KR100697917B1 - PTC current limiting device - Google Patents

Abstract

The present invention relates to a PTC fault current limiter. According to the present invention, there is provided a PTC fault current limiter which current-limits current using PTC characteristics, comprising: a PTC element having a PTC characteristic; At least two electrode portions disposed to face each other with the PTC element therebetween; And a molding part provided around the PTC element and the electrode part to surround the interface portion between the PTC element and the electrode part, the molding part including an insulating material made of an elastic material. As a result, the arc generated at the time of limiting the overcurrent or the short-circuit current can be effectively suppressed to prevent flashover between the electrodes.

PTC, Current Limiter, Molding, Insulator

Description

PTC current limiter {PTC current limiting device}

The following drawings attached to this specification are illustrative of preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 is a cross-sectional view showing a PTC fault current limiter according to the prior art.

2 is a cross-sectional view showing a PTC fault current limiter according to a preferred embodiment of the present invention.

3 is a cross-sectional view showing a modified structure of a PTC fault current limiter according to an embodiment of the present invention.

4 is a cross-sectional view showing a PTC fault current limiter according to another embodiment of the present invention.

Fig. 5 is a sectional view showing a PTC fault current limiter according to still another embodiment of the present invention.

Fig. 6 is a sectional view showing a PTC fault current limiter according to still another embodiment of the present invention.

Fig. 7 is a sectional view showing a PTC fault current limiter according to another embodiment of the present invention.

Figure 8 is a graph showing the operation waveform of blocking when the over-current of the PTC current limiter according to the present invention.

<Explanation of symbols for the main parts of the drawings>

110 ... PTC current limiter 120, 130 ... electrode

121, 131 ... contact electrodes 122, 132 ... current leads

140, 141, 142 Molding part 150 ... Coating layer

161, 162 ... 170 gas exhaust case

610 ... housing 620, 630 ... elastic member

710, 720 ... plates 730, 740 ... fasteners

The present invention relates to a PTC fault current limiter, and more particularly, to a PTC fault current limiter capable of preventing flashover between an arc and a contact electrode occurring between a PTC element and a contact electrode.

In general, the arc extinguishing circuit breaker is widely used as a countermeasure against short-circuit current in low and high voltage systems. However, the conventional circuit breaker takes a long time to break and has no current limiting function for the expected fault current value, so that the duration of the accident spreading effect is relatively long. In addition, the failure of short-circuit current interruption has a great effect on the surrounding power equipment and power system. Therefore, there is an increasing demand for a fault current limiter that can effectively limit the system short circuit current in a short time.

A limiter is a device that limits and blocks overcurrent and short-circuit current generated in a power system. In general, a current limiter may achieve a function using a material having a positive temperature coefficient (PTC) characteristic.

A material having a PTC characteristic has a relatively low resistance at room temperature to allow a good current to pass through. However, if the ambient temperature rises or a current exceeding the allowable value is generated and heats itself, the resistance may increase rapidly by several hundred times or more, thereby limiting the current. Therefore, when the circuit device is configured using this, various circuits can be protected.

In this regard, Japanese Patent Laid-Open No. Hei 10-321413 discloses a fault current limiter using PTC. Referring to Fig. 1 showing this technique, a conventional current limiter using PTC is formed by mixing conductive particles and welding the PTC polymer element 1 having the PTC characteristic and the PTC polymer element 1 to be disposed on both surfaces. The electrode 2, 3 and the 2nd electrode 4, 5 arrange | positioned in the state electrically connected to the surface of the 1st electrode 2, 3 are comprised.

In this case, the current limiter has a surface area of the PTC polymer element 1 larger than that of the first electrodes 2 and 3, and the surface areas 2 and 3 of the first electrode are larger than those of the second electrodes 4 and 5. Is equal to or equal to This structure can prevent an internal short circuit occurring at both ends of the first electrodes 2 and 3. In addition, by installing the molds 6 and 7 made of an insulating member around the PTC polymer element 1 to increase the insulation distance, flashover between the first electrodes 2 and 3 and the second electrodes 4 and 5 is prevented.

However, when the current limiter is used for limiting short circuit current of 100 V or more and 10 kA or more, due to the difference in heat capacity between the PTC polymer element 1 and the first electrodes 2 and 3 in contact therewith, There is a time difference in resistance generated. Therefore, a considerable resistance occurs at the contact interface between the PTC polymer element 1 and the first electrodes 2 and 3 before the resistance due to the heat generation of the PTC polymer element 1. As a result, heat stress is concentrated and an arc is generated at the interface between the PTC element 1 and the first electrodes 2 and 3, and a considerable noise is generated. This arc decomposes and carbonizes the PTC polymer element 1 and eventually causes dielectric breakdown. In addition, due to the arc and the heat generation of the PTC polymer 1 element itself, the PTC material is melted and vaporized so that the thickness of the PTC polymer element 1 is continuously thinned and the first electrodes 2 and 3 are formed of the PTC polymer element 1. It is impregnated inside.

