JPH10270217A - Current limiter and circuit breaker using PTC element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly reliable current limiting device which suppresses generation of a surge voltage generated when an overcurrent is limited by a current limiting device using a PTC element, and using the current limiting device. To provide a circuit breaker having a small size and an increased breaking capacity. SOLUTION: A PTC element 10 composed of a plurality of parts having different room temperature resistivity and / or phase transition temperature is fitted and connected to metal terminal plates 32 and 33 to connect a current limiting device 30.
To form

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current limiter and a circuit breaker for use in protecting an on-premise wiring system or a power device disposed in an on-premises wiring system from an excessive current such as a short-circuit current. More specifically, at least a plurality of P with different room temperature resistivity and / or phase transition temperature
With the PTC element composed of the TC part, the time from the occurrence of overcurrent to the resistance transition of the PTC element is given a width,
The present invention relates to a current limiter that suppresses generation of a surge voltage due to a resistance change of a PTC element, and a circuit breaker using the current limiter.

[0002]

2. Description of the Related Art For a wire such as a cable for supplying electric power or an electric cord of an electric product, a maximum current value (rated capacity) that can be passed through the wire is determined, and the maximum current value is larger than the determined value. When an electric current is applied to a wire, a spark may be generated at a contact point between the wire and another device to cause a fire, or an insulation coating of the wire may be melted by heating the wire, resulting in a leakage.

In order to prevent such an accident, when an excessive current exceeding a rated capacity flows through a wire, a function of interrupting the current to protect a premises wiring system is provided by a molded case circuit breaker (Molded Case). Circuit
Breaker: hereinafter abbreviated as MCCB). This MCCB is generally called a breaker, and is used by being inserted and connected between the on-premises wiring systems on the power supply side and the load side.

[0004] The structure of the MCCB generally includes an opening / closing mechanism for opening / closing an electric circuit and a trip device for automatically opening / closing an electric circuit in response to a current value greater than a rated current. The power supply side terminal and the load connection side terminal which are incorporated in the insulating container and which communicate with these current interrupt mechanisms are provided outside the insulating container. Here, the electric circuit refers to a wiring path between the power supply side terminal and the load connection side terminal in the MCCB.

In order to increase the current interrupting capacity of the MCCB, a device for limiting an overcurrent flowing through an electric circuit is provided by an MCC while leaving a tripping mechanism of the MCCB itself.
Attempts have been made to increase the substantial current blocking capacity of the MCCB by attaching it to B. Such current limiting devices include an electromagnetic repulsion mechanism, a current limiting fuse, and a PTC.
A resistance element and the like are being studied.

For example, Japanese Patent Laid-Open No. 4-351825 proposes a current limiter using a PTC element.
When the PTC element is heated to a temperature higher than a predetermined temperature (phase transition temperature) determined by a material constituting the PTC element, the resistance value sharply increases, and the current is limited. Therefore, according to the current limiter using the PTC element, Joule heat due to the resistance component of the PTC element is generated in the PTC element due to the overload current or the overcurrent,
The generated heat activates the opening / closing mechanism in the MCCB to cut off the overcurrent. Therefore, since the short-circuit current is limited by the high resistance of the PTC element, there is an advantage that the MCCB having a small breaking current capacity can have a high current breaking capacity in practical use.

[0007]

However, when a PTC element is used in this way, as shown in FIG. 5, the PTC element reaches a phase transition temperature due to an overcurrent, and the resistance value sharply increases. At the moment of increasing and limiting the current limit,
It can be seen that the voltage applied to the PTC element also increases rapidly, and its magnitude reaches 5 to 10 times the power supply voltage. The occurrence of such a sudden large voltage is called a surge,
This surge voltage causes damage such as dielectric breakdown of the PTC element, thereby making it impossible to cut off the electric current in the electric circuit, and causing an accident such as a sudden increase in the temperature of the PTC element causing burning of the current limiter.

The wiring from the power supply to the load has an impedance according to the thickness and length of the wiring, and the current at the time of a short circuit accident is determined from the wiring impedance and the power supply voltage. JIS-C8370 stipulates the wiring impedance to be applied in accordance with the breaking capacity as a short circuit breaking test circuit constant of MCCB.

