JP5188853B2 - SPD separation device - Google Patents

Description

  The present invention relates to an SPD disconnection device that disconnects an SPD from a power line when a failure occurs in an SPD (Surge Protective Device) that absorbs a surge voltage caused by a lightning strike and protects an electrical device.

  For the purpose of preventing lightning damage, a device that protects electrical equipment by absorbing surge voltage, which is a transient overvoltage caused by lightning strike, between the power line drawn from a single-phase or three-phase AC circuit to a factory or general household and the ground SPD is installed (for example, refer to Patent Document 1). As this SPD element, a zinc oxide varistor is generally used.

  This zinc oxide type varistor deteriorates with time due to repeated discharge of lightning surges or input of excessive lightning surges. When the zinc oxide varistor deteriorates, the leakage current increases and heat is generated, causing smoke and ignition due to thermal runaway. Further, when a large surge current exceeding the surge resistance of the SPD flows, the SPD breaks down and an electric device and the ground are short-circuited instantaneously. If the short-circuit state continues, it will adversely affect the power supply equipment and surrounding electrical equipment.

  In particular, when an SPD is installed at a location where the short-circuit capacity is large, it is necessary to provide a circuit breaker having a breaking capacity equal to or greater than the short-circuit capacity at the SPD installation location in order to avoid a short-circuit state caused by a SPD failure. If a circuit breaker having such a large breaking capacity is installed, the circuit breaker itself is increased in size, resulting in an increase in cost and a large installation space.

In addition, in the case of a direct lightning SPD that protects an electrical device from a very large energy such as a direct lightning strike, it is important to use a disconnecting device such as a circuit breaker, a leakage breaker, or a current fuse attached to the SPD. , Performance following the SPD performance, for example, circuit breakers that can withstand 10 x 350 μs waveform test current at 25 kA, equivalent to the direct lightning surge current specified in the standard, such as circuit breakers, earth leakage breakers, and current fuses. The current situation is that there is no device.
JP 2005-102415 A

  By the way, when an existing circuit breaker or earth leakage breaker is installed in the front stage of the SPD, the separation mechanism when a large surge current passes to the separation mechanism including the contact incorporated in the circuit breaker or earth leakage breaker. When the circuit breaker or earth leakage circuit breaker malfunctions due to the electromagnetic force acting instantaneously on the circuit, or when a large surge current is detected by the ZCT built in the circuit breaker or earth leakage circuit breaker Also, a malfunction that the circuit breaker for circuit breaker or earth leakage circuit breaker breaks also occurs due to the vibration output generated on the secondary side of the ZCT. When the malfunction of the circuit breaker for wiring or the earth leakage circuit breaker occurs, there is a problem that a normal SPD is disconnected from the power supply line.

  In addition, Joule heat generated by contact resistance or resistance of the conductive portion itself and electromagnetic repulsive force acting on the separation mechanism cause a momentary lifting phenomenon, resulting in a problem of contact welding. When such contact welding occurs, when an AC fault current flows through the circuit breaker or when an AC leakage current flows through the earth leakage breaker, the circuit breaker or earth leakage breaker may be normally interrupted. It will not be possible. If the circuit breaker and the earth leakage circuit breaker cannot be normally disconnected by this contact welding, the SPD cannot be disconnected from the power line when the SPD is broken, and the power line is short-circuited. A malfunction occurs.

  On the other hand, when a low-voltage current fuse is installed in the front stage of the SPD, for example, even a current fuse of about 100 A rated current having an AC 200 V / 100 kA breaking capacity performance is 25 kA comparable to the direct strike lightning surge current described above. When a 10 × 350 μs waveform test current is passed through a current fuse, the current fuse is blown or broken, making it difficult to withstand practical use. In this case, there is a problem that a normal SPD is disconnected from the power line.

  Therefore, the present invention has been proposed in view of the above-mentioned problems, and the object of the present invention is to disconnect a normal SPD due to a malfunction of a conventional circuit breaker for a wiring or an earth leakage circuit breaker, or by blowing a current fuse. An object of the present invention is to provide an SPD disconnecting device capable of preventing a faulty SPD safely by preventing the contact welding of a conventional circuit breaker or earth leakage circuit breaker.

