Overload protector and power equipment

Abstract

The invention is applicable to the technical field of lightning protection, and provides an overload protector and electrical equipment, the overload protector is used for being connected between two poles of a power supply circuit, and thermal coupling does not exist between the overload protector and a protected piezoresistor; the overload protector comprises an over-temperature release, an alternating current and direct current heating module and a high-voltage pulse bypass module, and the over-temperature release is thermally coupled with the alternating current and direct current heating module. Or when the operating voltage of the protected piezoresistor drops and is lower than the peak voltage of the power grid due to deterioration of the protected piezoresistor, the current simultaneously flows through the over-temperature release and the alternating current and direct current heating module which are connected with the protected piezoresistor in series, so that the alternating current and direct current heating module is heated, and when the temperature of the alternating current and direct current heating module reaches the operating temperature of the over-temperature release, the over-temperature release and the alternating current and direct current heating module are started. And the over-temperature release generates action separation, and the overload protector is separated from the power supply, so that the protected piezoresistor is also disconnected from the power supply.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of lightning protection, and particularly relates to an overload protector and a power device. BACKGROUND

[0002] The industry standard "Low Voltage Surge Protective Device IEC61643-11_2011" of the lightning protector clearly stipulates in Article 5.12 "Failure mode of SPD" that the lightning protector must have two failure modes: one is "open circuit", and the other is "short circuit". The open circuit failure type SPD (voltage limiting surge protective device) must be configured with an over-temperature tripping mechanism, and the short circuit failure type SPD must be configured with a thermal short circuit mechanism.

[0003] In the discharge circuit of the traditional SPD or TMOV (thermally protected metal oxide varistor), a zinc oxide varistor (MOV, metal oxide varistor) is connected in series. After the tunnel burns through, if it cannot quickly disconnect from the power grid, a serious safety risk will be caused. SUMMARY

[0004] The application aims to provide an overload protector and a power device, and aims to solve the problem that after the tunnel of the pressure sensitive resistor of the traditional voltage limiting surge protective device burns through, if it cannot quickly disconnect from the power grid, a serious safety risk will be caused.

[0005] A first aspect of the embodiments of the application provides an overload protector, which is used to be connected to at least two terminals of a power supply between which a protected pressure sensitive resistor is connected; there is no thermal coupling between the overload protector and the protected pressure sensitive resistor; the overload protector comprises an over-temperature tripping device, an AC / DC heating module and a high-voltage pulse bypass module, the high-voltage pulse bypass module is connected in parallel to both ends of the AC / DC heating module, the over-temperature tripping device is connected in series with the heating module, and the over-temperature tripping device is thermally coupled with the AC / DC heating module; the AC / DC heating module has electrocaloric characteristics, and in the case that the AC / DC current causes the over-temperature tripping device to reach an action temperature, the over-temperature tripping device triggers a tripping separation action to cut off the electrical connection between the overload protector and the power supply.

[0006] In some embodiments, the AC / DC heating module comprises a current limiting element and a heating element, and the current limiting element and the heating element are connected in series.

[0007] In some embodiments, the current limiting element and the heating element are welded back to back, or the current limiting element and the heating element are spaced apart and arranged separately.

[0008] In some embodiments, the heating element includes a varistor valve or a thermistor valve; The current limiting element includes a positive temperature coefficient thermistor, the Curie temperature of which is higher than the operating temperature of the over-temperature trip unit; or the current limiting element includes a fixed resistor.

[0009] In some embodiments, the heating element includes a varistor valve, the varistor valve having a higher rate of temperature rise than the protected varistor.

[0010] In some embodiments, the over-temperature trip unit includes a movable metal elastic electrode at one end, the end of which is soldered to the surface electrode of the heating element by low-temperature solder, and the first end of which is used to connect to the protected varistor or the terminal of the power supply; the melting point temperature of the low-temperature solder corresponds to the operating temperature of the over-temperature trip unit.

[0011] In some embodiments, the AC / DC heating module and the high-voltage pulse bypass module form a core module, and the over-temperature trip unit further includes: The housing has a welding window, a connection position, and a separation position, and the core module and the metal elastic electrode are mounted on the housing; The remote signaling switch includes two remote signaling switch contacts mounted on the housing; An arc-extinguishing slider and a pull-out spring are provided, the pull-out spring being movably mounted on a sliding guide rail of the housing; the metal elastic electrode includes a retaining section connected between an end and a beginning, the beginning of the metal elastic electrode extending to the outside of the housing, the retaining section being located outside the arc-extinguishing slider, and the end of the metal elastic electrode being soldered to the surface electrode of the heating element with low-temperature solder through the welding window, such that the retaining section holds the arc-extinguishing slider in the connection position and causes the arc-extinguishing slider to press against the remote signaling switch, thereby bringing the two remote signaling switch contacts into contact; and The pull-out spring is used to generate an elastic restoring force to drive the arc-extinguishing slider to move toward the separation position, pull the arc-extinguishing slider to reach and cover the welding window, so as to be placed between the surface electrode of the heating element and the end of the metal elastic electrode, and to separate the two remote signaling switch contacts.

[0012] In some embodiments, there are two over-temperature trip units, namely a first over-temperature trip unit and a second over-temperature trip unit; there are two AC / DC heating modules, namely a first AC / DC heating module and a second AC / DC heating module; the high-voltage pulse bypass module includes a switching device with three electrodes, and the overload protector includes a first external electrode, a second external electrode, and a third external electrode; The first over-temperature tripping device and the first AC-DC heating module are connected in series between the first external electrode and the second external electrode, and form a first series connection node and a first current channel; the second over-temperature tripping device and the second AC-DC heating module are connected in series between the first external electrode and the third external electrode, and form a second series connection node and a second current channel, and the second external electrode and the third external electrode form a third current channel, and the first current channel, the second current channel and the third current channel form a Y-shaped lightning protection circuit; the three electrodes of the switch device are connected with the first series connection node, the first external electrode and the second series connection node respectively. The first external electrode is connected with the first terminal of the power supply through at least one first voltage-dependent resistor; the second external electrode is connected with the second terminal of the power supply through at least one second voltage-dependent resistor; and the third external electrode is connected with the third terminal of the power supply through at least one third voltage-dependent resistor. In some embodiments, the high-voltage pulse bypass module comprises a switch device, which is a gas discharge tube, a solid discharge tube or a discharge gap, the lightning current level of the switch device is higher than the lightning current level of the protected voltage-dependent resistor, and the DC operating voltage of the switch device is higher than the DC voltage tolerance value of the overload protector.

[0013] The second aspect of the embodiments of the present application provides a power device, which comprises a power input interface, at least one voltage-dependent resistor and an overload protector as described above, the overload protector and the voltage-dependent resistor are connected between at least two terminals of the power input interface.

