Electric circuit protection device

Abstract

The purpose of the present disclosure is to provide a technology capable of cutting off power supply when an abnormal current occurs in a high-voltage electric circuit. This electric circuit protection device comprises: a first current circuit breaker having a first conductor piece forming a part of an electric circuit and a first igniter for cutting the first conductor piece; and a second current circuit breaker having a second conductor piece connected in series with the first conductor piece of the first current circuit breaker to form a part of the electric circuit and a second igniter for cutting the second conductor piece. Both the first current circuit breaker and the second current circuit breaker are pyrotechnic current circuit breakers operated by explosives ignited and burned by energy supplied from the outside. The sum of breaking energy of the first current circuit breaker and breaking energy of the second current circuit breaker is greater than or equal to energy flowing through the electric circuit.

Description

Electric circuit protection device

[0001] The present invention relates to an electric circuit protection device.

[0002] It is known that an electric circuit is provided with a pyrotechnic electric circuit breaker that urgently cuts off conduction in the electric circuit by operating when an abnormality occurs in a device constituting the electric circuit or when an abnormality occurs in a system on which the electric circuit is mounted (for example, Patent Documents 1 to 3).

[0003] Japanese National Publication of International Patent Application No. 2024-544914, U.S. Patent No. 10217595 Specification, U.S. Patent Application Publication No. 2006 / 0049027 Specification

[0004] There is a certain limit to the interruptible energy of a pyrotechnic electric circuit breaker. However, the relationship between the interruptible energy and the interruption performance of a pyrotechnic electric circuit breaker has not been proposed.

[0005] An object of the present disclosure is to provide a technology capable of cutting off power supply when an abnormal current occurs in a high-voltage electric circuit.

[0006] A first current breaker having a first conductor piece forming a part of an electric circuit and a first igniter for cutting the first conductor piece; a second current breaker connected in series with the first conductor piece of the first current breaker, having a second conductor piece forming a part of the electric circuit and a second igniter for cutting the second conductor piece, wherein both the first current breaker and the second current breaker are pyrotechnic current breakers that are operated by gunpowder ignited and combusted by energy supplied from the outside, the energy required to cut off the electricity flowing in the electric circuit is represented by formula (1), H is the inductance of the electric circuit, A is the current flowing through the electric circuit, and the sum of the breaking energy of the first current breaker and the breaking energy of the second current breaker is equal to or greater than the energy flowing through the electric circuit represented by the formula (1), the electric circuit protection device.

[0007] The above-described electrical circuit protection device includes a control unit that controls the timing of supplying ignition current to each of the first igniter and the second igniter, and the control unit may be capable of operating each of the first igniter and the second igniter at any timing.

[0008] In the above-described electrical circuit protection device, the control unit may activate the second igniter within 8.6 milliseconds after activating the first igniter.

[0009] In the above-described electrical circuit protection device, an abnormality detection unit is provided which is connected to the control unit and detects an abnormality in the electrical circuit, and the control unit may supply the ignition current to the first igniter and the second igniter at any timing when the abnormality detection unit detects the abnormality.

[0010] In the above-described electrical circuit protection device, the time required from the moment the ignition current is supplied to at least one of the first igniter and the second igniter until the current in the electrical circuit is interrupted may be 0.32 milliseconds or less.

[0011] In the above-described electrical circuit protection device, the first current circuit breaker and the second current circuit breaker may have different interruption energies.

[0012] According to the technology disclosed herein, power supply can be interrupted when an abnormal current occurs in a high-voltage electrical circuit.

[0013] Figure 1 is a circuit diagram of an electrical circuit protection device according to an embodiment. Figure 2 is a cross-sectional view of a circuit breaker cut along the height direction. Figure 3 is a top view of a conductor piece. Figure 4 is a diagram illustrating the circuit breaker's tripping principle. Figure 5 is a circuit diagram of an electrical circuit protection device according to a comparative example. Figure 6 is a graph verifying the tripping results of the electrical circuit protection device according to a comparative example. Figure 7 is a graph verifying the tripping results of the electrical circuit protection device according to a comparative example. Figure 8 is a graph verifying the tripping results of the electrical circuit protection device according to the embodiment. Figure 9 is a graph verifying the tripping results of the electrical circuit protection device according to the embodiment. Figure 10 is a graph verifying the tripping results of the electrical circuit protection device according to a comparative example. Figure 11 is a graph verifying the tripping results of the electrical circuit protection device according to a comparative example. Figure 12 is a graph verifying the tripping results of the electrical circuit protection device according to a comparative example. Figure 13 is a graph verifying the tripping results of the electrical circuit protection device according to this embodiment. Figure 14 is a graph showing the relationship between the maximum tripping energy of the circuit breaker and voltage. Figure 15 is a graph showing the experimental results of the changes in current and voltage before and after the operation of a circuit breaker when the circuit is interrupted by a single circuit breaker. Figure 16 is a graph showing the experimental results of the changes in current and voltage before and after the operation of a circuit breaker when multiple circuit breakers are operated sequentially to interrupt the circuit under Condition 1. Figure 17 is a graph showing the experimental results of the changes in current and voltage before and after the operation of a circuit breaker when multiple circuit breakers are operated sequentially to interrupt the circuit under Condition 2. Figure 18 is a graph showing the experimental results of the changes in current and voltage before and after the operation of a circuit breaker when multiple circuit breakers are operated sequentially to interrupt the circuit under Condition 3. Figure 19 is a graph showing the experimental results of the changes in current and voltage before and after the operation of a circuit breaker when multiple circuit breakers are operated sequentially to interrupt the circuit under Condition 4. Figure 20 is a graph showing the experimental results of the changes in current and voltage before and after the operation of a circuit breaker when multiple circuit breakers are operated sequentially to interrupt the circuit under Condition 5.

[0014] <Embodiments> An electrical circuit protection device according to an embodiment of the present disclosure will be described below with reference to the drawings. Note that each configuration and combination thereof in the embodiments are examples, and additions, omissions, substitutions, and other modifications can be made as appropriate without departing from the spirit of the present disclosure. The present disclosure is not limited by the embodiments, but is limited only by the claims.

[0015] <Outline Configuration> Figure 1 shows the configuration of an electrical circuit protection device (hereinafter also simply referred to as "protection device") 300 according to this embodiment. The protection device 300 according to this embodiment is equipped with two current circuit breakers 1A and 1B that can interrupt the power supply when an abnormal current occurs in an electrical circuit with high voltage (for example, 300V or more). The protection device 300 is used, for example, to interrupt an electrical circuit in the event of an abnormality in an electrical circuit included in an automobile, household electrical appliance, solar power generation system, etc., or in a system including the battery (for example, lithium-ion battery) of said electrical circuit. The protection device 300 may also be applied to power systems such as power transmission and distribution networks, railway systems, and renewable energy power sources.

[0016] The current circuit breakers 1A (an example of the "first current circuit breaker" in this disclosure) and 1B (an example of the "second current circuit breaker" in this disclosure) used in the protective device 300 are both pyrotechnic circuit breakers that operate using explosives that ignite and burn when energy such as ignition current is supplied from an external source. In the technology of this disclosure, current limiting fuses are not used as circuit breakers. Hereafter, current circuit breakers may be simply referred to as "circuit breakers".

[0017] As shown in Figure 1, the protective device 300 includes an electrical circuit 301 in which a DC power supply 302, a circuit breaker 1A, a circuit breaker 1B, and a switch 303 are connected in series. The DC power supply 302 can generate a high voltage from 300V to 1500V. The electrical circuit 301 also includes an ammeter 304 for measuring the current flowing through the circuit and a voltmeter 305 for measuring the voltage between circuit breaker 1A and circuit breaker 1B. Note that these ammeters 304 and voltmeters 305 are connected for the purpose of obtaining measurement values ​​and do not necessarily have to be used in the actual protective device 300.