In general, the impedance of a wire having a small short-circuit current is resistive, whereas the impedance of a wire having a large short-circuit current is inductive. For this reason, when using the PTC element to increase the breaking capacity of the MCCB, the wiring impedance is inductive, and when the PTC element rapidly increases the resistance and tries to limit the overcurrent, the inductance of the inductance increases. A surge voltage is generated such that the action prevents the current from decreasing.

[0010]

Therefore, the present inventors have studied to suppress the generation of a surge voltage due to the current limiting action of the PTC element, and to provide a more reliable current limiting device and a circuit breaker for wiring. And arrived at the present invention. That is,
According to the present invention, a PTC element having a positive temperature coefficient of resistance, whose resistance value increases when a predetermined phase transition temperature is reached, is provided in an electric circuit, and an overcurrent flows through the electric circuit, so that the PTC
A current limiter using a PTC element that suppresses an overcurrent by increasing a resistance value when a temperature of the element rises and reaches a resistance transition temperature, wherein the PTC element has a first terminal made of metal and a second terminal. The PTC is fitted between the two terminals to form a current path.
By varying the time required for the overcurrent to reach the phase transition temperature when the overcurrent is applied to the PTC element depending on the location within the element and slowing the time change of the total resistance of the PTC element due to the overcurrent, the PTC element A current limiter characterized by suppressing generation of surge voltage due to resistance change,
Is provided.

In such a current limiter, the PTC element is integrally formed of at least a plurality of PTC portions having different room temperature resistivity and / or phase transition temperature, and
It is preferable that the part C is electrically connected in series or in parallel between the first terminal and the second terminal made of metal. Further, as a PTC element, one end component PTC part having a PTC part having a different room temperature resistivity as an end component.
A functionally graded material in which the room temperature resistivity changes continuously or stepwise from the site to the other end component PTC site is also preferably used.

Further, as a PTC element used in such a current limiter, a PTC element composed of at least a plurality of parts whose room temperature resistivity is adjusted by adjusting a mixing ratio of cristobalite and a conductive material is used. By adjusting the amount of dichromium trioxide (Cr ₂ O ₃ ) to the element or divanadium trioxide (V ₂ O ₃ ) as a main component and adding to the vanadium trioxide,
A PTC element composed of at least a plurality of portions where the phase transition temperature of the C element is adjusted is preferable.

Further, according to the present invention, when an overcurrent such as a short-circuit current flows through the electric circuit, the temperature increases, and when the temperature reaches a predetermined phase transition temperature, the resistance value increases to limit the overcurrent. What is claimed is: 1. A circuit breaker provided with a current limiter having a flowing PTC element, wherein said current limiter includes at least a plurality of PTCs having different room temperature resistivity and / or phase transition temperature.
The present invention provides a current limiting device in which a current path is formed by fitting a PTC element including a portion between a first terminal and a second terminal made of metal.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION In the current limiting device and the circuit breaker using the PTC element according to the present invention described above, the PT
The resistance value gradually increases due to the resistance transition of the PTC portions having different room temperature resistivity and / or phase transition temperature sequentially forming the C element, and the current limit is started. Generation can be suppressed, and failure of the current limiter due to insulation breakdown or seizure of the PTC element can be avoided. In addition, the current limiting function of the PTC element makes it possible to increase the capacity of the low-capacity MCCB without increasing its size, that is, to increase the maximum current interrupting capacity. Hereinafter, embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

FIG. 1 shows a PT used in the current limiter of the present invention.
It is a perspective view showing one embodiment of C element. PTC element 1
0 is a thin plate-like PTC portion 2P, 2Q, 2R, 2S, 2T having five layers having different room temperature resistivity and / or phase transition temperature.
(Hereinafter referred to as 2P to 2T) are laminated and integrally formed. PTC part 2 at the end of PTC element 10
When the electrodes 3P and 3T are provided on the outer flat plate surface in the stacking direction of P and 2T, the PTC element 10 has PTC portions 2P to 2T connected in series between the electrodes 3P and 3T. At this time, in order to reduce the resistance value of the PTC element 10 and reduce the power loss due to self-heating in a steady state, it is preferable that the area of the electrodes 3P and 3T is large and the thickness of each PTC portion in the stacking direction is reduced. .