[0014] Compared with the prior art, the embodiments of the present application have the beneficial effect that when the voltage fluctuation of the power supply (such as a power grid or a power generation device) causes the voltage to exceed the DC operating voltage of the protected voltage-dependent resistor (i.e. the protected voltage-dependent resistor), or the DC operating voltage of the protected voltage-dependent resistor decreases due to degradation and is lower than the peak voltage of the power supply, the power supply will generate a DC or AC current in the protected voltage-dependent resistor, and the AC-DC current flows through the over-temperature tripping device and the AC-DC heating module in series with the protected voltage-dependent resistor, so that the AC-DC heating module generates a temperature rise, when the temperature of the AC-DC heating module reaches the operating temperature of the over-temperature tripping device, the over-temperature tripping device operates and separates, disconnecting the entire overload protector from the power supply, so that the protected voltage-dependent resistor is also disconnected from the power supply, preventing the protected voltage-dependent resistor from being damaged at high temperature or even burning due to the continuous AC-DC current overload. BRIEF DESCRIPTION OF DRAWINGS

[0015] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings needed in the embodiments will be briefly introduced as follows. Obviously, the drawings in the following description only relate to some embodiments of the present application, and for those skilled in the art, other drawings can be obtained based on these drawings without any creative effort.

[0016] Figure 1 is a lightning protection circuit schematic diagram provided by the prior art; Figure 2 is a module schematic diagram of the overload protector for the lightning protection circuit according to an embodiment of the present application; Figure 3 is a module schematic diagram of the overload protector for the lightning protection circuit according to an embodiment of the present application; Figure 4 is a module schematic diagram of the overload protector for the lightning protection circuit according to an embodiment of the present application; Figure 5 is a circuit schematic diagram of the overload protector for the lightning protection circuit according to an embodiment of the present application; Figure 6 is a structure schematic diagram of the overload protector according to an embodiment of the present application; Figure 7 is a structure schematic diagram of the core module of the overload protector according to an embodiment of the present application; Figure 8 is a structure schematic diagram of the overload protector according to an embodiment of the present application; Figure 9 is a structure schematic diagram of the overload protector according to an embodiment of the present application; Figure 10 is a circuit schematic diagram of the overload protector for the lightning protection circuit according to an embodiment of the present application; Figure 11 is a circuit schematic diagram of the overload protector for the lightning protection circuit according to an embodiment of the present application; Figure 12 is a structure schematic diagram of the core module of the overload protector according to an embodiment of the present application; Figure 13 is a structure schematic diagram of the overload protector according to an embodiment of the present application; Figure 14 is a circuit schematic diagram of the overload protector for the lightning protection circuit according to an embodiment of the present application. DETAILED DESCRIPTION

[0017] In order to make the technical problems, technical solutions and beneficial effects of the present application more clearly understood, the present application will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and not intended to limit the present application.

[0018] It should be noted that when a component is referred to as being "fixed to" or "set on" another component, it can be directly on or indirectly on that other component. When a component is referred to as being "connected to" another component, it can be directly connected to or indirectly connected to that other component.

[0019] It should be understood that the terms "length", "width", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this application and simplifying the 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. Therefore, they should not be construed as limitations on this application.

[0020] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, "multiple" means two or more, unless otherwise explicitly specified.

[0021] In traditional SPD discharge circuits, the varistor connected to the AC power supply exhibits 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 mains 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 mains voltage, 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] The pressure sensitive resistor entering the low resistance state is mostly in the "tunnel type burn-through" condition, that is, the two electrodes of the pressure sensitive resistor are connected by a needle hole-shaped low resistance channel. When the power grid generates current on the failed pressure sensitive resistor, the current will only flow through this low resistance channel and will not flow through other high resistance areas. The tunnel of carbonized zinc oxide that is burned black does not present a complete short circuit state of zero resistance, but a low resistance state from zero point several ohms to several hundred ohms. After the tunnel burn-through of the pressure sensitive resistor, if it cannot quickly disconnect from the power grid, the following serious safety risks will occur: 1. The rated power grid voltage is loaded on a low resistance channel of only zero point several ohms to several hundred ohms, which may produce tens to hundreds of amperes of alternating current, causing arc spraying or explosion of the pressure sensitive resistor.

[0025] 2. The failed short-circuit pressure sensitive resistor can no longer withstand the impact of lightning current. The several thousand amperes of lightning current concentrated in the small low resistance tunnel will cause the channel to heat up sharply, and the thermal stress may cause the pressure sensitive resistor to burst instantly. The fragments of the pressure sensitive resistor with conductive ability may threaten the safety of electrical equipment.

[0026] In order to reduce the high temperature fire safety risk caused by the short circuit failure of the pressure sensitive resistor, manufacturers configure overload tripping devices for the pressure sensitive resistor. There are the following ways for the common pressure sensitive resistor overload tripping device: 1. Series current fuse or air circuit breaker (Miniature Circuit Breaker, MCB) is connected outside the pressure sensitive resistor. When the pressure sensitive resistor fails and shorts and generates a large fault current, the fuse is melted or the air circuit breaker is opened to prevent the current from continuously heating the pressure sensitive resistor.

[0027] 2. The pressure sensitive resistor is connected in series with an external backup protector (Special Circuit Breaker, SCB), so that the fault current flows through the electromagnetic coil of the SCB, and the electromagnetic force pushes the contact switch apart to cut off the pressure sensitive resistor fault current greater than 3A.

[0028] 3. Temperature fuse or solder alloy fuse is mounted on the surface of the pressure sensitive resistor and connected in series. When the pressure sensitive resistor overheats, the low temperature fuse is melted to cut off the connection between the pressure sensitive resistor and the AC power grid. 4. A flexible metal electrode is provided on the surface of the pressure sensitive resistor, and the flexible electrode and the pressure sensitive resistor are welded together by low temperature solder. When the pressure sensitive resistor overheats, the low temperature solder point is melted, the flexible electrode is separated from the pressure sensitive resistor, and the fault current is cut off. 5. Based on the above-mentioned fourth design, a mechanical mechanism with a pull-out spring and an arc-extinguishing slider is added to improve the reliability of the tripping mechanism and increase the failure remote signaling alarm function.

[0029] The above-mentioned five types of AC overload tripping designs have certain safety hazards, and their respective defects are as follows: The first design, to ensure that lightning impact does not act, the AC operating current of the current fuse and the air switch is usually greater than 10A, so it cannot cut off the fault current below 10A. The second design is limited by the minimum drive current of the electromagnetic coil, and cannot act to cut off the fault current below 3A. The third, fourth and fifth designs rely on the melting of low-temperature alloy to generate tripping action, and the safety depends on the time delay action time of the over-temperature tripping mechanism. In the case of high TOV power frequency current impact (such as 10A or more), the voltage-dependent resistor often burns through to a short circuit state very quickly. Due to the time delay of heat conduction, the over-temperature tripping mechanism may not act to separate, and the short circuit current of the power grid increases to tens or even hundreds of amperes, which makes the voltage-dependent resistor face the safety risks of high-temperature spouting, explosion, and ignition of the encapsulated plastic.

