Circuit breaker

Abstract

To instantaneously cut off a conductor.SOLUTION: A circuit breaker comprising: a semiconductor element that interrupts a conducting wire when a gate is turned off; a reed switch that is turned on by a magnetic field generated by a short-circuit current flowing through the conducting wire; and a gate driver that turns off the gate when the reed switch is turned on.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a circuit breaker. [Background technology]

[0002] BACKGROUND ART Conventionally, there is known a switch that includes a mechanical switch connected to a main circuit and that cuts off the main circuit current when the mechanical switch is opened (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2015-225812 Summary of the Invention [Problem to be solved by the invention]

[0004] When a short-circuit current flows through a conductor, it is necessary to instantly interrupt the conductor. However, with mechanical switches, it is difficult to do so because there is a risk of an arc occurring when the conductor is interrupted.

[0005] An object of the present disclosure is to instantly disconnect a conductor. [Means for solving the problem]

[0006] The present disclosure provides: a semiconductor element that cuts off the conductor when the gate is turned off; a reed switch that is turned on by a magnetic field generated by a short-circuit current flowing through the conductor; and a gate driver that turns off the gate when the reed switch is turned on. [Effects of the Invention]

[0007] According to the present disclosure, the conductor can be instantly disconnected. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a configuration diagram illustrating an example of a circuit breaker according to a first embodiment. [Figure 2] FIG. 2 is a circuit diagram illustrating an example of a gate driver. [Figure 3] FIG. 3 is a configuration diagram showing a modified example of the circuit breaker according to the first embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described. Note that "connection" is not limited to physical connection, but may also mean electrical connection. For example, connecting an object α to an object β is not limited to the case where the object α is conductively connected to the object β (e.g., at the same potential), but may also include the case where the object α is conductively connected to the object β via the object γ.

[0010] Fig. 1 is a structural diagram showing an example of a circuit breaker according to a first embodiment. The circuit breaker 101 shown in Fig. 1 is a molded case circuit breaker that, when a short-circuit current caused by a short circuit in a circuit flows in the conductor 2, interrupts the conductor 2 using a semiconductor element 10. The circuit breaker 101 interrupts the flow of the short-circuit current in the conductor 2 by using the semiconductor element 10 to interrupt the conductor 2 through which the short-circuit current flows, thereby protecting the circuit from the short-circuit current. The circuit breaker 101 includes the semiconductor element 10, a reed switch 20, and a gate driver 30.

[0011] The semiconductor element 10 cuts off the conductor 2 when the gate G is turned off. In this example, the semiconductor element 10 is a semiconductor switch that is provided on the conductor 2 and cuts off or conducts the current I flowing through the conductor 2. The semiconductor element 10 is inserted in series with the conductor 2. The current I may be a direct current or an alternating current. FIG. 1 illustrates an example of the semiconductor element 10 as a bidirectional switch that can cut off or conduct the current I flowing in both directions through the conductor 2.

[0012] 1 has a configuration in which two IGBTs (Q1, Q2) that are semiconductor switching devices are connected in anti-series, a diode D1 is connected in anti-parallel to the IGBT (Q1), and a diode D2 is connected in anti-parallel to the IGBT (Q2). That is, this bidirectional switch has a configuration in which the emitters of the two IGBTs (Q1, Q2) are connected to each other, the anode of the diode D1 is connected to the emitter of the IGBT (Q1), the cathode of the diode D1 is connected to the collector of the IGBT (Q1), the anode of the diode D2 is connected to the emitter of the IGBT (Q2), and the cathode of the diode D2 is connected to the collector of the IGBT (Q2).

[0013] For convenience of explanation, the collectors of the IGBTs (Q1, Q2) are respectively referred to as terminals a, b of the bidirectional switch.