As a technical means for achieving the above-mentioned object, the present invention is installed in the front stage of the SPD inserted between the power line and the ground, and disconnects the SPD from the power line when the SPD fails. The SPD is disconnected from the power line by the contact mechanism against the SPD fault current, and the surge dedicated fuse has a predetermined surge current passing performance and excessive surge cutoff performance. disconnect city from the power supply line by surges dedicated fuse SPD against excessive surge current in excess of direct stroke surge current withstand of the SPD, it was functionally separated in the contact mechanism and the surge-only fuse the ability to disconnect the SPD from the power line It is characterized by. The SPD is preferably composed of a zinc oxide type varistor.

  Here, the SPD fault current means a small AC fault current due to a decrease in insulation between lines generated at the time of SPD failure, and a small AC leakage current due to a decrease in insulation between grounds generated at the time of SPD failure. In addition, as the surge dedicated fuse, it is possible to use a current fuse having predetermined surge current passing performance and excessive surge interruption performance. The predetermined surge current passing performance is determined based on the surge resistance performance of the SPD, and means a performance that can withstand the passage of surge current that can be absorbed by the SPD. The term “performance” means the capability of blocking an excessive surge current exceeding the surge current that can be absorbed by the SPD.

  The surge-dedicated fuses are grouped into current fuses, but are SPD-dedicated protection fuses, unlike general AC-rated current fuses. Therefore, the current does not always flow, and the current rating is limited to the performance capable of withstanding the maximum surge current corresponding to the SPD rated specification and the interruption performance against the excessive surge current.

  In the present invention, the SPD is disconnected from the power supply line by the contact mechanism against an SPD fault current consisting of a small AC accident current due to a decrease in insulation between lines and a small AC leakage current due to a decrease in insulation between grounds. In this case, even if the contact mechanism has a large size, only a current of about 100 A flows at a limited condition, so the breaking distance is short and high-speed breaking is unnecessary, and it becomes easy to prevent welding against excessive surge current passage. On the other hand, since a current fuse having a predetermined surge current passing performance and excessive surge cutoff performance is used as a surge-dedicated fuse, when an excessive surge current exceeding the surge current capability of the SPD flows, it is related to the presence or absence of SPD failure. Without disconnecting the surge dedicated fuse, the SPD is disconnected from the power line at high speed by the surge dedicated fuse.

  As described above, the function of separating the SPD from the power supply line at the time of the SPD failure is separated by the contact mechanism and the surge-dedicated fuse, so that when the SPD is normal, the contact mechanism corresponding to the conventional circuit breaker or earth leakage circuit breaker No malfunction or fusing of a surge-dedicated fuse equivalent to a conventional current fuse will occur.

  In addition, the specified excessive surge cutoff performance in the surge-dedicated fuse is greater than or equal to the maximum current value in the passing current region that exhibits the prescribed surge current passing performance, and is not more than 1.5 times the maximum current value. It is desirable to have If the surge-breaking performance of this surge-dedicated fuse is set to a breaking current range that exceeds 1.5 times the maximum current value of surge-resistant current-passing performance, the surge-dedicated fuse will be increased in cost. It is preferable to set it as the interruption | blocking electric current area | region of 1.5 times or less of the maximum electric current value of electric current passage performance.

  In the present invention, the SPD is disconnected from the power supply line by a contact mechanism for an SPD fault current that is a small AC accident current or an AC leakage current, and the SPD is powered by a surge dedicated fuse for an excessive surge current exceeding the surge current capability of the SPD. The function of separating the SPD from the power supply line in the event of SPD failure is separated from the function by the contact mechanism and the surge dedicated fuse.

  By separating the function between this contact mechanism and the surge dedicated fuse, when the SPD is normal, malfunction of the contact mechanism corresponding to the conventional circuit breaker or earth leakage circuit breaker, or the melting of the surge dedicated fuse equivalent to the conventional current fuse Will not occur. As a result, it is possible to prevent a normal SPD from being disconnected. In addition, the SPD is disconnected by a contact mechanism for small AC accident currents and AC leakage currents that occur when an SPD failure occurs, and the SPD is disconnected by a surge dedicated fuse for excessive surge currents that exceed the surge current capability of the SPD. Contact welding of the contact mechanism corresponding to the circuit breaker for wiring and the earth leakage circuit breaker does not occur. As a result, the faulty SPD can be safely separated. In this way, a highly reliable SPD separation device can be provided.

