds to the overload protector provided in the embodiments of this application. Figure 11 Another specific module structure diagram; Figure 15 This is a schematic diagram of the modular package structure of the overload protector provided in the embodiments of this application; Figure 16 This is a schematic diagram of the third circuit relationship of the overload protector provided in the embodiments of this application; Figure 17 This is a schematic diagram of the fourth circuit relationship of the overload protector provided in the embodiments of this application; Figure 18 This is a schematic diagram of the internal structure of the modular package of the overload protector provided in the embodiments of this application.

[0016] The markings in the diagram mean: 100-overload protector; MOV - Varistor, 11 - First side electrode, 12 - Second side electrode; 20 - AC / DC heating unit, PTC - thermistor; 30 - Over-temperature tripping mechanism; 31 - Flexible electrode; 311 - Movable terminal; 32 - Thermal fuse; 40 - High-voltage pulse bypass unit, GDT - Gas discharge tube; 50-Remote Signaling Switch; 60 - Arc extinguishing slider; 70 - Pull-out spring; 71 - Fixed terminal; 72 - Movable terminal; 80 - Outer shell. Detailed Implementation

[0017] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0018] It should be noted that when a component is referred to as "fixed to" or "set on" another component, it can be directly or indirectly fixed to or set on that other component. When a component is referred to as "connected to" another component, it can be directly or indirectly connected to that other component. The terms "upper," "lower," "left," "right," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the purpose of description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this patent. The terms "first" and "second" are used only for the purpose of description and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features. "A plurality" means two or more, unless otherwise explicitly specified.

[0019] In the description of this application, unless otherwise stated, " / " indicates that the objects before and after are in an "or" relationship. For example, A / B can mean A or B. "And / or" in this application is merely a description of the relationship between the related objects, indicating that three relationships can exist. For example, A and / or B can represent: A alone, A and B simultaneously, and B alone, where A and B can be single or multiple. Furthermore, in the description of this application, "at least one of the following" or similar expressions refer to any combination of these items, including any combination of single or multiple items. For example, at least one of a, b, and c can represent: a, b, c, a+b, a+c, b+c, a+b+c, where a, b, and c can be single or multiple.

[0020] To illustrate the technical solutions described in this application, the following detailed description is provided in conjunction with specific accompanying drawings and embodiments.

[0021] Traditional SPD discharge circuits include a metal oxide varistor (MOV) connected in series. Varistors connected to AC power supplies are susceptible to several common overload failure scenarios: 1. When the amplitude of the transient overvoltage (TOV) is higher than the operating voltage threshold (Uv) of the varistor, a power frequency current will flow through the varistor. When the heat power generated on the varistor exceeds the heat dissipation power of the varistor itself, the temperature of the varistor will continue to rise. If the TOV overvoltage lasts long enough, the varistor will thermally collapse and burn through, exhibiting a short-circuit burn-through state.

[0022] 2. During field service, if the energy of a lightning pulse or the cumulative number of impacts acting on the varistor exceeds the design limit of its valve plate, the operating voltage of the varistor will drop significantly, eventually resulting in a low resistance value and deterioration failure.

[0023] 3. For varistors that have been in field service for a long time, under the continuous stress of the power grid voltage, the operating voltage of the varistor will gradually decrease at the end of its service life. When its threshold is lower than the peak voltage of the rated power grid, power frequency current will flow through the varistor. The continuous power frequency current will eventually cause the varistor to fail due to overheating and short circuit.

[0024] MOV varistors that enter a low-resistance state mostly exhibit a "tunnel-type burn-through" condition, meaning that a pinhole-like low-resistance channel connects the two electrodes of the varistor. When the power grid generates current in the failed varistor, the current will only flow through this low-resistance channel and will not flow through other high-resistance regions. The blackened and carbonized zinc oxide tunnel does not exhibit a completely short-circuit state with zero resistance, but rather a low-resistance state ranging from a few tenths of an ohm to several hundred ohms.

[0025] If a varistor that has burned through a tunnel cannot be quickly disconnected from the power grid, the following serious safety risks will arise: 1. When the rated mains voltage is applied to a low-resistance channel with only a few tenths of an ohm to several hundred ohms, it may generate an AC current of tens to hundreds of amperes. Such a high current will cause the current channel to arc or cause the varistor to explode.

[0026] 2. A failed, short-circuited varistor can no longer withstand the impact of lightning current. A lightning current of several thousand amperes concentrated in a small, low-resistance tunnel will cause the channel to heat up rapidly. Thermal stress may cause the varistor to shatter instantly, and the splashed conductive fragments of the varistor may threaten the safety of electrical equipment.

