JP7819405B2 - Overcurrent detectors and circuit breakers - Google Patents

Description

This disclosure relates to overcurrent detectors and circuit breakers.

DC circuits may be equipped with a circuit breaker that interrupts current flow in the event of a short circuit. 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 within 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 this overcurrent detector, the fixed iron core surrounds the 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 due to the current cancels out the magnetic flux of the permanent magnet, causing the movable iron core to be pulled away from the fixed iron core.

Japanese Utility Model Application Publication No. 52-53361

However, with 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 fluctuates depending on the state of the contact surface between the movable iron core and the fixed iron core. This increases the variability in the current value required for the movable iron core to operate.

The present disclosure has been made in consideration of the above, and its purpose is to provide an overcurrent detector and circuit breaker that can reduce the variation in the current value required for the movable core to operate.

The overcurrent detector disclosed herein is an overcurrent detector that detects direct current flowing in 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 direct current flows in the conductor, the movable iron core is spaced apart from the fixed iron core. The magnetic path includes a magnetic flux rectifier. When direct current flows in the conductor in a first direction, the magnetic resistance of the magnetic flux rectifier decreases. When direct current flows in the conductor in a second direction opposite to the first direction, the magnetic resistance of the magnetic flux rectifier increases.

In the overcurrent detector disclosed herein, the fixed iron core and the movable iron core are spaced apart. Therefore, the surface condition of the movable iron core and the fixed iron core is less likely to affect the current value at which the movable iron core operates. This reduces the variation in the current value required for the movable iron core to operate.

1 is a schematic diagram showing a configuration of a circuit breaker according to a first embodiment; 1 is a cross-sectional view schematically illustrating a configuration of an overcurrent detector according to a first embodiment. 5A and 5B are schematic diagrams showing the relationship between the magnetic flux density and magnetic resistance in the magnetic flux rectifying unit and the current value of a direct current flowing through a first conductor. 3 is a schematic cross-sectional view showing a state in which a direct current flows in a first direction in a first conductor. FIG. 10 is a schematic cross-sectional view showing a state in which a direct current flows in a second direction in the first conductor. FIG. 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. FIG. 10 is a partial cross-sectional schematic view showing a method for comparing magnetic resistance of magnetic paths. FIG. 10 is a cross-sectional view illustrating a configuration of an overcurrent detector according to a second embodiment. FIG. 10 is a cross-sectional view showing a configuration of an overcurrent detector according to a third embodiment.

The following describes embodiments of the present disclosure based on the drawings. Note that the same or corresponding parts in the following drawings are given the same reference numerals, and their descriptions will not be repeated.

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 current to the load 93.

The circuit breaker 200 mainly comprises an overcurrent detector 100, a fuse 84, and a control circuit 80. The overcurrent detector 100 is attached to the first conductor 91 of the electric circuit 90. The overcurrent detector 100 detects direct current flowing through the first conductor 91. Specifically, for example, it detects 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.

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 power supplied from the second power supply 82 to blow or break the fuse 84.

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

In the electrical 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 the first direction 101. The direction opposite to the first direction 101 is referred to as the 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 electrical circuit 90.

In the electric circuit 90, the current supplied from the first power source 92 flows, for example, in the 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 flowing when a short circuit occurs in the electric circuit 90 and interrupts the electric circuit 90.

<Configuration of overcurrent detector>
Next, the configuration of the overcurrent detector 100 according to this embodiment will be described with reference to Figures 2 to 6. The cross section shown in Figure 2 is taken along line II-II in Figure 1. The cross section shown in Figure 2 is perpendicular to the first direction 101 and intersects with the overcurrent detector 100. Figure 2 shows the configuration of the overcurrent detector 100 in a state where no DC current flows through the first conductor 91. Figure 2 also shows the configuration of the overcurrent detector 100 as viewed in the first direction 101. As shown in Figure 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.

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

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.

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.

The first protrusion 24 is connected to the first member 21. The first protrusion 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 protrusion 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 protrusion 24 and the connecting member 23. The direction along the vertical direction Z and extending from the first protrusion 24 toward the connecting member 23 is referred to as the third direction 103. The direction opposite to the third direction 103 is referred to as the fourth direction 104.