  An embodiment of the SPD separating apparatus according to the present invention will be described in detail below. In the following embodiments, an AC single-phase three-wire system or an AC three-phase three-wire distribution line is installed in the front stage of the SPD inserted between the power line branched to the factory or general home and the ground. An SPD disconnecting device that disconnects the SPD from the power supply line is illustrated.

  As shown in FIG. 1, the SPD disconnecting device in this embodiment includes contact mechanisms 3 a to 3 c that disconnect the SPDs 1 a to 1 c from the power supply lines 2 a to 2 c with respect to the SPD fault current, a predetermined surge current passing performance, and an excessive surge cutoff. Surge-specific fuses 4a to 4c that have performance and disconnect SPDs 1a to 1c from power supply lines 2a to 2c against an excessive surge current. The SPDs 1a to 1c are composed of zinc oxide varistors.

  The SPD fault current, which is a condition for the contact mechanisms 3a to 3c to disconnect the SPDs 1a to 1c from the power supply lines 2a to 2c, includes a small AC fault current due to a decrease in line insulation that occurs when the SPD fails, and a ground isolation that occurs when the SPD fails There is a small AC leakage current due to the decrease.

  As the surge dedicated fuses 4a to 4c, current fuses having predetermined surge current passing performance and excessive surge interruption performance are used. The predetermined surge current passing performance is determined based on the surge resistance performance of the SPDs 1a to 1c, and can withstand the passage of surge current that can be absorbed by the SPDs 1a to 1c. The performance is a performance that cuts off an excessive surge current exceeding the surge current that can be absorbed by the SPDs 1a to 1c.

  The surge-dedicated fuses 4a to 4c are grouped into current fuses, but are SPD-dedicated protective fuses unlike general AC-rated current fuses. Therefore, the current does not always flow, and the current rating is limited to the performance capable of withstanding the maximum surge current corresponding to the SPD rated specification and the interruption performance against the excessive surge current.

  In this SPD disconnection device, when an SPD fault current consisting of a small AC fault current due to a decrease in insulation between lines and a small AC leakage current due to a decrease in insulation between grounds flows into the contact mechanisms 3a to 3c, the contacts of the contact mechanisms 3a to 3c are opened. Thus, the SPDs 1a to 1c are disconnected from the power supply lines 2a to 2c. In this case, even if the contact mechanisms 3a to 3c are large, only a current of about 100 A flows, so that the interruption distance is short and high-speed interruption is unnecessary, and it becomes easy to prevent welding against excessive surge current passage.

  Here, although the SPD fault current is about 100 A even when it is large, in the superposition test with the rated AC voltage applied to a zinc oxide varistor with a direct current lightning surge current withstand capability of 25 kA, a repeated application test with a 10 × 350 μsec waveform Carried out. In this case, the zinc oxide varistor gradually deteriorated, and the current suddenly increased from a leakage current of several amperes to 10 amperes, resulting in a complete short circuit. This phenomenon is a peculiar failure due to thermal runaway destruction of zinc oxide type varistors.

  On the other hand, since current fuses having predetermined surge current passing performance and excessive surge interruption performance are used as the surge dedicated fuses 4a to 4c, when an excessive surge current exceeding the surge current resistance of the SPDs 1a to 1c flows, the SPD 1a to Regardless of the failure of 1c, surge dedicated fuses 4a to 4c are cut off, and SPDs 1a to 1c are disconnected from power supply lines 2a to 2c by surge dedicated fuses 4a to 4c at high speed.

  The predetermined excessive surge cutoff performance in the surge-dedicated fuses 4a to 4c is equal to or higher than the maximum current value in the passing current region exhibiting the predetermined surge current passing performance, and 1.5 times or less the maximum current value. Has a region. If the excessive surge cutoff performance of the surge dedicated fuses 4a to 4c is set to a cutoff current region that exceeds 1.5 times the maximum current value of surge current passing performance, the surge dedicated fuses 4a to 4c may be increased in cost. Therefore, it is preferable to set the breaking current region to 1.5 times or less of the maximum current value of surge current passing performance.

