JPH079782B2 - Circuit breaker with overheat prevention device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Use of the Invention] The present invention detects an abnormal overheat of a circuit breaker that does not depend on an accident current such as a circuit overload, a short circuit, or an electric leakage, and burns the circuit breaker or an electric wire. The present invention relates to a circuit breaker with an overheat prevention attachment, which has a function of preventing the occurrence of heat.

[Background of the Invention]

One of the abnormal conditions that occurs in the circuit breaker is circuit overload,
There is abnormal overheating that does not depend on the accident current such as a short circuit or leakage, and the circuit breaker or electric wire is burned, or the coil of the electromagnetic trip device or current transformer for current detection built into the circuit breaker is overheated. There is a risk that a layer short may occur or the electronic circuit parts of the electronic trip device may be destroyed by heat, resulting in a malfunction even if an accident current flows.

The cause of this abnormal overheat is insufficient contact area of the terminal part of the circuit breaker, oxidation of the contact surface, insufficient or loose tightening torque of the terminal screw, creep of the wire, increase of contact resistance of the terminal part due to the inclusion of foreign matter, etc. , The contactor in the circuit breaker has fallen off, is consumed,
There is an increase in contact resistance due to oxidation, inclusion of foreign matter, insufficient current carrying capacity of wires, heating by an external heat source, abnormal rise in outside air temperature, etc.

Conventional circuit breakers were made to protect the circuit from overheating and burnout due to accident current, and no particular consideration was given to the prevention of burnout accidents of circuit breakers and electric wires due to abnormal overheating not due to accident current. . In the case of a thermal circuit breaker that uses bimetal to detect overcurrent, after abnormal occurrence of abnormal overheating of the load side terminal near the bimetal,
The circuit breaker can be tripped and operated by detecting it with a bimetal at an early stage.However, even if the trip is performed, the circuit breaker can be tripped against abnormal overheating of the power supply side terminals and contacts. Often after the vessel and wires have burned out.

An electromagnetic circuit breaker that magnetically detects an overcurrent or an electronic circuit breaker that detects an electronic circuit connected to a current transformer has no protection function against abnormal overheating of the circuit breaker itself.

Conventionally, as a countermeasure against this, the user side has been to apply temperature-indicating paint to the circuit breaker terminal part for early detection of abnormal overheating, which is unreliable because there is no criterion for abnormal overheating. It was a thing.

In addition, in Japanese Utility Model Publication No. 56-25156, a bimetal for overheat detection is attached near the terminal portion of the circuit breaker, and the displacement of the bimetal caused by abnormal overheating is interrupted through an interlocking mechanism consisting of a transmission plate and an operating rod. A circuit breaker with an overheat prevention device is shown, which transmits the signal to the open / close mechanism inside the device and causes it to trip, and the operating rod is projected from the surface of the circuit breaker to indicate the operation. In many cases, it cannot be applied unless the internal mechanism of the vessel is changed, and the applicable range is limited. Further, in this conventional example, although the circuit breaker alone can be prevented from overheating, it is used for centralized control of circuit breakers in the power supply system and for overheat protection of other equipment such as electromagnetic switching installed in the same circuit. It was not considered.

[Object of the Invention]

An object of the present invention is to change the internal mechanism of a circuit breaker without changing
Equipped with a protection function that can easily and reliably prevent burnout accidents of circuit breakers and electric wires due to abnormal overheating that does not depend on accident current, and that it is easy to install or replace overheat detection means, and to centrally manage circuit breakers. An object of the present invention is to provide a circuit breaker with an overheat prevention device, which can be used to prevent overheating of other devices installed in the same circuit.

[Outline of Invention]

The present invention comprises an overheat detecting means for outputting an electric signal in response to abnormal overheating of a wire connection terminal, and operates at least one of a trip device and an alarm device for opening a contactor of a circuit breaker by the electric signal. It is characterized by.
Specifically, the present invention specifically relates to a circuit breaker having a terminal for connecting an electric wire, a support member arranged near the terminal and detachably held in a casing of the circuit breaker, and a support member provided on the support member. It is a circuit breaker with an overheat prevention attachment having a structure provided with an overheat detecting means for outputting an electric signal according to abnormal overheat of a terminal. The supporting member may be a terminal cover that covers the terminal for connecting the electric wire, or may be an insulating support that mounts the inter-electrode barrier of the terminal for connecting the electric wire.