[0030] The applicant found that excessive power frequency current makes the voltage-dependent resistor heat up too quickly, so that the overload tripping device cannot act to separate in time before the voltage-dependent resistor is burned through to a short circuit, causing the voltage-dependent resistor to be impacted by the super-high power grid short circuit current and generate dangerous high temperature and heat. This is the main safety risk of traditional thermal protection type voltage-dependent resistor. To eliminate this risk, the problem of excessive power frequency current impact on the voltage-dependent resistor needs to be solved. The size of the power frequency current depends on the total impedance of the current loop, including the power supply internal resistance, the equivalent resistance of the voltage-dependent resistor, and the grounding resistance (if the voltage-dependent resistor is connected to the protective earth). The power supply internal resistance 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 to rely on the voltage-dependent resistor itself.

[0031] On the other hand, the traditional TMOV is applied to the photovoltaic high-voltage DC port, and due to the high voltage and the difficulty of breaking DC arc, a Y-type circuit composed of three thermal tripping voltage-dependent resistors is usually used for lightning protection, and a typical circuit structure is as follows: Figure 1As shown, a total of 12 TMOVs (TMOV1-12) are shown in the figure. The Y-type circuit is characterized in that each current channel is composed of two series-connected TMOVs. When one of the TMOVs fails due to lightning impact and is short-circuited, the photovoltaic voltage is loaded across the non-failed TMOV, so that the TMOV generates a voltage overload rate of 1.1-1.3 times, and a direct current of 0.1-1 A is generated on the varistor, which is relatively small, and can make the varistor heat at a relatively low temperature rise rate, so that the heat has sufficient time to conduct to the movable welding point of the tripping device and melt the low-temperature solder thereon, so that the tripping device can act to separate before the varistor overheats and short-circuits, thereby avoiding the generation of dangerous varistor short-circuit current, and ensuring the safety of the failed TMOV varistor. However, for an inverter with multiple photovoltaic string inputs as shown in Figure 1 A plurality of TMOVs are required. Since the TMOV with an arc extinguishing mechanism and a remote signaling switch has a relatively complex structure and a relatively high processing cost, such a lightning protection scheme will bring a relatively large cost pressure.

[0032] Figures 2 to 4 A principle schematic diagram of an overload protector provided by an embodiment of the present application is shown. For ease of illustration, only parts related to the present embodiment are shown, and details are as follows: An overload protector 100 is used to be connected to at least two terminals 11 and 12 of a power supply between which a protected varistor MOV1 is connected, wherein the first; there is no thermal coupling between the overload protector 100 and the protected varistor MOV1; the overload protector 100 comprises an AC / DC heating module 20, an over-temperature tripping device 30 and a high-voltage pulse bypass module 40, the high-voltage pulse bypass module 40 is connected in parallel across the AC / DC heating module 20, the over-temperature tripping device 30 is connected in series with the AC / DC heating module 20, and the over-temperature tripping device 30 is thermally coupled to the AC / DC heating module 20 (as shown by the dashed line in Figures 2-4 The AC / DC heating module 20 has electrocaloric characteristics. When the AC / DC heating module 20 is heated to the action temperature of the over-temperature tripping device 30, the over-temperature tripping device 30 is triggered to generate a tripping separation action, and the electrical connection between the overload protector 100 and the power supply is cut off.

[0033] The two terminals 11 and 12 of the power supply include a first terminal 11 and a second terminal 12. Exemplarily, the first terminal 11 and the second terminal 12 are respectively a live wire and a neutral wire, or respectively a positive electrode and a negative electrode. Figures 2 to 4 Three connection modes of the overload protector 100 and the protected varistor MOV1 connected to the power supply are shown. Among them, Figure 2In the example, the protected MOV 1 is connected to the first terminal 11, the over-temperature tripping device 30 is connected to the protected MOV 1, and the AC / DC heating module 20 is connected in series between the over-temperature tripping device 30 and the second terminal 12. Figure 3 In the example, the protected MOV 1 is connected to the first terminal 11, the AC / DC heating module 20 is connected to the protected MOV 1, and the over-temperature tripping device 30 is connected in series between the over-temperature tripping device 30 and the second terminal 12. Figure 4 In the example, the protected MOV 1 is connected to the second terminal 12, the AC / DC heating module 20 is connected to the protected MOV 1, and the over-temperature tripping device 30 is connected in series between the over-temperature tripping device 30 and the first terminal 11.

[0034] The working principle of the lightning protection scheme of the thermal separation type overload protector 100 of the embodiment is to provide a tripping separation action by means of the overload protector 100 which is used in series with the protected MOV 1 in an electrical manner but is independent of the protected MOV 1 in structure. The overload protector 100 is only in electrical communication with the protected MOV 1 without thermal coupling, and thus can be called a thermal separation type overload protector 100 to distinguish from the traditional tripping device which is in thermal coupling type TMOV and closely attached to the surface of the MOV.

[0035] The high-voltage pulse bypass module 40 provides a low-resistance discharge channel for the lightning high-voltage pulse, which can reduce the residual voltage of lightning and reduce the interference of the AC / DC heating module 20 on the lightning protection effect. The DC operating voltage of the high-voltage pulse bypass module 40 should be higher than the maximum voltage of the working power grid to prevent the high-voltage pulse bypass module 40 from being mistakenly triggered by the power grid.

[0036] When the voltage fluctuation of the power supply (such as a power grid or a power generation device) causes the voltage to exceed the DC operating voltage of the protected MOV 1, or the DC operating voltage of the protected MOV 1 decreases due to degradation and is lower than the peak voltage of the power supply, the power supply will generate a DC or AC current in the protected MOV 1, and the current will flow through the over-temperature tripping device 30 and the AC / DC heating module 20 connected in series with the protected MOV 1, causing the AC / DC heating module 20 to generate a temperature rise. When the temperature of the AC / DC heating module 20 reaches the operating temperature of the over-temperature tripping device 30, the over-temperature tripping device 30 will act to separate, disconnecting the entire overload protector 100 from the power supply, so that the protected MOV 1 is also disconnected from the power supply, preventing the protected MOV 1 from being damaged by the continuous AC / DC current overload and even burning.

[0037] Please refer to Figure 5In one embodiment, the high-voltage pulse bypass module 40 includes a switching device T1, which is a gas discharge tube, a solid discharge tube or a discharge gap (e.g. a graphite discharge gap, a spark gap), the lightning current flow level of the switching device T1 is higher than the lightning current flow level of the protected MOV 1, and the DC operating voltage of the switching device T1 is higher than the DC voltage withstand value of the overload protector 100.

[0038] Please refer to Figure 5 In one embodiment, the AC / DC heating module 20 includes a current-limiting element R2 and a heating element R1, which are connected in series.

[0039] The overload protector 100 does not need to be in contact or thermally coupled with the protected MOV 1, but a separate heating element R1 is added inside the overload protector 100, which is in electrical series with the externally protected MOV 1.

[0040] The current-limiting element R2 is used to greatly reduce the surge current through the current-limiting element R2 when the fault voltage is high, so as to avoid the instantaneous damage of the heating element R1 and the externally connected protected MOV 1 by the excessive surge current.

