JP2024051815A - DC circuit switch and switch system - Google Patents

Abstract

[Problem] To provide a switch for a DC circuit that can suppress the occurrence of arc discharge and can be applied to a DC circuit. [Solution] A switch for a DC circuit that makes or breaks a DC circuit includes a first electrode unit having a first terminal and a first sphere that is electrically connected to the first terminal and rotatably held, a second electrode unit having a second terminal and a second sphere that is electrically connected to the second terminal and is arranged to be able to roll, and a drive mechanism unit that operates to roll the second sphere into contact with the first sphere to make electrical connection between the first electrode unit and the second electrode unit, or to roll the second sphere away from contact with the first sphere to break connection between the first electrode unit and the second electrode unit. [Selected Figure] Figure 1

Description

The present invention relates to a switch for a DC circuit for conducting or interrupting a DC circuit, and a switch system including the switch.

Patent Document 1 relates to a circuit breaker invention, and discloses a circuit breaker in which, when the blade 29 is closed, the ball 28 is pushed and moves, bringing the blade 29 into contact with the contact piece 26 to close the circuit, and when the blade 29 is pulled back to open the circuit, the ball 28 is pushed back by the spring 31, maintaining a gap 35 between the blade 29 and the contact piece 26 and opening the circuit (Figures 4, 5, and 6).

Patent document 2 relates to a tip-over switch invention, and discloses the configuration of a switch in which a movable ball C rolls in response to tilt or tip-over, contacting two electrodes A and B to establish electrical continuity (Figure 1).

Patent document 3 relates to an invention for a ball holder for a ball-drop switch, and discloses the configuration of a ball-drop switch in which a ball 2 inside a case is vibrated and rolls, pushing down an operating shaft 5 and closing an associated switch 7 (Figs. 1 and 2).

Patent document 4 relates to a pressure switch invention and discloses the configuration of a pressure switch having a fixed contact 28 and a movable contact 25 in which a sphere 25 rotatably abuts against the end of a spring 24 (Figure 1).

Japanese Utility Model Publication No. 54-045972 Japanese Utility Model Application Publication No. 55-075039 Japanese Utility Model Application Publication No. 55-027811 JP 4-149923 A

Hiroyuki Ishida “Non-Arching Circuit Breaking Phenomena in Electrical Contacts due to Dark Bridge” IEICE Transactions on Electronics, Vol.E102-C, No.5, pp.238-245 (March 2020)

The switches or circuit breakers disclosed in the above patent documents are not specifically mentioned as being applicable to AC or DC circuits, but it is considered difficult to apply them to circuit breakers or switches for DC circuits because of the risk of sparks being generated by arc discharge.

Sparks caused by arc discharge occur when two electrodes separate while electricity is flowing, and can occur even with low voltages and small currents, such as a voltage of 10V and a current of 1A. In AC circuits, the circuit repeatedly crosses zero voltage or zero current, making it easy for the arc to break and making it difficult for arc discharge to occur. On the other hand, in DC circuits, the gap between the two electrodes becomes longer, increasing the arc resistance and preventing the arc from breaking until the current becomes smaller. As a result, when the DC circuit is interrupted, damage to the contact points of the electrodes is significant, making it difficult to improve the lifespan and reliability of the switch.

The inventors of this application have conducted extensive research and development into switches that can be used in DC circuits, and have now developed a new switch for DC circuits that can suppress the occurrence of arc discharge.

The object of the present invention is to provide a switch for a DC circuit that can suppress the occurrence of arc discharge and can be applied to a DC circuit, and a switch system including the switch.

The switch for a DC circuit of the present invention, which is for achieving the above object, is a switch for a DC circuit that conducts or cuts off a DC circuit, and is characterized by comprising: a first electrode portion having a first terminal and a first sphere that is electrically connected to the first terminal and rotatably held; a second electrode portion having a second terminal and a second sphere that is electrically connected to the second terminal and rotatably arranged; and a drive mechanism portion that operates to roll the second sphere into contact with the first sphere to conduct electricity between the first electrode portion and the second electrode portion, or to roll the second sphere away from contact with the first sphere to cut off electricity between the first electrode portion and the second electrode portion.