[0018] Circuit breakers 1A and 1B have the same configuration, the same specifications, the same structure, and the same breaking performance. Therefore, the same components in circuit breakers 1A and 1B are denoted by the same reference numerals. For convenience, to distinguish between the configurations of circuit breaker 1A and circuit breaker 1B, each component of circuit breaker 1A may be denoted with the numeral "first," and each component of circuit breaker 1B may be denoted with the numeral "second."

[0019] The circuit breakers 1A and 1B each have a conductive piece 50 that forms part of an electrical circuit 301 and an igniter 20 that generates energy to disconnect the conductive piece 50. The conductive piece 50 of circuit breaker 1A and the conductive piece 50 of circuit breaker 1B are connected in series to form part of an electrical circuit 301. The conductive piece 50 of circuit breaker 1A is an example of the "first conductive piece" in this disclosure, and the conductive piece 50 of circuit breaker 1B is an example of the "second conductive piece" in this disclosure. Furthermore, the igniter 20 of circuit breaker 1A is an example of the "first igniter" in this disclosure, and the igniter 20 of circuit breaker 1B is an example of the "second igniter" in this disclosure.

[0020] The igniter 20 has an impedance element 23 (see Figure 2) and an ignition unit 21 that operates due to the current flowing through the impedance element 23. The circuit breakers 1A and 1B in this embodiment are so-called pyrofuses (also called pyroswitches) that, as described later, cut the conductor piece 50 by the combustion energy of the explosives in the ignition unit 21 when current is supplied to the ignition unit 21.

[0021] In this embodiment, a DC power supply 302 is used, and the current flowing through the electrical circuit 301 is a DC current. However, the embodiment is not limited to this; an AC power supply may be used, and the current flowing through the electrical circuit 301 may also be an AC current.

[0022] In the example shown in Figure 1, the igniter 20 has an impedance element 23 that is separate from the ignition unit 21, but the impedance element 23 may be integrally included in the ignition unit 21 of the igniter 20.

[0023] Furthermore, the protective device 300 according to this embodiment includes a control unit 306. The control unit 306 is a computer such as a microcontroller or an ECU (Electronic Control Unit). The control unit 306 controls a drive circuit 308 that supplies ignition current to each igniter 20 individually, thereby controlling the timing of supplying ignition current to each igniter 20. The drive circuit 308 has a switching element that switches the power supply and the supply of ignition current to each igniter 20 between an off state and an on state. The control unit 306 can supply ignition current to each igniter 20 by switching the switching element from the off state to the on state. In addition, the control unit 306 has separate switching elements for circuit breaker 1A and circuit breaker 1B, and can supply ignition current to each igniter 20 at any timing. As a result, the control unit 306 can operate each igniter 20 at any timing.

[0024] Furthermore, a current sensor 307 (an example of the "abnormality detection unit" in this disclosure) is located within the electrical circuit 301. The current sensor 307 is electrically connected to the control unit 306. The current sensor 307 detects the current flowing through the electrical circuit 301 and outputs the detected value to the control unit 306. The current sensor 307 can detect when an abnormal current flows through the electrical circuit 301 and is a sensor that detects abnormalities in the electrical circuit 301. When the current sensor detects an abnormal current, the control unit 306 can supply ignition current to the igniter 20 of circuit breaker 1A and the igniter 20 of circuit breaker 1B, respectively, at any desired timing. For example, the control unit 306 may control the drive circuit 308 to simultaneously supply ignition current to the igniter 20 of circuit breaker 1A and the igniter 20 of circuit breaker 1B, or it may control the drive circuit 308 to have different timings for supplying ignition current to the igniter 20 of circuit breaker 1A and the igniter 20 of circuit breaker 1B. In this embodiment, an abnormal current is a high current not anticipated in the electrical circuit 301, and steady-state operation is a state in which no abnormal current occurs.

[0025] <Circuit Breakers> Next, the circuit breakers 1A and 1B will be described in more detail. Figure 2 is a vertical cross-sectional view of the circuit breaker 1A along the height direction (the direction in which the housing space 13, described later, extends). Figure 2 shows the state of the circuit breaker 1A before operation. Although Figure 2 illustrates an example of the configuration of the circuit breaker 1A, the circuit breaker 1B has the same configuration as the circuit breaker 1A.

[0026] The circuit breaker 1A includes a housing 10 as an outer shell member, an igniter 20, a projectile 40, a conductive piece 50, a coolant material 60, etc. The housing 10 has a housing space 13 that extends in one direction from a first end 11 on the upper end side to a second end 12 on the lower end side. This housing space 13 is a linearly formed space that allows the projectile 40 to move, and extends along the vertical direction of the circuit breaker 1A. As shown in Figure 2, the projectile 40 is housed in the housing space 13 formed inside the housing 10. However, in this specification, the vertical direction of the circuit breaker 1A merely indicates the relative positional relationship of each element in the circuit breaker 1A for the convenience of describing the embodiment.

[0027] [Housing] The housing 10 includes a housing body 100, a top holder 110, and a bottom container 120. The top holder 110 and the bottom container 120 are attached to the housing body 100, thereby forming an integrated housing 10.

[0028] The housing body 100 has, for example, a roughly rectangular prism shape. However, the shape of the housing body 100 is not particularly limited. Furthermore, the housing body 100 is formed with a cavity that runs through it in the vertical direction, and this cavity forms part of the storage space 13. In addition, the housing body 100 has an upper surface 101 to which the flange portion 111 of the top holder 110 is fixed, and a lower surface 102 to which the flange portion 121 of the bottom container 120 is fixed. In this embodiment, a cylindrical upper cylindrical wall 103 is erected on the outer circumference of the upper surface 101 of the housing body 100, extending upward from the upper surface 101. In this embodiment, the upper cylindrical wall 103 has, for example, a rectangular cylindrical shape, but it may have other shapes. Furthermore, a cylindrical lower cylindrical wall 104 is erected on the outer circumference of the lower surface 102 of the housing body 100, extending downward from the lower surface 102. In this embodiment, the lower cylindrical wall 104 has, for example, a rectangular cylindrical shape, but it may have other shapes. Furthermore, on the lower surface 102 of the housing body 100, a cylindrical mounting portion 106 is provided vertically from the lower surface 102 downwards around the cavity. In this embodiment, the mounting portion 106 is formed in a cylindrical shape to match the cavity, but it may have other shapes. The housing body 100 configured as described above can be made of an insulating material such as synthetic resin. For example, the housing body 100 may be made of nylon, which is a type of polyamide synthetic resin.

[0029] [Top Holder] Next, the top holder 110 will be described. The top holder 110 is, for example, a cylinder member having a stepped cylindrical shape, and the inside is hollow. The top holder 110 is composed of a small-diameter cylinder portion 112 located on the upper side (first end 11 side), a large-diameter cylinder portion 113 located on the lower side, a connecting portion 114 that connects them, and a flange portion 111 that extends outward from the lower end of the large-diameter cylinder portion 113. For example, the small-diameter cylinder portion 112 and the large-diameter cylinder portion 113 are arranged coaxially, and the large-diameter cylinder portion 113 has a larger diameter (inner diameter) than the small-diameter cylinder portion 112.

[0030] Furthermore, the contour of the flange portion 111 of the top holder 110 has a roughly rectangular shape that fits inside the upper cylindrical wall 103 of the housing body 100. The flange portion 111 may be integrally fastened to the upper surface 101 of the housing body 100 using screws or the like, or fixed with rivets or the like, while positioned inside the upper cylindrical wall 103. Alternatively, the top holder 110 may be joined to the housing body 100 with sealant applied between the upper surface 101 of the housing body 100 and the lower surface of the flange portion 111 of the top holder 110. This can improve the airtightness of the housing space 13 formed inside the housing 10. Alternatively, instead of sealant, or in combination with sealant, an O-ring may be interposed between the upper surface 101 of the housing body 100 and the flange portion 111 of the top holder 110 to improve the airtightness of the housing space 13.