[0041] In one embodiment, the current-limiting element R2 and the heating element R1 are welded back-to-back, and the heat generated by the current flowing through the current-limiting element R2 can be conducted to the heating element R1 to increase the temperature rise speed.

[0042] In one embodiment, the current-limiting element R2 and the heating element R1 are spaced apart and separately arranged (please refer to Figure 9 It can prevent the heating element R1 from conducting heat to the current-limiting element R2, which affects its performance and improves the stability of the circuit.

[0043] In one embodiment, the heating element R1 includes a varistor or a thermistor.

[0044] In one embodiment, the current-limiting element R2 includes a positive temperature coefficient thermistor, and the Curie temperature of the positive temperature coefficient thermistor is higher than the operating temperature of the over-temperature tripper 30. In one embodiment, the current-limiting element R2 includes a fixed resistor. For example, the resistance of the current-limiting element R2 is more than several hundred ohms.

[0045] Since the positive temperature coefficient thermistor has not only a current-limiting effect but also an over-temperature self-protection effect, it is safer than a resistor and has a smaller size. Considering the high requirement for thermal action sensitivity, the AC / DC heating module 20 can use a varistor in series with a positive temperature coefficient thermistor.

[0046] In one embodiment, the heating element R1 comprises a pressure-sensitive resistor valve piece, and the temperature rising rate of the pressure-sensitive resistor valve piece is higher than that of the protected pressure-sensitive resistor MOV1. For example, the equivalent heat capacity of the heating element R1 should be much smaller than that of the protected pressure-sensitive resistor MOV1, so the unit volume of the heating element R1 generates more heat power than the protected pressure-sensitive resistor MOV1 under the same current, and the temperature rising rate of the heating element R1 is always higher than that of the protected pressure-sensitive resistor MOV1. Thus, the heating element R1 can reach the action temperature before the protected pressure-sensitive resistor MOV1.

[0047] For example, if the temperature rising rate ratio of the pressure-sensitive resistor valve piece of the heating element R1 to the protected pressure-sensitive resistor MOV1 is K, then K=K1 / K2=(Uv1*V2) / (Uv2*V1), wherein K1 represents the temperature rising rate of the pressure-sensitive resistor valve piece of the heating element R1, K2 represents the temperature rising rate of the protected pressure-sensitive resistor MOV1, Uv1 is the direct current action voltage of the pressure-sensitive resistor valve piece of the heating element R1, Uv2 is the direct current action voltage of the protected pressure-sensitive resistor MOV1, V1 is the equivalent heat capacity volume of the pressure-sensitive resistor valve piece of the heating element R1, and V2 is the equivalent heat capacity volume of the protected pressure-sensitive resistor MOV1. The action voltage Uv value is in direct proportion to the temperature rising rate, and the equivalent heat capacity volume V is in inverse proportion to the temperature rising rate (the equivalent heat capacity volume needs to consider the heat storage factors of the metal electrode welded on the valve piece and the encapsulating material). As long as the temperature rising rate ratio K is greater than 1, the temperature rising rate of the pressure-sensitive resistor valve piece of the heating element R1 is always higher than that of the protected pressure-sensitive resistor MOV1.

[0048] Please refer to Figure 5 In one embodiment, the overload protector 100 forms two external electrodes, i.e. a first electrode 101 and a second electrode 102, for connecting the terminals of the protected pressure-sensitive resistor MOV1 or the power supply.

[0049] Please refer to Figure 5 and Figure 6 In one embodiment, the over-temperature tripping device 30 comprises a metal elastic electrode 301 with a movable end, and the movable end of the metal elastic electrode 301 is welded to the surface electrode 201 of the heating element R1 by a low-temperature solder 302, and the leading end of the metal elastic electrode 301 is used for connecting the terminals of the protected pressure-sensitive resistor MOV1 or the power supply; the melting point temperature of the low-temperature solder 302 corresponds to the action temperature of the over-temperature tripping device 30. It can be understood that the leading end of the metal elastic electrode 301 is one of the external electrodes of the overload protector 100.

[0050] For example, the metal elastic electrode 301 is welded on the surface electrode 201 of the heating element Rl by low temperature solder 302 with a melting point of 140°C, so that the temperature of the protected MOVl in series with the over temperature tripping device 30 will not exceed 140°C after the over temperature tripping device 30 is actuated to disconnect and cut off the current loop of the entire circuit, thus achieving the purpose of thermal protection of the protected MOVl by the independent overload protector 100.

[0051] Please refer to Figure 5 、 Figures 7-9 In one embodiment, the AC / DC heating module 20 and the high voltage pulse bypass module 40 form a core module 105, and the over temperature tripping device 30 further comprises: a housing 310 having a welding window 307, a connecting position 311 and a disconnecting position 312, and the core module 105 and the metal elastic electrode 301 are installed on the housing 310; a remote signaling switch 320 comprising two remote signaling switch contacts 321, 322 installed on the housing 310; an arc extinguishing slide 330 and a pull-out spring 340 movably installed on a sliding guide 314 of the housing 310; the metal elastic electrode 301 comprises a holding section 301C connected between a tail end 301B and a head end 301A, the head end 301A of the metal elastic electrode 301 extends to the outside of the housing 310, the holding section 301C is located outside the arc extinguishing slide 330, the tail end 301B of the metal elastic electrode 301 is welded with the surface electrode 201 of the heating element Rl by the low temperature solder 302 through the welding window 307, so that the holding section 301C holds the arc extinguishing slide 330 on the connecting position 311 and presses the arc extinguishing slide 330 against the remote signaling switch 320 to contact the two remote signaling switch contacts 321, 322; and the pull-out spring 340 is used to form an elastic restoring force to drive the arc extinguishing slide 330 to move towards the disconnecting position 312, pull the arc extinguishing slide 330 to cover the welding window 307 to place the tail end 301B of the metal elastic electrode 301 and the surface electrode 201 of the heating element Rl, place the surface electrode 201 of the heating element Rl and the tail end 301B of the metal elastic electrode 301, block the electrical connection between the tail end 301B of the metal elastic electrode 301 and the surface electrode 201 of the heating element Rl, and separate the two remote signaling switch contacts 321, 322.

[0052] The ends 301B of the metal elastic electrode 301 are welded to the surface electrode 201 of the heating element R1 by low-temperature soldering tin 302 with a melting point of 140°C. After the over-temperature tripping device 30 separates and cuts off the current loop of the entire circuit, the temperature of the protected MOV1 will not exceed 140°C, thereby achieving the purpose of thermal protection of the protected MOV1 by the independent overload protector 100.

[0053] The over-temperature tripping device 30 can be welded to the surface electrode of the MOV or the surface electrode of the thermistor. Considering that the temperature rise speed of the MOV is much higher than that of the thermistor under a small current of milliamperes, i.e., the thermal sensitivity of the MOV is higher under a small current, the metal elastic electrode 301 is generally welded to the surface electrode 201 of the MOV.