  For example, when a surge-dedicated fuse with 30 kA surge current performance and an SPD that causes a short-circuit failure with a 30 kA test current, the SPD causes a short-circuit failure in the vicinity of 1 to 2 msec, which is the wave tail length of a 10 × 350 μsec waveform. Also, it takes 2-3 msec from the circuit time constant for the AC short-circuit current to reach the maximum. Therefore, if the surge-dedicated fuse has a high-speed and sufficient cut-off distance and has a cut-off performance against the surge current, The SPD can be safely disconnected against a specific excessive surge without having a blocking performance.

  As described above, the function of separating the SPDs 1a to 1c from the power supply lines 2a to 2c when the SPD fails is separated by the contact mechanisms 3a to 3c and the surge dedicated fuses 4a to 4c, so that when the SPD is normal, the conventional wiring interruption is performed. The malfunction of the contact mechanism corresponding to the breaker and the earth leakage breaker and the fusing of the surge dedicated fuses 4a to 4c corresponding to the conventional current fuse do not occur. In addition, SPDs 1a to 1c are disconnected by contact mechanisms 3a to 3c for small AC fault currents and AC leakage currents generated at the time of SPD failure, and surge surge fuses are used for excessive surge currents exceeding the surge current tolerance of SPDs 1a to 1c. Since the SPDs 1a to 1c are separated by 4a to 4c, contact welding of a contact mechanism corresponding to a conventional circuit breaker or a ground fault circuit breaker does not occur.

  That is, since the contact mechanisms 3a to 3c exhibit a breaking function with a small alternating current accident current or alternating current leakage current, a high speed breaking or a large breaking ability is not required. In addition, it is possible to reduce the size by eliminating the disconnection mechanism that is required when interrupting large AC fault current as in the past, and it is interrupted by electromagnetic force that instantaneously acts on the disconnection mechanism with a large surge current. Occurrence of malfunctions that operate is eliminated. Contact welding against a large current surge does not occur in the contact mechanisms 3a to 3c.

  As shown in FIGS. 1 to 3, the SPD disconnecting device installed in front of the SPDs 1a to 1c inserted between the power supply lines 2a to 2c and the ground includes contact mechanisms 3a to 3c and surge dedicated fuses 4a to 4c. It becomes the composition. Electrical devices 5 are connected to the power lines 2a to 2c as loads. In addition, although the figure has illustrated the case where it connects to SPD1a-1c in order of fuse 4a-4c and contact mechanism 3a-3c for surge with respect to power supply lines 2a-2c, it is a contact with respect to power supply lines 2a-2c It is also possible to connect to the SPDs 1a to 1c in the order of the mechanisms 3a to 3c and the surge dedicated fuses 4a to 4c.

  The contact mechanisms 3a to 3c described above need to be automatically opened and closed when the AC accident current or AC leakage current is generated, in addition to being manually opened and closed. Accordingly, the contact mechanisms 3a to 3c shown in FIGS. 1 to 3 are provided with a disconnecting coil portion for automatically opening the contacts by supplying voltage from the power supply lines 2a to 2c when an AC accident current or an AC leakage current is generated. 6 is provided. Further, the detection signals of the overcurrent detection sensors 7a and 7c for detecting the AC fault current flowing through the contact mechanisms 3a to 3c due to the line insulation drop and the AC leakage current flowing through the contact mechanisms 3a to 3c due to the earth insulation drop are detected. On the basis of the detection signal from the leakage sensor 8, a coil driving unit 9 is provided for supplying the voltage from the power supply lines 2 a to 2 c to the disconnecting coil unit 6.

  Here, the conventional circuit breaker is provided with an instantaneous disconnection mechanism that automatically opens the contact by the energy of the AC fault current or the AC leakage current itself when the AC fault current or the AC leak current is generated. In contrast, in the contact mechanisms 3a to 3c shown in FIGS. 1 to 3, there is no instantaneous disconnection mechanism in the conventional circuit breaker for wiring, and the voltage from the power supply lines 2a to 2c is supplied to the disconnecting coil section 6. Thus, the separation coil section 6 is driven to automatically open the contact. However, when a failure occurs in the SPDs 1a to 1c, it becomes difficult to supply energy sufficient to drive the disconnecting coil unit 6 due to a voltage drop in the power supply lines 2a to 2c.