[0031] The cavity formed inside the small-diameter cylinder portion 112 of the top holder 110 functions as a space for housing a part of the igniter 20, as shown in Figure 2. Furthermore, the cavity formed inside the large-diameter cylinder portion 113 of the top holder 110 communicates with the cavity of the housing body 100 located below, forming a part of the housing space 13. The top holder 110, configured as described above, can be made from a suitable metal material such as stainless steel or aluminum, which have excellent strength and durability. However, the material used to form the top holder 110 is not particularly limited. Also, the above-described shape of the top holder 110 is just one example, and other shapes may be adopted.

[0032] [Bottom Container] Next, the bottom container 120 will be described. The bottom container 120 in this embodiment is a form of outer shell container. The bottom container 120 has a generally bottomed cylindrical shape with a hollow interior and is composed of a side wall portion 122, a bottom wall portion 123 connected to the lower end of the side wall portion 122, a flange portion 121 connected to the upper end of the side wall portion 122, etc. The side wall portion 122 has, for example, a cylindrical shape, and the flange portion 121 extends outward from the upper end of the side wall portion 122. The contour of the flange portion 121 in the bottom container 120 has a generally rectangular shape that fits inside the lower cylindrical wall 104 of the housing body 100. The flange portion 121 may, for example, be integrally fastened to the lower surface 102 of the housing body 100 using screws or the like while positioned inside the lower cylindrical wall 104, or it may be fixed by rivets or the like. Here, the bottom container 120 may be bonded to the housing body 100 with sealant applied between the lower surface 102 of the housing body 100 and the upper surface of the flange portion 121 of the bottom container 120. This can improve the airtightness of the containment space 13 formed inside the housing 10. Alternatively, instead of sealant, or in combination with sealant, an O-ring may be interposed between the lower surface 102 of the housing body 100 and the flange portion 121 of the bottom container 120 to improve the airtightness of the containment space 13.

[0033] The above description of the shape of the bottom container 120 is merely an example, and other shapes may be adopted. Furthermore, the cavity formed inside the bottom container 120 communicates with the housing body 100 located above it, forming part of the storage space 13. The bottom container 120, configured as described above, can be made from a suitable metal material such as stainless steel or aluminum, which has excellent strength and durability. By being made of a metal material, the bottom container 120 achieves miniaturization while ensuring rigidity to withstand operating pressure. However, the bottom container 120 is not limited to metal. For example, the bottom container 120 may be made of synthetic resin or a composite material made of synthetic resin with added carbon fiber or glass fiber.

[0034] As described above, the housing 10 in the embodiment is composed of a housing body 100, a top holder 110, and a bottom container 120 which are assembled integrally, and a housing space 13 is formed inside it that extends from the first end 11 to the second end 12. The igniter 20, projectile 40, the cut portion 53 of the conductive piece 50, and the coolant material 60, which will be described in detail below, are housed in this housing space 13.

[0035] The housing 10, which is assembled as a single unit, is fastened by metal bolts 130, with the flange portion 111 of the top holder 110 and the flange portion 121 of the bottom container 120 sandwiching the housing body 100. Note that the housing 10 is not limited to bolts 130; other fasteners may be used. In this case, the fasteners may also be made of metal.

[0036] [Ignition] Next, the ignition 20 will be described. The ignition 20 is an electric ignition device comprising an ignition unit 21 containing an ignition agent, an ignition body 22 that holds the ignition unit 21, and an impedance element 23 connected to the ignition unit 21 via a cable. The ignition body 22 is surrounded by, for example, an insulating resin. The ignition unit 21 has electrical terminals exposed to the outside via the ignition body 22 as a pair of conductive pins. One of these conductive pins is connected to the impedance element 23 via a cable 291, and the other is connected to the drive circuit 308 (see Figure 1) via a cable 292.

[0037] The igniter body 22 comprises a roughly cylindrical body portion 226 housed inside the small-diameter cylinder portion 112 of the top holder 110, and a connector portion 225 located on the upper part of the body portion 226. The igniter body 22 is fixed to the small-diameter cylinder portion 112, for example, by press-fitting the body portion 226 into the inner circumferential surface of the small-diameter cylinder portion 112. In addition, a constricted portion, which is recessed on the outer circumferential surface compared to other parts, is formed in an annular shape along the circumferential direction of the body portion 226 in the axial middle part of the body portion 226, and an O-ring 223 is fitted into this constricted portion. The O-ring 223 is made of, for example, rubber (e.g., silicone rubber) or synthetic resin, and functions to improve airtightness between the inner circumferential surface of the small-diameter cylinder portion 112 and the body portion 226.

[0038] The connector portion 225 in the igniter 20 is positioned to protrude to the outside through an opening 112A formed at the upper end of the small-diameter cylinder portion 112. The connector portion 225 has, for example, a cylindrical shape that covers the sides of the conductive pins and is configured to connect to the power supply side connector.

[0039] As shown in Figure 2, the ignition unit 21 of the igniter 20 is positioned to face the housing space 13 of the housing 10 (more specifically, the cavity formed inside the large-diameter cylinder portion 113). The ignition unit 21 is configured, for example, to house the igniter powder within an igniter cup. For example, the igniter powder is housed within the igniter cup of the igniter unit 21 in contact with a bridge wire (resistor) that is strung together to connect the base ends of a pair of conductive pins. As the igniter powder, for example, ZPP (zirconium potassium perchlorate), ZWPP (zirconium tungsten potassium perchlorate), THPP (titanium hydride potassium perchlorate), lead tricinate, etc. may be used.

[0040] The output of the igniter 20 can be adjusted depending on the type and amount of igniter used. Increasing the amount of igniter increases the ejection speed of the projectile 40, thereby improving the shutoff performance of the circuit breakers 1A and 1B.

[0041] When the igniter 20 is activated, an ignition current for igniting the igniter is supplied from the control unit 306 to the conductive pin. As a result, the bridge wire in the ignition unit 21 heats up, causing the igniter in the igniter cup to ignite and burn, generating combustion products such as combustion gases. Then, as the igniter burns in the igniter cup of the igniter unit 21, the pressure inside the igniter cup increases, causing the split surface 21A of the igniter cup to split, and the combustion products are released from the igniter cup into the containment space 13. More specifically, the combustion products from the igniter cup are released into the recess 411 of the piston portion 41 of the projectile 40, which will be described later, located in the containment space 13.

[0042] [Projectile] Next, the projectile 40 will be described. The projectile 40 is made of an insulating material such as synthetic resin, and includes a piston portion 41 and a rod portion 42 connected to the piston portion 41. The piston portion 41 has a generally cylindrical shape and an outer diameter that roughly corresponds to the inner diameter of the large-diameter cylinder portion 113 in the top holder 110. For example, the diameter of the piston portion 41 may be slightly smaller than the inner diameter of the large-diameter cylinder portion 113. The shape of the projectile 40 can be appropriately changed according to the shape of the housing 10, etc.

[0043] Furthermore, a cylindrical recess 411 is formed on the upper surface of the piston portion 41, and the ignition unit 21 is received in this recess 411. The bottom surface of the recess 411 is formed as a pressure receiving surface 411A that receives energy from the ignition unit 20 when the ignition unit 20 is in operation. In addition, a constricted portion, which is recessed on the outer circumferential direction of the piston portion 41, is formed in the axial middle portion of the piston portion 41, and an O-ring 43 is fitted into this constricted portion. The O-ring 43 is made of rubber (e.g., silicone rubber) or synthetic resin, and functions to improve airtightness between the inner circumferential surface of the large-diameter cylinder portion 113 and the piston portion 41.

