Overcurrent detectors and circuit breakers

Abstract

An overcurrent detector (100) detects DC current flowing through a conductor (91). The overcurrent detector (100) comprises a fixed iron core (2) and a movable iron core (3). The fixed iron core (2) constitutes a gap (71). The movable iron core (3) is disposed in the gap (71). The fixed iron core (2) and the movable iron core (3) constitute a magnetic path (11). The magnetic path (11) surrounds the conductor (91). When DC current is not flowing through the conductor (91), the movable iron core (3) is separated from the fixed iron core (2). The magnetic path (11) has a magnetic flux rectifier (7). When DC current flows through the conductor (91) in a first direction (101), the magnetic resistance of the magnetic flux rectifier (7) is reduced. When DC current flows through the conductor (91) in a second direction (102) opposite to the first direction (101), the magnetic resistance of the magnetic flux rectifier (7) is increased.

Description

[Technical Field]

[0001] The present disclosure relates to overcurrent detectors and circuit breakers. [Background technology]

[0002] A DC circuit may be provided with a circuit breaker that interrupts current flowing when a short circuit occurs. The circuit breaker has an overcurrent detector. The overcurrent detector detects current. An overcurrent detector may be required to detect current flowing in only one direction of current flow in a DC circuit. In other words, an overcurrent detector may be required to have polarity. As an example of an overcurrent detector with polarity, Japanese Utility Model Laid-Open Publication No. 52-53361 (Patent Document 1) discloses an overcurrent detector having a fixed iron core, a movable iron core, a spring, and a permanent magnet. In the above overcurrent detector, the fixed iron core surrounds a conductor. The spring applies a spring force to the movable iron core. The permanent magnet attracts the movable iron core to the fixed iron core. When a current greater than a set value flows through the conductor, the magnetic flux based on the current cancels out the magnetic flux of the permanent magnet, causing the movable iron core to be separated from the fixed iron core. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 52-53361 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the overcurrent detector disclosed in Patent Document 1, the attractive force between the movable iron core and the fixed iron core generated by the permanent magnet varies depending on the state of the contact surface between the movable iron core and the fixed iron core, which increases the variability in the current value required for the movable iron core to operate.

[0005] The present disclosure has been made in view of the above, and its purpose is to provide an overcurrent detector and a circuit breaker that can reduce the variation in the current value required for the movable core to operate. [Means for solving the problem]

[0006] The overcurrent detector according to the present disclosure is an overcurrent detector that detects a direct current (DC) flowing through a conductor. The overcurrent detector includes a fixed iron core and a movable iron core. The fixed iron core defines a gap. The movable iron core is disposed in the gap. The fixed iron core and the movable iron core define a magnetic path. The magnetic path surrounds the conductor. When no DC current flows through the conductor, the movable iron core is spaced apart from the fixed iron core. The magnetic path includes a magnetic flux rectifier. When a DC current flows through the conductor in a first direction, the magnetic resistance of the magnetic flux rectifier is reduced. When a DC current flows through the conductor in a second direction opposite to the first direction, the magnetic resistance of the magnetic flux rectifier is increased. [Effects of the Invention]

[0007] In the overcurrent detector according to the present disclosure, the fixed core and the movable core are spaced apart. Therefore, the surface condition of each of the movable core and the fixed core is less likely to affect the current value at which the movable core operates. This reduces the variation in the current value required for the movable core to operate. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is a schematic diagram showing the configuration of a circuit breaker according to a first embodiment. [Figure 2] 1 is a cross-sectional view schematically illustrating a configuration of an overcurrent detector according to a first embodiment. [Figure 3] 4 is a schematic diagram showing the relationship between the magnetic flux density and magnetic resistance in the magnetic flux rectifying section and the current value of a direct current flowing through a first conductor. FIG. [Figure 4] 3 is a cross-sectional view showing a state in which a direct current flows in a first direction in a first conductor. FIG. [Figure 5]4 is a cross-sectional view showing a state in which a direct current flows in a second direction in the first conductor. FIG. [Figure 6] 4 is a schematic diagram showing the relationship between the magnitude of the electromagnetic driving force applied to the movable iron core and the current value of the direct current flowing through the first conductor. FIG. [Figure 7] FIG. 10 is a partial cross-sectional schematic view showing a method for comparing magnetic resistance of magnetic paths. [Figure 8] 10 is a cross-sectional view schematically illustrating a configuration of an overcurrent detector according to a second embodiment. FIG. [Figure 9] FIG. 10 is a cross-sectional view illustrating a configuration of an overcurrent detector according to a third embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. In the following drawings, the same or corresponding parts are designated by the same reference numerals, and the description thereof will not be repeated.

[0010] Embodiment 1 <Circuit breaker configuration> First, the configuration of a circuit breaker 200 according to the first embodiment will be described with reference to Fig. 1. As shown in Fig. 1, the circuit breaker 200 is attached to an electric circuit 90. The electric circuit 90 mainly includes a first power source 92, a load 93, and a first conductor 91. The first conductor 91 electrically connects the first power source 92 and the load 93 in series. The first power source 92 is a DC power source. The first power source 92 supplies a current to the load 93.

[0011] The circuit breaker 200 mainly includes an overcurrent detector 100, a fuse 84, and a control circuit 80. The overcurrent detector 100 is attached to a first conductor 91 of an electric circuit 90. The overcurrent detector 100 detects a direct current flowing through the first conductor 91. Specifically, for example, the overcurrent detector 100 detects a current flowing through the first conductor 91 when a short circuit occurs in the electric circuit 90. The overcurrent detector 100 inputs a signal to the control circuit 80. The fuse 84 is attached to the electric circuit 90. The control circuit 80 is separated from the electric circuit 90. When the control circuit 80 receives a signal from the overcurrent detector 100, the control circuit 80 blows the fuse 84.