[0054] In one embodiment, the AC / DC heating module 20 and the parallel high-voltage pulse bypass module 40 are loaded into the shell 310, and the over-temperature tripping device 30, the auxiliary arc extinguishing slider 330, and the remote signaling switch 320 are added to form a complete single-channel (referring to the connection of two electrodes of a power supply) overload protector 100 as shown in Figure 7

[0055] The assembly process of the single-channel overload protector 100 is as follows: 1) The current-limiting element R2 and the heating element R1 are stacked and connected in series through a flat electrode 303, and the switch device T1 is connected in parallel through two flat electrodes 304 and 305 to form the core module 105 of the overload protector 110. It can be understood that the first end 301A of the metal elastic electrode 301 extends to the outside of the shell 310, i.e., the flat electrode 305 and the first end 301A of the metal elastic electrode 301 are connected or serve as the first external electrode 101 and the second external electrode 102, respectively, and the flat electrode 304 includes the surface electrode 201.

[0056] 2) The core module 115 is loaded into the pit 306 of the plastic middle shell 313, and is fixed with the middle shell 313 by pouring epoxy resin, and only the welding area of the surface electrode 201 of the heating element R1 is exposed at the welding window 307 of the pit 306 for welding the end 301B of the metal elastic electrode 301; 3) The two switch contacts 321 and 322 of the remote signaling switch 320 are loaded into the slot of the plastic middle shell 313. ​

[0057] 4)Put the arc-extinguishing slider 330 into the sliding guide 314 of the plastic middle shell 313 and slide to the rightmost position, i.e. the connecting position 311, so that the lower end of the arc-extinguishing slider 330 presses against the movable switch contact 321 of the remote signaling switch 320 and touches the fixed switch contact 322 of the remote signaling switch 320, and the two remote signaling switch contacts 321 and 322 form a connected state; 5)Insert the first outer terminal 101 of the overload protector 100 into the positioning hole of the plastic middle shell 313, press the metal elastic electrode 301 into the pre-opened solder window 307 of the plastic middle shell 313 and against the surface electrode 201 of the core module 105, and then use a soldering iron to reliably solder them together by low-temperature alloy soldering; 6)Solder the first outer terminal 101 and the flat electrode 305 of the core module 115 together with high-temperature soldering; 7)Press the end hooks of the two pull-out springs 340 into the buckle position columns of the arc-extinguishing slider 330 and the plastic middle shell 313 respectively, so that the arc-extinguishing slider 330 is tensioned by the pull-out springs 340; 8)Put the plastic outer shell (not shown) into the plastic middle shell 310, and the assembly process of the overload protector 100 is completed.

[0058] The working process of the single-channel overload protector 100 is as follows: The overload protector 100 is used in series with the protected MOV 1. Under normal circumstances, the operating voltage of the protected MOV 1 is higher than the peak voltage of the power grid, and no current flows through the protected MOV 1 and the overload protector 100, so the overload protector 100 does not generate heat.

[0059] After the protected MOV 1 is damaged, its operating voltage will gradually and continuously decrease, and when it is significantly lower than the peak voltage of the power grid, a continuous current will flow through the protected MOV 1 and the overload protector 100, and the protected MOV 1 and the internal MOV (i.e. the heating element R1) of the overload protector 100 will generate heat. However, the volume of the internal MOV of the overload protector 100 is much smaller than that of the protected MOV 1, so the temperature rise rate of the internal MOV of the overload protector 100 is higher than that of the protected MOV 1. When the internal MOV of the overload protector 100 reaches 140°C, the low-temperature solder 302 of the over-temperature tripping device 30 softens, causing the end 301B of the metal elastic electrode 301 of the over-temperature tripping device 30 to rapidly separate from the solder window 307 under the tension of the spring, and the arc-extinguishing slider 330 is pulled out of the sliding guide 314 under the tension of the spring. At this time, the movable switch contact 321 of the remote signaling switch 320 is separated from the fixed switch contact 322, and the overload protector 100 is in a disconnected state. Figure 8The rightmost (i.e. connection bit 311) slide to the leftmost (i.e. separation bit 312), the slider covers the welding window 307, preventing the end 301B of the metal elastic electrode 301 of the thermal trip unit 30 from electrically connecting with the surface electrode 201 of the core module 1153, cutting off the current loop of the protected pressure sensitive resistor MOV1, preventing it from continuously heating. At the same time, after the arc extinguishing slider 330 reaches the separation bit 312, the movable switch contact 321 of the remote signaling switch 320 originally pressed by the arc extinguishing slider 330 is released, the movable switch contact 321 is popped up under the action of its own elastic force and separated from the fixed switch contact 322, changing from the normal closed communication state to the open circuit state, completing the remote signal alarm function.

[0060] Example 1: For Figures 7 to 9 As shown, the single-channel overload protector 100, if applied to U CPV 1200Vdc photovoltaic DC port, and adopts Figure 5 or Figure 10 The lightning protection circuit shown, the selection of each element in the overload protector 100 can be arranged as follows: Switching device T1: select the diameter of 8mm, length of 6mm, DC operating voltage of 1000Vdc, rated discharge current of 20KA two-pole SMD patch type gas discharge tube.

[0061] Heating element R1: use a diameter of 10mm, thickness of 1mm, pressure sensitive voltage of 90Vdc patch type pressure sensitive resistor silver valve.

[0062] Current limiting element R2: select a diameter of 8mm, thickness of 2.5mm, room temperature resistance of 1KΩ, Curie temperature of 160°C patch type thermistor silver valve.

[0063] Low temperature solder 302: Sn42Bi58 low temperature alloy solder with a melting point of 138°C should be selected for welding the movable terminal of the trip unit.

[0064] The overload release 100 made of the above elements is tested for overload failure simulation with a protected MOV 1 (for example, a 25D821K MOV with a valve diameter of 25 mm, a valve thickness of 4 mm, a breakdown voltage of 820 Vdc, and a lightning current of 10 KA), and the test is connected according to the IEC-61643-31_2019 standard. That is, the protected MOV 1 and the overload protector 100 are connected in series, and a 1200 Vdc DC voltage is applied to both until they are separated. The test results are as follows: after the voltage is loaded, the overload protector 100 operates and releases in 5 seconds, the maximum DC current is 150 mA, and the maximum temperature of the protected MOV 1 is 115°C. The operation time and the maximum temperature of the MOV both meet the requirements of the IEC-61643-31_2019 standard. If the test is performed according to the IEC-61643-31_2019 standard, the overload protector 100 is not released, the remote communication switch 320 remains closed, and the MOV is not damaged, which meets the requirements of the IEC-61643-31_2019 standard. Figure 10 The protected MOV 1 and MOV 2 are connected in series with the overload protector 100, and the 8 / 20 uS lightning generator is used for action load lightning test (the connection and 1200 Vdc power supply are loaded according to the IEC-61643-11_2011 standard). After 15 times of 10 KA lightning test (divided into 3 groups, 5 times each, and 60 seconds interval), the overload protector 100 does not release, the remote communication switch 320 remains closed, and the MOV is not damaged, which meets the requirements of the IEC-61643-11_2011 standard.