[0044] A rod portion 42 of the projectile 40 is, for example, a rod-shaped member having an outer peripheral surface with a smaller diameter than that of a piston portion 41, and is integrally connected to the lower end side of the piston portion 41. A lower end surface of the rod portion 42 is formed as a cutting surface 421 for cutting a cut portion 53 from a conductor piece 50 when the circuit breaker 1A operates. Although the rod portion 42 in the present embodiment has a substantially cylindrical shape, the shape thereof is not particularly limited, and can be changed according to the shape and size of the cut portion 53 to be cut from the conductor piece 50 when the circuit breaker 1A operates. For example, the rod portion 42 may have a columnar shape such as a circular column or a prismatic column. In the initial position of the projectile 40 shown in FIG. 2, the region on the distal end side including the cutting surface 421 in the rod portion 42 of the projectile 40 is positioned in a hollow portion of the housing body 100, which forms a part of the accommodation space 13. A diameter of the rod portion 42 is, for example, slightly smaller than an inner diameter of an inner peripheral surface of the housing body 100, and is configured such that the outer peripheral surface of the rod portion 42 is guided along the inner peripheral surface when the projectile 40 is fired.

[0045] Although details of the projectile 40 configured as described above will be described later, when the igniter 20 operates, the upper surface of the piston portion 41 including the pressure receiving surface 411A receives energy from the igniter 20, whereby the projectile 40 is fired from the initial position shown in FIG. 2 and moves at high speed toward the second end portion 12 side (downward) along the accommodation space 13. Specifically, as shown in FIG. 2, the piston portion 41 of the projectile 40 is accommodated inside a large-diameter cylinder portion 113 in a top holder 110, and is slidable in the axial direction along an inner wall surface of the large-diameter cylinder portion 113. In the present embodiment, the piston portion 41 of the projectile 40 has a substantially cylindrical shape, but the shape thereof is not particularly limited. An appropriate shape and size can be adopted for the outer shape of the piston portion 41 according to the shape and size of the inner wall surface of the large-diameter cylinder portion 113.

[0046] [Conductor piece] Next, the conductor piece 50 will be described. Figure 3 is a top view of the conductor piece 50 according to the embodiment. The conductor piece 50 is a conductive metal body that constitutes part of the components of the circuit breaker 1A and forms part of a predetermined electrical circuit when the circuit breaker 1A is attached to the electrical circuit, and is sometimes referred to as a bus bar. The conductor piece 50 can be formed of, for example, a metal such as copper (Cu). However, the conductor piece 50 may be formed of a metal other than copper, or may be formed of an alloy of copper and another metal. Examples of metals other than copper contained in the conductor piece 50 include manganese (Mn), nickel (Ni), platinum (Pt), and the like.

[0047] In one aspect shown in Figure 3, the conductor piece 50 is formed as an elongated flat plate as a whole, and includes a first connection end 51 and a second connection end 52 at both ends, and a to-be-cut portion 53 located in an intermediate portion between these ends. Connection holes 51A and 52A are respectively provided in the first connection end 51 and the second connection end 52 of the conductor piece 50. These connection holes 51A and 52A are used for connection to other conductors (for example, lead wires) in the electrical circuit. In Figure 2, illustration of the connection holes 51A and 52A in the conductor piece 50 is omitted. In addition, the to-be-cut portion 53 of the conductor piece 50 is disposed so as to cross the accommodation space 13, and is a portion that is forcibly and physically cut by the rod portion 42 of the projectile 40 when an abnormality such as an excessive current occurs in the electrical circuit to which the circuit breaker 1A is applied. Notches (slits) 54 are formed at both ends of the to-be-cut portion 53 in the conductor piece 50 so that the to-be-cut portion 53 is easily cut. In Figure 3, the thickness and / or width of the to-be-cut portion 53 is formed thinner (smaller) than the thickness and / or width of the first connection end 51 and the second connection end 52.

[0048] Here, the conductor piece 50 can take on various forms, and its shape is not particularly limited. In the example shown in Figure 3, the surfaces of the first connecting end 51, the second connecting end 52, and the cut portion 53 form the same plane, but this is not the case. For example, the conductor piece 50 may be connected to the first connecting end 51 and the second connecting end 52 with the cut portion 53 in a perpendicular or inclined position. Furthermore, the planar shape of the cut portion 53 on the conductor piece 50 is not particularly limited. Of course, the shapes of the first connecting end 51 and the second connecting end 52 on the conductor piece 50 are also not particularly limited. In addition, the notch 54 on the conductor piece 50 can be omitted as appropriate. In this embodiment, the portion to be cut 53 is cut at two locations where notches 54 are formed, separating it from the first connecting end 51 and the second connecting end 52. However, the portion to be cut (also referred to as the portion to be cut) 53 is not limited to this configuration. It may also be cut near the center by the rod portion 42, or either the boundary between the first connecting end 51 and the portion to be cut 53, or the boundary between the second connecting end 52 and the portion to be cut 53, and the cut end may be bent toward the bottom container 120 so as to separate them.

[0049] In this embodiment, the housing body 100 has a pair of conductor piece holding holes 105A and 105B. The pair of conductor piece holding holes 105A and 105B extend in a cross-sectional direction perpendicular to the vertical direction (axial direction) of the housing body 100. More specifically, the pair of conductor piece holding holes 105A and 105B extend in a straight line across the cavity (housing space 13) of the housing body 100. The conductor piece 50 configured as described above is held in the housing body 100 with the conductor piece inserted through the pair of conductor piece holding holes 105A and 105B formed in the housing body 100. In the example shown in Figure 2, the first connecting end 51 of the conductor piece 50 is held with the conductor piece holding hole 105A inserted, and the second connecting end 52 is held with the conductor piece holding hole 105B inserted. Furthermore, in this state, the portion to be cut 53 of the conductor piece 50 is positioned in the cavity (housing space 13) of the housing body 100. As described above, the conductor piece 50 mounted on the housing body 100 is held in a position perpendicular to the extending direction (axial direction) of the housing space 13, such that the portion to be cut 53 crosses the housing space 13. Note that the reference numeral L1 in Figure 3 indicates the outer circumference position of the rod portion 42 located at the top of the conductor piece 50 when it is mounted on the housing body 100 of the circuit breaker 1A. In this embodiment, the conductor piece 50 is installed such that the outer circumference position L1 of the rod portion 42 generally coincides with the positions of the notches 54 located at both ends of the portion to be cut 53. In this embodiment, for example, since the cross-sectional area of ​​the housing space 13 is larger than the cross-sectional area of ​​the portion to be cut 53, a gap is formed on the side of the portion to be cut 53.

[0050] [Coolant Material] Next, the coolant material 60 placed in the housing space 13 of the housing 10 will be described. As shown in Figure 2, before the operation of the circuit breaker 1A (igniter 20), the cut portion 53 of the conductor piece 50, which is held in the pair of conductor piece holding holes 105A and 105B in the housing body 100, is horizontally positioned across the housing space 13 of the housing 10. Hereinafter, the area (space) in the housing space 13 of the housing 10 on the side of the cut portion 53 of the conductor piece 50 where the projectile 40 is positioned will be called the "initial projectile placement area AR1", and the area (space) located on the opposite side from the projectile 40 will be called the "arc extinguishing area AR2". Note that, as described above, before operation, a gap is formed on the side of the cut portion 53 which is positioned across the housing space 13, so the initial projectile placement area AR1 and the arc extinguishing area AR2 are not completely isolated by the cut portion 53, but are in communication with each other. Of course, depending on the shape and size of the part to be cut 53, the initial projectile placement area AR1 and the arc extinguishing area AR2 may be completely isolated by the part to be cut 53.

[0051] The arc-extinguishing region AR2 of the containment space 13 is a region (space) for receiving the cut portion 53 that is severed by the rod portion 42 of the projectile 40 fired when the circuit breaker 1A (igniter 20) is activated. Coolant material 60 is placed in this arc-extinguishing region AR2 as an arc-extinguishing material. The coolant material 60 is a coolant that suppresses arc generation when the current is interrupted, or extinguishes (eliminates) the generated arc by absorbing the heat energy of the arc and the cut portion 53 generated when the projectile 40 cuts the cut portion 53 of the conductor piece 50, thereby cooling it.