On the other hand, when electrodes are provided on the side surface of the PTC element 10, that is, one surface where the surface in the thickness direction of the PTC portions 2 P to 2 T is exposed, and the surface facing the surface, the PTC element 10 Parts 2P to 2T are connected in parallel between the electrodes. However, in this case, since the area of the electrode surface is small and the distance between the electrodes is long, the resistance value of the entire PTC element becomes large.
It is not preferable as a PTC element used for a current limiter. Therefore, when a PTC element is configured by connecting PTC parts in parallel, for example, as in the PTC element 11 shown in FIG. 2, the area of the electrode surfaces 6 and 7 is large and the electrodes 6 and 7 are large.
It is preferable to arrange the PTC sites 5P to 5T having different room temperature resistivity and / or phase transition temperature in a plane so that the distance between them becomes shorter.

The arrangement order of the room temperature resistivity and / or the phase transition temperature of each of the PTC sites 2P to 2T and 5P to 5T constituting these PTC elements 10 and 11 is not necessarily the room temperature resistivity and / or the phase transition temperature. There is no need to order from low to high. Further, in the present embodiment, the PTC element is constituted by five PTC parts. However, it is needless to say that the number of PTC parts can be changed as needed, and there is no particular limitation as long as the number is plural. Further, in order to realize desired PTC characteristics,
In the C element 10, the thickness of each of the PTC parts 2P to 2T is changed, or in the PTC element 11, each of the PTC parts 5P to 5T is changed.
It is also possible to arbitrarily change and set the area ratio of T. Alternatively, a PTC site having a different room temperature resistivity and / or phase transition temperature is used as an end component, and the room temperature resistivity and / or phase transition temperature is continuously or stepwise changed between the end components. A PTC element made of such a functionally gradient material can also be suitably used for the current limiter of the present invention.

In the present invention, such a PTC element has a room temperature resistivity of about 10 to 100 mΩ · cm, a phase transition temperature of 200 ° C. to 260 ° C., and a resistance rise rate at the phase transition temperature of about 1000. Cristobalite-based composite ceramics that are twice or more are preferably used. In cristobalite-based composite ceramics, cristobalite and various conductive materials such as molybdenum disilicide (MoSi ₂ ), tungsten disilicide (WSi ₂ ),
Conductive silicide such as titanium disilicide (TiSi ₂ ), molybdenum carbide (MoC), tungsten carbide (WC), titanium carbide (TiC), silicon carbide (SiC)
Various kinds of PT having different room temperature resistivity by changing the mixing ratio with a conductive carbide such as molybdenum (Mo), tungsten (W), and heat-resistant metal such as titanium (Ti).
C material can be produced.

As means for changing the room temperature resistivity of each part constituting the PTC element, a compounding ratio of a plurality of conductive materials having different electric conductivity to the cristobalite-based composite ceramic is changed, for example, cristobalite and MoSi _2. Mo in composite ceramics of Mo and Mo
It is also effective to change the ratio between Si ₂ and Mo.

The PTC material has a room temperature resistivity of about 1 to 10 mΩ · cm and a phase transition temperature of about 60 ° C. to 150 ° C.
° C and the rate of rise of resistance at the phase transition temperature is about 100
Vanadium oxide (V ₂ O ₃ ) -chromium oxide (Cr ₂ O ₃ ) -based ceramics having 0 times or more properties are also preferably used, and various PTCs having different phase transition temperatures by changing the amount of chromium oxide added. It is possible to make the material.

Other materials for the PTC element include:
Examples include lead titanate (PbTiO ₃ ) ceramics, barium titanate (BaTiO ₃ ) ceramics, bismuth titanate (BiTiO ₃ ) ceramics, and solid solutions thereof. Even in such materials, the phase transition temperature, room temperature resistivity, and the rate of resistance rise at the phase transition temperature can be controlled by adding an alkaline earth metal or the like to form a solid solution, or by changing the mixing ratio of these materials. can do. Further, a polyethylene-carbon composite material or a polyolefin-carbon composite material can be used, and the resistance at room temperature can be controlled by changing the amount of the conductive powder contained therein.