Example of Invention

An embodiment of the present invention will be described below with reference to FIGS. In the figure, common parts are allotted with the same reference numerals.

FIG. 1 is a circuit diagram of an embodiment of the present invention, in which 1 is a contact of each pole for opening and closing an electric path, 2 is a power source side terminal, 3 is a load side terminal, and each terminal has a third diagram shown in FIG. , Fig. 4, Fig. 5
The electric wire 4 is connected as shown in FIGS. 9, 9 and 10.
Reference numeral 5 is a heater for heating the bimetal 6 of the thermal trip device shown in FIG. Reference numeral 7 is a temperature sensing element (temperature sensor) for detecting overheat. In this example, a thermistor is used as this temperature sensing element, and the thermistor 7 installed near terminals 2 and 3 of each pole is connected in parallel to each pole terminal. The abnormal overheat detecting means is configured in combination with the determination circuit 8 which detects the abnormal overheat by converting the resistance value of the thermistor 7 which changes according to the temperature of 1 to a voltage and comparing it with a normal level. The signal output from the determination circuit 8 when the terminal portion is abnormally overheated is power-amplified by the trip circuit 9, and the trip device 10 is operated.

FIG. 2 shows an example of the circuit configuration, in which the load side line voltage of the circuit breaker is converted into a DC voltage of an appropriate size through the transformer 11 and the rectifier 12, and the Zener diode 13 of the judgment circuit 8 is further converted. Thermistor 7 connected in parallel as a constant voltage by
And a resistor 14, 15, 16, 17 are applied to the bridge, and a voltage corresponding to the resistance value of the thermistor 7 and a voltage corresponding to the normal level set by the resistors 15, 16, 17 are applied to the comparator 18
The output of the comparator 18 is added to the thyristor gate circuit 19 of the trip circuit 9, and the thyristor 20 controls the energization of the trip device 10. The circuit boards forming the judgment circuit 8 and the trip circuit 9 are installed in a circuit breaker.

In this circuit configuration, when abnormal overheating exceeding the allowable temperature occurs in any of the terminals 2 and 3 of each pole, the output of the comparator 18 becomes high level due to the resistance change of the thermistor 7 corresponding to this, and therefore the thyristor 20 Energize to excite the coil of the trip device 10. The trip device 10 is similar to the voltage trip device normally used to trip the circuit breaker by an external signal, and the trip device 10 incorporated in the circuit breaker operates as shown in FIG. The trip shaft 21 common to all poles rotates counterclockwise to remove the latch 22 and trip an opening / closing mechanism (not shown) to open the contact 1 of each pole.

Although not shown in the figure, it is possible to add an operation indicator such as that used in an earth leakage breaker, and display an operation signal for distinguishing it from the overcurrent trip by the output signal of the determination circuit 8.

In the above embodiment, the case where the thermistor is used as the temperature sensitive element has been described, but similarly, as the temperature sensitive element whose electric output changes according to temperature, a thermocouple utilizing thermoelectromotive force and radiant heat are detected. An infrared sensor or the like can also be used.

The above-mentioned overheat prevention mounting can be applied not only to a thermal circuit breaker but also to an electromagnetic circuit breaker that magnetically detects an overcurrent.

FIGS. 3 to 10 show examples of how the temperature sensitive element is attached to the breaker terminal portion. Although the following example shows the power source side terminal, the same applies to the load side terminal. In addition, for abnormal overheating of the circuit breaker contactor, the contactor is close to the power supply side terminal and is connected to the power supply side terminal via the circuit breaker internal conductor that is a good conductor of heat. Can be detected sufficiently.

FIG. 3 shows that the temperature sensitive element 7 is embedded near the terminal of the molded case 23 of the circuit breaker to which the terminal 2 is attached, the temperature of the terminal 2 is detected through the molded case 23, and the main circuit of the temperature sensitive element 7 is detected. In this example, the lead wire 24 of the temperature sensitive element 7 is arranged on the back surface of the mold case 23 having a relatively low temperature and is connected to the circuit board provided in the mold case 23.