The switch system of the present invention is also characterized by comprising the DC circuit switch and an AC circuit switch connected in parallel to the DC circuit switch.

The present invention provides a switch for a DC circuit that has a short arc duration during interruption and can suppress the occurrence of arc discharge, and a switch system that includes this switch for a DC circuit and a switch for an AC circuit that is connected in parallel to the switch for a DC circuit.

1 is a diagram illustrating a configuration example of a switch for a DC circuit according to an embodiment of the present invention. 10A and 10B are diagrams illustrating an example of the operation of the DC circuit switch in the present embodiment. 1 is a diagram showing a configuration example of a switch system incorporating a switch for a DC circuit according to an embodiment of the present invention; FIG. 2 is a diagram showing the configuration of a circuit (characteristics measurement circuit) for a characteristics measurement experiment. FIG. 13 shows a measured current waveform. FIG. 13 is a diagram showing a voltage waveform at timing t4. FIG. 4 is a diagram showing an arc duration of the AC circuit switch 2.

The following describes an embodiment of the present invention with reference to the drawings. However, these embodiment examples do not limit the technical scope of the present invention. The following describes an embodiment of the present invention with reference to specific drawings.

Figure 1 is a diagram showing an example of the configuration of a switch for a DC circuit according to an embodiment of the present invention. The switch for a DC circuit 1 is configured with a cathode side 10, an anode section 20, and a drive mechanism section 30 that tilts at least one of the cathode section 10 and the anode section 20 so as to establish or break electrical continuity between the cathode section 10 and the anode section 20. The cathode section 10 and the anode section 20 are fixed and placed on a flat plate 40, and as described below, the drive mechanism section 30 raises and lowers the end of the flat plate 40 to drive the cathode section 10 and the anode section 20 to tilt. The flat plate 40 is an insulating plate such as an acrylic plate.

The cathode section 10 has a cathode terminal 11, a first sphere 12 that is electrically connected to the cathode terminal 11 and is held rotatably, and a first holder 13 that supports the first sphere 12.

The first sphere 12 is a conductive metal sphere (preferably an iron sphere), and the first holder 13 is a structure in which the first sphere 12 is sandwiched between two conductive metal plates (e.g., aluminum plates) 13a and screwed in place, and in order to form a gap between the metal plates 13a, a spherical spacer 14 of the same diameter as the first sphere 12 is arranged in parallel with the first sphere 12. Note that the spherical spacer 14 does not have to be spherical in shape, and it is sufficient that the metal plates 13a are a material capable of holding and forming a gap equal to the diameter of the first sphere 12, and furthermore, it does not have to be a conductive material such as a metal body.

The conductive metal bolt 15 is fastened with a nut 16 so that the first sphere 12 can rotate while the first sphere 12 is sandwiched between two metal plates 13a, one above the other. Specifically, the metal bolt 15 is passed through holes drilled in the four corners of the two metal plates 13a. Preferably, a recess is provided in the area of the metal plate 13a where the first sphere 12 is in contact, and the metal plate 13a holds the first sphere 12 rotatably. Alternatively, instead of the recess in the metal plate 13a, for example, a through hole may be formed in the central axis of the first sphere 12, and the first sphere 12 may be sandwiched between the metal plates 13a and the metal bolt 15 may be passed through the through hole to hold the first sphere 12 rotatably on the metal plate 13a. The tip of the metal bolt 15 functions as the cathode terminal 11.

In the configuration example shown in FIG. 1, the spherical spacer 14 is attached in a state where it is sandwiched between the metal plates 13a by the metal bolts 15, similar to the holding configuration of the first sphere 12. The spherical spacer 14a does not have to be rotatably attached to the metal plates 13a, and is positioned so as to maintain the distance between the two metal plates 13a.