Accordingly, the current limiter according to the related art attempts to increase the contact pressure by using a pressurizing structure that adjusts the surface area of the first and second electrodes 2 and 3, but is generated at the interface with the actual PTC polymer element 1. Arc generation due to the time difference of the resistance and the electron repulsion force is inevitable, and it is not easy to avoid deterioration of the current-limiting characteristics and flashover between the electrodes due to the generated arc.

In addition, the molds 6 and 7 made of insulating members provided at both ends of the PTC polymer element 1 proposed by the prior art are positive in terms of securing an insulation distance, but the PTC polymer element 1 and the first electrode 2, Arc generated in 3) can not be removed at source, and it is difficult to expect noise mitigation when blocking.

For the reason described above, the current limiter is capable of limiting noise and no arc current in the low current region, but arc generation is inevitable in high-capacity large-capacity structures, and the arc causes deterioration and life reduction of the PTC device.

 The present invention has been made to solve the above problems, to effectively suppress the arc generated when limiting the overcurrent or short-circuit current and to prevent the flashover between the electrodes to provide a PTC fault current limiter that can be used in a high pressure system as well as a low pressure system For that purpose.

PTC fault current limiter according to the present invention for achieving the above object is a PTC fault current limiter for current limiting current using a PTC characteristic, PTC element having a PTC characteristic; At least two electrode portions disposed to face each other with the PTC element therebetween; And a molding part disposed around the PTC device and the electrode part to surround the interface portion between the PTC device and the electrode part, the molding part including an insulating material made of an elastic material.

Preferably, the molding part has an insulation resistance of 10 ³ to 10 ²⁰ ohm and is a thermosetting or thermoplastic resin having an elongation of 5% or more.

In this case, the electrode unit, a contact electrode in contact with the PTC element; And a current lead connected to the contact electrode to energize the contact electrode with the system circuit, wherein the molding part is configured to surround all of the contact electrode and a part of the current lead.

Preferably, the PTC device comprises at least one polymer selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), epoxy (EPOXY), silicon (SILICON) and polyvinyldifluoride (PVDF); One or more conductive particles selected from the group consisting of carbon, metals and metal oxides; And antioxidants.

More preferably, it further comprises a coating layer interposed between the PTC element and the electrode portion and the molding portion.

According to another embodiment of the present invention, the molding part is provided with a gas exhaust port for communicating the PTC element with the outside.

According to another embodiment of the present invention, it may further include a case for receiving the molding.

On the other hand, the PTC device according to another embodiment of the present invention may further include a pressing means for pressing the electrode portion toward the PTC element, the pressing force of the pressing means is preferably at least 1 bar atmospheric pressure.

At this time, the pressing means, the housing for receiving the PTC element and a pair of electrode portion; And an elastic member elastically biased to be supported by an inner surface of the housing so as to press the electrode part toward the PTC element.

Alternatively, the pressing means may include a pair of plates arranged to sandwich the PTC element and the electrode portion therebetween; And a fastening member for fastening the pair of plates to each other.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the specification and claims should not be construed as having a conventional or dictionary meaning, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

2 is a cross-sectional view showing a PTC fault current limiter according to a preferred embodiment of the present invention.

Referring to FIG. 2, the PTC fault current limiter according to the present embodiment includes a PTC element 110, two or more electrode parts 120 and 130 and PTC elements 110 arranged to interpose the PTC element 110 therebetween. And a molding part 140 provided around the electrode parts 120 and 130.

As described above, the PTC element 110 is an element that suppresses overcurrent in the power system by rapidly increasing the electrical resistance at a specific temperature value as the ambient temperature rises.

Although the physical properties of the PTC device 110 vary depending on the current value to be limited, in this embodiment, the specific resistance is 100 Ωm or less at 25 ° C., and the specific resistance at the switching temperature at which Joule heat is generated due to the current supply is It is preferable to make it 10 ⁵ times or more of the specific resistance in said 25 degreeC. In addition, the PTC device 110 may be designed to withstand voltages of 100V AC or more while maintaining electrical and thermal stability, and to be designed such that no flashover occurs when an overvoltage of 30kV or more is applied per cm. In addition, the PTC element 110 should not be tripped when energizing the current before and after the 1A, so that the constant current, for example, 1A before and after the current is supplied to the circuit. In addition, when over current more than 10 times of normal operating current is energized, resistance rises within 1/2 cycle (16.7 ms for 1 cycle) to limit over current, and the operation time gets faster as the short circuit current increases. It is preferable to be manufactured to be able to reduce to the previous state within a few minutes after the limiting operation of the overcurrent.