4 to 6 show a temperature sensor unit 25 in which the temperature sensitive element 7 for the terminal 2 of each pole is held by another resin-molded insulating support 26 and is integrated to insulate the terminals. In the example in which the temperature sensor unit 25 is attached to the mold case 23 using the attachment groove 27 of the inter-electrode barrier (not shown) which is attached after the electric wire is connected, as shown in FIG. Is provided with a groove 29 into which the inter-electrode barrier is fitted together with an attachment projection 28 that engages with the attachment groove 27 of the mold case 23, so that the inter-electrode insulation by the inter-electrode barrier can be performed without any problem.

If such a temperature sensor unit 25 is used, the temperature sensitive element 7 as an additional component can be attached to the circuit breaker and the lead wire.
Wiring of 24 can be done easily.

7 and 8 show an example in which the temperature sensor unit 25 is formed in a plate shape so that it can be sandwiched between the back surface of the mold case 23 and the board surface, and 30 is a mounting hole for the temperature sensor unit 25. Therefore, the temperature sensing element 7 held by the insulating support 26 of the temperature sensor unit 25 can detect the temperature of both the power source side terminal 2 and the load side terminal 3 by one unit. In this case, since the temperature sensitive element 7 is separated from the terminal portion, it is desirable to use an infrared sensor or the like that detects radiant heat as the temperature sensitive element 7.

9 and 10 show an example in which the temperature sensitive element 7 is attached to the terminal cover 31 used for insulation of the breaker terminal portion, and a special insulating support for holding the temperature sensitive element 7 is not necessary, There is an advantage that the temperature sensing element 7 and the terminal cover 31 can be attached to the device terminal portion at the same time.

A specific example of the mounting structure of the temperature sensitive element 7 to the temperature sensor unit 25 or the terminal cover 31 is shown in FIGS. 11 and 12.

FIG. 11 shows a case where a contact type temperature sensitive element such as a thermistor or a thermocouple is used.
Insert it into the hole 33 provided in 26 (or the terminal cover 31) and elastically hold it by the spring 34 so that it can move in the longitudinal direction, and make the tip of the insulator 32 contact the breaker terminal. Thus, the temperature of the terminal portion can be accurately detected while electrically insulating the temperature sensitive element 7 from the charging terminal portion.

FIG. 12 shows a case where a non-contact type temperature sensitive element such as an infrared sensor is used. The temperature sensitive element 7 is embedded in an insulator 35 such as ceramic and provided on the insulating support 26 (or the terminal cover 31) of the temperature sensor unit. Radiant heat energy that enters the opening 38 of the insulating support 26 through the filter 37 that inserts into the hole 36 to shield visible light such as external light and allows only radiant heat energy from the breaker terminal portion to pass. Is transmitted to the temperature sensitive element 7 and converted into an electric signal by utilizing the change in conductivity of the semiconductor due to infrared absorption.

13 to 16 show circuit configurations of other embodiments of the present invention.

FIG. 13 is a modification of FIG. 1, in which the temperature sensitive element 7 is connected to the power source side terminal 2
Also, the number of elements is reduced by arranging the electrodes between the load side terminals 3 and burying them in the mold case 23 as in FIG. 3, for example.

In FIG. 14, an overcurrent is detected by the current transformer 39, and after a time delay corresponding to the magnitude of the overcurrent, the trip device 10 'is activated by the signal output from the trip circuit 9'and the contactor is activated. 1
This is an example of application to an electronic circuit breaker that opens the circuit. In this case, by simply adding the temperature sensitive element 7 and the judgment circuit 8, when the abnormal overheat of the terminal part is detected, the judgment circuit 8 moves to the trip circuit 9 '. The tripping device 10 'can be operated by outputting a signal, and the tripping circuit 9 and tripping device 10 for preventing overheating as shown in FIG. 1 need not be provided. The same applies to the case of an earth leakage breaker.