[0052] The arc extinguishing region AR2 in the circuit breaker 1A is a space for receiving the cut portion 53 that has been severed from the first connecting end 51 and the second connecting end 52 of the conductor piece 50 by the projectile 40, and at the same time, it has significance as a space for effectively extinguishing the arc generated when the projectile 40 cuts the cut portion 53. In order to effectively extinguish the arc generated when the cut portion 53 is severed from the conductor piece 50, a coolant material 60 is placed in the arc extinguishing region AR2 as an arc extinguishing material.

[0053] In one embodiment, the coolant material 60 is solid. In another embodiment, the coolant material 60 is formed from a shape-retaining material. A shape-retaining material, as used here, is a material that maintains a constant shape when no external force is applied, and can maintain its integrity (not fall apart) even if deformation occurs when an external force is applied. For example, a fibrous material molded into a desired shape can be exemplified as a shape-retaining material. In this embodiment, the coolant material 60 is formed from metal fibers that are shape-retaining materials. Here, the metal fibers forming the coolant material 60 may include at least one of steel wool and copper wool. However, the above embodiments of the coolant material 60 are examples and are not limited to these. For example, the coolant material 60 may be formed from conductive materials other than metal fibers, such as carbon fibers or a resin material mixed with a conductive filler.

[0054] The coolant material 60 is, for example, formed into a roughly disc shape and placed at the bottom of the bottom container 120.

[0055] <Circuit Breaker Operation> Figure 4 shows the circuit breaker 1A's circuit breaker principle. States (A) to (D) in Figure 4 show the state when an abnormal current occurs and the circuit breaker 1A interrupts the electrical circuit 301. When an abnormal current is interrupted, the circuit breaker 1A operates in the following order (i) to (iv).

[0056] (i) State (A) Under normal conditions, the load current is energized through the conductor piece 50. Since the resistance of the conductor piece 50 is on the order of several mΩ, it can be considered that there is virtually no loss.

[0057] (ii) State (B) When an abnormal current occurs and the operating current flows to the ignition unit 21 in the ignition device 20 of the circuit breaker 1A, the bridge wire (resistor) 215 inside the ignition unit 21 heats up.

[0058] (iii) State (C) When the bridge wire 215 of the igniter 20 heats up, the igniter charge filled around it ignites and burns, generating products containing combustion gas. Here, the ignition part 21 of the igniter 20 has its splitting surface 21A facing the pressure-receiving surface 411A of the projectile 40. Therefore, the pressure (combustion energy) of the combustion gas released from the splitting surface 21A of the ignition part 21 is transmitted to the pressure-receiving surface 411A of the piston part 41. As a result, the projectile 40 is pushed down forcefully, and the lower end surface (cutting surface 421) of the rod part 42 cuts the conductor piece 50.

[0059] (iv) State (D) The cut portion 53, severed from the conductor piece 50 by the projectile 40, is received in the arc extinguishing region AR2 where the coolant material 60 is located. The circuit breaker 1A has the coolant material 60 located in the arc extinguishing region AR2. Therefore, the cut portion 53 received in the arc extinguishing region AR2 comes into contact with the coolant material 60 and is rapidly cooled. As a result, even if an arc is generated in the cut portion, the coolant material 60 absorbs the energy of the arc, and the arc can be extinguished quickly and effectively. As a result, the first connection end 51 and the second connection end 52 located at both ends of the conductor piece 50 become electrically closed, and the predetermined electrical circuit to which the circuit breaker 1A is applied is forcibly interrupted.

[0060] By the way, the energy (J) flowing through the electrical circuit 301 can be expressed by the following equation (1). Here, H is the inductance of the electrical circuit, and A is the current flowing through the electrical circuit.

[0061] The inventors of the present invention have found that a protective device can interrupt the current if the sum of the maximum interruption energies (interruptible energy) of the circuit breakers connected in series in the protective device is greater than or equal to the energy flowing through the electrical circuit 301 shown in equation (1) above. First, the maximum interruption energy that can be interrupted by a single circuit breaker was investigated. First, a protective device with only one circuit breaker was prepared, and the interruption energy by a single circuit breaker and the energy of the electrical circuit were verified. Figure 5 shows the configuration of a protective device 500 related to a comparative example prepared for verification. The protective device 500 shown in Figure 5 is the same as the protective device 300 shown in Figure 1, except that only one circuit breaker 1A is provided.

[0062] Table 1 below shows the tripping results of the protective device 500 shown in Figure 5 when the voltage is 900V, the currents are 25kA, 20kA, 15kA, and 10kA, and the inductances are 12μH, 22μH, 32μH, 54μH, and 100μH. In Table 1, the energy (J) flowing through the electrical circuit and the tripping result for each current value and inductance value are represented by the symbols "○" and "×". "○" indicates that the current was successfully tripped, and "×" indicates that the current was not successfully tripped.

[0063]

[0064] Figure 6 is a graph showing the changes in current and voltage before and after the operation of circuit breaker 1A when the voltage is 900V, the current is 15kA, and the inductance is 22μH. The vertical axis on the left of Figure 6 represents current (kA), the vertical axis on the right of Figure 6 represents voltage (V), and the horizontal axis of Figure 6 represents time (ms). In Figure 6, line L1 shows the change in current measured by ammeter 304, line L2 shows the output voltage of DC power supply 302, and line L3 shows the change in voltage measured by voltmeter 305. The output voltage of DC power supply 302 was measured using a voltmeter in the vicinity of DC power supply 302.

[0065] As shown in Figure 6, the current value indicated by line L1 becomes 0A at around 0.88ms, and since the current remains stable at 0A thereafter, it can be determined that the current has been interrupted. From this graph, it was confirmed that the current can be interrupted when the voltage is 900V, the current is 15kA, and the inductance is 22μH (when the energy flowing through the electrical circuit is 2475J). The interruption time was 0.37ms. The interruption time is the time required from the point when the current value begins to decay until the current value measured by the ammeter 304 becomes constant at 0A. Protective devices 300 and 500 are preferable because a shorter interruption time reduces the time during which abnormal current flows. The voltage indicated by line L3 rises when an arc is generated when circuit breaker 1A is activated, but it converges to 900V as the power supply voltage of 900V continues to be applied.

[0066] Figure 7 is a graph showing the changes in current and voltage before and after operation of circuit breaker 1A when the voltage is 900V, the current is 20kA, and the inductance is 22μH. The vertical axis on the left of Figure 7 represents current (kA), the vertical axis on the right of Figure 7 represents voltage (V), and the horizontal axis of Figure 7 represents time (ms). In Figure 7, line L1 shows the change in current measured by ammeter 304, line L2 shows the output voltage of DC power supply 302, and line L3 shows the change in voltage across circuit breaker 1A. As shown in Figure 7, the current shown by line L1 does not stabilize at 0A, confirming that the current could not be interrupted under these conditions. The voltage shown by line L3 is thought to have been measured as a wavy waveform because the components inside circuit breaker 1A were deformed by changes in arc, heat, and pressure due to the formation of an electrical circuit via an arc inside the circuit breaker 1A. The same applies to the current shown by line L2.

[0067] In addition, the actual interruption results were measured for the following cases from Table 1: when the inductance is 12 μH and the currents are 25 kA and 20 kA; when the inductance is 22 μH and the currents are 20 kA and 15 kA; when the inductance is 32 μH and the currents are 15 kA and 10 kA; when the inductance is 54 μH and the current is 10 kA; and when the inductance is 100 μH and the current is 10 kA. For each inductance, it can be assumed that the interruption result will be "○" when the energy flowing through the electrical circuit is smaller than when the interruption result is "○" (i.e., when the current is lower).

[0068] Furthermore, the maximum breaking energy of circuit breaker 1A could be derived from the results in Table 1. The maximum breaking energy of circuit breaker 1A can be calculated using the following equation (2).

[0069] Here, E is the voltage of the electrical circuit 301. However, the maximum breaking energy varies depending on the specifications of the circuit breaker 1A used.

[0070] Table 2 below shows the tripping energy of circuit breaker 1A at various voltages. The tripping energy is calculated using formula (2) above, and in Table 2, the calculated tripping energy is rounded to the first decimal place.