[0014] In the bidirectional switch shown in FIG. 1, when a current flows from terminal a to terminal b, the gate driver 30 applies a gate voltage Vg to the gate G of the IGBT (Q1) to turn on the IGBT (Q1). As a result, the current I flows from terminal a through the IGBT (Q1) and diode D2 to terminal b. Alternatively, when a current flows from terminal a to terminal b, the gate driver 30 may apply a gate voltage Vg to the gates G of both IGBTs (Q1, Q2) to turn on both IGBTs (Q1, Q2). As a result, the current I flows from terminal a through the IGBT (Q1) and IGBT (Q2) to terminal b.

[0015] Conversely, when a current is to flow from terminal b to terminal a, the gate driver 30 applies a gate voltage Vg to the gate G of the IGBT (Q2) to turn on the IGBT (Q2). As a result, the current I flows from terminal b through the IGBT (Q2) and diode D1 to the terminal a. Alternatively, when a current is to flow from terminal b to terminal a, the gate driver 30 may apply a gate voltage Vg to the gates G of both IGBTs (Q1, Q2) to turn on both IGBTs (Q1, Q2). As a result, the current I flows from terminal b through the IGBT (Q2) and IGBT (Q1) to the terminal a.

[0016] The semiconductor switching elements are not limited to IGBTs (Insulated Gate Bipolar Transistors) and may be other semiconductor switching elements such as GTO (Gate Turn Off) thyristors. The diodes D1 and D2 may be body diodes of semiconductor elements such as MOSFETs (Metal Oxide Semiconductor Field Effect Transistors). If the current I is a direct current flowing from terminal a to terminal b, the diode D2 and the IGBT (Q2) may be omitted. If the current I is a direct current flowing from terminal b to terminal a, the diode D1 and the IGBT (Q1) may be omitted.

[0017] The reed switch 20 is turned on by a magnetic field H generated by a short-circuit current flowing through the conductor 2. The short-circuit current is a current that flows through the conductor 2 due to a short circuit. The current value of the short-circuit current is much larger than the current I that flows through the conductor 2 under normal conditions (when not short-circuited), for example, 10 kA or more. The reed switch 20 may have a known structure. When a strong magnetic field H generated by the short-circuit current flowing through the conductor 2 is applied to the reed switch 20, the individual reeds in the reed switch 20 are attracted to each other by magnetic attraction, and the contacts of the individual reeds close (reed switch 20 turns on). When the magnetic field H applied to the reed switch 20 weakens, the magnetic attraction force that attracts the individual reeds to each other also weakens, and the contacts open (reed switch 20 turns off).

[0018] Gate driver 30 is a circuit that turns off the gate of semiconductor element 10 by turning on reed switch 20. When the gate of semiconductor element 10 is turned off, conductor 2 is interrupted by semiconductor element 10. Therefore, the flow of short-circuit current in conductor 2 is interrupted, and circuit breaker 101 can protect the circuit from the short-circuit current.

[0019] Thus, in the circuit breaker 101 according to the first embodiment, when a short-circuit current flows through the conductor 2, the magnetic field H generated by the short-circuit current quickly turns on the reed switch 20. When the reed switch 20 turns on, the gate driver 30 quickly turns off the gate of the semiconductor element 10, thereby instantaneously breaking the conductor 2. Furthermore, compared to a mechanical switch, the semiconductor element 10 generates almost no arc when breaking the conductor 2, so it can instantaneously break the conductor 2.

[0020] The gate driver 30 may have a self-holding circuit 35 that turns off the gate of the semiconductor element 10 when the reed switch 20 is turned on. By including the self-holding circuit 35, the gate driver 30 can prevent the gate of the semiconductor element 10 from being accidentally released from its off state. When the gate of the semiconductor element 10 is released from its off state, the semiconductor element 10 releases the interruption of the conductor 2, allowing the conductor 2 to become conductive. For example, if the gate of the semiconductor element 10 is accidentally released from its off state at a time when it should not be released, the interruption of the conductor 2 may be released, potentially causing a short-circuit current to flow through the conductor 2 again. By including the self-holding circuit 35 in the gate driver 30, the likelihood of such an event occurring can be reduced.