[0012] The control circuit 80 has a second power supply 82, a second conductor 81, a switch 83, and an igniter 85. The second power supply 82 is, for example, a DC power supply. The second conductor 81 electrically connects the second power supply 82, the switch 83, and the igniter 85 in series. The switch 83 controls the opening and closing of the control circuit 80. The igniter 85 uses the power supplied from the second power supply 82 to melt or blow out the fuse 84.

[0013] The fuse 84 and the igniter 85 constitute a fuse unit 89. The fuse 84 is electrically connected to a first conductor 91. The fuse 84 is electrically connected in series with each of a first power source 92 and a load 93.

[0014] In the electric circuit 90, the direction passing through the first power source 92, the circuit breaker 200, and the load 93 in this order is referred to as a first direction 101. The direction opposite to the first direction 101 is referred to as a second direction 102. From another perspective, the second direction 102 is the direction passing through the load 93, the circuit breaker 200, and the first power source 92 in this order in the electric circuit 90.

[0015] In the electric circuit 90, the current supplied from the first power source 92 flows, for example, in a first direction 101. In other words, in the electric circuit 90, the current flowing in the first direction 101 is, for example, a current of positive polarity. In the electric circuit 90, the current flowing in the second direction 102 is a current of reverse polarity. The circuit breaker 200 detects the current that flows when a short circuit occurs in the electric circuit 90, and interrupts the electric circuit 90.

[0016] <Configuration of overcurrent detector> Next, the configuration of the overcurrent detector 100 according to this embodiment will be described with reference to Figs. 2 to 6. The cross section shown in Fig. 2 is taken along line II-II in Fig. 1. The cross section shown in Fig. 2 is perpendicular to the first direction 101 and intersects with the overcurrent detector 100. Fig. 2 shows the configuration of the overcurrent detector 100 in a state where no DC current flows through the first conductor 91. Fig. 2 also shows the configuration of the overcurrent detector 100 as viewed in the first direction 101. As shown in Fig. 2, the overcurrent detector 100 mainly includes a fixed iron core 2, a movable iron core 3, a stopper 6, a spring 4, and a magnet 5.

[0017] The stator core 2 defines a first gap 71. The stator core 2 is spaced apart from the first conductor 91. The stator core 2 is made of, for example, a soft magnetic material. The stator core 2 has a first member 21, a second member 22, a connecting member 23, a first protruding portion 24, and a second protruding portion 25.

[0018] As shown in FIG. 2, the first member 21 extends along the vertical direction Z. The vertical direction Z is a direction perpendicular to the first direction 101. The second member 22 is spaced apart from the first member 21. The second member 22 is provided on the opposite side of the first conductor 91 from the first member 21. From another perspective, the first conductor 91 is provided between the first member 21 and the second member 22. The second member 22 extends along the vertical direction Z.

[0019] The connecting member 23 is provided between the first member 21 and the second member 22. The connecting member 23 is connected to both the first member 21 and the second member 22. The connecting member 23 extends along the left-right direction X. The left-right direction X is a direction perpendicular to both the first direction 101 and the up-down direction Z.

[0020] The first protruding portion 24 is continuous with the first member 21. The first protruding portion 24 extends from the first member 21 along a direction from the first member 21 toward the second member 22. In the vertical direction Z, the first protruding portion 24 is provided on the opposite side of the connecting member 23 with respect to the first conductor 91. From another perspective, in the vertical direction Z, the first conductor 91 is provided between the first protruding portion 24 and the connecting member 23. The direction along the vertical direction Z and extending from the first protruding portion 24 toward the connecting member 23 is defined as a third direction 103. The direction opposite to the third direction 103 is defined as a fourth direction 104.

[0021] The second protruding portion 25 is continuous with the second member 22. The second protruding portion 25 extends from the second member 22 in a direction from the second member 22 toward the first member 21. The second protruding portion 25 is spaced apart from the first protruding portion 24. The second protruding portion 25 is provided on the opposite side of the first conductor 91 from the connecting member 23. From another perspective, the first conductor 91 is provided between the second protruding portion 25 and the connecting member 23 in the vertical direction Z.

[0022] The fixed core 2 has a first end face 31 and a second end face 32. A first gap 71 is defined between the first end face 31 and the second end face 32. The first end face 31 is defined by a first protruding portion 24. The first end face 31 is inclined with respect to the up-down direction Z in a direction from the second member 22 to the first member 21. The second end face 32 is defined by a second protruding portion 25. The second end face 32 is inclined with respect to the up-down direction Z in a direction from the first member 21 to the second member 22. The width of the first gap 71 in the left-right direction X increases toward the fourth direction 104.

[0023] As shown in FIG. 2, the movable core 3 is disposed in the first gap 71. When no DC current flows through the first conductor 91, the movable core 3 is spaced apart from the fixed core 2. The movable core 3 is disposed between the first protruding portion 24 and the second protruding portion 25. The movable core 3 is provided on the opposite side of the first conductor 91 from the connecting member 23. From another perspective, the first conductor 91 is provided between the movable core 3 and the connecting member 23 in the vertical direction Z. The movable core 3 is made of, for example, a soft magnetic material.

