JPH10275710A - Ptc current limiter provided with ptc element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a PTC current limiter provided with a backup function in which surge voltage is prevented. SOLUTION: A PTC current limiter 10 is provided with a PTC element body 11 and a resistor 12 provided with an opening, in which the PTC element body 11 is fitted, on the center part thereof. The PTC element body 11 is fitted in the opening part of the resistor 12, and, to upper and lower surfaces of a thing in which these are integrally formed, metal electrode plates 13 and 14 are fix-bonded and connected. A resistance value of the resistor 12 is so set as to be 10-50 times of a resistance value of the PTC element body 11 at room temperature. Thereby load current flows through the PTC element body 11 in a steady state, and it is suppressed with the resistor at generation of surge voltage and short circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power transmission / distribution system or a power device disposed on a transmission / distribution system line or the like from an overcurrent such as a short-circuit current or an overload current flowing through the line. In particular, a PT having a PTC element whose resistance value increases with an increase in temperature
It relates to a C current limiter.

[0002]

2. Description of the Related Art In recent years, in order to protect power equipment disposed on a transmission / distribution system or a line such as a transmission / distribution system from an overcurrent such as a short-circuit current flowing through the transmission / distribution system, the resistance value increases due to an increase in temperature. An element having a positive temperature coefficient of resistance (PTC (Positive Temperature Coefficient) thermistor, hereinafter referred to as a PTC element) is used. It has been proposed to connect to a railway line for use. When a current limiting device equipped with a PTC element plate of this type is used along with a circuit breaker on a line of a power transmission and distribution system, for example, when an overcurrent such as a short-circuit current flows through this line, a joule is inserted into the PTC element plate. Heat is generated and the temperature of the PTC element plate rises. Then, since the PTC element has a positive temperature coefficient of resistance, when the specific resistance suddenly increases (generally called a phase transition temperature), the resistance value sharply increases, and this line has a high resistance. The flowing overcurrent is suppressed (current limit), and the circuit breaker is operated thereafter to cut off the line. On the other hand, when the temperature of the PTC element returns to normal temperature after the recovery from the accident, the resistance value returns to the original low resistance value, so the PTC element automatically recovers, and when the circuit breaker is turned on again, this line is connected. A normal predetermined load current flows.

[0003]

However, in the current limiter using the above-mentioned PTC element plate alone, if a surge voltage occurs on the line for some reason, the resistance of the PTC element at room temperature is low. In addition, there is a problem that the surge voltage cannot be suppressed. Further, when an overcurrent exceeding an allowable value flows through the line for some reason and the PTC element plate is destroyed, there is a problem that the current limiting operation cannot be performed after the breakdown. The present invention has been made in view of the above-described problems, and an object of the present invention is to provide a PTC current limiter that can prevent a surge voltage and has a backup function.

[0004]

SUMMARY OF THE INVENTION The present invention relates to a PTC whose resistance value increases with an increase in temperature.
PT provided with a PTC element body having an element formed in a predetermined shape
In order to solve the above-mentioned problem, in the C current limiter, in the invention described in claim 1, a resistor having a resistance value larger than a resistance value of the PTC element body at normal temperature is provided adjacent to the PTC element body. It is arranged.

[0005] As described above, the PTC element is located adjacent to the PTC element body.
If a resistor that is larger than the resistance value of the element body at normal temperature is arranged, if a surge voltage occurs on the line for some reason, the resistor suppresses the surge voltage, so that the surge voltage can be prevented. . Further, when an overcurrent exceeding a permissible value flows through the line for some reason and the PTC element plate is broken, the PTC element body is suppressed by a resistor having a resistance value larger than the resistance value at normal temperature (current limiting). Therefore, even if the PTC element plate is broken, the current limiting function can be maintained, and the backup function can be provided.

When the accident is resolved and the power supply to the line is resumed, current flows through the PTC element body, and the temperature of the PTC element body gradually decreases, so that the PTC element body is cooled. When the temperature reaches room temperature, a normal load current flows through the line. As a result, the reliability of this type of current limiter is improved, and the reliability of a line such as a transmission and distribution system including such a current limiter is improved.