[0065] Reference Figure 10 In one embodiment, for the protection of a three-terminal power supply input, the first terminal 11 and the second terminal 12, and the first terminal 11 and the third terminal 13 are respectively connected to an independent overload protector 100. Among them, the first terminal 11, the second terminal 12, and the third terminal 13 of the three-terminal power supply are respectively connected in series with the protected MOV 1, MOV 2, and MOV 3. The two overload protectors 100 can simultaneously protect the three MOVs 1, 2, and 3. The MOV 1 and the MOV 2 are respectively connected to the first external electrode 101 and the second external electrode 102 of the first overload protector 110, and the MOV 1 and the MOV 3 are respectively connected to the first external electrode 101 and the second external electrode 102 of the second overload protector 110.

[0066] In this embodiment, the two overload protectors 110 work independently and protect different MOVs. When one of them fails, it can be replaced individually, saving costs. In addition, compared with the conventional overvoltage protection mode of a three-terminal power supply input, three SPDs or TMOVs with over-temperature release mechanisms are required. In this embodiment, at least one over-temperature release mechanism is saved, reducing costs and the required space.

[0067] refer to Figures 11 to 13 In another embodiment, when used to protect the circuit of a three-terminal power input, the overload protector 100 includes a first external electrode 101, a second external electrode 102, and a third external electrode 103. These are respectively used to connect the live wire, neutral wire, and ground wire, or the positive terminal, negative terminal, and ground wire of the three-terminal power supply.

[0068] The overload protector 100 has two over-temperature trip units, namely the first over-temperature trip unit 31 and the second over-temperature trip unit 32; there are two AC / DC heating modules, namely the first AC / DC heating module 21 and the second AC / DC heating module 22; the high-voltage pulse bypass module 40 includes a switching device T2 with three electrodes; the first over-temperature trip unit 31 and the first AC / DC heating module 21 are connected in series between the first external electrode 101 and the second external electrode 102, forming a first series node; the second over-temperature trip unit 32 and the second AC / DC heating module 22 are connected in series between the first external electrode 101 and the third external electrode 103 and the first current channel, forming a second series node and a second current channel; and the second external electrode 102 and the third external electrode 103 form a third current channel, and the first current channel, the second current channel and the third current channel form a Y-type surge protection circuit. The three electrodes of the switching device T2 are connected to the first series node, the first external electrode 101, and the second series node, respectively. The first external electrode 101 is connected to the first terminal 11 of the power supply through at least one first varistor MOV1. The second external electrode 102 is connected to the second terminal 12 of the power supply through at least one second varistor MOV2. The third external electrode 103 is connected to the third terminal 12 of the power supply through at least one third varistor MOV3. The first varistor MOV1, the second varistor MOV2, and the third varistor MOV3 are the varistors being protected. The Y-type surge protection circuit is suitable for typical photovoltaic DC ports.

[0069] In this embodiment, the overload protector 100 for the three-terminal power input is made into a single unit, saving costs.

[0070] The assembly process of the above three-channel overload protector 100 is as follows: 1) Assemble the switching device T2, two thermistors R2, two varistors R1, and four flat electrodes according to... Figure 12 The circuit schematic shown is overlaid and soldered together to form the core module 106 of the protector. In practice, it can be considered as combining two... Figure 7One side of the flat electrodes 305 of the core module 105 is shown back-to-back welded. Two of the flat electrodes 305 are replaced with one, and the flat electrodes 305 will be welded with the middle electrode of the switching device T2 and the first outer electrode 101, and the two end electrodes of the switching device T2 will be welded with the surface electrodes 201 of the two heating elements R1 respectively. The surface electrodes 201 of the two heating elements R1 are connected to the second outer electrode 102 of the first over-temperature release 31 and the third outer electrode 103 of the second over-temperature release 32 respectively.

[0071] 2) The core module 106 is installed in the pit 306 (see Figure 9 ) of the plastic middle shell 313, the first end 301A of the metal elastic electrode 301 of the first over-temperature release 31 is connected to the second outer electrode 102, and the first end 301A of the metal elastic electrode 301 of the second over-temperature release 32 is connected to the third outer electrode 103. The core module 106 and the middle shell 313 are fixed together with the epoxy resin, and only the welding area of the surface electrode 201 of the heating element R1 is exposed at the window 307 for welding the second end 301B of the metal elastic electrode 301; 3) The four switch contacts of the two sets of remote signaling switches 320 are installed in the slot positions of the plastic middle shell 313 respectively; 4) The two arc extinguishing sliders 330 are installed in the sliding guide rails 314 of the plastic middle shell 313 respectively and are slid to the connecting position 311, so that the lower end of the arc extinguishing slider 330 tightly presses the movable switch contact 321 of the remote signaling switch 320 and touches the fixed switch contact 322 of the remote signaling switch 320, forming a connected state; 5) The first outer terminal 101 is inserted into the positioning hole of the plastic middle shell 313, the two metal elastic electrodes 301 are pressed into the pre-opened welding window 307 of the plastic middle shell 313 and abut against the two surface electrodes 201 of the core module 106, and then the two are welded together using low-temperature alloy solder at 140°C; 6) The end hooks of the four pull-out springs 340 are pressed into the buckle position column of the arc extinguishing slider 330 and the buckle position column 315 of the plastic middle shell 313, so that the arc extinguishing slider 330 is tensioned by the pull-out spring 340; 7) The plastic outer shell (not shown) is sleeved on the plastic middle shell 313, and the assembly process of the three-channel overload protector 100 is completed.

[0072] The three-channel overload protector 100 can form a lightning protection circuit as Figure 5 shown, and the working process of the circuit is as follows: The first terminal 11, the second terminal 12 and the third terminal 13 of the three-terminal power supply are respectively connected in series with the protected varistors MOV1, MOV2 and MOV3, and the first external electrode 101, the second external electrode 102 and the third external electrode 103 of the three-channel overload protector 100 are respectively connected in series with the protected varistors MOV1, MOV2 and MOV3. Under normal circumstances, the operating voltage of the protected varistors MOV1, MOV2 and MOV3 is higher than the peak voltage of the power grid, and no current flows through the protected varistors MOV1, MOV2 and MOV3 and the overload protector 100, so the overload protector 100 does not generate heat.