Preferably, the PTC element 110 is a plate-like structure, the shape may be of circular, elliptical or polygonal. In addition, the area and thickness are preferably designed in consideration of factors such as the use conditions of the PTC element 110, that is, the constant current, the overcurrent to be limited and the operating time.

According to this embodiment, the PTC element 110 is preferably composed of a polymer having a PTC characteristic. In more detail, the PTC device 110 has a configuration in which a conductive particle is impregnated into a polymer.

The polymer may be any one or more polymers selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), epoxy (EPOXY), silicon (SILICON), and polyvinyl difluoride (PVDF). In addition, the conductive particles may be any one or more materials selected from the group consisting of carbon, metals, and metal oxides (TiB ₂ ). In addition, antioxidants may be further added to prevent oxidation of the PTC polymer.

More preferably, an inorganic additive may be further added to the PTC polymer to further improve low resistance at room temperature and high resistance at high temperature.

The electrode parts 120 and 130 include contact electrodes 121 and 131 in contact with the PTC element 110 and current leads 122 and 132 for energizing the contact electrodes 121 and 131 to the system circuit.

The contact electrodes 121 and 131 may be made of copper foil or other metal based elements. In addition, the contact electrodes 121 and 131 may be attached to both surfaces of the PTC device 110 in a form of reducing contact resistance as much as possible, such as, for example, lamination or free contact.

The contact area of the contact electrodes 121 and 131 may be determined so that flashover does not occur between the contact electrodes 121 and 131 when the PTC device 110 is operated in consideration of the area and thickness of the PTC device 110.

The current leads 122 and 132 are connected to the contact electrodes 121 and 131 to energize the contact electrodes 121 and 131 with the power system. In more detail, one end of the current leads 122 and 132 is electrically connected to the contact electrode, and the other end thereof is extended to be connected to an external circuit. In addition, the current leads 122 and 132 are manufactured using a metallic material, and preferably have a cross-sectional area and a thickness suitable for the system current carrying capacity.

More preferably, the current limiter may be provided with a connection electrode (not shown) interposed between the contact electrodes 121 and 131 and the current leads 122 and 132. The connection electrode is made of a metal having a relatively low resistance to facilitate current flow from the power system to the current limiter.

The molding part 140 is configured to surround the interface portion between the PTC device 110 and the contact electrodes 121 and 131. That is, molding is performed around the PTC element 110, the contact electrodes 121 and 131, and the current leads 122 and 132. The molding part 140 is made of an insulator having elasticity. Preferably, the molding part 140 has an insulation resistance of 10 ³ to 10 ²⁰ ohm to provide sufficient insulation strength. In addition, in order to prevent the molding unit 140 from being destroyed in response to the momentary shock generated when the current is limited, it is preferable to be configured to have an elongation of at least 5%. The molding part 140 is made of a thermosetting or thermoplastic resin, for example, silicone resin, polyurethane, etc. may be adopted. However, the present invention is not limited thereto.

When the PTC device 110 is operated due to an overcurrent, an arc may occur instantaneously between interfaces with the contact electrodes 121 and 131, and the characteristic of the PTC device 110 may be degraded due to the arc. In addition, when the arc generation is repeated, the performance of the PTC device 110 may be further degraded and thus may be impossible to use. However, in the present invention, the molding unit 140 configured to directly enclose the PTC element 110 generates instantaneous impact energy at the interface between the PTC element 110 and the contact electrodes 121 and 131 during the current-limiting operation of the PTC element 110. Instantly absorbs the initial arc and extinguishes it.

 In addition, an arc generated between the contact electrodes 121 and 131 at both ends of the PTC element 110 and the interface between the PTC element 110 and the PTC element 110 skips the PTC element 110 and causes the contact electrodes 121 and 131 at both ends. Flashover can be induced between. Therefore, it is important to secure an insulation distance without flashover. In the present invention, the molding part 140 is configured to cover all of the PTC element 110 and the contact electrodes 121 and 131 and a part of the current leads 122 and 132 to provide a sufficient insulation distance at both ends of the PTC element 110. Secure. That is, it is possible to secure a substantial dielectric strength around the contact electrodes 121 and 131, thereby preventing flashover.

Furthermore, the molding part 140 may improve contact resistance characteristics by sealing a space in which the PTC element 110 and the contact electrodes 121 and 131 may not be completely contacted.