According to the second aspect of the present invention, the resistance of the resistor is set to be 10 to 50 times the resistance of the PTC element at room temperature. Surge voltage occurs and PTC
When the temperature of the element body rises, its resistance value becomes 100 to normal temperature.
Although the surge voltage cannot be suppressed only by the PTC element body because it rapidly increases to about 1000, the use of a resistor having a resistance value of 10 to 50 times the resistance value of the PTC element body at normal temperature makes it possible to rapidly reduce the surge voltage. A large increase in resistance is alleviated, and a surge voltage can be sufficiently suppressed.

According to the third aspect of the present invention, the above-mentioned resistor is made of a material having good thermal conductivity, large heat capacity and heat absorption. When the resistor is formed from such a material having heat absorption, the resistor efficiently absorbs the heat released from the PTC element body that has been heated due to an overcurrent, so that the resistor can be used for a long time. Therefore, even if an overload current flows through the PTC element body and the PTC element body generates heat, the PTC element body can be prevented from reaching the phase transition temperature.

When an overcurrent flows through the PTC element body and the temperature of the PTC element body and the resistor arranged adjacent to the PTC element body rises, the temperature rise causes the PTC element body and the PTC element body to be arranged adjacent thereto. The resistor will thermally expand. At this time, if these coefficients of thermal expansion are different, the degree of expansion is also different, so that stress is generated at these contact portions. For this reason, there arises a problem that the PTC element or the resistor is damaged based on the stress. Therefore,
According to the fourth aspect of the present invention, the PTC element body and the resistor are configured by selecting a material that makes the thermal expansion coefficient of the PTC element body and the thermal expansion coefficient of the resistor equal. In this way, by making the thermal expansion coefficients of the PTC element body and the resistor equal, the temperature of the PTC element body and the resistor arranged adjacent to the PTC element body rise, and even if they are thermally expanded, they become uniform. P can be thermally expanded
It is possible to prevent a stress from being generated at a contact portion between the TC element body and the resistor, and also to prevent a problem that the TC element body and the resistor are damaged.

[0010]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
An embodiment of a PTC current limiter having a TC element will be described. FIG. 1 is a cross-sectional view illustrating a schematic configuration of a PTC current limiter 10 according to the present embodiment. FIG. 1A is a diagram illustrating a vertical cross-section thereof. FIG. FIG. 4 is a view showing a cross section of a central part of FIG.

The PTC current limiting device 10 of this embodiment has a PTC element body 11 formed by molding its planar shape into a circle.
And an opening 12 for fitting the PTC element body 11 in the center thereof.
a, and a resistor 12 formed by shaping its planar shape into a circle.
The PTC element body 11 is fitted into a, and these are fixed with an adhesive or the like to be integrally formed. The PTC current limiter 10 is formed by fixing and connecting the first metal electrode plate 13 and the second metal electrode plate 14 on the upper and lower surfaces of the PTC element body 11 having the resistor 12 integrally formed in this manner. Is done.

The PTC element body 11 has an element having a positive resistance temperature coefficient (PTC: Positive Temperature Coefficient thermistor, hereinafter referred to as a PTC element) whose resistance value increases as the temperature rises, for example, V ₂ O ₃ -C
The temperature at which the specific resistance of a V ₂ O ₃ ceramic such as r ₂ O ₃ , bismuth titanate (BiTiO ₃ ) ceramic or a solid solution thereof, or a composite ceramic material such as cristobalite-carbon increases sharply (generally, Is a phase transition temperature) of about 100 ° C. to 280 ° C., using a PTC element whose resistance at room temperature is small and whose resistance rapidly increases when the phase transition temperature is reached. It is formed by molding.

The resistor 12 is made of a resistive material such as ceramics or metal. An opening 12a is provided at the center of the resistor 12 for fitting the PTC element 11, and the resistor 12 is formed so that its planar shape is a circular plate. It is formed. Here, the resistance of the resistor 12 is set to be 10 to 50 times the resistance of the PTC element 11 at room temperature. If the resistor 12 is formed using a resistance material having good thermal conductivity, large heat capacity, and heat absorption, the resistor 12 efficiently absorbs the heat released from the PTC element body 11 whose temperature has increased. Overload current flows through the PTC element body 11 for a long time,
Even if the TC element 11 generates heat, the PTC element 11 can be prevented from reaching the phase transition temperature. If the resistor 12 is formed using a resistance material such that the coefficient of thermal expansion of the resistor 12 becomes equal to the coefficient of thermal expansion of the PTC element 11, the PT
Even if the C element 11 and the resistor 12 thermally expand, the thermal expansion can be performed uniformly, so that it is possible to prevent stress from being generated at the contact portion between the PTC element 11 and the resistor 12 and damage them. Can be prevented.