[0021] When a short-circuit current flows through the conductor 2, the conductor 2 is instantly cut off by the semiconductor element 10, as described above. The cutting off of the conductor 2 stops the flow of the short-circuit current. When the flow of the short-circuit current stops, the magnetic field H generated by the short-circuit current weakens and disappears, turning off the reed switch 20. The self-holding circuit 35 keeps the gate of the semiconductor element 10 off, even when the magnetic field H generated by the short-circuit current weakens due to the cutting off of the conductor 2, turning off the reed switch 20. This prevents the gate driver 30 from erroneously releasing the gate off of the semiconductor element 10 by turning off the reed switch 20. This reduces the possibility of the short-circuit current flowing again through the conductor 2, as described above.

[0022] The circuit breaker 101 may further include a control circuit 40 that generates a control signal Sg to be supplied to the gate driver 30. The control circuit 40 may be provided inside the circuit breaker 101 or outside the circuit breaker 101.

[0023] When the control signal Sg is an ON command for the gate G of the semiconductor element 10, the self-holding circuit 35 keeps the gate G of the semiconductor element 10 OFF (gate OFF) even if the reed switch 20 is OFF. As a result, if the control signal Sg is an ON command, even if the reed switch 20 is turned OFF due to the disappearance of the magnetic field H caused by the interruption of the conductor 2, the gate of the semiconductor element 10 is kept OFF by the self-holding circuit 35. Therefore, as described above, it is possible to reduce the possibility of an event occurring in which a short-circuit current flows again in the conductor 2. The ON command for the gate G refers to a control signal that turns the gate G ON.

[0024] When the control signal Sg changes from an ON command for the gate G of the semiconductor element 10 to an OFF command for the gate G, the self-holding circuit 35 releases the gate OFF hold of the semiconductor element 10. As a result, when the control signal Sg changes from an ON command to an OFF command, the self-holding circuit 35 can release the gate OFF hold. At this time, even if the self-holding circuit 35 releases the gate OFF hold, the gate driver 30 maintains the gate OFF of the semiconductor element 10. This prevents the semiconductor element 10 from being released from shutting off even if the gate OFF hold by the self-holding circuit 35 is released, and reduces the possibility of an event occurring in which a short-circuit current flows again through the conductor 2. The OFF command for the gate G refers to a control signal that turns off the gate G.

[0025] The control circuit 40 may change the control signal Sg from an ON command to an OFF command based on a first operation input from the user, thereby allowing the user to release the gate OFF state held by the self-holding circuit 35 by providing a predetermined first operation input to the control circuit 40.

[0026] When the control signal Sg changes from an OFF command to an ON command, the gate driver 30 turns on the gate G of the semiconductor element 10. As a result, after the cause of the short-circuit current is removed, the control signal Sg changes from an OFF command to an ON command, which releases the interruption of the conductor 2 by the semiconductor element 10 and allows the conduction of the conductor 2 to be safely resumed.

[0027] The control circuit 40 may change the control signal Sg from an OFF command to an ON command based on a second operation input from the user. This allows the user to safely resume continuity of the conductor 2 by providing a predetermined second operation input to the control circuit 40, so that the conductor 2 is made conductive after the cause of the short-circuit current is removed.

[0028] The user's operation input (first operation input and second operation input) is input via an operation input interface provided in the circuit breaker 101. Examples of the operation input interface include, but are not limited to, a button, a switch, an operation panel, etc. For example, the user's operation input may be a signal input to the control circuit 40 from outside the circuit breaker 101 wirelessly or via a wire.

[0029] For example, when the control circuit 40 detects a first operation input (first operation input), it changes the control signal Sg from an ON command to an OFF command. This releases the self-holding circuit 35 from holding the gate OFF. Subsequently, when the control circuit 40 detects a second operation input (second operation input) within a predetermined time after the detection of the first operation input (first operation input), it changes the control signal Sg from an OFF command to an ON command. This allows the second operation input to be applied after the cause of the short-circuit current has been removed, thereby releasing the interruption of the conductor 2 and safely restoring continuity to the conductor 2.