[0073] After any one of the protected varistors MOV1, MOV2 and MOV3 (for example, MOV1) is damaged and becomes a low resistance or short circuit state, it will cause the power supply voltage (for example, the photovoltaic cell voltage) to be higher than the operating voltage of the current loop composed of the remaining varistors (MOV2 and MOV3) in the circuit, thereby generating a continuous direct current, and the protected varistors MOV2 and MOV3 and the heating element R1 inside the overload protector 100 will generate heat, but the volume of the heating element R1 is much smaller than that of the protected varistors MOV2 and MOV3. Therefore, the heating element R1 has a higher temperature rise rate than the protected varistors MOV2 and MOV3. After the heating element R1 reaches 140°C, the low-temperature solder 302 at the end 301B of the metal elastic electrode 301 softens, causing the metal elastic electrode 301 to quickly separate from the welding window 307 under the tension of the spring 340, and the arc extinguishing slider 330 slides from the connected position 311 to the separated position 312 under the tension of the spring 340. The slider covers the welding window 307, preventing electrical communication between the metal elastic electrode 301 and the surface electrode 201 of the core module 106, cutting off the current loop of the protected varistors MOV1, MOV2 and MOV3, and preventing them from continuously generating heat. At the same time, after the arc extinguishing slider 330 slides to the separated position 312, the movable switch contact 321 of the remote signaling switch 320 that was pressed by the arc extinguishing slider 330 is released, the movable switch contact 321 is popped up under the action of its own elastic force and separates from the fixed switch contact 322, changing from a normally closed communication state to an open open state, and completing the remote signal alarm function.

[0074] Example 2, For Figures 12 to 13 The three-channel overload protector 100 shown in FIG. 1 is applied to a U CPV The photovoltaic DC port is 1200Vdc, and the lightning protection circuit shown in FIG. 2 is used. Figure 11 The selection of each element in the overload protector 100 can be arranged as follows: Switching device T2: a three-pole SMD patch type gas discharge tube with a diameter of 8 mm, a length of 10 mm, a direct current operating voltage of 1000 Vdc, and a rated discharge current of 20 KA.

[0075] Heating element R1: a patch type silver printed varistor with a diameter of 10 mm, a thickness of 1 mm, and a pressure sensitive voltage of 90 Vdc.

[0076] Current limiting element R2: a patch type silver printed thermistor with a diameter of 8 mm, a thickness of 2.5 mm, a normal temperature resistance of 1 KΩ, and a Curie temperature of 160°C.

[0077] Low temperature solder 302: a low temperature alloy solder with a melting point of 138°C of Sn42Bi58, used for soldering the movable terminal of the release.

[0078] The overload release 100 sample made of the above elements, together with three protected MOV1, MOV2, and MOV3 (for example, 25D821K MOV, with a valve diameter of 25 mm, a valve thickness of 4 mm, a pressure sensitive voltage of 820 Vdc, and a lightning current of 10 KA, an epoxy encapsulated MOV) forms a lightning protection circuit as shown in Figure 11 The overload protection circuit is subjected to overload failure simulation test, and the test connection is carried out according to IEC-61643-31_2019 standard, that is, one of the protected MOV1 or MOV2 is short-circuited by copper wire, and then a 1200 Vdc direct current stabilized power supply is loaded between the first electrode 11 and the third electrode 13 until the release is separated. The test results show that: after voltage loading, the maximum direct current is 150 mA, the overload protector 100 acts to release in 5 seconds, and the maximum temperature of the protected MOV is 115°C. The action time and the maximum temperature of the protected MOV both meet the requirements of the IEC-61643-31_2019 standard. If the test is carried out according to Figure 11 The protected MOV and the overload protector 100 are connected in series, and the action load lightning test is carried out by using an 8 / 20uS lightning generator (the connection and loading of 1200 Vdc power supply are carried out according to IEC-61643-11_2011 standard). After 15 times of 10 KA lightning test (divided into 3 groups, 5 times for each group, and 60 S interval for each time), the overload protector 100 does not act to release, the remote signaling switch 320 remains closed, and the protected MOV is not damaged. The test results meet the requirements of the IEC-61643-11_2011 standard.

[0079] Please refer to Figure 14 , Two single-channel overload protectors 100 similar to Figure 10 are integrated into a plastic shell to form a lightning protection circuit as shown inFigure 11 The three-channel overload protector 100 shown in the T-shaped structure is more suitable for forming Figure 1 The Y-shaped circuit structure shown is applied to, for example Figure 14 The high-voltage photovoltaic DC port shown can replace the traditional Figure 1 Lightning protection circuit, which brings significant cost reduction and safety performance improvement to customer equipment.

[0080] The thermal separation type overload protector 100 does not need to exchange heat with the protected MOV1, MOV2, and MOV3, and only needs to be electrically connected to the protected MOV1, MOV2, and MOV3 according to the circuit shown, while the over-temperature tripping device 30 is arranged on the surface electrode 201 of the heating element R1, and the low-temperature solder 302 of the over-temperature tripping device 30 is melted by the heat of the heating element R1 to cause the over-temperature tripping device 30 to act and separate. Figure 14

[0081] The core elements of the overload protector 100 are the heating element R1 and the metal elastic electrode 301 of the over-temperature tripping device 30 welded on the surface of the heating element R1, and the other elements around it, such as the current limiting element R2, the switching device T1, T2, etc. are only auxiliary devices, such as the current limiting element R2 responsible for limiting the amplitude of the direct current, and the switching device T1, T2 providing a low-resistance pulse bypass channel for the heating element R1 to reduce the residual voltage of lightning strike. These two types of auxiliary devices do not need to have heat transfer between them and the heating element R1, so they can be freely placed anywhere, as long as they are electrically connected according to the circuit principle.

[0082] In the overload protector 100, the heating element R1, the current limiting element R2, the switching device T1, and the over-temperature tripping device 30, except that the over-temperature tripping device 30 must be in close contact with the heating element R1 for heat conduction, the rest of the elements can be freely placed, and can be welded on the circuit board as separate components for electrical connection with the PCB copper skin, or the above-mentioned several components can be integrated and welded together to form a compact integrated module.

[0083] ​The overload protector 100 is provided with two current channels, one is a direct current channel for providing a path for heating current, the channel has the characteristics of low starting voltage (such as 100Vdc~200Vdc), high equivalent resistance (such as several hundred ohms or more), and the volume is only several tenths of the protected MOV1, MOV2 and MOV3, the electric heating effect is obvious, and the temperature rise rate is much higher than that of the protected MOV1, MOV2 and MOV3; the other is a lightning impulse channel, the channel has the characteristics of high starting voltage, which can prevent direct current heating current from flowing through the channel, and presents a negative resistance characteristic, and the equivalent resistance is very low after being triggered to conduct by a high voltage pulse, which can reduce the residual voltage of lightning.

[0084] The main component of the over-temperature release 30 is a metal elastic electrode 301, the first end 301A of the metal elastic electrode 301 is inserted into the support hole of the shell 310, and the tail end 301B is welded on the surface electrode 201 of the heating element R1 by low-temperature alloy soldering with a temperature of 120~140°C, and the arc extinguishing slide block 330 and the pull-out spring are used to help the over-temperature release 30 to accelerate separation and reliable arc extinguishing.