Preferably, the PTC fault current limiter according to the present embodiment further includes a PTC element 110 and a coating layer 150 interposed between the electrode parts 120 and 130 and the molding part 140. The coating layer 150 is added to improve the interfacial adhesion between the molding part 140 and the PTC device 110 and the molding part 140 and the electrode parts 120 and 130. For example, the silicone resin, polyurethane, or Epoxy resins can be employed. However, the present invention is not limited thereto.

According to another embodiment of the present invention, the PTC fault current limiter may be variously modified in the shape of the molding part within the scope of the present invention. Referring to FIG. 3, the molding part 141 of the PTC current limiter according to the present embodiment may be configured to surround the PTC current limiter 110 and expose a circumferential surface thereof.

4 and 5 are cross-sectional views showing a PTC fault current limiter according to other embodiments of the present invention. In Figs. 4 and 5, the same reference numerals as in the previous drawings refer to the same members having the same functions, and thus detailed description thereof is omitted.

First, referring to FIG. 4, gas exhaust ports 161 and 162 are formed in the molding part 142 of the PTC current limiter according to the present embodiment. When the PTC current limiter acts as a current limiter, the PTC device 110 may be decomposed to generate gas. The decomposition gas contains carbonized conductive metal particles, and when the conductive metal particles are adsorbed onto the PTC device 110, carbonized conductive paths are formed to adversely affect insulation. In addition, when cracking gas is momentarily generated during the current-limiting action, an internal pressure due to cracking gas is increased, and the molding part 140 having elasticity may be over-expanded. In this case, the gas exhaust pipes 161 and 162 formed in the molding part 142 may discharge the decomposition gas of the PTC device 110 to the outside, thereby solving the above problems.

At least one of the gas exhaust pipes 161 and 162 may be provided to more effectively discharge the decomposition gas of the PTC device.

Meanwhile, referring to FIG. 5, the PTC fault current limiter according to the present embodiment further includes a case 170 provided to accommodate the molding part 140. The case 170 supports the structure of the molding part 140 and suppresses excessive expansion of the molding part 140 during a current-limiting action. In addition, the molding unit 140 is protected from the external environment, that is, light, moisture, and a pollution source.

The case 170 may be made of an insulating material such as polyethylene, polypropylene, or bakelite. However, the present invention is not limited thereto and may be variously modified and employed by those skilled in the art within the scope for achieving the object of the present invention.

6 shows a PTC fault current limiter according to another embodiment of the present invention. In Fig. 6, the same reference numerals as in the previous drawings refer to the same members having the same function, and thus the detailed description thereof will be omitted.

Referring to FIG. 6, the PTC fault current limiter according to the present embodiment further includes pressurizing means for pressing the electrode parts 120 and 130 toward the PTC element 110. The pressing means includes a housing 610 and elastic members 620 and 630.

The housing 610 accommodates all of the PTC element 110 and the contact electrodes 121 and 131 and a part of the current leads 122 and 132. Some of the current leads 122 and 132 extend through the housing 610 to be connected to the power system.

The elastic members 620 and 630 are supported on the inner surface of the housing 610 and are configured to surround the outer circumferential portions of the current leads 122 and 132, thereby contacting the current leads 122 and 132 with the contact electrodes 121 and 131. To the side. As a result, the contact electrodes 121 and 131 are pressed toward the PTC element 110. Preferably, the elastic members 620 and 630 may be provided in one or both current leads of the pair of current leads 122 and 132.

On the other hand, the pressing force of the elastic members (620, 630) is designed to have at least the atmospheric pressure (1bar) or more in order to correspond to the interface separation of the PTC element 110 and the contact electrodes 121, 131 due to the electromagnetic repulsive force generated in a short circuit accident It is preferable. In addition, it is preferable to maintain the pressing force of 1 bar or more even when the thickness of the PTC element 110 is reduced to 1/2 due to the repeated current-limiting action.

The elastic members 620 and 630 may be configured of, for example, coil springs provided to surround the outer circumferential surfaces of the current leads 122 and / or 132. However, the present invention is not limited thereto, and various modifications may be employed by those skilled in the art within the scope for achieving the object of the present invention.

 Figure 7 shows a PTC fault current limiter according to another embodiment of the present invention. In Fig. 7, since the same reference numerals as in the previous drawings indicate the same members having the same function, detailed description thereof will be omitted.

Referring to FIG. 7, the pressurizing means of the PTC current limiter according to the present embodiment includes a fastening member for fastening the upper and lower plates 710 and 720 and the upper and lower plates 710 and 720.