[0024] The direction from the movable core 3 toward the first conductor 91 is a third direction 103. The movable core 3 is movable along the vertical direction Z. The position of the movable core 3 before it moves is set to a first position T1. The movement of the movable core 3 causes the overcurrent detector 100 to send a signal to the switch 83 (see FIG. 1). From another perspective, the movement of the movable core 3 causes the fuse 84 (see FIG. 1) to break.

[0025] The movable core 3 has a first surface 41, a second surface 42, a third surface 43, and a fourth surface 44. The first surface 41 is the surface of the movable core 3 closest to the first conductor 91. The first surface 41 extends along a direction perpendicular to the up-down direction Z. The second surface 42 is located on the opposite side of the first surface 41. The second surface 42 extends along a direction perpendicular to the up-down direction Z. In the left-right direction X, the width of the second surface 42 is greater than the width of the first surface 41.

[0026] The third surface 43 is continuous with each of the first surface 41 and the second surface 42. The third surface 43 is inclined in a direction from the second member 22 to the first member 21 with respect to the vertical direction Z. The third surface 43 faces the first end surface 31 of the stator core 2. The third surface 43 may be substantially parallel to the first end surface 31.

[0027] The fourth surface 44 is continuous with each of the first surface 41 and the second surface 42. The fourth surface 44 is inclined in a direction from the first member 21 to the second member 22 with respect to the up-down direction Z. The fourth surface 44 faces the second end surface 32 of the fixed core 2. The fourth surface 44 may be substantially parallel to the second end surface 32. The width of the movable core 3 in the left-right direction X increases toward the fourth direction 104.

[0028] The stopper 6 is attached to the first conductor 91, for example. The stopper 6 is provided in the third direction 103 relative to the movable core 3. The stopper 6 limits the movement distance of the movable core 3 in the third direction 103. The stopper 6 is provided between the movable core 3 and the first conductor 91. The stopper 6 is made of an electrically insulating material.

[0029] The spring 4 is attached to the movable core 3. The spring 4 contacts the movable core 3 at the second surface 42. The spring 4 applies a return force K to the movable core 3. The return force K is the elastic force of the spring 4. The return force K is along a fourth direction 104. From another perspective, the fourth direction 104 is the direction from the first conductor 91 toward the movable core 3. When the movable core 3 is located at the first position T1, the magnitude of the return force K may be, for example, greater than 0. The movement of the movable core 3 from the first position T1 in the fourth direction 104 may be limited, for example, by a housing (not shown) of the overcurrent detector 100.

[0030] The magnet 5 is provided, for example, between the first member 21 and the second member 22. The magnet 5 is in contact with, for example, each of the first member 21 and the second member 22. The magnet 5 is provided, for example, on the opposite side of the first conductor 91 with respect to the connecting member 23. From another perspective, the connecting member 23 is provided, for example, between the magnet 5 and the first conductor 91 in the vertical direction Z. The magnet 5 is spaced apart from the connecting member 23. From another perspective, a space 99 is formed between the magnet 5 and the connecting member 23. The magnet 5 is fixed to the fixed iron core 2.

[0031] The magnet 5 is shaped, for example, like a rod. The magnet 5 extends along the left-right direction X. The magnet 5 is, for example, a permanent magnet. The magnet 5 has a first end 51 and a second end 52. At the first end 51, the magnet 5 contacts the first member 21. The first end 51 is, for example, a north pole. The second end 52 is located on the opposite side of the first end 51. At the second end 52, the magnet 5 contacts the second member 22. The second end 52 is, for example, a south pole.

[0032] The magnet 5, the first member 21, the connecting member 23, and the second member 22 form a second magnetic path 12. The second magnetic path 12 surrounds the space 99. The magnetic flux generated by the magnet 5 is referred to as a first magnetic flux F1. The first magnetic flux F1 passes through the second magnetic path 12. When viewed in a first direction 101, the direction in which the first magnetic flux F1 flows is, for example, clockwise.

[0033] 2, the fixed core 2, the movable core 3, and the first gap 71 form a first magnetic path 11. The first magnetic path 11 surrounds each of the first conductor 91 and the stopper 6. The first magnetic path 11 is a path for magnetic flux generated when a current flows through the first conductor 91.

[0034] The first magnetic path 11 has a magnetic flux rectifying section 7 and a magnetic path section 19. The magnetic flux rectifying section 7 is a portion of the first magnetic path 11 to which the first magnetic flux F1 is supplied from the magnet 5. From another perspective, in the magnetic flux rectifying section 7, the first magnetic path 11 overlaps with the second magnetic path 12. Note that in FIG. 2, for ease of explanation, the two-dot chain line indicating the second magnetic path 12 and the two-dot chain line indicating the first magnetic path 11 are shown shifted so as not to overlap each other.

[0035] The magnetic flux rectifying unit 7 may be magnetically saturated by the first magnetic flux F1. The magnetic flux rectifying unit 7 is composed of, for example, the connecting member 23, a portion of the first member 21, and a portion of the second member 22. From another perspective, the connecting member 23 constitutes at least a portion of the magnetic flux rectifying unit 7. In a cross section perpendicular to the direction in which the first magnetic flux F1 flows, the cross-sectional area of ​​the magnet 5 (first cross-sectional area S1) is larger than the cross-sectional area of ​​the magnetic flux rectifying unit 7 (second cross-sectional area S2). The cross-sectional area of ​​the portion of the stator core 2 that constitutes the magnetic flux rectifying unit 7 and that has the smallest cross-sectional area in the cross section perpendicular to the direction in which the first magnetic flux F1 flows is defined as the second cross-sectional area S2. Specifically, the second cross-sectional area S2 is, for example, the cross-sectional area of ​​the connecting member 23 in the cross section perpendicular to the direction in which the first magnetic flux F1 flows.