  Accordingly, in the contact mechanisms 3a to 3c shown in FIG. 1 to FIG. 3, the rectifier circuit 25 and the capacitor 26 are provided to rectify the AC voltage taken from the power supply lines 2a to 2c by the rectifier circuit 25 and charge the capacitor 26. Then, the charging energy of the capacitor 26 is supplied to the separation coil unit 6 through the coil driving unit 9. In this way, even if there is a voltage drop in the power supply lines 2a to 2c due to the failure of the SPDs 1a to 1c, the disconnecting coil unit 6 is driven by the charging energy of the capacitor 26 to contact the contact mechanisms 3a to 3c. The SPDs 1a to 1c can be reliably disconnected from the power supply lines 2a to 2c.

  Further, the surge dedicated fuse shown in FIGS. 1 to 3 is provided with a cutoff detection unit 27 for detecting that the surge dedicated fuses 4a to 4c are blown at the time of SPD failure, and a detection signal from the cutoff detection unit 27 is received. It outputs to the coil part 6 for isolation | separation. Thereby, it is detected by the interruption detection unit 27 that the surge dedicated fuses 4a to 4c are blown at the time of SPD failure, and the disconnecting coil unit 6 is driven based on the detection signal to automatically connect the contacts of the contact mechanisms 3a to 3c. Open. In this way, even when at least one of the surge-dedicated fuses 4a to 4c is interrupted by an excessive lightning surge, the contact mechanisms 3a to 3c are automatically opened so that the failed SPDs 1a to 1c can be removed from the power lines 2a to 2c. Can be surely disconnected from.

  In the SPD disconnecting device of the embodiment shown in FIG. 1, the surge dedicated fuses 4a to 4c, the contact mechanisms 3a to 3c, and the SPDs 1a to 1c are configured in independent storage cases 10 to 12, respectively. The storage case 10 for the surge dedicated fuses 4a to 4c is provided with power supply side connection terminals 13a to 13c and load side connection terminals 14a to 14c for the surge dedicated fuses 4a to 4c. The storage cases 11 of the contact mechanisms 3a to 3c are provided with power supply side connection terminals 15a to 15c and load side connection terminals 16a to 16c of the contact mechanisms 3a to 3c. The storage cases 13 of the SPDs 1a to 1c are provided with power supply side connection terminals 17a to 17c and ground terminals 18 of the SPDs 1a to 1c.

  In the SPD disconnecting device of the embodiment shown in FIG. 2, the surge dedicated fuses 4 a to 4 c and the contact mechanisms 3 a to 3 c are configured in the same storage case 19, and the SPDs 1 a to 1 c are configured in another storage case 12. ing. The storage case 19 in which the surge-dedicated fuses 4a to 4c and the contact mechanisms 3a to 3c are integrally configured has power supply side connection terminals 13a to 13c of the surge dedicated fuses 4a to 4c and load side connection terminals 16a to 16a of the contact mechanisms 3a to 3c. 16c is provided. The storage cases 12 of the SPDs 1a to 1c are provided with power supply side connection terminals 17a to 17c and ground terminals 18 of the SPDs 1a to 1c.

  The SPD disconnecting device of the embodiment shown in FIG. 3 comprises surge dedicated fuses 4a to 4c, contact mechanisms 3a to 3c, and SPDs 1a to 1c in the same storage case 20. The storage case 20 in which the surge-dedicated fuses 4a to 4c, the contact mechanisms 3a to 3c, and the SPDs 1a to 1c are integrally formed has power supply side connection terminals 13a to 13c of the surge-dedicated fuses 4a to 4c and ground terminals 18 of the SPDs 1a to 1c. Is provided.

  As shown in FIG. 2, when the surge dedicated fuses 4a to 4c and the contact mechanisms 3a to 3c are configured in the same storage case 19, the surge dedicated fuses 4a to 4c and the contact mechanisms 3a to 3c are respectively independent storage cases. 10 and 11 (see FIG. 1), the load side connection terminals 14a to 14c of the surge-dedicated fuses 4a to 4c and the power source side connection terminals 15a to 15c of the contact mechanisms 3a to 3c become unnecessary. Since the number of points can be reduced and a connection process is not required, the number of assembly steps can be reduced, and the apparatus can be downsized.