There are no particular restrictions on producing the PTC element 10 and the like using the various materials described above, and various known methods are used. For example, in the case of a ceramic material, first, a slurry is prepared by mixing a raw material powder with an organic solvent, a plasticizer, and a binder for each of various PTC sites having different room temperature resistivity and / or phase transition temperature. A green sheet is manufactured by a sheet forming method such as a doctor blade method or a calendar roll method. Alternatively, water, a plasticizer, a binder, and the like are added to the raw material powder and kneaded, and a sheet is formed from the obtained kneaded soil by extrusion molding. Next, the produced various green sheets are punched into an appropriate shape or the like, laminated to have a desired lamination structure and layer thickness, pressed, and fired to form an integrally fired PT.
A C element can be manufactured. In the obtained laminate,
Processing is performed as necessary, but if electrodes are provided on the end faces in the stacking direction of the obtained stacked body, a PTC element 10 in which PTC sites are connected in series is obtained, and the PTC element 10 is perpendicular to the stacked face of the stacked body. PTCs in which the PTC parts are connected in parallel by performing cutting with an appropriate width in the direction and providing electrodes on this cut surface
The element 11 can be manufactured.

As a method of manufacturing a PTC element other than the integral firing, a method in which a press die is filled with a raw material of a PTC portion having a sequentially different composition and press-molded, and the obtained laminated molded body is fired, And a method in which a slip of each raw material powder is produced, and a molded body produced by a method of sequentially injecting the slip into a casting mold is fired. The method of manufacturing a PTC element by such a method is as follows.
The sintering characteristics are similar to the main components of the PTC material, and it is particularly useful when the operating characteristics of the PTC element can be changed by some additives. Furthermore, by continuously changing the raw material composition to be supplied by a thermal spraying method or the like,
It is also possible to produce a PTC element in which the room temperature resistivity and / or the phase transition temperature changes continuously within the PTC element.

However, due to the choice of the room temperature resistivity and / or the phase transition temperature and the rate of resistance rise at the phase transition temperature, a plurality of completely different PTC materials are used to form the PT.
When a C element must be manufactured, it is difficult to use the above method. In such a case, if it is desired to connect the PTC parts produced from various materials by various methods as a part in series between the electrodes, the parts at each PTC part are baked via a conductive paste and integrated. Or a method of joining them with a conductive adhesive to integrate them. On the other hand, when it is desired to electrically connect the components at a plurality of PTC sites in parallel, a method of connecting the components at each PTC site using a resin adhesive or a heat-resistant adhesive having an insulating and small electric capacity is simple. is there. Note that such a method of manufacturing a PTC element is also useful as another method of manufacturing a PTC element using a ceramic material that can be integrally molded and fired as described above.

Next, the PTC thus produced is
A current limiter using an element will be described. FIG. 3 is a perspective view showing an embodiment of the current limiter 30 of the present invention,
As the element, the PTC element 10 shown in FIG. 1 is used. The current limiter 30 is joined such that the flat surface of the PTC element 10 or 11 is sandwiched between the terminal plates 32 and 33 having a long flat plate shape, and a current path is formed.

Terminal plates 32 and 33 formed in a long plate shape
For example, a metal material having good conductivity such as copper, aluminum, and stainless steel is used. Terminal boards 32, 33
Are placed on the flat surface of the PTC element 10 formed in a thin plate shape so as to be superposed on the PTC element 1 with a conductive adhesive or the like.
0, or metallized on the electrode surface of the PTC element 10 with nickel, silver, platinum, or the like, and fixed by metal brazing or welding to be electrically connected. Therefore, the flow path area of the current is large, and PT
Since the C element 10 is thin, the resistance value of the PTC element 10 becomes small, and it is possible to prevent a reduction in power loss due to the PTC element. Furthermore, since the good conductive metal used for the terminal plates 32 and 33 is generally excellent in heat transfer,
It also plays the role of radiating the heat generated in the PTC element 10 by the steady current. The terminal boards 32 and 33 have MCC
Mounting holes 32A and 33A used for connection with B and wiring are provided.