The second protrusion 25 is connected to the second member 22. The second protrusion 25 extends from the second member 22 in a direction from the second member 22 toward the first member 21. The second protrusion 25 is spaced apart from the first protrusion 24. The second protrusion 25 is provided on the opposite side of the connecting member 23 from the first conductor 91. From another perspective, the first conductor 91 is provided between the second protrusion 25 and the connecting member 23 in the vertical direction Z.

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 in the direction from the second member 22 to the first member 21 with respect to the up-down direction Z. The second end face 32 is defined by a second protruding portion 25. The second end face 32 is inclined in the direction from the first member 21 to the second member 22 with respect to the up-down direction Z. The width of the first gap 71 in the left-right direction X increases toward the fourth direction 104.

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 protrusion 24 and the second protrusion 25. The movable core 3 is disposed on the opposite side of the first conductor 91 from the connecting member 23. From another perspective, the first conductor 91 is disposed 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.

The direction from the movable core 3 toward the first conductor 91 is the 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 referred to as the first position T1. As the movable core 3 moves, the overcurrent detector 100 sends a signal to the switch 83 (see Figure 1). From another perspective, as the movable core 3 moves, the fuse 84 (see Figure 1) is blown.

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 in 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 in 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.

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 the 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 fixed core 2. The third surface 43 may be substantially parallel to the first end surface 31.

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 the direction from the first member 21 to the second member 22 with respect to the vertical 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 horizontal direction X increases toward the fourth direction 104.

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 iron core 3. The stopper 6 limits the movement distance of the movable iron core 3 in the third direction 103. The stopper 6 is provided between the movable iron core 3 and the first conductor 91. The stopper 6 is made of an electrically insulating material.

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

The magnet 5 is, for example, provided between the first member 21 and the second member 22. The magnet 5 is, for example, in contact with each of the first member 21 and the second member 22. The magnet 5 is, for example, provided on the opposite side of the connecting member 23 from the first conductor 91. From another perspective, the connecting member 23 is, for example, provided 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.

The magnet 5 is, for example, rod-shaped. 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.

The magnet 5, the first member 21, the connecting member 23, and the second member 22 form the 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 the first magnetic flux F1. The first magnetic flux F1 passes through the second magnetic path 12. When viewed in the first direction 101, the direction in which the first magnetic flux F1 flows is, for example, clockwise.

As shown in Figure 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.

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 the 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 Figure 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 that they do not overlap each other.

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, a 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 fixed core 2 that constitutes the magnetic flux rectifying unit 7 and that has the smallest cross-sectional area in a 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 a cross section perpendicular to the direction in which the first magnetic flux F1 flows.

The magnetic path section 19 is a portion of the first magnetic path 11 that is different from the magnetic flux rectifying section 7. The magnetic path section 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 section 19 is, for example, a portion of the first magnetic path 11 excluding the magnetic flux rectifying section 7. The magnetic path section 19 is spaced apart from the second magnetic path 12.

In Figure 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 direct current flowing through the first conductor 91. Note that in this specification, the absolute value of the amount of electricity flowing (current) is simply referred to as the current value. In Figure 3, the 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 direct current flowing through the first conductor 91. In Figure 3, the 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 direct current flowing through the first conductor 91.

In Figure 3, the 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).

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

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

As shown in FIG. 4, when a direct 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 direct 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 direct 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 direct 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 direct current flows through the first conductor 91.

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

As shown in Figure 3, when a direct current flows in the first conductor 91 in the first direction 101, the slope of the first graph G1 with respect to the horizontal axis is larger than when no current flows in the first conductor 91. When a direct current flows in the first conductor 91 in the first direction 101, the magnetic resistance of the magnetic flux rectifier unit 7 is smaller than when no current flows in the first conductor 91. The second magnetic resistance Rm2 may be substantially constant regardless of the current value of the direct current flowing in the first conductor 91.

As shown in FIG. 4 , when the second magnetic flux F2 flows from the stator core 2 through the movable core 3 and 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 the 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 the 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 the third direction 103.

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.

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 contacts the stopper 6 is the second position T2. From another perspective, the second position T2 is the position of the movable core 3 when its operation is complete. The stopper 6 limits the movement of the movable core 3 from the second position T2 to the third direction 103.

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.