[0036] The magnetic path portion 19 is a portion of the first magnetic path 11 that is different from the magnetic flux rectifying portion 7. The magnetic path portion 19 is a portion of the first magnetic path 11 to which the first magnetic flux F1 is not substantially supplied from the magnet 5. The magnetic path portion 19 is, for example, a portion of the first magnetic path 11 excluding the magnetic flux rectifying portion 7. The magnetic path portion 19 is spaced apart from the second magnetic path 12.

[0037] In Fig. 3, the vertical axis represents the magnetic flux density and magnetic resistance in the magnetic flux rectifier unit 7, and the horizontal axis represents the current value of the DC current flowing through the first conductor 91. In this specification, the absolute value of the amount of electricity flowing (current) is simply referred to as the current value. In Fig. 3, a first graph G1 shown by a solid line represents the relationship between the magnetic flux density in the magnetic flux rectifier unit 7 and the current value of the DC current flowing through the first conductor 91. In Fig. 3, a second graph G2 shown by a dashed line represents the relationship between the magnetic resistance of the magnetic flux rectifier unit 7 and the current value of the DC current flowing through the first conductor 91.

[0038] 3, a first reference line 61 indicates the position where the current value of the DC current is 0. The portions of the first graph G1 and second graph G2 located on the first arrow C1 side of the first reference line 61 indicate the magnetic flux density and magnetic resistance when a DC current flows in the first direction 101 (forward direction). The portions of the first graph G1 and second graph G2 located on the second arrow C2 side of the first reference line 61 indicate the magnetic flux density and magnetic resistance when a DC current flows in the second direction 102 (reverse direction).

[0039] 3, the magnetic flux rectifying unit 7 is substantially magnetically saturated when no DC current flows through the first conductor 91. When no DC current flows through the first conductor 91, the initial magnetic flux density B1 in the magnetic flux rectifying unit 7 is, for example, 0.9 to 1 times the saturation magnetic flux density B2 of the stator core 2.

[0040] As shown in FIG. 3, when no DC current flows through the first conductor 91, the magnetic resistance of the magnetic flux rectifier section 7 (first magnetic resistance Rm1) is greater than the magnetic resistance of the magnetic path section 19 (second magnetic resistance Rm2).

[0041] As shown in FIG. 4, when a DC current flows through the first conductor 91, a second magnetic flux F2 is generated. The second magnetic flux F2 passes through the first magnetic path 11. When a DC current flows through the first conductor 91 in the first direction 101, the direction in which the second magnetic flux F2 flows is clockwise as viewed in the first direction 101. From another perspective, when a DC current flows through the first conductor 91 in the first direction 101, the first magnetic flux F1 and the second magnetic flux F2 flow in opposite directions in the flux rectifier unit 7. In this case, the first magnetic flux F1 and the second magnetic flux F2 cancel each other out in the flux rectifier unit 7. In other words, as shown in FIG. 3, when a DC current flows through the first conductor 91 in the first direction 101, the magnetic flux density in the flux rectifier unit 7 is smaller than when no DC current flows through the first conductor 91.

[0042] 3, as the slope of first graph G1 relative to the horizontal axis increases, the magnetic resistance of magnetic flux rectifier unit 7 decreases. Conversely, as the slope of first graph G1 relative to the horizontal axis decreases, the magnetic resistance of magnetic flux rectifier unit 7 increases. In other words, when a DC current of an arbitrary current value flows through first conductor 91, the magnetic resistance of magnetic flux rectifier unit 7 is inversely proportional to the value obtained by dividing the amount of change in the magnetic flux density of magnetic flux rectifier unit 7 by the amount of change in the current value of the DC current.

[0043] 3, the slope of the first graph G1 with respect to the horizontal axis is larger when a DC current flows in the first conductor 91 in the first direction 101 compared to when no current flows in the first conductor 91. When a DC current flows in the first conductor 91 in the first direction 101 compared to when no current flows in the first conductor 91, the magnetic resistance of the magnetic flux rectifier unit 7 is smaller. Regardless of the current value of the DC current flowing in the first conductor 91, the second magnetic resistance Rm2 may be substantially constant.

[0044] As shown in FIG. 4 , when the second magnetic flux F2 flows from the stator core 2 through the movable core 3 into the stator core 2, the first end face 31 and the fourth face 44 each become north poles, and the second end face 32 and the third face 43 each become south poles. In this case, a magnetic attraction force is generated between the movable core 3 and the stator core 2. Specifically, a first magnetic attraction force M1 is applied to the movable core 3 in a direction from the third face 43 toward the first end face 31, and a second magnetic attraction force M2 is applied to the movable core 3 in a direction from the fourth face 44 toward the second end face 32. The first magnetic attraction force M1 and the second magnetic attraction force M2 are combined to apply an electromagnetic driving force M3 to the movable core 3. The electromagnetic driving force M3 is a force in a direction along the third direction 103.

[0045] When a direct current flows in the first direction 101 in the first conductor 91, the magnetic resistance of the magnetic flux rectifier 7 decreases, and the magnetic flux flowing from the fixed core 2 through the movable core 3 into the fixed core 2 increases. As the magnetic flux flowing from the fixed core 2 through the movable core 3 into the fixed core 2 increases, the electromagnetic driving force M3 increases. When the electromagnetic driving force M3 is greater than the restoring force K, the movable core 3 moves in the third direction 103.