PT when overcurrent is applied to current limiter 30
The current limiting mechanism of the C element will be described. When the PTC portions 2P to 2T constituting the PTC element 10 have different room temperature resistivity, the PTC element 10 has a width at room temperature resistivity along the direction of conduction between the terminal plates 32 and 33. . Since the calorific value of each part of the PTC parts 2P to 2T due to the current is proportional to the room temperature resistivity of each part, the larger the room temperature resistivity, the larger the calorific value per unit volume and the faster the temperature rise rate. For this reason, when an overcurrent flows through the current limiter 30, the phase transition temperature is sequentially reached with a time lag from the PTC portion having a large room temperature resistivity and the resistance transition occurs, and the resistance value of the entire PTC element 10 gradually increases. Will be done. Therefore, since the current limit of the overcurrent is started slowly, the generation of the surge voltage is suppressed. The final PTC at the time when the resistance values of all the PTC sites 2P to 2T have increased
The final current limiting value of the overcurrent is determined by the resistance value of the element 10.

On the other hand, the PTC element 1 shown in FIG.
1, when the PTC portions 5P to 5T have different room temperature resistivities, the PTC element 11 is manufactured by using the PTC element 10 used in the current limiter 30 shown in FIG. Has a range in room temperature resistivity in a plane perpendicular to the direction of current flow between terminals. In this case, the amount of heat generated by the current is inversely proportional to the room temperature resistivity of each PTC site.
The lower the room temperature resistivity of the PTC portion, the greater the amount of heat generated per unit volume, and the faster the temperature rise rate. For this reason, the phase transition temperature is sequentially reached with a time difference from the PTC portion having a small room temperature resistivity, and the resistance transition occurs, so that the resistance value of the entire PTC element 11 gradually increases. Therefore, also in this case, similarly to the case where the PTC element 10 shown above is used, the start of the overcurrent current limiting is gently started, so that the generation of the surge voltage is suppressed.

Further, the above-mentioned PTs having different room temperature resistivity
Even when a PTC element composed of PTC parts having different phase transition temperatures is used instead of the PTC element composed of the C part, generation of a surge voltage, which is a problem to be solved by the present invention, can be suppressed. Here, assuming that the PTC sites 2P to 2T constituting the PTC element 10 shown in FIG. 1 have different phase transition temperatures, and that there is almost no difference in room temperature resistivity.
When an overcurrent flows to the PTC element, each PTC element
Since the calorific value per unit volume of the part is almost equal, each P
The TC site heats up at about the same rate. Therefore,
A resistance transition occurs sequentially from a PTC site having a low phase transition temperature, and the resistance value of the entire PTC element gradually increases. That is, the time from the occurrence of the overcurrent to the resistance transition of the PTC element has a certain amount of time, and the start of the overcurrent limiting can be started gently, so that the generation of the surge voltage is suppressed.

Similarly, when the PTC portions 5P to 5T constituting the PTC element 11 shown in FIG. 2 have different phase transition temperatures and have almost no difference in room temperature resistivity, Since the temperature rises at substantially the same rate, the resistance transition occurs sequentially from the PTC portion having the lower phase transition temperature, and the resistance value of the entire PTC element gradually increases. That is, the time from the occurrence of the overcurrent to the resistance transition of the PTC element has a certain amount of time, and the start of the overcurrent limiting can be started gently, so that the generation of the surge voltage is suppressed.

Further, the difference in the temperature rise rate of the PTC site due to the difference in the room temperature resistivity, the difference in the time to reach the phase transition temperature of the PTC site due to the difference in the phase transition temperature, and
By taking into account the electrode area of the C site and the resistance rise rate,
It goes without saying that a gentle initial current limit of the overcurrent according to the purpose and application can be achieved, and the generation of a surge voltage can be suppressed.

Actually, the current limiter using the various PTC elements described above is, for example, as shown in FIG. 4, various types of three-phase type current limiter 30 shown in FIG. MC
It is arranged and used between the CB 50 and the power supply cables 54X, 54Y, 54Z. The MCCB 50 has a main contact connected to an electric circuit, an opening / closing mechanism for opening / closing the main contact, an arc-extinguishing chamber for extinguishing an arc generated when the main contact is opened, and an overcurrent such as an overload current or a short-circuit current. An operation switch 5 having a built-in release mechanism for releasing the opening / closing mechanism and tripping the main contact, and operating the opening / closing mechanism to connect the main contact to an electric circuit.
1, a power supply side terminal 52X, 52Y, 52Z for connecting the MCCB 50 to a power supply side electric circuit, and a load side terminal 53X, 53Y, 53Z for connecting the MCCB 50 to a load side electric circuit.
And In addition, 55X, 55Y, and 55Z are load wiring cables.