  As shown in FIG. 3, when the surge dedicated fuses 4a to 4c, the contact mechanisms 3a to 3c and the SPDs 1a to 1c are configured in the same storage case 20, the load side connection terminals 14a to 14c of the surge dedicated fuses 4a to 4c In addition to the power supply side connection terminals 15a to 15c of the contact mechanisms 3a to 3c, the load side connection terminals 16a to 16c of the contact mechanisms 3a to 3c and the power supply side connection terminals 17a to 17c of the SPDs 1a to 1c are not required, thereby further reducing the number of parts. This eliminates the need for a connecting step, further reducing the number of assembly steps, and further miniaturizing the apparatus.

  On the other hand, as described above, the surge dedicated fuses 4a to 4c and the contact mechanisms 3a to 3c, or the surge dedicated fuses 4a to 4c, the contact mechanisms 3a to 3c, and the SPDs 1a to 1c are configured in the same storage case 19, 20. Thus, by reducing the size of the device, the contact mechanisms 3a to 3c through which a large surge current such as a direct lightning strike flows and the coil driving unit 9 are arranged close to each other. Therefore, problems such as malfunction due to induction caused by the strong electric field effect of surge current on the electronic circuit components constituting the coil drive unit 9 and destruction of the electronic circuit components occur. As countermeasures, component arrangement and shield structure in the surge dedicated fuses 4a to 4c, the contact mechanisms 3a to 3c, and the coil driving unit 9 are important.

  For example, the distance between the contact mechanisms 3a to 3c through which a large surge current flows and the surge dedicated fuses 4a to 4c are separated from the electronic circuit parts as much as possible to reduce the influence, or to increase the distance. When this is difficult, it is necessary to take measures to insert an electric field shielding component such as an aluminum foil between the contact mechanisms 3a to 3c and the surge dedicated fuses 4a to 4c and the electronic circuit component. Even in this case, the electronic circuit component affected by the surge current is often a specific component, and an individual measure generally taken as a design element by experimental verification is common. As described above, the distance between parts, the direction of parts, the availability of shielding, etc. are design elements, and in order to make it more efficient and effective, the unique characteristics of the parts can be clarified by adopting an integrated structure It becomes easy.

  Furthermore, although the SPD disconnection device fails due to exceeding its performance guarantee value against an excessive lightning surge, it is preferable to make it a safe failure state even in that case. That is, it is designed by providing a weak portion against excessive lightning surge at one place among the connection terminals of the surge dedicated fuses 4a to 4c, the contact mechanisms 3a to 3c and the storage cases 10 to 12, 19, and 20. Therefore, it is possible to specify the failure location, and it is easy to design the pressure relief for the internal pressure increase energy at the time of failure. As a result, the pressure release portion only needs to partially take measures against a part near the failure location, so that a structure for preventing parts from scattering against pressure release can be easily achieved and the cost can be reduced.

  As described above, since it becomes easy to identify a failure point for an excessive lightning surge, the surge fuses 4a to 4c, the contact mechanisms 3a to 3c, and the connection terminals of the storage cases 10 to 12, 19, and 20 are connected to each other. There is no need to increase the design margin for thermal and mechanical strength. As a result, it is possible to design components that match the maximum current passing energy of the interrupting performance of the surge-dedicated fuses 4a to 4c, and to design a structure that can withstand the electromagnetic force acting on the contact mechanisms 3a to 3c by passing lightning surges. In addition to the fuses 4a to 4c and the contact mechanisms 3a to 3c, or the surge dedicated fuses 4a to 4c, the contact mechanisms 3a to 3c, and the SPDs 1a to 1c are integrated in the same storage case, the contact mechanisms 3a to 3c are electrically conductive. Due to the effect of reducing the number of members used, such as reducing the cross-sectional area of the member and reducing the thickness of the storage case, the cost can be further reduced and the size can be reduced.

  4A and 4B illustrate the specific structures of the contact mechanisms 3a to 3c described above. The contact mechanisms 3 a to 3 c include a fixed contact portion 21 and a movable contact portion 22 disposed so as to face the fixed contact portion 21 so as to face each other. A structure is provided in which a pair of magnetic iron pieces 23 and 24 that cause the movable contact portion 22 to be attracted to the fixed contact portion 21 by the electromagnetic force that appears due to the dicurrent are arranged to face each other.