[0071]

[0072] As can be seen from Table 2, the higher the voltage, the more difficult it becomes for circuit breakers 1A and 1B to interrupt the current, and therefore the maximum interrupting energy (energy that can be interrupted) decreases. Thus, in Table 2, the interrupting energy decreases as the voltage increases.

[0073] Furthermore, as can be seen in Table 2, the maximum interrupting energy (maximum interruptible energy) of a single circuit breaker 1A used in this evaluation when the voltage is 900V is 3000J. As can be seen from Table 2, the protective device 500 was able to interrupt the current when the energy flowing through the electrical circuit was less than 3000J. On the other hand, the protective device 500 was unable to interrupt the current when the energy flowing through the electrical circuit was greater than 3000J.

[0074] Next, we verified the tripping results when the voltage was set to 500V. Table 3 below shows the tripping results of the protective device 500 shown in Figure 5 when the voltage was set to 500V, the currents were 30kA, 25kA, 20kA, 15kA, 10kA, and 8.2kA, and the inductances were 12μH, 22μH, 32μH, 54μH, and 100μH. In Table 3, the energy (J) flowing through the electrical circuit and the tripping result for each current value and inductance value are represented by the symbols "○", "△", and "×". "○" indicates that tripping was successful, "△" indicates that tripping was apparent, but the insulation resistance value after tripping was lower than the standard, or it took a long time to complete the tripping, and "×" indicates that tripping was not successful. Note that in Table 3, the calculated cutting energy is rounded to the first decimal place when the current is 8.2 kA and the inductance is 12 μH, 22 μH, 32 μH, and 54 μH.

[0075]

[0076] As can be seen from Table 2, when the voltage is 500V, the maximum breaking energy (maximum energy that can be broken) of the 1A circuit breaker used in this evaluation is 4025J. Looking at Table 3, if the value is less than 4000J, the breaking result is marked with "○".

[0077] Next, we verified the tripping results when the voltage was set to 300V. Table 4 below shows the tripping results of the protective device 500 shown in Figure 5 when the voltage was set to 300V, the currents were 30kA, 25kA, 20kA, 15kA, and 10kA, and the inductances were 12μH, 22μH, 32μH, 54μH, and 100μH. In Table 4, the energy (J) flowing through the electrical circuit and the tripping result for each current value and inductance value are represented by the symbols "○", "△", and "×". "○" indicates that tripping was successful, "△" indicates that tripping was apparent, but the insulation resistance value after tripping was lower than the standard, or it took a long time to complete the tripping, and "×" indicates that tripping was not successful.

[0078]

[0079] As can be seen from Table 2, when the voltage is 300V, the maximum breaking energy (maximum energy that can be broken) of the 1A circuit breaker used in this evaluation is 5196J. Looking at Table 4, if the value is less than 5000J, the breaking result is marked with "○".

[0080] Furthermore, as can be seen from Table 2, it was estimated that the maximum breaking energy of circuit breaker 1A when the voltage is 1200V is 2598J, and the maximum breaking energy of circuit breaker 1A when the voltage is 1500V is 2324J.

[0081] In recent years, protective devices have been required to have sufficient interruption performance in high-voltage electrical circuits. For example, electric vehicles use high-voltage electrical circuits of 900V. A protective device 500 with only one 1A circuit breaker has a maximum interruption energy of 3000J at 900V. If the energy flowing through the electrical circuit is greater than 3000J, the protective device 500 in the comparative example cannot obtain satisfactory interruption results.

[0082] The protective device 300 according to this embodiment includes two circuit breakers, 1A and 1B. The inventors of this application have found that a good interruption result can be obtained by making the sum of the interruption energy of circuit breaker 1A and the interruption energy of circuit breaker 1B equal to or greater than the energy flowing through the electrical circuit 301 shown in the above formula (1).

[0083] Figure 8 is a graph verifying the tripping results using the protective device 300 according to this embodiment, which includes circuit breakers 1A and 1B. Figure 8 is a graph showing the changes in current and voltage before and after operation of circuit breakers 1A and 1B when the voltage is 900V, the current is 15kA, and the inductance is 22μH. The vertical axis on the left of Figure 8 represents current (kA), the vertical axis on the right of Figure 8 represents voltage (V), and the horizontal axis of Figure 8 represents time (ms). In Figure 8, line L1 shows the change in current measured by ammeter 304, line L2 shows the output voltage of DC power supply 302, and line L3 shows the change in voltage measured by voltmeter 305. In other words, in this evaluation, the same standard of electrical energy is supplied simultaneously to the two circuit breakers 1A and 1B. The output voltage of DC power supply 302 was measured using a voltmeter in the vicinity of DC power supply 302. The same applies to Figures 9 to 13 described later.

[0084] As shown in Figure 8, the current value indicated by line L1 becomes 0A at around 0.7ms, and the current remains stable at 0A thereafter, indicating that the current has been interrupted. From this graph, it was confirmed that the protective device 300 according to this embodiment can interrupt the current when the voltage is 900V, the current is 15kA, and the inductance is 22μH (when the energy flowing through the electrical circuit is 2475J). The interruption time was 0.27ms, which is shorter than the interruption time of protective device 500 (the interruption time in Figure 6 was 0.37ms) compared to the example in Figure 6 which uses one circuit breaker 1A in the same interruption circuit. The voltage indicated by line L3 rises due to arc generation when circuit breakers 1A and 1B are operated, similar to the example in Figure 6, but converges to 900V as the power supply voltage of 900V continues to be applied. The same applies to Figure 9, which will be described later.

[0085] Figure 9 is a graph verifying the tripping result using the protective device 300 according to this embodiment. Figure 9 is a graph showing the changes in current and voltage before and after operation of circuit breakers 1A and 1B (both of the same specifications connected in series) when the voltage is 900V, the current is 20kA, and the inductance is 22μH. Therefore, the conditions for the tripping circuit are the same as those in Figure 7 (where there was only one circuit breaker 1A and tripping was impossible). The vertical axis on the left of Figure 9 represents current (kA), the vertical axis on the right of Figure 9 represents voltage (V), and the horizontal axis of Figure 9 represents time (ms). Also, in Figure 9, line L1 shows the change in current measured by the ammeter 304, line L2 shows the output voltage of the DC power supply 302, and line L3 shows the change in voltage across circuit breakers 1A and 1B measured by the voltmeter 305. In other words, in this evaluation as well, the same standard of electrical energy is supplied simultaneously to two circuit breakers 1A and 1B of the same specifications. As shown in Figure 9, the current value indicated by line L1 becomes 0A at around 0.7ms, and the current remains stable at 0A thereafter, indicating that the current can be interrupted. From this graph, it was confirmed that when the voltage is 900V, the current is 20kA, and the inductance is 22μH (when the energy flowing through the electrical circuit is 4400J), a single circuit breaker could not interrupt the current, but the protective device 300 according to this embodiment was able to interrupt the current. The interruption time was 0.30ms.

[0086] The maximum breaking energy of circuit breakers 1A and 1B is the same, which is 3000 J each when the maximum breaking energy is 900 V. Therefore, the sum of the breaking energy of circuit breaker 1A and circuit breaker 1B is 6000 J, and the protective device 300 was able to interrupt the current because the energy flowing through the electrical circuit became 4400 J.

[0087] Figure 10 is a graph verifying the interruption results using the protective device 500 according to the comparative example, with one circuit breaker 1A used. Figure 10 is a graph showing the changes in current and voltage before and after operation of circuit breakers 1A and 1B when the voltage is 1200V, the current is 20kA, and the inductance is 12μH. The vertical axis on the left of Figure 10 represents current (kA), the vertical axis on the right of Figure 10 represents voltage (V), and the horizontal axis of Figure 10 represents time (ms). In Figure 10, line L1 shows the change in current measured by ammeter 304, line L2 shows the output voltage of DC power supply 302, and line L3 shows the change in voltage measured by voltmeter 305. As shown in Figure 10, the current value shown by line L1 can be seen to increase instantaneously around 2.3ms, but then it becomes 0A and stabilizes at 0A, so it can be determined that the current has been interrupted. From this graph, it was confirmed that the protective device 300 according to this embodiment can interrupt the current when the voltage is 1200V, the current is 20kA, and the inductance is 12μH (when the energy flowing through the electrical circuit is 2400J). The interruption time was 0.68ms. In the graph of Figure 10, the point at which the interruption was completed is indicated by an arrow. In this example, the reason why the voltage shown by line L3 rose again after initially dropping to 0V is thought to be because some form of arc remained, such as insufficient cooling by the coolant.