The anode section 20 has an anode terminal 21, a second sphere 22 that is electrically connected to the anode terminal 21 and is arranged so as to be able to roll, and a second holder 23 that holds the second sphere 22. The second sphere 22 is a conductive metal sphere (preferably an iron sphere), and the second holder 23 is composed of a conductive metal tubular member (e.g., an aluminum pipe) that holds the second sphere 22 inside so as to be able to roll.

The second spheres 22 are preferably arranged in parallel inside the second holder 23 in contact with each other. This is to provide more contact points between the second spheres 22 and the second holder 23 and to make the contact more reliable. The inner diameter of the second holder 23 is larger than the diameter of the second spheres 22, the second strap can roll inside the second holder 23, and the sizes of the second spheres 22 may be the same or different. In the configuration example of FIG. 1, four second spheres 22 are arranged inside the second holder 23, and the two second spheres 22 on both sides have a diameter of 15 mm, and the two inner second spheres 22 have a diameter of 10 mm, but the diameter of the second spheres 22 can be selected appropriately.

The opening 23a at one end of the second holder 23 is positioned opposite the first sphere 12, and the second sphere 22 comes into contact with the first sphere 12 by rolling so that a part of the second sphere 22 protrudes from the opening 23a at one end.

The cathode section 10 and the anode section 20 are arranged on the flat plate 40 so that the first sphere 12 and the second sphere 22 face each other, and are positioned so that the distance between the contact portion of the first sphere 12 with which the second sphere 22 comes into contact and the opening 23a on one end side of the second holder 23 is smaller than the diameter of the second sphere 22. This allows the first sphere 12 to function as a stopper that limits the rolling of the second sphere 22. Preferably, the distance is sufficient so that the second sphere 22 comes into contact with the first sphere 12 just by slightly protruding (sticking out) from the opening 23a on one end side.

A conductive metal bolt 25 is drilled through the circumferential surface near the other end opening 23b of the second holding body 23, penetrating from the outer circumferential surface to the inner circumferential surface so as to protrude toward the inner circumferential surface side, and the outer circumferential surface side protruding portion 25a of the metal bolt 25 functions as the anode terminal 21, and the inner circumferential surface side protruding portion 25b functions as a stopper 25b that limits the rolling of the second sphere 22, preventing the second sphere 22 from spilling out of the other end opening 23 due to rolling. Also, the other end side of the second holding body 23 may be configured to be closed without providing the stopper 25b.

The drive mechanism 30 tilts the anode section 20 by raising and lowering the end of the flat plate 40. To establish electrical continuity between the cathode section 10 and the anode section 20, the drive mechanism 30 rolls the second sphere 22 into contact with the first sphere 12, or to block electrical continuity between the cathode section 10 and the anode section 20, the drive mechanism 30 operates to roll the second sphere 22 away from contact with the first sphere 12, specifically, to drive the anode section 20 to tilt so that the second sphere 22 rolls.

The configurations of the cathode section 10 and the anode section 20 may be reversed, i.e., the first sphere 12 of the cathode section 10 may be arranged to be rollable and the second sphere 22 of the anode section 20 may be held to be rotatable. In this case, the drive mechanism section 30 drives the cathode section 10 to tilt so that the first sphere 12 rolls.

The drive mechanism 30 is configured using a linear actuator, such as a motor-driven electric cylinder.

Figure 2 shows an example of the operation of the switch for a DC circuit in this embodiment, with Figure 2(a) showing the switch ON (conducting) state and Figure 2(b) showing the switch OFF (non-conducting/cut-off) state. As shown in Figure 2(a), the drive mechanism 30 tilts the anode part 20, specifically, raises the other end side of the second holder 23 so that it is higher than the cathode part 10, and rolls the second sphere 22 in a direction approaching the first sphere 12, bringing the second sphere 22 into contact with the first sphere 12, thereby establishing a conductive state.

Also, as shown in FIG. 2(b), the drive mechanism 30 tilts the anode 20 in the opposite direction to the state shown in FIG. 2(a), specifically, lowers the other end of the second holder 23 so that it is lower than the cathode 10, causing the second sphere 22 in contact with the first sphere 12 to roll in a direction away from the first sphere 12, and moving the second sphere away from the first sphere, thereby establishing a non-conductive state (disconnected state).