[0027] To reduce the safety risk of high-temperature fire caused by short-circuit failure of varistors, manufacturers equip varistors with overload tripping devices. Common overload tripping devices for varistors include the following: 1. Connect a current fuse or an air circuit breaker (MCB) in series outside the varistor. When the varistor fails and short-circuits, generating a large fault current, the fuse will blow or the air circuit breaker will open to prevent the current from continuously heating the varistor. 2. A varistor is connected in series with an external backup protector (SCB, Special Circuit Breaker), so that the fault current flows through the electromagnetic coil of the SCB, and the electromagnetic force pushes the contact switch to separate, thereby cutting off the fault current of the varistor greater than 3A. 3. Mount a thermal fuse or solder an alloy fuse on the surface of the varistor and connect it in series. If the varistor overheats, the low-temperature fuse will melt and disconnect the varistor from the AC power grid. 4. An elastic metal electrode is placed on the surface of the varistor, and the elastic electrode is soldered to the varistor with low-temperature solder. When the varistor heats up and exceeds the temperature, the low-temperature solder joint melts, causing the elastic electrode to detach from the varistor and cut off the fault current. 5. Based on the fourth design above, a mechanical mechanism with a pull-out spring and an arc-extinguishing slider is added to improve the reliability of the tripping mechanism and add a failure remote alarm function.

[0028] All five AC overload tripping designs mentioned above have certain safety hazards, and their respective defects are as follows: The first design, to ensure it doesn't trip during lightning strikes, typically requires AC operating currents greater than 10A for the current fuse and circuit breaker, thus failing to cut off fault currents below 10A. The second design is limited by the minimum drive current of the electromagnetic coil, also unable to trip for fault currents below 3A. Designs 3, 4, and 5 rely on fusing the cryogenic alloy to achieve disconnection. Their safety depends on the delay time of the over-temperature tripping mechanism. Under high TOV power frequency current surges (e.g., above 10A), the varistor often burns through quickly, entering a short-circuit state. Due to the delay in heat conduction, the over-temperature tripping mechanism may not have enough time to disconnect, causing the short-circuit current in the power grid to instantly increase to tens or even hundreds of amps. This extremely high short-circuit fault current exposes the varistor to safety risks such as high-temperature flames, explosions, and the ignition of the encapsulating plastic.

[0029] The technicians applying this application discovered that excessive power frequency current causes the varistor to heat up too quickly, to the point that the overload tripping device cannot trip in time before the varistor burns through and short-circuits. This results in the varistor being subjected to extremely high grid short-circuit current surges, causing dangerously high temperatures and heat generation. This is the main safety risk of traditional thermal protection varistors. To eliminate this risk, the problem of excessive power frequency current surges in varistors must be addressed. The magnitude of the power frequency current depends on the total impedance of the current loop, including: the internal resistance of the power grid, the equivalent resistance of the varistor, and the grounding resistance (if the varistor is connected to protective ground). The internal resistance of the power grid and the grounding resistance are determined by the power supply system and cannot be changed. The only way to change the equivalent total impedance is through the varistor itself.

[0030] Based on this, this application provides a solution.

[0031] like Figure 1 , Figure 2 and Figure 10As shown, this application embodiment provides an overload protector 100, which is used to connect between two electrodes P1 and P2 of a power supply circuit. The overload protector 100 includes: a varistor MOV, an AC / DC heating unit 20, and an over-temperature tripping mechanism 30 connected in series in the power supply circuit, and a high-voltage pulse bypass unit 40 connected in parallel with the AC / DC heating unit 20. The AC / DC heating unit 20 is thermally coupled to the varistor MOV, and the over-temperature tripping mechanism 30 is directly or indirectly thermally coupled to at least one of the thermistor PTC and the varistor MOV. The AC / DC heating unit 20 is used to trigger the over-temperature tripping mechanism 30 to operate and disconnect from the power supply circuit at a predetermined temperature.

[0032] The overload protector 100 provided in this application embodiment actively and significantly increases the total impedance of the AC circuit by inserting an AC / DC heating unit 20 with a certain resistance value into the AC circuit of the varistor MOV. This can significantly reduce the grid current level of the varistor MOV, prolong the time for the varistor MOV to heat up evenly, and provide sufficient time for the over-temperature tripping mechanism 30 to conduct heat, melt solder, and trip.

[0033] The overload protector 100, the varistor MOV, the AC / DC heating unit 20, and the over-temperature tripping mechanism 30 provided in this application embodiment are electrically connected in series, and the series connection order of the three is not limited.