The first metal electrode plate 13 and the second metal electrode plate 14 are formed of a metal plate such as copper, aluminum, stainless steel or the like in the form of a metal plate whose plane shape is square or circular. Element body 11 provided with a resistor 12 by bonding, brazing, welding, or the like.
Are fixed to the upper and lower surfaces.

The PTC current limiter 10 configured as described above has
Since the resistance element 12 having a resistance value of 10 to 50 times the resistance value of the PTC element body 11 at normal temperature is provided, when a normal load current flows, most of the load current is PTC.
It flows through the element body 11. Therefore, it is possible to prevent power loss in a steady state. On the other hand, this P
When a surge voltage occurs in the TC current limiter 10, the surge voltage can be sufficiently prevented by using the resistor 12 having a resistance value of 10 to 50 times the resistance value of the PTC element body 11 at normal temperature. . Further, when an overcurrent such as a short-circuit current flows, Joule heat is generated in the PTC element body 11 and the temperature rises, and the resistance value becomes 100 to 100 at normal temperature.
Since the current increases by 1000 times, the overcurrent flows through the resistor 12. Therefore, the overcurrent is suppressed (current-limited) by the resistor 12.

A current limiter 10 (hereinafter, referred to as a PTC current limiter 10) having a PTC element body 11 configured as described above is connected in series to a line L of a power transmission and distribution system, and an overcurrent flowing through this line L is connected. A description will be given based on FIG. 2 showing an example of limiting (current limiting) the current. In FIG. 2, the PTC current limiter 10 is connected in series via a circuit breaker (not shown) between the AC power supply 40 and the load 50 on the line L including the AC power supply 40 and the load 50.

First, a normal operation will be described.
When the circuit breaker is closed (operating state), the AC power supply 40
When the normal load current is supplied to the line L,
A load current flows to the load 50 through the electrode plate 13, the PTC element body 11, and the electrode plate. At this time, since the resistance value of the PTC element body 11 at room temperature is small, the PTC element body 1
Even if 1 is connected to the line L, the power loss is small.

Normally, since there are L and R components in a line, a surge voltage may be generated depending on the use state of the load 50. Here, the resistor 12 is connected to the PTC current limiter 10.
When the PTC element 11 is not provided, the surge voltage cannot be suppressed because the temperature of the PTC element body 11 rises and the resistance rapidly increases to about 100 to 1000 times that at normal temperature.
A surge voltage as shown in FIG. However, when a high-resistance resistor 12 having a resistance value of 10 to 50 times the resistance value of the PTC element body 11 at normal temperature is arranged adjacent to the PTC element body 11 as in the present embodiment, the temperature of the PTC element body 11 rises. Then, when the resistance suddenly increases to about 100 to 1000 times the normal temperature, a surge flows through the resistor 12, so that the rapid change in resistance is reduced, and as shown in FIG. 12, the surge voltage is suppressed.

Here, if for some reason an accident occurs in which the load disposed at the point X on the line L downstream of the PTC current limiter 10 is short-circuited, a short-circuit current flows through the line L. When an overcurrent exceeding the rated current flows through the PTC element body 11, the PTC element body 11 generates heat due to Joule heat and the temperature rises, and the temperature reaches the phase transition temperature. The specific resistance increases,
Its resistance value rapidly increases 100 to 1000 times that at normal temperature.

Then, since the resistance value of the resistor 12 becomes smaller than the resistance value of the PTC element body 11 which has reached the phase transition temperature, an overcurrent flows through the resistor 12.
Thus, the overcurrent is suppressed (current-limited) by the high-resistance resistor 12. For this reason, the PTC element body 1
In No. 1, since the temperature does not rise to reach the NTC (Negative Temperature Coefficient) region, it is possible to prevent the PTC element body 11 from being broken due to a long-term overcurrent.

The planar shapes of the PTC element 11, the resistor 12, and the metal electrode plates 13 and 14 are not limited to the above-mentioned circular shapes,
FIG. 1C (FIG. 1C is similar to FIG. 1B)
A similar effect can be exerted by forming the PTC current limiter 10 so that its planar shape is square as shown in FIG.