  4 (A) and 4 (B) show a state in which the movable contact portion 22 is in contact with the fixed contact portion 21, and the fixed contact portion 21 is formed by crimping or brazing the fixed contact 21b to the tip portion of the fixed contact plate 21a. Similarly, the movable contact portion 22 has a structure in which the movable contact 22b is fixed to the tip of the movable contact plate 22a by caulking or brazing. One magnetic iron piece 23 having a U-shaped cross section is fixed to the outside of the front end portion of the fixed contact plate 21a by caulking or screwing, and has a U-shaped cross section outside the front end portion of the movable contact plate 22a. The other magnetic iron piece 24 is fixed with caulking or screws. One magnetic iron piece 23 on the fixed contact side and the other magnetic iron piece 24 on the movable contact side form a pair, and are arranged to face each other with a gap g between them.

  In the contact mechanisms 3a to 3c having such a structure, when a large surge current flows, a magnetic flux Φ is generated in the pair of magnetic iron pieces 23 and 24 and the gap g. As a result, the magnetic iron piece 23 on the fixed contact side via the gap g and An attractive force acts between the magnetic iron piece 24 on the movable contact side. By the action of this attractive force, the electromagnetic repulsive force generated between the fixed contact 21b and the movable contact 22b is canceled out, and the movable contact 22b can be prevented from being lifted from the fixed contact 21b by the electromagnetic repulsive force.

  In the contact mechanisms 3a to 3c, the fixed contact plate 21a and the fixed contact 21b, and the movable contact plate 22a and the movable contact 22b are made of an alloy of tungsten carbide and silver. As described above, if the material of the fixed contact plate 21a and the fixed contact 21b, the movable contact plate 22a and the movable contact 22b is an alloy of tungsten carbide and silver, it is possible to improve the welding resistance and the interruption performance. .

  When general silver is used as a material, the melting point of silver is 760 ° C., but when tungsten is used as the material, the melting point of tungsten is 3382 ° C., so that the welding resistance is improved. Easy to plan. However, the contact resistance of tungsten is very large compared to silver, and a general contact mechanism in which a load current always flows has a high temperature rise and cannot be used. However, in the SPD disconnecting device, the time during which surge current flows through the contact mechanisms 3a to 3c Since it is instantaneous, the point where the contact resistance is large is within an allowable range.

  The present invention is not limited to the above-described embodiments, and can of course be implemented in various forms without departing from the gist of the present invention. It includes the equivalent meanings recited in the claims and the equivalents recited in the claims, and all modifications within the scope.

In the embodiment of the SPD disconnecting device according to the present invention, it is a schematic circuit configuration diagram showing a surge-dedicated fuse and a contact mechanism provided in the front stage of the SPD that is grounded to the power line. FIG. 5 is a schematic circuit configuration diagram in which the surge dedicated fuse and the contact mechanism of FIG. 1 are integrally configured in another embodiment of the present invention. FIG. 5 is a schematic circuit configuration diagram in which the surge dedicated fuse, the contact mechanism, and the SPD of FIG. 1 are integrally configured in another embodiment of the present invention. (A) is a front view which shows schematic structure of the contact of a contact mechanism, (B) is a side view of (A).

Explanation of symbols

1a-1c SPD
2a-2c Power line 3a-3c Contact mechanism 4a-4c Surge dedicated fuse

Claims (3)

Installed before the SPD inserted between the power line and the ground, and disconnects the SPD from the power line when the SPD fails, and includes a contact mechanism for disconnecting the SPD from the power line and a surge-dedicated fuse. The SPD is disconnected from the power line by the contact mechanism against a fault current, and the surge dedicated fuse has a predetermined surge current passing performance and an excessive surge cutoff performance, and an excessive surge exceeding the surge current capability for the direct lightning strike of the SPD disconnect city from the power line the SPD by the surge-only fuse with respect to the current, SPD disconnect device characterized by the ability to disconnect the SPD from the power supply line was functionally separated between the surge dedicated fuse and the contact mechanism.   The predetermined surge surge cutoff performance in the surge-dedicated fuse is a cutoff current region that is not less than the maximum current value in the passing current region that exhibits the predetermined surge current passing performance and not more than 1.5 times the maximum current value. The SPD separation device according to claim 1, comprising:   The SPD separation device according to claim 1 or 2, wherein the SPD is composed of a zinc oxide varistor element.

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