[0088] Figure 11 is a graph verifying the interruption results using the protective device 500 according to the comparative example (i.e., an example using one circuit breaker 1A). The graph shows the changes in current and voltage before and after the operation of circuit breaker 1A when the voltage is 1500V, the current is 20kA, and the inductance is 12μH. The vertical axis on the left of Figure 11 represents current (kA), the vertical axis on the right of Figure 11 represents voltage (V), and the horizontal axis of Figure 11 represents time (ms). In Figure 11, line L1 shows the change in current measured by ammeter 304, line L2 shows the output voltage of DC power supply 302, and line L3 shows the change in voltage measured by voltmeter 305. As shown in Figure 11, since the current shown by line L1 does not stabilize at 0A, it was confirmed that the current could not be interrupted under these conditions (voltage 1500V, current 20kA, inductance 12μH).

[0089] Figure 12 is a graph verifying the interruption result using a comparative example protection device 500 (i.e., an example using one circuit breaker 1A). Figure 12 is a graph showing the changes in current and voltage before and after the operation of circuit breaker 1A when the voltage is 1500V, the current is 15kA, and the inductance is 12μH. The vertical axis on the left of Figure 12 represents current (kA), the vertical axis on the right of Figure 12 represents voltage (V), and the horizontal axis of Figure 12 represents time (ms). In Figure 12, line L1 shows the change in current measured by ammeter 304, line L2 shows the output voltage of DC power supply 302, and line L3 shows the change in voltage measured by voltmeter 305. As shown in Figure 12, the current value shown by line L1 becomes 0A around 2.3ms and remains stable at 0A thereafter, so it can be determined that the current has been interrupted. From this graph, it was confirmed that the protective device 300 according to this embodiment can interrupt the current when the voltage is 1500V, the current is 15kA, and the inductance is 12μH (when the energy flowing through the electrical circuit is 1350J). The interruption time was 0.34ms.

[0090] Figure 13 is a graph verifying the tripping result using the protective device 300 according to this embodiment (i.e., when two circuit breakers of the same specifications are connected in series and the same operating energy is supplied to the two circuit breakers 1A and 1B simultaneously). Figure 13 is a graph showing the changes in current and voltage before and after operation of circuit breakers 1A and 1B when the voltage is 1500V, the current is 20kA, and the inductance is 12μH. The vertical axis on the left of Figure 13 represents current (kA), the vertical axis on the right of Figure 13 represents voltage (V), and the horizontal axis of Figure 13 represents time (ms). In Figure 13, line L1 shows the trend of the total current (kA) of the entire electrical circuit 301 as measured by the ammeter 304, line L2 shows the voltage (potential difference) of the upstream circuit breaker 1A, line L3 shows the trend of the current value (A) of the igniter 20 used in circuit breakers 1A and 1B, and line L4 shows the trend of the voltage (potential difference) of the downstream circuit breaker 1B. As shown in Figure 12, the current value shown by line L1 becomes 0A around 3.0m and remains stable at 0A thereafter, so it can be determined that the current is being interrupted. From this graph, it was confirmed that the protective device 300 according to this embodiment can interrupt the current when the voltage is 1500V, the current is 20k, and the inductance is 12μH (when the energy flowing through the electrical circuit is 2400J). The interruption time was 0.32ms.

[0091] Figure 14 is a graph showing the relationship between maximum cutoff energy and voltage, as shown in Table 2. The vertical axis of Figure 14 represents maximum cutoff energy (J), and the horizontal axis represents voltage (V). In Figure 14, the five values ​​shown in Table 2 are plotted, and each point is connected by a straight line.

[0092] In a circuit with a voltage of 1500V, the energy flowing through electrical circuit 301 is 2400J, while Table 2 shows that the maximum energy that can be interrupted by a single circuit breaker is 2324J, indicating insufficient interrupting capacity. However, by connecting two circuit breakers 1A and 1B in series, the voltage across each circuit breaker becomes 750V. From the graph in Figure 14, it can be estimated that the maximum interrupting energy at 750V is 3300J. Therefore, it can be estimated that the maximum interrupting energy per circuit breaker is approximately 3300J based on the trend in Table 2. Thus, in the example shown in Figure 13, it is considered that current interruption became possible.

[0093] From the above, it has been confirmed that the protective device 300 can interrupt the current when the sum of the maximum interruption energy of circuit breaker 1A and the maximum interruption energy of circuit breaker 1B is equal to or greater than the energy flowing through the electrical circuit. In the above embodiment, circuit breaker 1A and circuit breaker 1B have the same maximum interruption energy, but this disclosure is not limited to this. For example, the maximum interruption energy of circuit breaker 1A and the maximum interruption energy of circuit breaker 1B may be different. Furthermore, the protective device 300 may be equipped with three or more circuit breakers. In this case as well, each circuit breaker is connected in series with respect to the others, and the protective device 300 can interrupt the current when the sum of the maximum interruption energies of each circuit breaker is equal to or greater than the energy flowing through the electrical circuit.

[0094] Furthermore, the maximum breaking energy of a circuit breaker is not limited to the value calculated by equation (2) above. The maximum breaking energy of a circuit breaker can be derived by performing various tests in which the voltage, current, and inductance values ​​of the electrical circuit are changed.

[0095] Next, we verified the tripping performance of two circuit breakers 1A and 1B connected in series, when they were operated sequentially with a time difference, rather than simultaneously. The results are shown below. Note that both circuit breakers 1A and 1B are of the same specifications.

[0096] <Comparative Example (Single Circuit Breaker)> First, as a comparative example, an experiment was conducted on the interruption performance when the circuit was interrupted by a single circuit breaker (in this experiment, referred to as circuit breaker 1A) without connecting the two circuit breakers 1A and 1B in series. In other words, this comparative example is an experimental example of the circuit configuration of the protective device 500 shown in Figure 5. Figure 15 is a graph showing the experimental results of the current and voltage changes before and after the operation of circuit breaker 1A when the circuit is interrupted by a single circuit breaker 1A. This experiment was conducted with a voltage of 500V, a current of 20kA, and an inductance of 35μH. In Figure 15, line L1 shows the change in current measured by ammeter 304, line L3 shows the change in voltage measured by voltmeter 305, and line L5 shows the change in the energized current of the ignition part 21 of circuit breaker 1A.

[0097] As shown in Figure 15, when the ignition unit 21 of the circuit breaker 1A is energized and the circuit breaker 1A operates, the current value begins to decrease at around 0.8 ms as shown by line L1, but an abnormal current of about 2 to 4 kA continues to flow, and the current is not properly interrupted (in Figure 15, the current converges to around 0 kA at around 13.5 ms, but this is not due to interruption). Furthermore, since light emission was observed at around 9.1 ms in the video of the circuit breaker 1A, it was also confirmed from the video that the current was not properly interrupted and an abnormal current continued to flow.