The connection of the current limiter 30 to the MCCB 50 is as follows:
For example, in the case of the power supply cable 54Z, the mounting hole 33A of the terminal plate 33 of the current limiter 30 is mounted on the power supply side terminal 52Z of the MCCB 50 and screwed, and then the mounting of each terminal plate 32 of the current limiter 30 is performed. This is performed by screwing the power supply cable 54Z on the power supply side into the hole 32A. Similar connection is made with the power supply cables 54X, 54Y and MCCB.
The power supply cables 54X, 54Y, 54
Z is connected to MCCB 50 via each current limiter 30.
On the other hand, load wiring cables are connected to the load-side terminals 53X, 53Y, and 53Z for each phase. This allows the current limiter 3 for each phase
MCCB 50 with 0 will be connected to the wiring.

In the premises wiring system as shown in FIG.
Even if an overcurrent exceeding the maximum current breaking capacity of the CCB 50 flows, the current limiting device having the PTC element of the present invention has the same current limiting effect as that of the conventional PTC element.
With the advantage that the maximum current interrupting capacity of B50 can be increased as it is, the occurrence of surge voltage can be suppressed by gradually starting the current limiting. This is to prevent problems such as breakdown of the PTC element due to generation of surge voltage, and problems such as seizure of the PTC element and connection terminals due to rapid heat generation of the PTC element, which are problems when the conventional PTC element is used. There is an effect that can be done. Of course, the current limiter having the PTC element 10 and the like of the present invention does not affect the state where the rated current flows and the interruption of the current equal to or less than the maximum interruption capacity of the MCCB 50.

The embodiments of the current limiter of the present invention and the circuit breaker using the current limiter have been described above. However, the present invention is not limited to such an embodiment, and the gist of the present invention is described. It should be understood that various changes may be made without departing from the scope of the invention. For example, the shape of the PTC element in the present invention may be a circular or polygonal plate, or may be an elliptical cylinder or a polygonal cylinder, depending on the shape of the PTC element or the like, or arbitrarily. It goes without saying that the shape of the terminal plate can be appropriately changed. In addition, a block-shaped PTC element having a low resistance can be used.

[0036]

Hereinafter, the present invention will be described in more detail with reference to examples. Table 1 shows the material properties, shapes, and the like of the PTC elements used in the current limiters of Examples 1 and 2 and Comparative Example. Example 1 uses a PTC element having a room temperature resistivity by changing the mixing ratio of cristobalite and metal molybdenum, and Example 2 changes the phase transition temperature by changing the amount of Cr ₂ O ₃ added. using V ₂ O ₃ -Cr ₂ O ₃ based PTC element remembering width. As a comparative example, a PTC element having the same material system as the PTC element of Example 1 and having both a constant room temperature resistivity and a constant phase transition temperature was used.
An element was used. Each of these devices was connected to the MCCB shown in Table 1, and a short circuit current cutoff test based on JIS-8370 was performed in the test circuit shown in Table 1.

[0037]

[Table 1]

The test results are shown in Table 2. In the first and second embodiments of the present invention using a PTC element having a room temperature resistivity or a phase transition temperature, the maximum passing current passing through the MCCB is limited from 125 kA to 48 kA,
B blocked well. In each case, no surge voltage occurred, and the temperature of the PTC element at the time of current interruption was 340 ° C. or less. Furthermore, the PTC after the test
The state of the device was observed, but no abnormality was observed.

On the other hand, in the comparative example having no variation in the room temperature resistivity or the phase transition temperature, the maximum passing current passing through the MCCB is limited to 125 kA to 48 kA and is cut off by the MCCB. A surge voltage of about 6 times the power supply voltage is generated, and the temperature of the PTC element is also 600 ° C.
, And cracks were observed between the PTC element and the electrode in the PTC element after current interruption.

As described above, by using a PTC element having a room temperature resistivity and / or a phase transition temperature range in the current limiter in the PTC element, generation of a surge voltage and rapid heating of the PTC element due to the surge voltage are prevented. The current limiter itself was also protected.