[0034] In some embodiments of this application, the AC / DC heating unit 20 includes at least one of a positive temperature coefficient thermistor (PTC) or a resistor. The AC / DC heating unit 20 may include one or more PTCs connected in series, or one or more resistors connected in series, or it may include a PTC and a resistor connected in series.

[0035] If the AC / DC heating unit 20 uses a resistor, its resistance value should be between several hundred ohms and several thousand ohms in order to have a significant current limiting effect on overload voltage, thereby reducing the impact power of current on the varistor MOV and avoiding instantaneous damage to the varistor MOV.

[0036] In some optional embodiments, the AC / DC heating unit 20 uses a resistor with a resistance value between 500 ohms and 5000 ohms. For example, in some specific embodiments, the AC / DC heating unit 20 uses a resistor with a resistance value of 500 ohms, 600 ohms, 700 ohms, 800 ohms, 1000 ohms, 1200 ohms, 1500 ohms, 1800 ohms, 2000 ohms, 2500 ohms, 3000 ohms, 3500 ohms, 4000 ohms, 4500 ohms, 5000 ohms, etc.

[0037] In other embodiments, if the AC / DC heating unit 20 uses a positive temperature coefficient thermistor PTC, its resistance at room temperature should be between tens of ohms and thousands of ohms, so as to have a significant current limiting effect on overload voltage, thereby reducing the impact power of current on the varistor MOV and avoiding instantaneous damage to the varistor MOV.

[0038] In some optional embodiments, the AC / DC heating unit 20 uses a positive temperature coefficient (PTC) thermistor, whose resistance at room temperature should be between 50 ohms and 5000 ohms. In some specific embodiments, the AC / DC heating unit 20 uses a PTC thermistor with a resistance at room temperature of 50 ohms, 80 ohms, 100 ohms, 150 ohms, 200 ohms, 250 ohms, 300 ohms, 350 ohms, 400 ohms, 450 ohms, 500 ohms, 600 ohms, 700 ohms, 800 ohms, 1000 ohms, 1200 ohms, 1500 ohms, 1800 ohms, 2000 ohms, 2500 ohms, 3000 ohms, 3500 ohms, 4000 ohms, 4500 ohms, 5000 ohms, etc.

[0039] In some embodiments of this application, such as Figure 1 , Figure 10 As shown, the AC / DC heating unit 20 preferably uses a positive temperature coefficient thermistor (PTC).

[0040] In one specific embodiment, inserting an 800-ohm thermistor PTC at room temperature can suppress the power frequency current flowing through the 25D511K varistor V (DC operating voltage of 510Vdc) to below 0.5A under a TOV transient overvoltage impact of 800Vac. Simultaneously, it can also suppress the current sinking from the 220Vac power grid to the varistor MOV to below 0.3A after the varistor fails and short-circuits. When 800Vac voltage is applied across the 25D511K varistor, the varistor will short-circuit and fail within 0.5 seconds. Due to the thermal conduction delay, the tripping mechanism cannot disengage within such a short time, inevitably generating a dangerous short-circuit current. However, when the 25D511K varistor is connected in series with the 800-ohm thermistor PTC, applying 800Vac voltage extends the short-circuit failure time of the varistor to 5 seconds or more. This provides valuable time for the over-temperature tripping mechanism 30 to conduct heat and melt solder, allowing it to trip safely.

[0041] In some embodiments of this application, such as Figure 1 and Figure 10As shown, the AC / DC heating unit 20 preferably uses a positive temperature coefficient thermistor (PTC). The Curie temperature of the PTC is 20°C to 40°C higher than the operating temperature of the over-temperature trip mechanism 30, so that the over-temperature trip mechanism 30 operates within a range of 20°C to 40°C below the Curie temperature, thereby limiting the maximum temperature of the entire overload protector 100. In addition, it can prevent the PTC from prematurely tripping at low temperatures, thus preventing the over-temperature trip mechanism 30 from failing to reach its operating temperature and thus preventing it from tripping smoothly.

[0042] Under transient overvoltage loading, the positive temperature coefficient thermistor PTC and varistor MOV generate heat together and transfer the heat to the over-temperature trip mechanism 30, causing it to disconnect. Even if the varistor MOV fails and enters a low-resistance short-circuit state, the thermistor PTC continues to generate heat and transfers the heat to the varistor MOV, causing the varistor MOV to continue to heat up, eventually causing the over-temperature trip mechanism 30 to disconnect.

[0043] When the MOV varistor is damaged by lightning current and enters a low-resistance burn-through state, the PTC thermistor will continue to heat up under the action of 220Vac voltage and transfer the heat to the MOV varistor and the over-temperature trip unit. Eventually, it will also melt the solder joints of the over-temperature trip unit, thereby allowing the failed MOV varistor to be safely disconnected from the power grid.