[0030] The control circuit 40 outputs a control signal Sg (ON command) that turns on the semiconductor element 10 or a control signal Sg (OFF command) that turns off the semiconductor element 10. Under normal conditions, the gate driver 30 switches the semiconductor element 10 on or off in accordance with the control signal Sg output from the control circuit 40.

[0031] Under normal conditions, when the control circuit 40 outputs a control signal Sg that turns on the semiconductor element 10 and the reed switch 20 turns on, the gate driver 30 turns off the gate of the semiconductor element 10 regardless of the control signal Sg that turns on the semiconductor element 10. This allows the circuit breaker 101 to shorten the time required from when a short-circuit current occurs in the conductor 2 to when the conductor 2 is interrupted, compared to a configuration in which the control circuit 40 is interposed in the control path from when the reed switch 20 turns on to when the gate of the semiconductor element 10 is turned off. Therefore, the circuit breaker 101 can quickly protect the circuit from a short-circuit current flowing in the conductor 2.

[0032] The circuit breaker 101 may further include a current detection device 5 that detects a predetermined current to be detected flowing through the conductor 2. The current detection device 5 may be provided inside the circuit breaker 101 or may be provided outside the circuit breaker 101. The predetermined current to be detected is, for example, an overcurrent whose absolute value is equal to or greater than a predetermined first threshold and less than the current value of a short-circuit current. The predetermined current to be detected may also be a minute current (for example, a leakage current due to a ground fault, etc.) whose absolute value is greater than zero and equal to or less than a predetermined second threshold. The second threshold is smaller than the first threshold.

[0033] When a predetermined current to be detected is detected by the current detection device 5, the control circuit 40 changes the control signal Sg from an ON command that turns on the semiconductor element 10 to an OFF command that turns off the semiconductor element 10. The gate driver 30 turns off the gate of the semiconductor element 10 in accordance with the OFF command. As a result, the conductor 2 is interrupted by the semiconductor element 10, and the flow of the current to be detected flowing through the conductor 2 is interrupted. Therefore, the circuit breaker 101 can protect the circuit from the current to be detected, such as an overcurrent.

[0034] The current detection device 5 includes, for example, a magnetic core 3, a winding 4, and a current detection circuit 6.

[0035] The magnetic core 3 is an annular magnetic member that surrounds the conductive wire 2. An example of a material that constitutes the magnetic core 3 is a soft magnetic material such as an Fe-Ni based magnetic alloy. However, the material that constitutes the magnetic core 3 is not limited thereto.

[0036] As the magnetic field acting on the magnetic core 3 becomes stronger, the magnetic flux density passing through the magnetic core 3 also increases. Furthermore, when the magnetic field acting on the magnetic core 3 becomes even stronger and exceeds a predetermined value, the magnetic flux density passing through the magnetic core 3 stops changing. In other words, the magnetic core 3 becomes magnetically saturated.

[0037] The winding 4 is wound around the magnetic core 3. When a direct current or alternating current flows through the winding 4, a magnetic field is generated inside the winding 4. If the magnetic core 3 is not magnetically saturated, the magnetic flux density passing through the magnetic core 3 changes in response to changes in the magnetic field generated inside the winding 4. Note that the number of turns, cross-sectional area, etc. of the winding 4 are not limited.

[0038] The current detection circuit 6 detects the target current based on the voltage generated in the winding 4. The method for detecting the target current may be a known method. For example, when the current detection circuit 6 detects the target current, it outputs a detection signal indicating that the target current has been detected to the control circuit 40.