As shown in Figure 5, when a direct current flows in the first conductor 91 in the second direction 102, the direction of flow of the second magnetic flux F2 is counterclockwise when viewed in the first direction 101. From another perspective, when a direct 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 magnetic flux rectifier unit 7. In other words, as shown in Figure 3, when a direct current flows in the first conductor 91 in the second direction 102, the magnetic flux density in the magnetic flux rectifier unit 7 is greater than when no direct current flows in the first conductor 91.

As shown in Figure 3, when a direct current flows in the first conductor 91 in the second direction 102, the slope of the first graph G1 with respect to the horizontal axis is smaller 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 unit 7 is larger than when no current flows in the first conductor 91.

In Figure 6, the vertical axis shows the magnitude of the electromagnetic driving force M3 applied to the movable iron core 3, and the horizontal axis shows the current value of the DC current flowing through the first conductor 91. In Figure 6, the third graph G3 shows the relationship between the magnitude of the electromagnetic driving force M3 applied to the movable iron core 3 and the current value of the DC current flowing through the first conductor 91.

In Figure 6, the second reference line 62 indicates the position where the current value of the DC current flowing through the first conductor 91 is 0. The portion of the third graph G3 located on the first arrow C1 side from the second reference line 62 indicates the magnitude of the electromagnetic driving force M3 when a DC current flows in the first direction 101 (forward direction). The portion of the third graph G3 located on the second arrow C2 side from the second reference line 62 indicates the magnitude of the electromagnetic driving force M3 when a DC current flows in the second direction 102 (reverse direction).

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

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

As shown in Figure 6, when a DC current flows in the first direction 101 in the first conductor 91, there exists a DC current value at which the electromagnetic driving force M3 is greater than the initial return 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 is the same as the magnitude of the return force K is referred to 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 iron core 3 (see Figure 4) begins to move. In other words, when the current value of the DC current flowing in the first direction 101 in the first conductor 91 is equal to or greater than the operating current value A, the overcurrent detector 100 inputs a signal to the control circuit 80 (see Figure 1).

As shown in Figure 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 return force K2. From another perspective, when the movable iron core 3 is located at the second position T2 and no DC current is flowing through the first conductor 91, the return force K is greater than the electromagnetic driving force M3.

As shown in Figure 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 return 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 iron 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 iron core 3 does not need to move. When a DC current flows in the first conductor 91 in the second direction 102, the movable iron core 3 does not need to move, regardless of the current value of the DC current.

As shown in Figure 3, when the current value of the direct current flowing in the first direction 101 in the first conductor 91 is less than the operating current value A, the magnetic resistance of the flux rectifier unit 7 is greater than the magnetic resistance of the magnetic path unit 19 (second magnetic resistance Rm2).

<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.

A current whose value changes over time is passed through the first conductor 91. Specifically, for example, an alternating current whose direction of flow changes over time is passed through the first conductor 91. 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.

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 amount of 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 amount of change per unit time of the magnetic flux flowing in the magnetic path.

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 current flows in the first conductor 91 in the first direction 101 with the magnetic resistance when current flows in the first conductor 91 in the second direction 102.

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.

When comparing the magnetic resistance of the magnetic flux rectifier unit 7 with that of 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 that of the magnetic path unit 19.

Next, the effects of the overcurrent detector 100 and circuit breaker 200 of embodiment 1 will be explained.

The overcurrent detector 100 according to embodiment 1 has a fixed iron core 2 and a movable iron core 3. When no DC current flows through the first conductor 91, the movable iron core 3 is spaced apart from the fixed iron core 2. This reduces the effect of frictional forces that occur between the movable iron core 3 and the fixed iron core 2 when the movable iron core 3 operates. This reduces the variation in the current value required for the movable iron core 3 to operate.

In the overcurrent detector 100 according to embodiment 1, the first magnetic path 11 includes a flux rectifier 7. When a direct current flows in the first direction 101 through the first conductor 91, the magnetic resistance of the flux rectifier 7 decreases. When a direct current flows in the second direction 102 through the first conductor 91, 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 direct current flows in the first direction 101 is greater than the magnetic flux when the direct current flows in the second direction 102. This allows the overcurrent detector 100 to detect a direct current flowing in the first direction 101 without detecting a direct current flowing in the second direction 102.