[0046] As shown in Fig. 4, when a direct current flows in the first direction 101 in the first conductor 91, the movable core 3 moves from the first position T1 to the third direction 103. The position of the movable core 3 when it comes into contact with the stopper 6 is set to the second position T2. ​​From another perspective, the second position T2 is the position of the movable core 3 when the operation of the movable core 3 is complete. The movement of the movable core 3 from the second position T2 to the third direction 103 is restricted by the stopper 6.

[0047] When the movable core 3 is located at the second position T2, the movable core 3 is separated from, for example, the fixed core 2. From another perspective, when the movable core 3 is located at the second position T2, a second gap 72 is formed between the first protrusion 24 and the movable core 3. When the movable core 3 is located at the second position T2, a third gap 73 is formed between the second protrusion 25 and the movable core 3.

[0048] 5, when a DC current flows in the first conductor 91 in the second direction 102, the direction of the second magnetic flux F2 is counterclockwise as viewed in the first direction 101. From another perspective, when a DC current flows in the first conductor 91 in the second direction 102, the first magnetic flux F1 and the second magnetic flux F2 flow in the same direction in the flux rectifier unit 7. In other words, when a DC current flows in the first conductor 91 in the second direction 102, the magnetic flux density in the flux rectifier unit 7 is greater than when no DC current flows in the first conductor 91 as shown in FIG.

[0049] 3, the slope of the first graph G1 with respect to the horizontal axis is smaller when a direct current flows in the first conductor 91 in the second direction 102 than when no current flows in the first conductor 91. When a direct current flows in the first conductor 91 in the second direction 102, the magnetic resistance of the magnetic flux rectifier 7 is larger than when no current flows in the first conductor 91.

[0050] 6, the vertical axis represents the magnitude of the electromagnetic driving force M3 applied to the movable core 3, and the horizontal axis represents the current value of the DC current flowing through the first conductor 91. In FIG. 6, a third graph G3 represents the relationship between the magnitude of the electromagnetic driving force M3 applied to the movable core 3 and the current value of the DC current flowing through the first conductor 91.

[0051] 6, the second reference line 62 indicates the position where the current value of the DC current flowing through the first conductor 91 is zero. The portion of the third graph G3 located on the first arrow C1 side of the second reference line 62 indicates the magnitude of the electromagnetic driving force M3 when the DC current flows in the first direction 101 (forward direction). The portion of the third graph G3 located on the second arrow C2 side of the second reference line 62 indicates the magnitude of the electromagnetic driving force M3 when the DC current flows in the second direction 102 (reverse direction).

[0052] 6, the shape of third graph G3 is asymmetric with respect to second reference line 62. When the current value of the DC current is the same, the magnitude of electromagnetic driving force M3 when the DC current flows in first direction 101 is greater than the magnitude of electromagnetic driving force M3 when the DC current flows in second direction 102.

[0053] 6, the magnitude of the return force K when the movable core 3 is located at the first position T1 (see FIG. 2) is shown as an initial return force K1. The magnitude of the return force K when the movable core 3 is located at the second position T2 (see FIG. 4) is shown as a post-movement return force K2. The post-movement return force K2 is greater than the initial return force K1.

[0054] As shown in FIG. 6, when a DC current flows in the first conductor 91 in the first direction 101, there exists a DC current value at which the electromagnetic driving force M3 is greater than the initial returning force K1. When a DC current flows in the first direction 101, the DC current value at which the magnitude of the electromagnetic driving force M3 becomes equal to the magnitude of the returning force K is defined as the operating current value A. From another perspective, the operating current value A is the current value of the DC current flowing in the first direction 101 when the movable core 3 (see FIG. 4) starts to move. In other words, when the current value of the DC current flowing in the first conductor 91 in the first direction 101 is equal to or greater than the operating current value A, the overcurrent detector 100 inputs a signal to the control circuit 80 (see FIG. 1).

[0055] 6, when the current value of the DC current flowing through the first conductor 91 is 0, the electromagnetic driving force M3 is smaller than the post-movement returning force K2. From another perspective, when the movable core 3 is located at the second position T2 and no DC current flows through the first conductor 91, the returning force K is larger than the electromagnetic driving force M3.

[0056] 6, when the current value of the DC current flowing in the first conductor 91 in the second direction 102 is equal to or less than the operating current value A, the magnitude of the electromagnetic driving force M3 is smaller than the initial returning force K1. From another perspective, when the current value of the DC current flowing in the first conductor 91 in the second direction 102 is equal to or less than the operating current value A, the movable core 3 does not move. For example, even when the current value of the DC current flowing in the first conductor 91 in the second direction 102 is equal to or less than three times the operating current value A, the movable core 3 does not need to move. When a DC current flows in the first conductor 91 in the second direction 102, the movable core 3 does not need to move, regardless of the current value of the DC current.

[0057] As shown in FIG. 3, when the current value of the DC current flowing in the first direction 101 in the first conductor 91 is equal to or less than the operating current value A, the magnetic resistance of the magnetic flux rectifier section 7 is greater than the magnetic resistance (second magnetic resistance Rm2) of the magnetic path section 19.

[0058] <Method for comparing magnetic resistance> Next, a method for comparing magnetic resistance of a magnetic path will be described with reference to Fig. 7. For example, the magnetic resistance is compared using a measurement coil 111 and a voltmeter 112. As shown in Fig. 7, the measurement coil 111 is wound around, for example, the magnetic flux rectifier 7. Both ends of the measurement coil 111 are connected to the voltmeter 112.