[0044] The overload protector 100 provided in this application embodiment mainly utilizes the low resistance region of the positive temperature coefficient thermistor PTC before its operation to provide current limiting. It almost does not need to use the high resistance region of the thermistor PTC after its operation. This is because, in most cases, the over-temperature tripping structure has already obtained sufficient temperature to operate and disconnect before the thermistor PTC operates.

[0045] Once the temperature of the PTC thermistor exceeds its Curie temperature (commonly known as the operating temperature), the resistance of the PTC will increase rapidly and exponentially with rising temperature, causing the current to decrease rapidly. The subsequent decrease in heating power, in turn, slows down the temperature rise. Finally, the overload protector 100 as a whole will reach thermal equilibrium at a certain temperature (typically 10°C to 30°C above the Curie temperature of the PTC).

[0046] Regardless of whether the varistor MOV fails due to a short circuit, the thermistor PTC will continuously generate heat and transfer it to the over-temperature trip mechanism 30, ultimately causing it to trip smoothly. Furthermore, because the positive temperature coefficient thermistor PTC has a temperature-based negative feedback regulation mechanism for power, there is no need to worry about the temperature of the varistor MOV becoming uncontrollable, nor about the delay time of the over-temperature trip mechanism 30. Even with a long delay, the temperature of the varistor MOV will be limited to a safe range, preventing unsafe overheating situations. This significantly improves the overall safety performance of the overload protector 100.

[0047] To ensure the MOV (Metal Oxide Varistor) can disconnect from the power grid after failure, the room-temperature resistance and Curie temperature of the PTC (Potentially Transmitter Temperature) need to be correctly selected. Specifically, the heat dissipation power P of the entire overload protector 100 at a certain temperature (set to X°C) above the tripping temperature (Y°C) is first tested. B Then according to formula R B =U 2 / P B Calculate the resistance value R required to reach thermal equilibrium at a rated voltage of 220Vac. B Check the resistance-temperature characteristic curve of the PTC thermistor to see if the resistance of the PTC at X°C is less than the calculated value R. B If so, it can be ensured that the electrical power generated by the thermistor PTC at 220Vac is sufficient to heat the entire overload protector 100 to above Y°C, ensuring that the over-temperature tripping mechanism 30 smoothly reaches its operating temperature and trips. To ensure the rapid heating effect of the thermistor PTC on the over-temperature tripping structure, the Curie temperature of the thermistor PTC should be higher than X°C. At the same time, to avoid accidentally melting the electrode solder of the thermistor PTC after it flips over, the Curie temperature of the thermistor PTC should not be selected too high.

[0048] In one specific embodiment, to ensure that the varistor MOV can disconnect from the power grid after failure, the heat dissipation power P of the entire overload protector 100 at 20°C (e.g., 160°C) above the tripping temperature is first tested. B Then according to formula R B =U 2 / P B Calculate the resistance value R required to reach thermal equilibrium at a rated voltage of 220Vac. B Check the resistance-temperature characteristic curve of the PTC thermistor to see if the resistance of the PTC thermistor at 160°C is less than the calculated value R. BIf so, it can be ensured that the electrical power generated by the thermistor PTC at 220Vac is sufficient to heat the entire overload protector 100 to above 140°C, ensuring that the over-temperature tripping mechanism 30 smoothly reaches its operating temperature and trips. Therefore, in order to ensure the rapid heating effect of the thermistor PTC on the over-temperature tripping structure, the Curie temperature of the thermistor PTC should be higher than 160°C.

[0049] Meanwhile, to avoid accidentally melting the electrode solder of the PTC thermistor after it flips, the Curie temperature of the PTC thermistor should not be too high, and should be controlled below 180°C.

[0050] In some embodiments of this application, the AC / DC heating unit 20 includes a positive temperature coefficient thermistor PTC. The Curie temperature of the positive temperature coefficient thermistor PTC is not higher than 180°C, so that in the extreme case where the over-temperature tripping mechanism 30 cannot operate normally due to mechanical reasons, the maximum temperature of the entire overload protector 100 can be limited, for example, to below the solder melting temperature, to prevent the soldered parts from collapsing and disintegrating due to the melting of the solder.

[0051] In one specific embodiment, the Curie temperature of the positive temperature coefficient thermistor PTC is not higher than 180°C, which can be used to limit the maximum temperature of the entire overload protector 100 to below 210°C.

[0052] In some embodiments, the Curie temperature of the positive temperature coefficient (PTC) thermistor is 160~180°C. In some embodiments, the Curie temperature of the PTC thermistor is 165~180°C. In some embodiments, the Curie temperature of the PTC thermistor is 160~175°C. In some embodiments, the Curie temperature of the PTC thermistor is 165~175°C.