In the example of Figure 2, an example of the operation of raising and lowering the end of the anode part 20 is shown, but it is also possible to raise and lower the end of the cathode part 10 to create a relative height difference between the cathode part 10 and the anode part 20, forming an incline that rolls the second sphere 22.

Figure 3 is a diagram showing an example of the configuration of a switch system incorporating the DC circuit switch of this embodiment. The switch system 100 is a switch system in which the DC circuit switch 1 of this embodiment and an existing commercially available AC circuit switch 2 are connected in parallel, and also includes an emergency switch 3 that cuts off the circuit when both the DC circuit switch 1 and the AC circuit switch 2 become unable to cut off.

The configuration in which the DC circuit switch 1 is connected in parallel with the AC circuit switch 2 allows the DC circuit switch 1 to be incorporated while still allowing the AC circuit switch 2 currently in use to be used as is, so the DC circuit switch 1 can be introduced without making any major changes to the AC switch 2 currently in use.

Next, we will explain the characteristics measurement experiment to measure the characteristics of the switch for the DC circuit in this embodiment.

Figure 4 shows the configuration of a circuit (characteristics measurement circuit) for the characteristics measurement experiment. The characteristics measurement circuit is formed by the switch system 100 shown in Figure 3, i.e., the switch system 100 in which the DC circuit switch 1 and the AC circuit switch 2 in this embodiment are connected in parallel and the emergency switch 3 is further connected in series to the switch system 100, the load resistor 200, the ammeter 300, the current measurement resistor 400, and the DC power source 500.

The AC circuit switch 2 is a commercially available switch device capable of passing and cutting off current up to AC300[V] and 15[A], the DC power supply 500 (Takasago GP060-20R) is a power supply device capable of outputting up to DC60[V] and 20[A], the current measurement resistor 400 is a metal clad resistor (0.1[Ω] and 50[W]), and the load resistor 200 is a cement resistor (1[kΩ] and 10[W]), specifically, 20 resistors of 50[kΩ] each connected in parallel on one board. Using this resistor, the passing current was changed to measure the characteristics.

As shown in the figure, a digital oscilloscope is connected across the current measurement resistor 400 to measure the current, and a digital oscilloscope is connected across the parallel-connected DC circuit switch 1 and AC circuit switch 2 to measure the voltage.

Figure 5 shows the measured current waveform. t1 is the timing when the AC circuit switch 2 is turned ON (conducting).

t2 is the timing when the DC circuit switch 1 is turned ON (conductive). At this timing, the iron balls (first ball 12 and second ball 22) come into contact at a point and conduct electricity (in FIG. 5, the change in current at t2 is small, so it is shown as a section). When using commercially available general iron balls, when the iron balls come into contact with each other, sparks are generated by mechanical bounce, destroying the surface film of the iron balls and causing conduction. At this time, welding (a state in which the contact points melt and solidify and adhere) may occur. However, in the embodiment of the present invention, since the AC circuit switch 2 is ON, the voltage applied to the DC circuit switch 1 is low. Therefore, welding does not occur. In this way, by connecting the DC circuit switch 1 and the AC circuit switch 2 in parallel and turning the AC circuit switch 1 ON first, welding can be prevented. The surfaces of the iron balls (first ball 12 and second ball 22) were polished with, for example, #600 abrasive paper and ultrasonically cleaned in purified water. Therefore, the surface coating is removed, and there is electrical continuity. In other words, it is preferable that the first sphere 12 and the second sphere 22 are iron spheres that do not have a surface coating.

t3 is the timing when the AC circuit switch 2 is turned OFF (non-conducting/cut off). A slight change in current can be confirmed. t4 is the timing when the DC circuit switch 1 is turned OFF. The pair of iron balls, the first sphere 12 and the second sphere 22, are separated by gravity due to the tilt.

Figure 6 shows the voltage waveform at time t4. A DC circuit with a voltage of DC 50 V and a current of 14 A was interrupted. At this time, the time that the arc discharge occurred, i.e., the arc duration, was approximately 7 ms.