[0085] The component of the over-temperature release 30 for providing a remote signal is a remote signaling switch 320 with normally closed switch contacts, the movable switch contact 321 of the remote signaling switch 320 is normally pressed down by the arc extinguishing slide block 330 and touches the fixed switch contact 322 of the switch, when the over-temperature release 30 is separated, the arc extinguishing slide block 330 slides transversely, so that the pressure on the movable switch contact 321 of the remote signaling switch 320 is released, the movable switch contact 321 moves back under the action of its own elasticity, so that the two switch contacts are in a separated state, the remote signal changes to an open circuit state, and the external detector is notified that the SPD has failed.

[0086] The heating element R1 is selected as a pressure-sensitive resistor valve, and the following conditions should be met in selection: after the specification and model of the protected pressure-sensitive resistor are determined, the electric power generated by the pressure-sensitive resistor valve per unit volume should be higher than that generated by the protected pressure-sensitive resistor per unit volume, specifically, it is necessary to ensure that the temperature rise rate of the pressure-sensitive resistor valve in the overload protector 100 is higher than that of the protected pressure-sensitive resistor.

[0087] An embodiment of the present application also provides an electric power device, which comprises a power input interface, at least one pressure-sensitive resistor, and the overload protector 100 of any one of the above embodiments, the overload protector 100 and the pressure-sensitive resistor MOV1 are connected between at least two terminals of the power input interface.

[0088] Those skilled in the art can clearly understand that, for the convenience and brevity of description, only the division of the above functional units and modules is taken as an example, and in actual application, the above functions can be completed by different functional units and modules according to needs, that is, the internal structure of the device is divided into different functional units or modules to complete all or part of the functions described above. Each functional unit and module in the embodiment can be integrated in one processing unit, or each unit can exist physically, or two or more units can be integrated in one unit. The integrated unit can be realized in the form of hardware or in the form of a software functional unit. In addition, the specific name of each functional unit and module is only for convenient distinction, and does not limit the protection scope of the application. The specific working process of the units and modules in the system can refer to the corresponding process in the foregoing method embodiments, which will not be described here.

[0089] In the above embodiments, the description of each embodiment has its own emphasis, and the parts not described or recorded in a certain embodiment can be referred to the related description of other embodiments.

[0090] The above embodiments are only used to illustrate the technical solutions of the present application, but not to limit them; although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or make equivalent replacement for part of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present application, and should be included in the protection scope of the present application.

Claims

1. An overload protector, characterized in that, The overload protector is used to connect to at least two terminals of the power supply with the protected varistor; there is no thermal coupling between the overload protector and the protected varistor; the overload protector includes an over-temperature trip unit, an AC / DC heating module, and a high-voltage pulse bypass module, the high-voltage pulse bypass module is connected in parallel across the two ends of the AC / DC heating module, the over-temperature trip unit is connected in series with the heating module, and there is thermal coupling between the over-temperature trip unit and the AC / DC heating module; the AC / DC heating module has electrothermal characteristics, and when it heats up to the operating temperature of the over-temperature trip unit under the action of AC / DC current, it triggers the over-temperature trip unit to trip and disconnect, cutting off the electrical connection between the overload protector and the power supply.

2. The overload protector as described in claim 1, characterized in that, The AC / DC heating module includes a current limiting element and a heating element, wherein the current limiting element and the heating element are connected in series.

3. The overload protector as described in claim 2, characterized in that, The current limiting element is welded back-to-back with the heating element, or the current limiting element and the heating element are spaced apart and separately arranged.

4. The overload protector as described in claim 2, characterized in that, The heating element includes a varistor valve or a thermistor valve; The current limiting element includes a positive temperature coefficient thermistor, the Curie temperature of which is higher than the operating temperature of the over-temperature trip unit; or the current limiting element includes a fixed resistor.

5. The overload protector as described in claim 2, characterized in that, The heating element includes a varistor valve, and the temperature rise rate of the varistor valve is higher than the temperature rise rate of the protected varistor.

6. The overload protector as described in claim 2, characterized in that, The over-temperature trip unit includes a movable metal elastic electrode at one end, the end of which is soldered to the surface electrode of the heating element by low-temperature solder, and the first end of which is used to connect to the protected varistor or the terminal of the power supply. The melting point of the low-temperature solder corresponds to the operating temperature of the over-temperature trip unit.

7. The overload protector as described in claim 6, characterized in that, The AC / DC heating module and the high-voltage pulse bypass module form a core module, and the over-temperature trip unit also includes: The housing has a welding window, a connection position, and a separation position, and the core module and the metal elastic electrode are mounted on the housing; The remote signaling switch includes two remote signaling switch contacts mounted on the housing; An arc-extinguishing slider and a pull-out spring are provided, the pull-out spring being movably mounted on a sliding guide rail of the housing; the metal elastic electrode includes a retaining section connected between an end and a beginning, the beginning of the metal elastic electrode extending to the outside of the housing, the retaining section being located outside the arc-extinguishing slider, and the end of the metal elastic electrode being soldered to the surface electrode of the heating element with low-temperature solder through the welding window, such that the retaining section holds the arc-extinguishing slider in the connection position and causes the arc-extinguishing slider to press against the remote signaling switch, thereby bringing the two remote signaling contacts into contact; The pull-out spring is used to generate an elastic restoring force to drive the arc-extinguishing slider to move toward the separation position, pull the arc-extinguishing slider to reach and cover the welding window, so as to be placed between the surface electrode of the heating element and the end of the metal elastic electrode, and to separate the two remote signaling switch contacts.

8. The overload protector as described in any one of claims 1 to 7, characterized in that, The over-temperature trip unit consists of two components, namely a first over-temperature trip unit and a second over-temperature trip unit; the AC / DC heating module consists of two components, namely a first AC / DC heating module and a second AC / DC heating module; the high-voltage pulse bypass module includes a switching device with three electrodes; and the overload protector includes a first external electrode, a second external electrode, and a third external electrode. The first over-temperature trip unit and the first AC / DC heating module are connected in series between the first external electrode and the second external electrode, forming a first series node and a first current channel; The second over-temperature trip unit and the second AC / DC heating module are connected in series between the first external electrode and the third external electrode, forming a second series node and a second current channel. The second external electrode and the third external electrode form a third current channel. The first current channel, the second current channel, and the third current channel form a Y-type surge protection circuit. The three electrodes of the switching device are respectively connected to the first series node, the first external electrode, and the second series node. The first external electrode is connected to a first terminal of the power supply via at least one first varistor; the second external electrode is connected to a second terminal of the power supply via at least one second varistor; and the third external electrode is connected to a third terminal of the power supply via at least one third varistor.

9. The overload protector as described in any one of claims 1 to 7, characterized in that, The high-voltage pulse bypass module includes a switching device, which is a gas discharge tube, a solid discharge tube, or a discharge gap. The lightning current level of the switching device is higher than the lightning current level of the protected varistor, and the DC operating voltage of the switching device is higher than the DC voltage withstand voltage of the overload protector.

10. An electrical device, characterized in that, It includes a power input interface, at least one varistor, and an overload protector as described in any one of claims 1-9, wherein the overload protector and the varistor are connected between at least two terminals of the power input interface.

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