[0053] like Figure 1 As shown, in some embodiments of this application, the AC / DC heating unit 20, the varistor MOV, and the over-temperature tripping mechanism 30 can be connected in series in the direction of current or in the opposite direction of current.

[0054] In some embodiments of this application, such as Figure 2As shown, the varistor MOV and the AC / DC heating unit 20 are back-to-back welded together via a common flat metal electrode, enabling efficient thermal coupling between them. This allows for direct heat transfer between the varistor MOV and the AC / DC heating unit 20. Here, we define the surface of the first electrode 11 of the varistor MOV as being used to weld to the AC / DC heating unit 20; the electrode on the side of the varistor MOV facing away from the AC / DC heating unit 20 is designated as the second electrode 12.

[0055] The structure of the varistor MOV and the AC / DC heating unit 20 being integrated back-to-back avoids the safety hazard of the MOV failing due to low resistance and being unable to disconnect from the power grid.

[0056] Thanks to the integrated back-to-back welding structure of the AC / DC heating unit 20 and the varistor MOV, heat transfer between the AC / DC heating unit 20 and the varistor MOV is highly efficient. Heat is continuously conducted to the over-temperature tripping mechanism 30, ultimately causing it to trip smoothly, which further enhances the safety performance of the entire overload protector 100.

[0057] In some embodiments, the over-temperature tripping mechanism 30 can be soldered either onto the surface metal electrode of the varistor MOV or onto the surface metal electrode of the AC / DC heating unit 20. The surface metal electrode of the varistor MOV refers to its first side electrode 11 and second side electrode 12.

[0058] In some embodiments of this application, such as Figure 3 As shown, the over-temperature tripping mechanism 30 includes an elastic electrode 31 with a movable terminal at its end. This movable terminal is welded to either the first electrode 11 or the second electrode 12 of the varistor MOV via a cryogenic alloy (not shown). The melting point of the cryogenic alloy is the operating temperature of the over-temperature tripping mechanism 30. When the temperature of the varistor MOV rises, the cryogenic alloy melts due to reaching its melting temperature, and the movable terminal at the end of the elastic electrode 31 springs open and detaches from the surface of the second electrode 12 of the varistor MOV, thereby completing the tripping process.

[0059] In one alternative embodiment, such as Figure 3 As shown, the movable terminal 311 at the end of the elastic electrode 31 is welded to the surface of the second side electrode 12 of the varistor MOV by a low-temperature alloy.

[0060] In other embodiments, such as Figure 4As shown, the over-temperature tripping mechanism 30 includes a thermal fuse 32, which is soldered to either the first electrode 11 or the second electrode 12 of the varistor MOV. The melting point of the thermal fuse 32 is the operating temperature of the over-temperature tripping mechanism 30. When the temperature of the varistor MOV rises, the thermal fuse 32 melts because it reaches its melting temperature, thereby physically breaking the circuit.

[0061] In one alternative embodiment, such as Figure 4 As shown, the thermal fuse 32 is soldered to the surface of the second electrode 12 of the varistor MOV.

[0062] In some embodiments of this application, the welding position of the over-temperature tripping mechanism 30 can be flexibly arranged. The over-temperature tripping mechanism 30 can be arranged at the center of the surface electrode of the varistor MOV or at the edge of the surface electrode of the varistor MOV. For example, it can be arranged at the root of the outer metal electrode of the varistor MOV near the edge of the varistor MOV, so as to simplify the processing and welding process of the over-temperature tripping mechanism 30.

[0063] like Figure 3 and Figure 4 As shown, the welding position of the over-temperature tripping mechanism 30 can be offset from the center of the varistor MOV. Specifically, the welding position of the over-temperature tripping mechanism 30 is located at the root of the outer metal electrode of the varistor MOV. This simplifies the machining and welding process of the over-temperature tripping mechanism 30.

[0064] When welding the over-temperature tripping mechanism 30 to the varistor MOV, since the welding position of the over-temperature tripping mechanism 30 is off-center from the center of the varistor MOV, the high temperature required for welding can be applied as close as possible to the edge of the varistor MOV, for example, as close as possible to the root of the outer electrode of the varistor MOV. The high temperature does not need to be transferred or applied to the center of the varistor MOV, which also avoids the adverse effects of welding high temperature on the varistor MOV.

[0065] For example, Figure 3 As shown, the movable terminal 311 at the end of the elastic electrode 31 is welded to the root position of the outer electrode of the varistor MOV, specifically the root position of the second side electrode 12.