[0098] <Example (Multiple Circuit Breakers)> Next, as an example, two circuit breakers 1A and 1B were connected in series, and an experiment was conducted on the tripping performance when each circuit breaker was operated sequentially with a time difference, rather than simultaneously. In other words, this example is an experimental example of the circuit configuration of the protective device 300 shown in Figure 1. In this example, experiments were conducted under the following five conditions: Condition 1: Voltage 500V, Current 20kA, Inductance 35μH, Time difference 3.8ms Condition 2: Voltage 500V, Current 20kA, Inductance 35μH, Time difference 7.1ms Condition 3: Voltage 500V, Current 20kA, Inductance 35μH, Time difference 8.6ms Condition 4: Voltage 900V, Current 15.5kA, Inductance 35μH, Time difference 2.5ms Condition 5: Voltage 900V, Current 15.5kA, Inductance 35μH, Time difference 3.5ms

[0099] Figure 16 is a graph showing the experimental results of the current and voltage changes before and after the operation of circuit breakers 1A and 1B when multiple circuit breakers 1A and 1B are operated sequentially under condition 1 to interrupt the circuit. In Figure 16, line L1 shows the change in current measured by ammeter 304, line L3 shows the change in voltage measured by voltmeter 305, line L5 shows the change in the current flowing through the ignition part 21 of circuit breaker 1A, and line L6 shows the change in the current flowing through the ignition part 21 of circuit breaker 1B.

[0100] Under condition 1, as shown in Figure 16, when the ignition unit 21 of circuit breaker 1A is energized and circuit breaker 1A operates, the current value begins to decrease at around 0.8 ms as shown by line L1, but an abnormal current of about 2 to 4 kA continues to flow, and the current is not properly interrupted until circuit breaker 1B operates. However, when the ignition unit 21 of circuit breaker 1B is energized and circuit breaker 1B operates 3.8 ms after the operation of circuit breaker 1A, the current value becomes 0 kA as shown by line L1, confirming that the current can be properly interrupted.

[0101] Figure 17 is a graph showing the experimental results of the current and voltage changes before and after the operation of multiple circuit breakers 1A and 1B when the circuit is interrupted by sequentially operating them under condition 2. Lines L1, L3, L5, and L6 shown in Figure 17 are the same as in Figure 16.

[0102] In condition 2, as in condition 1, as shown in Figure 17, when the ignition unit 21 of circuit breaker 1A is energized and circuit breaker 1A operates, the current value begins to decrease at around 0.8 ms as shown by line L1, but an abnormal current of about 2 to 4 kA continues to flow, and the current is not properly interrupted until circuit breaker 1B operates. However, when the ignition unit 21 of circuit breaker 1B is energized and circuit breaker 1B operates 7.1 ms after the operation of circuit breaker 1A, the current value becomes 0 kA as shown by line L1, confirming that the current can be properly interrupted.

[0103] Figure 18 is a graph showing the experimental results of the current and voltage changes before and after the operation of circuit breakers 1A and 1B when multiple circuit breakers 1A and 1B are operated sequentially under condition 3 to interrupt the circuit. Lines L1, L3, L5, and L6 shown in Figure 18 are the same as in Figure 16.

[0104] In condition 3, as in condition 1, as shown in Figure 18, when the ignition unit 21 of circuit breaker 1A is energized and circuit breaker 1A operates, the current value begins to decrease at around 0.8 ms as shown by line L1, but an abnormal current of about 2 to 4 kA continues to flow, and the current is not properly interrupted until circuit breaker 1B operates. However, when the ignition unit 21 of circuit breaker 1B is energized and circuit breaker 1B operates 8.6 ms after the operation of circuit breaker 1A, the current value becomes 0 kA as shown by line L1, confirming that the current can be properly interrupted.

[0105] Figure 19 is a graph showing the experimental results of the current and voltage changes before and after the operation of circuit breakers 1A and 1B when multiple circuit breakers 1A and 1B are operated sequentially under condition 4 to interrupt the circuit. Lines L1, L3, L5, and L6 shown in Figure 19 are the same as in Figure 16.

[0106] In condition 4, as in condition 1, as shown in Figure 19, when the ignition unit 21 of circuit breaker 1A is energized and circuit breaker 1A operates, the current value begins to decrease at around 0.8 ms as shown by line L1, but an abnormal current of about 2 to 6 kA continues to flow, and the current is not properly interrupted until circuit breaker 1B operates. However, when the ignition unit 21 of circuit breaker 1B is energized and circuit breaker 1B operates 2.5 ms after the operation of circuit breaker 1A, the current value becomes 0 kA as shown by line L1, confirming that the current can be properly interrupted.

[0107] Figure 20 is a graph showing the experimental results of the current and voltage changes before and after the operation of circuit breakers 1A and 1B when multiple circuit breakers 1A and 1B are operated sequentially under condition 5 to interrupt the circuit. Lines L1, L3, L5, and L6 shown in Figure 20 are the same as in Figure 16.

[0108] In condition 5, as in condition 1, as shown in Figure 20, when the ignition unit 21 of circuit breaker 1A is energized and circuit breaker 1A operates, the current value begins to decrease at around 0.8 ms as shown by line L1, but an abnormal current of about 2 to 7 kA continues to flow, and the current is not properly interrupted until circuit breaker 1B operates. However, when the ignition unit 21 of circuit breaker 1B is energized and circuit breaker 1B operates 3.5 ms after the operation of circuit breaker 1A, the current value becomes 0 kA as shown by line L1, confirming that the current can be properly interrupted.

[0109] Based on the experimental results of the above-described embodiment, even when two circuit breakers 1A and 1B are connected in series and operated sequentially with a time difference rather than simultaneously, it can be said that the current flowing through the electrical circuit 301 can be properly interrupted if the second circuit breaker 1B is operated within 8.6 ms after the first circuit breaker 1A is operated.

[0110] The protective device 300 according to this embodiment can quickly and reliably shut off the power supply in the event of an excessive abnormal current occurring due to an accident, lightning strike, contact with birds or animals, or deterioration over time in power systems such as electric vehicles, hybrid vehicles, power transmission and distribution networks, railway systems, and renewable energy sources.

[0111] While embodiments of the electrical circuit protection device relating to this disclosure have been described above, each embodiment disclosed herein can be combined with any other features disclosed herein.

[0112] 1A: Current circuit breaker 1B: Current circuit breaker 3: Control device 10: Housing 11: First end 12: Second end 13: Enclosure space 20: Ignition device 50: Conductor piece 300: Electrical circuit protection device 301: Electrical circuit 302: DC power supply 303: Switch 304: Ammeter 305: Voltmeter 306: Control unit 307: Current sensor 308: Drive circuit

Claims

1. A first current circuit breaker having a first conductor piece that forms part of an electrical circuit and a first igniter for cutting the first conductor piece; and a second current circuit breaker having a second conductor piece connected in series with the first conductor piece of the first current circuit breaker to form part of the electrical circuit and a second igniter for cutting the second conductor piece, wherein both the first and second current circuit breakers are pyrotechnic current circuit breakers that operate using gunpowder that is ignited and burned by energy supplied from an external source, and the energy required to interrupt the electricity flowing through the electrical circuit is shown by equation (1), An electrical circuit protection device in which H is the inductance of the electrical circuit, A is the current flowing through the electrical circuit, and the sum of the interrupting energy of the first current circuit breaker and the interrupting energy of the second current circuit breaker is greater than or equal to the energy flowing through the electrical circuit as shown in formula (1).

2. The electrical circuit protection device according to claim 1, comprising a control unit that controls the timing of supplying ignition current to each of the first igniter and the second igniter, wherein the control unit can operate each of the first igniter and the second igniter at any timing.

3. The electrical circuit protection device according to claim 2, wherein the control unit activates the second igniter within 8.6 milliseconds after activating the first igniter.

4. The electrical circuit protection device according to claim 2, comprising an abnormality detection unit connected to the control unit for detecting an abnormality in the electrical circuit, wherein the control unit supplies the ignition current to the first igniter and the second igniter at an arbitrary timing when the abnormality detection unit detects the abnormality.

5. The electrical circuit protection device according to claim 2 or 4, wherein the time required from the time the ignition current is supplied to at least one of the first igniter and the second igniter until the current in the electrical circuit is interrupted is 0.32 milliseconds or less.

6. The electrical circuit protection device according to any one of claims 1 to 4, wherein the first current circuit breaker and the second current circuit breaker each have different interruption energies.

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