[0059] A current whose value changes over time is passed through the first conductor 91. Specifically, for example, an alternating current whose flow direction changes over time is passed through the first conductor 91. A magnetic flux generated by the current flowing through the first conductor 91 flows through the magnetic flux rectifier 7. As the value of the current flowing through the first conductor 91 changes over time, the magnetic flux flowing through the magnetic flux rectifier 7 increases or decreases. This generates an induced electromotive force in the measurement coil 111. The magnitude of the induced electromotive force generated in the measurement coil 111 is substantially proportional to the amount of change per unit time of the magnetic flux flowing through the magnetic flux rectifier 7. Therefore, by using the voltmeter 112 to measure the magnitude of the induced electromotive force generated in the measurement coil 111, the amount of change per unit time of the magnetic flux flowing through the magnetic flux rectifier 7 can be measured.

[0060] Φ=I / Rm (Formula 1) In Equation 1, Φ represents the magnetic flux flowing in the magnetic path surrounding the conductor. I represents the current value of the current flowing in the conductor. Rm represents the magnetic resistance of the magnetic path. As shown in Equation 1, the greater the magnetic resistance of the magnetic path, the less magnetic flux flows in the magnetic path. Therefore, when the same AC current is passed through the first conductor 91, the greater the magnetic resistance of the magnetic path, the smaller the change per unit time of the magnetic flux flowing in the magnetic path. Therefore, the magnetic resistance of the magnetic path can be compared by comparing the change per unit time of the magnetic flux flowing in the magnetic path.

[0061] Specifically, the amount of change per unit time of the magnetic flux flowing through the magnetic flux rectifier 7 when the current flows in the first direction 101 is compared with the amount of change per unit time of the magnetic flux flowing through the magnetic flux rectifier 7 when the current flows in the second direction 102. This makes it possible to compare the magnetic resistance when a current flows in the first conductor 91 in the first direction 101 with the magnetic resistance when a current flows in the first conductor 91 in the second direction 102.

[0062] Rm=L / μS (Equation 2) In Equation 2, Rm represents the magnetic resistance of the magnetic path. L represents the length of the magnetic path. μ represents the magnetic permeability of the magnetic path. S represents the cross-sectional area of ​​the magnetic path. As shown in Equation 2, as the length of the magnetic path increases, the magnetic resistance of the magnetic path increases, and as the cross-sectional area of ​​the magnetic path increases, the magnetic resistance of the magnetic path decreases. When comparing the magnetic resistance of two different magnetic paths, the measurement points are determined so that the lengths of the two magnetic paths are substantially the same and the cross-sectional areas of the two magnetic paths are substantially the same.

[0063] When comparing the magnetic resistance of the magnetic flux rectifier unit 7 with the magnetic path unit 19, a first measurement coil (not shown) is wound around the magnetic flux rectifier unit 7, and a second measurement coil (not shown) is wound around the magnetic path unit 19. Specifically, measurement coils are wound around each of the magnetic flux rectifier unit 7 and the magnetic path unit 19 so that the length of the portion of the magnetic flux rectifier unit 7 to be measured and the length of the portion of the magnetic path unit 19 to be measured are substantially the same, and the cross-sectional area of ​​the portion of the magnetic flux rectifier unit 7 to be measured and the cross-sectional area of ​​the portion of the magnetic path unit 19 to be measured are substantially the same. A current whose value changes over time is passed through the first conductor 91. The amount of change per unit time of the magnetic flux flowing through the magnetic flux rectifier unit 7 is compared with the amount of change per unit time of the magnetic flux flowing through the magnetic path unit 19. This allows the magnetic resistance of the magnetic flux rectifier unit 7 to be compared with the magnetic resistance of the magnetic path unit 19.

[0064] Next, the effects of the overcurrent detector 100 and the circuit breaker 200 according to the first embodiment will be described.

[0065] The overcurrent detector 100 according to the first embodiment has a fixed core 2 and a movable core 3. When no direct current flows through the first conductor 91, the movable core 3 is spaced apart from the fixed core 2. This reduces the effect of frictional force that occurs between the movable core 3 and the fixed core 2 when the movable core 3 operates. This reduces variations in the current value required for the movable core 3 to operate.

[0066] In the overcurrent detector 100 according to the first embodiment, the first magnetic path 11 includes a flux rectifier 7. When a DC current flows in the first conductor 91 in the first direction 101, the magnetic resistance of the flux rectifier 7 decreases. When a DC current flows in the first conductor 91 in the second direction 102, the magnetic resistance of the flux rectifier 7 increases. Therefore, when considering the magnetic flux flowing from the fixed core 2 through the movable core 3 into the fixed core 2, the magnetic flux when the DC current flows in the first direction 101 is larger than the magnetic flux when the DC current flows in the second direction 102. This allows the overcurrent detector 100 to detect a DC current flowing in the first direction 101 without detecting a DC current flowing in the second direction 102.

[0067] The overcurrent detector 100 according to the first embodiment has a spring 4. The spring 4 applies a restoring force K to the movable core 3. Therefore, when a direct current flows in the first conductor 91 in the first direction 101, causing the movable core 3 to move, and then the current stops flowing through the first conductor 91, the restoring force K allows the movable core 3 to automatically return to the position (first position T1) of the movable core 3 before the movable core 3 moved.