[0066] To reduce the residual voltage of lightning strike pulses, a high-voltage pulse bypass unit 40 must be connected in parallel across the AC / DC heating unit 20 to provide a low-resistance path for the lightning strike pulse current, preventing excessively high residual voltage from the lightning strike current flowing through the AC / DC heating unit 20. The minimum DC operating voltage of the high-voltage pulse bypass unit 40 must be greater than the peak voltage of the power frequency voltage it needs to withstand, ensuring that the high-voltage pulse bypass unit 40 is not triggered by the power frequency voltage before or after the varistor MOV short-circuit failure.

[0067] It is also necessary to ensure that the operating voltage of the varistor MOV connected in series with the high-voltage pulse bypass unit 40 is greater than the maximum peak voltage of the normal working power grid, so as to prevent the formation of a continuous power frequency follow current after the lightning pulse opens the high-voltage pulse bypass unit 40, and ensure that the power frequency current only flows through the AC / DC heating unit 20 and not through the high-voltage pulse bypass unit 40, thus ensuring the effective current suppression effect of the AC / DC heating unit 20 on the power frequency current.

[0068] The high-voltage pulse bypass unit 40 connected in parallel with the AC / DC heating unit 20 can be any switching element with sufficient lightning strike current carrying capacity.

[0069] In some embodiments of this application, such as Figure 1 and Figure 10 As shown, the high-voltage pulse bypass unit 40 includes any one of a gas discharge tube (GDT), a solid-state discharge tube, a graphite discharge gap, and a spark gap. In some optional embodiments, the high-voltage pulse bypass unit 40 includes a gas discharge tube (GDT).

[0070] The high-voltage pulse bypass unit 40 is electrically connected in parallel with the AC / DC heating unit 20.

[0071] In some embodiments, the high-voltage pulse bypass unit 40 may be thermally coupled to at least one of the varistor MOV and the AC / DC heating unit 20.

[0072] For example, in Figure 2 Based on the core module shown, the high-voltage pulse bypass unit 40 can be soldered onto the second side electrode 12 of the varistor MOV. Figure 5 In this design, a high-voltage pulse bypass unit 40 is soldered onto the shielded second electrode 12 of the varistor MOV. This unit can also be soldered side-by-side with the AC / DC heating unit 20 onto the same electrode of the varistor MOV. Figure 6 As shown.

[0073] like Figure 5 As shown, the high-voltage pulse bypass unit 40 is welded to the second side electrode 12 of the varistor MOV to maintain thermal coupling with the varistor MOV. In this embodiment, the AC / DC heating unit 20 can be welded to the center of the first side electrode 11, or it can be offset from the center of the first side electrode 11 and located at the root of the first side electrode 11 of the varistor MOV.

[0074] In this embodiment, the over-temperature tripping mechanism 30 can be welded to the surface of the second side electrode 12 of the varistor MOV, located on the same side as the high-voltage pulse bypass unit 40, or it can be welded to the surface of the first side electrode 11, located on the same side as the AC / DC heating unit 20. Furthermore, regardless of whether the over-temperature tripping mechanism 30 is located on the surface of the first side electrode 11 or the second side electrode 12, the over-temperature tripping mechanism 30 can be offset from the center position of the corresponding electrode of the varistor MOV, which will not be elaborated further.

[0075] like Figure 6 As shown, the high-voltage pulse bypass unit 40 and the AC / DC heating unit 20 are welded side by side to the first side electrode 11 of the varistor MOV to maintain thermal coupling with the varistor MOV.

[0076] like Figure 7 As shown, in some embodiments of this application, the over-temperature tripping mechanism 30 can be welded to the electrode surface of the AC / DC heating unit 20 on the side opposite to the varistor MOV. In this embodiment, the high-voltage pulse bypass unit 40 is welded side-by-side with the AC / DC heating unit 20; therefore, both the high-voltage pulse bypass unit 40 and the AC / DC heating unit 20 are offset from the center of the electrode surface of the varistor MOV. Optionally, the over-temperature tripping mechanism 30 can also be welded to the electrode surface of the high-voltage pulse bypass unit 40 on the side opposite to the varistor MOV. Further optionally, as... Figure 7 The over-temperature tripping mechanism 30 shown includes an elastic electrode 31. Optionally, the over-temperature tripping mechanism 30 can be replaced by a thermal fuse 32, the structure and connection of which are as described above and will not be repeated here.