[0041]

[Table 2]

[0042]

As described above, according to the current limiting device of the present invention, the PTC element is composed of a plurality of PTC sites having different room temperature resistivity and / or phase transition temperature.
Since the overcurrent limit by the TC element is gradually performed, P
Generation of a surge voltage due to a sudden change in resistance of the TC element and rapid generation of heat of the PTC element due to generation of the surge voltage are suppressed. Further, there is an effect that dielectric breakdown and seizure of the PTC element can be prevented. Also, due to the current limiting effect of the PTC element, the same current cutoff effect as when a large-capacity MCCB is used can be obtained even when a small-capacity MCCB is used.
Since the installation cost of the CB can be greatly reduced, and there is almost no need to replace parts,
It has the advantage of excellent maintainability.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of a PTC element used for a current limiter of the present invention.

FIG. 2 is a perspective view showing another embodiment of the PTC element used in the current limiter of the present invention.

FIG. 3 is a perspective view showing one embodiment of a current limiting device of the present invention.

FIG. 4 shows a current limiter of the present invention connected to a circuit breaker (MCC).
It is a top view which shows the example attached to B).

FIG. 5 is an explanatory diagram showing operating characteristics of a conventional circuit breaker (MCCB).

[Explanation of symbols]

2P ・ 2Q ・ 2R ・ 2S ・ 2T ... PTC site, 3P ・ 3
T: electrode, 5P, 5Q, 5R, 5S, 5T: PTC site, 6: electrode, 7: electrode, 10: PTC element, 11: P
TC element, 30: current limiter, 32: terminal plate, 32A: mounting hole, 33: terminal plate, 33A: mounting hole, 50: MCCB,
51: operation switch, 52X, 52Y, 52Z: power supply side terminal, 53X, 53Y, 53Z: load side terminal, 54X
54Y / 54Z: three-phase power supply cable, 55X / 55
Y / 55Z: Load wiring cable.

Claims (6)

[Claims] 1. A PTC element having a positive temperature coefficient of resistance whose resistance value rises at a predetermined phase transition temperature is provided in an electric circuit, and an overcurrent flows through the electric circuit, so that the temperature of the PTC element rises. A current limiting device using a PTC element that suppresses an overcurrent by increasing a resistance value when the resistance transition temperature is reached, wherein the PTC element is provided between a first terminal and a second terminal made of metal. The PTC element is fitted to form a current path, and the time required for the overcurrent to reach the phase transition temperature when the overcurrent is applied to the PTC element varies depending on the position in the PTC element, and the time of the total resistance of the PTC element due to the overcurrent. A current limiter characterized by suppressing the generation of a surge voltage due to a change in resistance of the PTC element by making the change slow. 2. The method according to claim 1, wherein the PTC element has a room temperature resistivity and / or
Alternatively, the PTC portions are integrally formed of at least a plurality of PTC portions having different phase transition temperatures, and the PTC portions are electrically connected in series or in parallel between the first terminal and the second terminal made of metal. 2. The method according to claim 1, wherein
Current limiter as described. 3. The method according to claim 2, wherein the PTC element has a room temperature resistivity and / or
Or, using PTC sites having different phase transition temperatures as end components,
2. The functionally graded material, wherein the room temperature resistivity changes continuously or stepwise from one end component PTC site to the other end component PTC site.
Or the current limiter according to 2. 4. The PTC device according to claim 2, wherein the PTC element is composed of at least a plurality of portions whose room temperature resistivity is adjusted by adjusting a mixing ratio of cristobalite and a conductive material. Current limiter. 5. The PTC element comprising divanadium trioxide (V ₂ O ₃ ) as a main component and adjusting the amount of dichromium trioxide (Cr ₂ O ₃ ) to be added to the divanadium trioxide. 4. The current limiting device according to claim 2, wherein the current limiting device comprises at least a plurality of portions in which a phase transition temperature of the PTC element is adjusted. 6. When an overcurrent such as a short-circuit current flows in an electric circuit,
When the temperature rises and the temperature reaches a predetermined phase transition temperature, the resistance value increases, and a current limiter including a PTC element that limits the overcurrent is provided. A circuit breaker for wiring, wherein the current limiter is the current limiter according to any one of claims 1 to 5.