[0039] 2 is a circuit diagram showing an example of a gate driver. The gate driver 30 generates a gate voltage Vg to be applied to the semiconductor element 10 via a gate line 31. The gate driver 30 has a resistor R1, a resistor R2, a transistor 32, and a self-holding circuit 35. The transistor 32 is an NPN transistor. The self-holding circuit 35 has a PNP transistor 33 and an NPN transistor 34.

[0040] Transistor 32 has a collector C connected to a power supply line VCC via a resistor R1, a base B to which a control signal Sg is input, and an emitter E connected to a gate line 31. Gate line 31 is connected to ground GND via a resistor R2.

[0041] In this example, each transistor is a bipolar transistor, but may be another type of transistor such as a MOSFET.

[0042] In normal operation, before a short-circuit current flows through the conductor 2, the reed switch 20 is off, and so the self-holding circuit 35 does not function. When the control signal Sg is a signal to turn on the semiconductor element 10 (in this example, a high-level on command), the gate driver 30 turns on the transistor 32 to generate a high-level gate voltage Vg. This turns on the gate G of the semiconductor element 10, allowing the conductor 2 to conduct. On the other hand, when the control signal Sg is a signal to turn off the semiconductor element 10 (in this example, a low-level off command), the gate driver 30 turns off the transistor 32 to generate a low-level gate voltage Vg. This turns off the gate G of the semiconductor element 10, and the conductor 2 is interrupted.

[0043] When the reed switch 20 is turned on, the self-holding circuit 35 electrically connects the gate line 31 of the semiconductor element 10 to ground GND. This turns off the gate G of the semiconductor element 10 and interrupts the conductive wire 2. In this example, the reed switch 20 is inserted in series between the gate line 31 and the input section 36 of the self-holding circuit 35, so when the reed switch 20 is turned on, the gate line 31 of the semiconductor element 10 is electrically connected to ground GND by the self-holding circuit 35.

[0044] The self-holding circuit 35 is a latch circuit having a transistor 33 and a transistor 34. The transistor 33 has an emitter E connected to the emitter E of the transistor 32, a base B connected to the collector C of the transistor 34, and a collector C connected to the base B of the transistor 34 and one end (input 36) of the reed switch 20. The transistor 34 has an emitter E connected to ground GND, a collector C connected to the base B of the transistor 33, and a base B connected to the collector C of the transistor 33 and one end (input 36) of the reed switch 20.

[0045] When the reed switch 20 is turned on while the transistor 32 is on, a base current flows from the power supply line VCC to the base B of the transistor 34 via the transistor 32 and the reed switch 20. This turns on the transistor 34, causing a current to flow from the emitter E to the base B of the transistor 33. The current flowing to the base B of the transistor 33 turns the transistor 33 on, causing a base current to flow to the base B of the transistor 34 via the transistor 33. As a result, even when the reed switch 20 is turned off, the current continues to flow to the base B of the transistor 34 via the transistor 33, so the electrical connection between the gate line 31 and ground GND (the gate of the semiconductor element 10 is off) is maintained by the self-holding circuit 35.

[0046] Since the control signal Sg is an ON command, the ON state of the transistor 32 is maintained, and therefore, current is supplied from the power supply line VCC to the self-holding circuit 35 via the transistor 32. Therefore, since the control signal Sg is an ON command, the self-holding circuit 35 can keep the gate of the semiconductor element 10 OFF even if the reed switch 20 is OFF.

[0047] When the control signal Sg changes from an ON command to an OFF command, the transistor 32 turns OFF. This cuts off the current supply to the self-holding circuit 35, and both transistors 33 and 34 turn OFF. As a result, the self-holding circuit 35 releases the electrical connection between the gate line 31 and ground GND (holding the gate OFF). At this time, the gate line 31 is connected to ground GND via resistor R2, so the gate OFF of the semiconductor element 10 is maintained by the gate driver 30.

[0048] When the control signal Sg changes from an OFF command to an ON command, the transistor 32 turns ON again, and the gate driver 30 outputs the gate voltage Vg that turns the gate G ON.