[0077] Or, such as Figure 8 and Figure 9 As shown, the over-temperature tripping mechanism 30 can be soldered to the surface of the second electrode 12 of the varistor MOV. Wherein, as... Figure 8 As shown, the over-temperature tripping mechanism 30 may include an elastic electrode 31, the structure and connection method of which are as described above and will not be repeated here, or, as... Figure 9 As shown, the over-temperature tripping mechanism 30 may include a thermal fuse 32, the structure and connection method of which are as described above and will not be repeated here.

[0078] like Figure 10 As shown, in some embodiments of this application, the varistor MOV, the AC / DC heating unit 20 and the over-temperature tripping mechanism 30 are connected in series in the direction of current or in the opposite direction of current.

[0079] In some embodiments of this application, in Figure 2 Based on the core modules shown, such as Figure 11As shown, the high-voltage pulse bypass unit 40 is welded to the electrode surface of the AC / DC heating unit 20 on the side away from the varistor MOV. The electrodes of the high-voltage pulse bypass unit 40 and the AC / DC heating unit 20, which are welded together, can be connected to a common electrode.

[0080] In some embodiments of this application, such as Figure 12 As shown, the over-temperature tripping mechanism 30 may include an elastic electrode 31, the movable terminal 311 of which is welded to the electrode of the high-voltage pulse bypass unit 40 on the side away from the AC / DC heating unit 20 by a cryogenic alloy. In this embodiment, the AC / DC heating unit 20 may be offset from the center position of the first side electrode 11, so that the high-voltage pulse bypass unit 40 is offset from the center position of the first side electrode 11, thereby causing the welding position of the over-temperature tripping mechanism 30 to be offset from the center position of the first side electrode 11. In other optional embodiments, the over-temperature tripping mechanism 30 may include a thermal fuse 32, which is welded to the electrode of the high-voltage pulse bypass unit 40 on the side away from the AC / DC heating unit 20. Its structure and connection method are as described above and will not be repeated here.

[0081] In some embodiments of this application, such as Figure 13 and Figure 14 As shown, the over-temperature tripping mechanism 30 can be soldered onto the surface of the second side electrode 12 of the varistor MOV. In this embodiment, as... Figure 13 As shown, the AC / DC heating unit 20 may include an elastic electrode 31, the specific structure and connection of which will not be described in detail, and may also include a thermal fuse 32, such as... Figure 14 As shown, its specific structure and connection method are as described above and will not be repeated here. Optionally, in this embodiment, the welding position of the AC / DC heating unit 20 is offset from the center position of the second side electrode 12.

[0082] If the over-temperature tripping mechanism 30 is directly thermally coupled to the varistor (MOV), the tripping speed will be relatively faster. If it is directly thermally coupled to the thermistor (PTC), the tripping speed will be relatively slower, especially under low current conditions. In practical applications, the thermal coupling method of the over-temperature tripping mechanism 30 can be set according to the required tripping time.

[0083] Furthermore, in many embodiments, the high-voltage pulse bypass unit 40 can also be placed independently outside the AC / DC heating unit 20 through thermal decoupling, only needing to maintain electrical connection with the AC / DC heating unit 20 through conductive components. The conductive components mentioned here may include, but are not limited to, the copper foil of a circuit board or other conductive cables.

[0084] In some embodiments of this application, such as Figure 15As shown, the overload protector 100 also includes a housing 80, in which the varistor MOV, AC / DC heating unit 20 and high-voltage pulse bypass unit 40 are all housed and filled with sealant to form an integrated encapsulated module.

[0085] In some embodiments, the over-temperature tripping mechanism 30 is disposed within the housing 80. The housing 80 has a window (not shown), through which the over-temperature tripping mechanism 30 is welded to the surface of either the AC / DC heating unit 20 or the varistor MOV. When the high-voltage pulse bypass unit 40 is thermally coupled to the AC / DC heating unit 20, the over-temperature tripping mechanism can also be welded to the high-voltage pulse bypass unit 40.

[0086] In some embodiments of this application, such as Figure 16 , Figure 17 and Figure 18 As shown, the overload protector 100 also includes an arc-extinguishing slider 60 and a pull-out spring 70 disposed within the housing 80 and interconnected. The pull-out spring 70 is used to pull the arc-extinguishing slider 60 to the window and block the over-temperature tripping mechanism 30 when it trips. Normally, in order to achieve effective physical isolation and insulation between the over-temperature tripping mechanism 30 and its welded location, the distance between the over-temperature tripping mechanism 30 and its welded location after tripping needs to be at least 8mm. In the embodiments of this application, by setting the arc-extinguishing slider 60 to assist in the isolation of the over-temperature tripping mechanism 30, effective physical isolation and insulation can be achieved at a smaller distance. For example, if the thickness of the arc-extinguishing slider 60 is 2mm, an air isolation effect equivalent to 8mm can be achieved.