The overcurrent detector 100 according to embodiment 1 has a spring 4. The spring 4 applies a return force K to the movable core 3. Therefore, when a direct current flows in the first direction 101 through the first conductor 91, causing the movable core 3 to move, and then the current stops flowing through the first conductor 91, the return force K allows the movable core 3 to automatically return to the position it was in before it moved (first position T1).

In the overcurrent detector 100 according to embodiment 1, 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 reduces the magnetic attraction force acting on the movable core 3 when direct current stops flowing through the first conductor 91. In other words, the magnetic attraction force acting on the movable core 3 due to the first magnetic flux F1 can be suppressed.

As the cross-sectional area of a permanent magnet increases, the magnetic flux generated by the permanent magnet increases. According to the overcurrent detector 100 of embodiment 1, 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. Therefore, the magnetic flux supplied from the magnet 5 to the magnetic flux rectifier 7 can be increased.

In the above, a configuration has been described in which the first conductor 91 constitutes the electrical circuit 90 and the overcurrent detector 100 does not have the first conductor 91, but the configuration of the overcurrent detector 100 according to embodiment 1 is not limited to the above configuration. The overcurrent detector 100 may have the first conductor 91. The first conductor 91, which is part of the overcurrent detector 100, may be electrically connected to each of the first power source 92 and the load 93.

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 direction of movement of the movable core 3 so that the movable core 3 moves along the third direction 103. This prevents the movable core 3 from coming into contact with the fixed core 2 as the movable core 3 moves.

Embodiment 2.
Next, the configuration of the overcurrent detector 100 according to embodiment 2 will be described using Fig. 8. The overcurrent detector 100 according to embodiment 2 differs from the overcurrent detector 100 according to embodiment 1 in configuration mainly in that the first conductor 91 is surrounded by the second magnetic path 12, but in other respects is similar to the configuration of the overcurrent detector 100 according to embodiment 1. The following description will focus on the differences from the configuration of the overcurrent detector 100 according to embodiment 1.

As shown in Figure 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 the 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 arranged in the fourth direction 104 relative to the connecting member 23. The magnet 5 is surrounded by the first magnetic path 11. When viewed in the first direction 101, the direction in which the first magnetic flux F1 flows is counterclockwise. The stopper 6 is in contact with the magnet 5.

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 the flow of DC current through the first conductor 91 passes through the first magnetic path 11.

In the overcurrent detector 100 according to embodiment 2, 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 prevents 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.

Embodiment 3.
Next, the configuration of the overcurrent detector 100 according to embodiment 3 will be described using Fig. 9. The overcurrent detector 100 according to embodiment 3 differs from the overcurrent detector 100 according to embodiment 1 in configuration mainly in that it has two magnet portions and a yoke 8, but is otherwise similar to the overcurrent detector 100 according to embodiment 1. The following description will focus on the differences from the configuration of the overcurrent detector 100 according to embodiment 1. The cross-sectional schematic diagram shown in Fig. 9 corresponds to the cross-sectional schematic diagram shown in Fig. 2.

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 the 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 protrusion 24.

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 protrusion 25.

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 the fourth end 54. The second magnet portion 59 is in contact with the yoke 8 at the fifth end 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.

As shown in Figure 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.

In the overcurrent detector 100 according to embodiment 3, the magnet 5 is sandwiched between the yoke 8 and the fixed core 2. In other words, the magnet 5 is sandwiched between two separate components. This makes it easier to position the magnet 5 during the manufacture of the overcurrent detector 100 compared to when the magnet 5 is positioned so that it is sandwiched between an integrated component (such as the fixed core 2). This reduces the time required to assemble the overcurrent detector 100.

The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of the present disclosure is indicated by the claims, not the above description, and is intended to include meanings equivalent to the claims and all modifications within the scope thereof.

2 Fixed iron core, 3 Movable iron core, 4 Spring, 5 Magnet, 6 Stopper, 7 Magnetic flux rectifier, 8 Yoke, 11 First magnetic path, 12 Second magnetic path, 19 Magnetic path portion, 21 First member, 22 Second member, 23 Connecting member, 24 First protruding portion, 25 Second protruding portion, 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 portion, 59 Second magnet portion, 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 source, 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 returning force, K1 initial returning force, K2 returning 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 (6)

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