The PTC element 110, the contact electrodes 121 and 131, and the current leads 122 and 132 are disposed between the upper and lower plates 710 and 720, and the current leads 122 and 132 are connected to an external circuit. The through hole 721 is provided at the center thereof.

Fastening holes 711 and 712 are provided around the upper and lower plates 710 and 720, and the fastening members fix the upper and lower plates 710 and 720 to each other through the fastening holes 711 and 712. In detail, the fastening holes 711 and 712 pass through the bolt 730 and the nut 740 is fastened to the bolt 730 to fix the upper and lower plates 710 and 720 to each other.

Preferably, the pressing means further includes elastic members 620 and 630 provided to surround the current leads 122 and 132. The elastic members 620 and 630 are supported on the inner surfaces of the plates 710 and 720, and are compressed along the outer circumferential surfaces of the current leads 122 and 132 to be elastically biased. As a result, the contact electrodes 121 and 131 pressurize the PTC element 110. The pressing force of the elastic members 620 and 630 is substantially the same as in the above-described embodiment.

Meanwhile, in FIG. 7, the elastic members 620 and 630 are disposed on both current leads 122 and 132, but may be disposed only on some current leads as necessary.

Although the configuration of the pressing means has been specifically disclosed in the above-described embodiments, the present invention is not limited thereto, and various modifications of the pressing means for pressing the electrode parts 120 and 130 toward the PTC element 110 may be employed. It must be understood.

FIG. 8 is a graph showing a blocking operation waveform when an overcurrent is applied in the PTC fault current limiter according to the present invention, and manufactured according to the embodiment of FIG. 2. In the experiment, the voltage was applied to both ends of the PTC device and the fault current was applied to the sample by applying the fault current from 2kV to 30kV and the current-limiting characteristics were examined. Referring to FIG. 8, it can be seen that the current flow is quickly and accurately blocked in the case of a low current of 2 kA as well as in a case where a high current of 10 kA, 15 kA, 20 kA, or 30 kA flows, thereby effectively blocking the overcurrent.

 As described above, although the present invention has been described by way of limited embodiments and drawings, the present invention is not limited thereto and is intended by those skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of equivalents of the claims to be described.

As described above, the PTC fault current limiter according to the present invention effectively suppresses and removes arcs generated between the PTC element and the contact electrode when the overcurrent or short-circuit current is limited, thereby preventing flashover between the electrodes. Therefore, not only low pressure system but also high pressure system can operate more reliably current-limiting action.

Claims (12)

In the PTC fault current limiter which current-limits current using the PTC characteristic, PTC element having a PTC characteristic; At least two electrode portions disposed to face each other with the PTC element therebetween; And PTC limiter comprising a; molded part formed around the PTC element and the electrode portion to surround the interface portion between the PTC element and the electrode portion, the insulating material of the elastic material. The method of claim 1, The molding part has a PTC resistance of 10 ³ to 10 ²⁰ ohms, characterized in that the thermosetting or thermoplastic resin having an elongation of 5% or more. The method of claim 1, wherein the electrode unit, A contact electrode in contact with the PTC element; And And a current lead connected to the contact electrode to energize the contact electrode with a system circuit. And the molding part surrounds all of the contact electrode and part of the current lead. The method of claim 1, wherein the PTC device, At least one polymer selected from the group consisting of high density polyethylene (HDPE), low density polyethylene (LDPE), epoxy (EPOXY), silicone (SILICON), and polyvinyldifluoride (PVDF); One or more conductive particles selected from the group consisting of carbon, metals and metal oxides; And PTC fault current limiter comprising an antioxidant. The method of claim 1, PTC limiter, characterized in that it further comprises a coating layer interposed between the PTC element and the electrode portion and the molding portion. The method of claim 1, And a gas exhaust port communicating with the PTC element and the outside is formed in the molding part. The method of claim 1, PTC limiter further comprises a case surrounding the outer surface of the molding part. The method of claim 1, PTC limiter further comprises a pressing means for pressing the electrode portion toward the PTC element. The method of claim 8, PTC pressure limiter, characterized in that the pressing force of the pressing means is more than atmospheric pressure. The method of claim 8 or 9, wherein the pressing means, A housing accommodating the PTC element and the pair of electrode portions; And And an elastic member elastically biased and supported on an inner surface of the housing to press the electrode portion to the PTC element side. The method of claim 8 or 9, wherein the pressing means, A pair of plates arranged to sandwich the PTC element and the electrode portion therebetween; And PTC limiter, characterized in that it comprises a fastening member for fastening the pair of plates by fastening to each other. The method of claim 11, And a resilient biased elastic member supported on the inner surface of the plate so as to press the electrode portion to the PTC element side.

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