[0087] In some embodiments of this application, such as Figure 16 , Figure 17 and Figure 18 As shown, the overload protector 100 also includes a remote signaling switch 50, which is disposed inside the housing 80 via a window. The remote signaling switch 50 includes a movable terminal 72 and a fixed terminal 71. When the over-temperature tripping mechanism 30 fails to trip, the movable terminal 72 of the remote signaling switch 50 is located between the arc-extinguishing slider 60 and the inner wall of the housing 80. After the over-temperature tripping mechanism 30 trips and the arc-extinguishing slider 60 slides to the window, the movable terminal 72 and the fixed terminal 71 separate.

[0088] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. An overload protector, characterized in that, For connection between the two poles of a power supply circuit; the overload protector includes: a varistor, an AC / DC heating unit, and an over-temperature tripping mechanism connected in series in the power supply circuit, and a high-voltage pulse bypass unit connected in parallel with the AC / DC heating unit, wherein the AC / DC heating unit is thermally coupled to the varistor, and the over-temperature tripping mechanism is directly or indirectly thermally coupled to at least one of the AC / DC heating unit and the varistor; the AC / DC heating unit is used to trigger the over-temperature tripping mechanism to act and disconnect from the circuit at a predetermined temperature.

2. The overload protector as described in claim 1, characterized in that, The AC / DC heating unit is a resistor with a resistance value between 500 ohms and 5,000 ohms, so as to have a significant current-limiting effect on overload voltage; or, the AC / DC heating unit is a positive temperature coefficient thermistor with a room temperature resistance value between 50 ohms and 5,000 ohms, so as to have a significant current-limiting effect on overload voltage.

3. The overload protector as described in claim 2, characterized in that, The AC / DC heating unit is a positive temperature coefficient thermistor. The Curie temperature of the positive temperature coefficient thermistor is 20°C to 40°C higher than the operating temperature of the over-temperature tripping mechanism, so that the over-temperature tripping mechanism operates below the Curie temperature, thereby limiting the maximum temperature of the entire overload protector.

4. The overload protector as described in claim 2, characterized in that, The AC / DC heating unit includes a positive temperature coefficient thermistor with a Curie temperature not exceeding 180°C. This is to limit the maximum temperature of the entire overload protector to below 210°C in the extreme case where the over-temperature tripping mechanism fails to spring back normally due to mechanical reasons, thus preventing the welded components from collapsing and disintegrating due to the melting of solder.

5. The overload protector as described in claim 1, characterized in that, The varistor and the AC / DC heating unit are stacked together back-to-back via a common flat metal electrode, giving the varistor and the AC / DC heating unit direct thermal coupling characteristics.

6. The overload protector as described in claim 5, characterized in that, The over-temperature tripping mechanism is welded to the surface electrode of the varistor, or to the surface electrode of the AC / DC heating unit.

7. The overload protector as described in claim 6, characterized in that, The over-temperature tripping mechanism includes an elastic electrode with a movable terminal at its end. The movable terminal is welded to the electrode surface of either side of the varistor or the surface electrode of the AC / DC heating unit by a low-temperature alloy. The melting point of the low-temperature alloy is the operating temperature of the over-temperature tripping mechanism. Alternatively, the over-temperature tripping mechanism includes a thermal fuse, which is welded to the electrode surface of either side of the varistor or the surface electrode of the AC / DC heating unit; the melting point temperature of the thermal fuse is the operating temperature of the over-temperature tripping mechanism.

8. The overload protector as described in claim 5, characterized in that, The over-temperature tripping mechanism is arranged at the center of the surface electrode of the varistor; or, the over-temperature tripping mechanism is arranged at the root of the outer metal electrode of the varistor near the edge of the varistor, so that the processing and welding process of the over-temperature tripping mechanism can be simplified.

9. The overload protector as described in any one of claims 1 to 8, characterized in that, The high-voltage pulse bypass unit is electrically connected in parallel with the AC / DC heating unit. The high-voltage pulse bypass unit and the AC / DC heating unit are welded side by side to the surface metal electrode of the varistor. Alternatively, the high-voltage pulse bypass unit can be placed independently outside the AC / DC heating unit in a thermally decoupled manner and maintained electrically connected to the AC / DC heating unit through conductive components.

10. The overload protector as described in any one of claims 1 to 8, characterized in that, The high-voltage pulse bypass unit includes any one of a gas discharge tube, a solid discharge tube, a graphite discharge gap, and a spark gap; and / or, the DC operating voltage of the high-voltage pulse bypass unit is higher than the DC voltage withstand requirement designed for the overload protector.

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