In the above embodiment, the PTC element 11 is disposed at the center of the resistor 12 so that the PTC current limiter 10
The PTC element 11 and the resistor 1
2 can be variously modified. Hereinafter, the modified example will be described.

First Modification FIG. 4 is a sectional view showing a schematic configuration of a PTC current limiter 20 of the first modification. The PTC current limiter 20 of the first modification has a PTC element body 2 formed by molding its planar shape into a square.
1, a resistor 22 formed on the side of the PTC element body 21 by shaping its planar shape into a square, and a resistor 22 formed integrally with the PTC element body 21 and the resistor 22 by bonding or the like. The first metal electrode plate 23 and the second metal electrode plate 24 are fixedly connected to the upper and lower surfaces of the PTC element body 21 having

The constituent materials of the PTC element body 21, the resistor 22, the first metal electrode plate 23 and the second metal electrode plate 24 are the same as those of the above-described embodiment. The operation of the PTC current limiter 20 configured as described above is also the same as that of the above-described embodiment, and the description thereof will be omitted.

Even when the PTC current limiter 20 is configured as described above, the surge voltage can be suppressed by the PTC element body 21 and the overcurrent such as a short-circuit current can be suppressed by the resistor 22 (current limit). It becomes possible to do.

FIG. 5 is a sectional view showing a schematic configuration of a PTC current limiter 30 according to a second modification. The PTC current limiter 30 of Modification 2 has a P-shape formed by shaping its planar shape into a circle or a square.
A TC element 31 and a second part below the PTC element 31
A resistor 32 disposed with a metal electrode plate 34 interposed therebetween and formed by shaping its planar shape into a circle or a rectangle, and a PTC element body 2 disposed with a second metal electrode plate 34 interposed therebetween
The first metal electrode plate 33 has a U-shaped cross-section for fixing and connecting the resistor 1 and the resistor 22 and has an extended portion 33a extending outward from a central portion thereof.

The constituent materials of the PTC element body 31, the resistor 32, the first metal electrode plate 33, and the second metal electrode plate 34 are the same as those of the above-described embodiment. Further, the operation of the PTC current limiter 30 configured as described above is the same as that of the above-described embodiment, and the description thereof will be omitted.

Even when the PTC current limiter 30 is configured as described above, the surge voltage can be suppressed by the PTC element body 31 and the overcurrent such as a short-circuit current can be suppressed by the resistor 32 (current limit). It becomes possible to do.

It should be noted that the PTC current limiter of the present invention is not limited to the above-described embodiment and each modified example.
The circuit breaker for low-voltage wiring, the circuit breaker for high voltage and extra high voltage or higher can also be used by being built in or separately arranged in series. It can also be used to protect thyristor devices, or can be used in place of current limiting fuses for low voltage network distribution.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a schematic configuration of a PTC current limiter according to an embodiment of the present invention.

FIG. 2 is a diagram showing an example of connecting the PTC current limiter of FIG. 1 to a line of a power transmission and distribution system.

FIG. 3 is a waveform diagram showing current waveforms and voltage waveforms flowing through a PTC current limiter when a resistor according to the present invention is used and when it is not used.

FIG. 4 is a sectional view showing a first modification of the PTC current limiter of the present embodiment.

FIG. 5 is a sectional view showing a second modification of the PTC current limiter of the present embodiment.

[Explanation of symbols]

10,20,30 ... PTC current limiter, 11,21,31 ... PT
C element body, 13,23,33 ... first metal electrode plate, 14,2
4, 34: second metal electrode plate, 40: AC power supply, 50: load

Claims (4)

[Claims] 1. A PTC current limiter comprising a PTC element body formed in a predetermined shape with a PTC element whose resistance value increases with an increase in temperature, wherein the PTC element body has a resistance value larger than the resistance value of the PTC element body at room temperature. A PTC current limiter including a PTC element, wherein a resistor having a resistance value is arranged adjacent to the PTC element body. 2. The PTC current limiter provided with a PTC element according to claim 1, wherein the resistance of the resistor is set to 10 to 50 times the resistance of the PTC element at room temperature. 3. A PTC limit comprising a PTC element according to claim 1, wherein said resistor is made of a material having good thermal conductivity, large heat capacity and heat absorption. Sink. 4. The PTC element body and the resistor are selected from a material such that the thermal expansion coefficient of the PTC element body and the thermal expansion coefficient of the resistor become equal. A PTC current limiter comprising the PTC element according to claim 1.