[0068] According to the overcurrent detector 100 of the first embodiment, when the movable core 3 is located at the second position T2, the movable core 3 is separated from the fixed core 2. Therefore, the first magnetic flux F1 generated by the magnet 5 is hardly supplied to the movable core 3. This makes it possible to reduce the magnetic attractive force acting on the movable core 3 when the DC current stops flowing through the first conductor 91. In other words, it is possible to suppress the magnetic attractive force acting on the movable core 3 due to the first magnetic flux F1.

[0069] As the cross-sectional area of ​​a permanent magnet increases, the magnetic flux generated by the permanent magnet increases. In the overcurrent detector 100 according to the first embodiment, the magnet 5 is a permanent magnet. In a cross section perpendicular to the direction in which the first magnetic flux F1 flows, the cross-sectional area of ​​the magnet 5 is larger than the cross-sectional area of ​​the magnetic flux rectifier 7. This allows the magnetic flux supplied from the magnet 5 to the magnetic flux rectifier 7 to be increased.

[0070] In the above, the first conductor 91 constitutes the electric circuit 90, and the overcurrent detector 100 does not have the first conductor 91. However, the configuration of the overcurrent detector 100 according to the first embodiment is not limited to the above configuration. The overcurrent detector 100 may have the first conductor 91. The first conductor 91, which is a part of the overcurrent detector 100, may be electrically connected to each of the first power source 92 and the load 93.

[0071] The magnet 5 may be an electromagnet. At the second position T2, the movable core 3 may be in contact with the fixed core 2. The overcurrent detector 100 may have a guide (not shown). The guide limits the movement direction of the movable core 3 so that the movable core 3 moves along the third direction 103. This makes it possible to prevent the movable core 3 and the fixed core 2 from coming into contact with each other when the movable core 3 moves.

[0072] Embodiment 2 Next, the configuration of the overcurrent detector 100 according to the second embodiment will be described with reference to Fig. 8. The overcurrent detector 100 according to the second embodiment differs from the overcurrent detector 100 according to the first embodiment in that the first conductor 91 is surrounded by the second magnetic path 12, but the other points are the same as the configuration of the overcurrent detector 100 according to the first embodiment. Below, the differences from the configuration of the overcurrent detector 100 according to the first embodiment will be mainly described.

[0073] As shown in FIG. 8 , the first conductor 91 is surrounded by the second magnetic path 12. From another perspective, the first conductor 91 is located between the magnet 5 and the magnetic flux rectifier 7. The first conductor 91 is located in a space 99. In the vertical direction Z, the magnet 5 is located between the first conductor 91 and the movable iron core 3. The magnet 5 is provided in a fourth direction 104 with respect to the connecting member 23. The magnet 5 is surrounded by the first magnetic path 11. When viewed in the first direction 101, the flow direction of the first magnetic flux F1 is counterclockwise. The stopper 6 is in contact with the magnet 5.

[0074] When the magnet 5 is a permanent magnet, the magnet 5 is a constant magnetic flux source. Therefore, the magnetic resistance of the magnet 5 is greater than the magnetic resistance of the magnetic path section 19. As a result, the magnetic flux (second magnetic flux F2) generated by a DC current flowing through the first conductor 91 passes through the first magnetic path 11.

[0075] In the overcurrent detector 100 according to the second embodiment, the first conductor 91 is surrounded by the second magnetic path 12. Therefore, in manufacturing the overcurrent detector 100, after assembling the overcurrent detector 100 using an unmagnetized magnet 5, the magnet 5 can be magnetized by passing a direct current through the first conductor 91. This makes it possible to prevent the components of the overcurrent detector 100 from moving due to the magnetic force of the magnet 5, compared to assembling the overcurrent detector 100 using a magnetized magnet 5 in advance. As a result, the time required to assemble the overcurrent detector 100 can be reduced.

[0076] Embodiment 3 Next, the configuration of the overcurrent detector 100 according to the third embodiment will be described with reference to Fig. 9. The overcurrent detector 100 according to the third embodiment differs from the overcurrent detector 100 according to the first embodiment mainly in that it has two magnet units and a yoke 8, but is otherwise similar to the overcurrent detector 100 according to the first embodiment. The following description will focus on the differences from the configuration of the overcurrent detector 100 according to the first embodiment. The cross-sectional schematic diagram shown in Fig. 9 corresponds to the cross-sectional schematic diagram shown in Fig. 2.

[0077] As shown in FIG. 9 , the magnet 5 may have a first magnet portion 58 and a second magnet portion 59. The first magnet portion 58 is positioned in a fourth direction 104 relative to the fixed core 2. The first magnet portion 58 has a third end 53 and a fourth end 54. The third end 53 is, for example, a north pole. The fourth end 54 is located opposite the third end 53. The fourth end 54 is, for example, a south pole. At the third end 53, the first magnet portion 58 is in contact with, for example, the first member 21 and the first protruding portion 24.

[0078] The second magnet portion 59 is positioned in the fourth direction 104 relative to the fixed core 2. The second magnet portion 59 is spaced apart from the first magnet portion 58. The second magnet portion 59 has a fifth end 55 and a sixth end 56. The fifth end 55 is, for example, a north pole. The sixth end 56 is located opposite the fifth end 55. The sixth end 56 is, for example, a south pole. At the sixth end 56, the second magnet portion 59 is in contact with, for example, the second member 22 and the second protruding portion 25.