[0049] Fig. 3 is a configuration diagram showing a modified example of the circuit breaker according to the first embodiment. A circuit breaker 101a shown in Fig. 3 differs from the circuit breaker 101 shown in Fig. 1 in the form of a bidirectional switch, which is an example of a semiconductor element 10. The bidirectional switch shown in Fig. 3 differs from the bidirectional switch shown in Fig. 1 in that the collectors of two IGBTs (Q1, Q2) are connected to each other. The bidirectional switch shown in Fig. 3 also operates in the same manner as the above-described operation of the bidirectional switch shown in Fig. 1.

[0050] In the present disclosure, the control circuit 40 is an electronic circuit such as a central processing unit (CPU), a field programmable gate array (FPGA), or an application specific integrated circuit (ASIC). The control circuit 40 may be a computer (e.g., a microcomputer) having a processor. The control circuit 40 executes various control operations described herein by executing a program such as instruction code stored in a memory or by being a circuit designed for a specific application.

[0051] Although the embodiments have been described above, they are presented as examples and the present invention is not limited to these embodiments. The embodiments can be implemented in various other forms, and various combinations, omissions, substitutions, modifications, etc. can be made without departing from the spirit of the invention. These embodiments and their modifications are included within the scope and spirit of the invention, and are also included in the scope of the invention and its equivalents as set forth in the claims. [Explanation of symbols]

[0052] 2 conductors 3 Magnetic Core 4 windings 5 Current detection device 6 Current detection circuit 10 Semiconductor elements 20 Reed Switch 30 Gate Driver 31 Gate Line 32, 33, 34 Transistors 35 Self-holding circuit 36 Input section 40 Control circuit 101,101a circuit breaker

Claims

1. a semiconductor element that cuts off the conductor when the gate is turned off; a reed switch that is turned on by a magnetic field generated by a short-circuit current flowing through the conductor; a gate driver that turns off the gate when the reed switch is turned on.

2. The circuit breaker according to claim 1 , wherein the gate driver has a self-holding circuit that turns off the gate when the reed switch is turned on.

3. 3. The circuit breaker according to claim 2, wherein the self-holding circuit holds the gate of the semiconductor element in an OFF state even when the reed switch is turned off due to a weakening of the magnetic field caused by the interruption of the conductor.

4. a control circuit for generating a control signal to be supplied to the gate driver; 4. The circuit breaker according to claim 3, wherein when the control signal is an ON command for the gate, the self-holding circuit holds the gate OFF even when the reed switch is OFF.

5. The circuit breaker according to claim 4 , wherein the self-holding circuit releases the gate from being held in the OFF state when the control signal changes from the ON command to an OFF command for the gate.

6. The circuit breaker according to claim 5 , wherein the gate driver maintains the gate off even when the self-holding circuit releases the gate off hold.

7. The circuit breaker according to claim 6 , wherein the gate driver turns on the gate when the control signal changes from the OFF command to the ON command.

8. The circuit breaker according to claim 5 , wherein the control circuit changes the control signal from the ON command to the OFF command based on an operation input by a user.

9. The circuit breaker according to claim 7 , wherein the control circuit changes the control signal from the OFF command to the ON command based on an operation input by a user.

10. a control circuit for generating a control signal to be supplied to the gate driver; The circuit breaker according to claim 1 , wherein the gate driver turns off the gate when the reed switch is turned on while the control signal is an on command for the gate.

11. a current detection device for detecting a predetermined current to be detected flowing through the conductor; The circuit breaker according to claim 10 , wherein the control circuit changes the control signal from the ON command to an OFF command for the gate when the current to be detected is detected by the current detection device.

12. The circuit breaker according to claim 2 , wherein the self-holding circuit electrically connects a gate line of the semiconductor element to ground when the reed switch is turned on.

13. 13. The circuit breaker of claim 12, wherein the reed switch is inserted in series between the gate line and the input of the self-holding circuit.

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