The reason why the current is limited to 14[A] is due to the allowable current value of DC circuit 1. Also, the reason why the voltage is set to DC50[V] is due to the voltage that can be generated by the DC power supply used.

Figure 7 shows the arc duration of the AC circuit switch 2. The arc duration was measured in a circuit configuration in which the AC circuit switch 2 used in the characteristic measurement circuit of Figure 4 was used alone (without connecting the DC circuit switch 1 in parallel). The voltage was DC 50 [V]. As shown in Figure 7, when the AC circuit switch 2 was cut off, the arc duration was about 100 [ms] at a cut-off current of 5.8 [A]. On the other hand, in the characteristic measurement circuit of Figure 4 (switch system 100), as mentioned above, the arc duration was about 7 [ms] at a cut-off current of 14 [A], which is more than twice as long, and it was clear that the arc duration was significantly shorter and the cut-off performance was dramatically improved.

In the DC circuit switch 1 of this embodiment, the rollable second sphere 22 rolls and contacts the rotatable first sphere 12. Therefore, the contact point of at least one of the first sphere 12 and the second sphere 22 is different each time, so the contact surface is fresh. If the contact surface is fresh, it is believed that the interrupting performance will be maintained.

As described above, the present invention provides a switch for DC circuits that can be applied to DC circuits with dramatically improved interruption performance by significantly shortening the arc duration during interruption and suppressing the occurrence of arc discharge.

In Japan, 100V AC is generally used for power supply, but for example, solar power generation, which has been expanding rapidly in recent years, generates DC. Currently, the generated DC power is converted to AC power by an inverter, but because the inverter causes energy loss, research is also being conducted on DC power supply using DC power as is, and this invention contributes to DC power supply.

The present invention is not limited to the above-described embodiment, and any design changes that would occur to a person with ordinary knowledge in the field of the present invention, including various modifications and alterations, are of course included in the present invention, provided they do not deviate from the gist of the present invention.

1: DC circuit switch, 2: AC circuit switch, 3: Emergency switch, 10: Cathode, 11: Cathode terminal, 12: First sphere, 13: First holder, 13a: Metal plate, 14: Spacer, 15: Metal bolt, 16: Nut, 20: Anode, 21: Anode terminal, 22: Second sphere, 23: Second holder (metal tubular member), 23a: One end opening, 23b: Other end opening, 25: Metal bolt, 25a: Outer circumferential protruding portion, 25b: Inner circumferential protruding portion, 30: Drive mechanism, 40: Flat plate, 100: Switch system, 200: Load resistor, 300: Ammeter, 400: Current measuring resistor, 500: DC power source

Claims (8)

A switch for a DC circuit that connects or disconnects a DC circuit,
a first electrode portion including a first terminal and a first sphere electrically connected to the first terminal and rotatably held;
a second electrode portion including a second terminal and a second sphere electrically connected to the second terminal and arranged to be capable of rolling;
a drive mechanism that operates to roll the second sphere into contact with the first sphere to establish electrical continuity between the first electrode portion and the second electrode portion, or to roll the second sphere away from contact with the first sphere to interrupt electrical continuity between the first electrode portion and the second electrode portion. The switch for a DC circuit according to claim 1, characterized in that the first sphere is held rotatably between two metal plates. The switch for a DC circuit according to claim 1, characterized in that the second sphere is rotatably disposed within a metal tubular member. The switch for a DC circuit according to claim 3, characterized in that a plurality of the second spheres are disposed within the metal tubular member. The switch for a DC circuit according to claim 4, characterized in that the first sphere and the second sphere are iron spheres without a surface coating. The switch for a DC circuit according to claim 1, characterized in that the drive mechanism tilts the second electrode portion so that the second sphere rolls. A switch for a DC circuit according to any one of claims 1 to 6,
A switch system comprising: an AC circuit switch connected in parallel with the DC circuit switch. 8. The switch system according to claim 7, wherein the switch for the AC circuit is made conductive, and then the switch for the DC circuit is made conductive.

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