[0079] The overcurrent detector 100 has a yoke 8. The yoke 8 is in contact with each of the first magnet portion 58 and the second magnet portion 59. Specifically, the first magnet portion 58 is in contact with the yoke 8 at a fourth end portion 54. The second magnet portion 59 is in contact with the yoke 8 at a fifth end portion 55. The first magnet portion 58 and the second magnet portion 59 are sandwiched between the yoke 8 and the fixed core 2. The yoke 8 is made of a soft magnetic material.

[0080] 9, the fixed core 2, the first magnet portion 58, the yoke 8, and the second magnet portion 59 form the second magnetic path 12. From another perspective, the yoke 8 forms a magnetic path connecting the first magnet portion 58 and the second magnet portion 59. The second magnetic path 12 surrounds each of the first conductor 91 and the movable core 3.

[0081] In overcurrent detector 100 according to embodiment 3, magnet 5 is sandwiched between yoke 8 and fixed core 2. In other words, magnet 5 is sandwiched between two separate components. This makes it easier to arrange magnet 5 during manufacturing of overcurrent detector 100 compared to when magnet 5 is arranged so that it is sandwiched between an integrated component (for example, fixed core 2). This reduces the time required to assemble overcurrent detector 100.

[0082] The embodiments disclosed herein are to be considered as illustrative in all respects and not restrictive. The scope of the present disclosure is defined by the claims, not by the above description, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof. [Explanation of symbols]

[0083] 2 fixed core, 3 movable core, 4 spring, 5 magnet, 6 stopper, 7 magnetic flux rectifier section, 8 yoke, 11 first magnetic path, 12 second magnetic path, 19 magnetic path section, 21 first member, 22 second member, 23 connecting member, 24 first protruding section, 25 second protruding section, 31 first end face, 32 second end face, 41 first surface, 42 second surface, 43 third surface, 44 fourth surface, 51 first end, 52 second end, 53 third end, 54 fourth end, 55 fifth end, 56 sixth end, 58 first magnet section, 59 second magnet section, 61 first reference line, 62 second reference line, 71 first gap, 72 second gap, 73 third gap, 80 control circuit, 81 second conductor, 82 second power supply, 83 switch, 84 fuse, 85 Igniter, 89 fuse unit, 90 electric circuit, 91 first conductor, 92 first power source, 93 load, 99 space, 100 overcurrent detector, 101 first direction, 102 second direction, 103 third direction, 104 fourth direction, 111 measuring coil, 112 voltmeter, 200 circuit breaker, A operating current value, B1 initial magnetic flux density, B2 saturation magnetic flux density, C1 first arrow, C2 second arrow, F1 first magnetic flux, F2 second magnetic flux, G1 first graph, G2 second graph, G3 third graph, K return force, K1 initial return force, K2 return force after movement, M1 first magnetic attractive force, M2 second magnetic attractive force, M3 electromagnetic driving force, Rm1 first magnetic resistance, Rm2 second magnetic resistance, S1 first cross-sectional area, S2 second cross-sectional area, T1 first position, T2 2nd position, X horizontal direction, Z vertical direction.

Claims

1. An overcurrent detector that detects a direct current flowing in a conductor, a fixed core forming a gap; a movable core disposed in the gap, the fixed core and the movable core form a magnetic path surrounding the conductor, When the DC current is not flowing through the conductor, the movable iron core is separated from the fixed iron core, the magnetic path has a magnetic flux rectifying portion, When the DC current flows in the conductor in a first direction, the magnetic resistance of the magnetic flux rectifier unit is reduced, When the DC current flows in the conductor in a second direction opposite to the first direction, the magnetic resistance of the magnetic flux rectifier unit increases, It also has a spring. When the DC current flows in the conductor in the first direction, the moving direction of the movable iron core is defined as a third direction. the spring applies a restoring force to the movable core along a fourth direction that is a direction opposite to the third direction; a stopper provided in the third direction with respect to the movable iron core, When the DC current flows through the conductor, a magnetic attraction force is generated in the movable iron core, When a position of the movable iron core before the movable iron core moves is defined as a first position, and a position of the movable iron core when the movable iron core moves from the first position in the third direction and comes into contact with the stopper due to the DC current flowing in the conductor in the first direction is defined as a second position, When the movable core is located at the second position, the movable core is spaced apart from the fixed core, an overcurrent detector, wherein when the movable core is located at the second position and the direct current is not flowing through the conductor, the restoring force is greater than the magnetic attractive force applied to the movable core;

2. When the current value of the DC current flowing in the first direction at which the movable iron core starts to move is defined as an operating current value, The overcurrent detector according to claim 1 , wherein the movable core does not move when a current value of the direct current flowing in the second direction in the conductor is equal to or less than the operating current value.

3. the magnetic path has a magnetic path portion different from the magnetic flux rectifying portion, 3. The overcurrent detector according to claim 2, wherein when the current value of the DC current flowing through the conductor is equal to or less than the operating current value, the magnetic resistance of the magnetic flux rectifier portion is greater than the magnetic resistance of the magnetic path portion.

4. Equipped with a magnet, The overcurrent detector according to claim 1 , wherein the magnetic flux rectifier is supplied with magnetic flux from the magnet.

5. the magnet is a permanent magnet, 5. The overcurrent detector according to claim 4, wherein a cross-sectional area of ​​the magnet is larger than a cross-sectional area of ​​the magnetic flux rectifier in a cross section perpendicular to a direction in which the magnetic flux flows.

6. An overcurrent detector according to any one of claims 1 to 3; a fuse electrically connected to the conductor; The circuit breaker, wherein the fuse is cut off due to movement of the movable core.

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