FIG. 15 shows a thermosensitive element 7 ′ whose electric output changes at a specific temperature, such as a thermoswitch whose contacts are opened and closed by a bimetal, or a temperature sensitive reed switch which is a combination of a temperature sensitive ferrite and a reed switch. Here is an example. In this example, in the circuit breaker for detecting an overcurrent by the electromagnetic trip device 40, the temperature sensitive elements 7'installed in the vicinity of the respective pole terminals 2 and 3 are connected in parallel so that the temperature sensitive element 7'is generated when abnormal overheating occurs. By closing the contact of ', the trip circuit 9 outputs a signal to the trip device 10 to perform the trip operation. If the current-carrying capacity of the temperature sensitive element 7'is large, the trip device 10 can be directly operated without power amplification in the trip circuit 9. In this case, the mounting structure of the temperature sensitive element 7'may be the same as that of the thermistor, thermocouple or the like.

FIG. 16 shows an example in which only the alarm is issued without tripping the circuit breaker when the terminal portion is abnormally overheated. The output signal of the judgment circuit 8 is amplified by the thyristor, transistor, etc. in the alarm output circuit 41, and the alarm terminal 42 An external alarm device (lamp, buzzer, etc.) 43 is activated through the device, and the alarm device 43 can be installed in the control room to centrally manage the circuit breaker in the power supply system. If necessary, it can be used together with the tripping operation.

17 and 18 show an example of an overheat display device for each pole terminal, which is suitable for use together with the tripping operation of the circuit breaker by the temperature sensitive element. It shows a good conductor of heat elastically held by the terminal cover 31. The temperature measuring portion 44 is brought into contact with each electrode terminal 2 or the electric wire terminal 45 connected to the electrode terminal 2 to transfer heat to the holding portion 44 ', and the terminal cover
Temperature indication label (or temperature indication paint application part) provided on the surface of 31
The color of 46 is changed to indicate overheating. In this case, a mechanical display may be performed using a shape memory alloy or the like as the display device.

Although the protection of the circuit breaker itself has been described above, the temperature sensitive element is also attached to another device such as an electromagnetic switch installed in the same circuit to detect abnormal overheating of the device and detect the internal circuit breaker. It can also be used as a system for actuating a trip device.

〔The invention's effect〕

According to the present invention, it is possible to detect an abnormal overheat of the circuit breaker terminal portion and perform a tripping operation or an alarm without largely changing the mechanical portion of the circuit breaker. It is widely applied to various types of circuit breakers, such as type, to prevent the circuit breakers and electric wires from being burnt out and to improve their reliability as protectors. Multi-faceted control such as centralized control of circuit breakers in the system and protection of other devices from abnormal overheating by tripping circuit breakers by temperature detection signals of other devices such as electromagnetic switches attached to the circuit Thus, it is possible to obtain a circuit breaker with an overheat prevention device that can be easily used and in which the overheat detecting means can be easily attached or replaced.

[Brief description of drawings]

FIG. 1 is a circuit diagram of an embodiment of the present invention, FIG. 2 is an internal circuit diagram of a portion shown by a block in FIG. 1, and FIG. 3 is a partial cutaway showing an example of a mounting form of a temperature sensing element. FIG. 4 is a side view, FIG. 4 is a plan view showing another example of the mounting form of the temperature sensitive element, FIG. 5 is a partially cut side view, FIG. 6 is a partial perspective view thereof, and FIG.
FIG. 8 is a plan view showing another example of the mounting form of the temperature sensitive element, FIG. 8 is a partially cutaway side view thereof, and FIG. 9 is a partially cut plan view showing another example of the mounting form of the temperature sensitive device. FIG. 10, FIG. 10 is a side view of a part thereof, FIG. 11, FIG. 12 is a sectional view showing a specific example of the temperature sensitive element holding structure, and FIGS. 13 to 16 are other embodiments of the present invention. FIG. 17 is a plan view showing an example of an overheat display device for each pole terminal, and FIG. 18 is a side view with a part thereof cut away. 1: Contact 2,3: Wire connection terminal 7,7 ', 8: Overheat detection means (7,7': Temperature sensor, 8: Judgment circuit) 10,10 ': Tripping device 43: Alarm device

Claims (3)

[Claims] 1. A circuit breaker having terminals for connecting electric wires,
A support member arranged near the terminal and detachably held in the casing of the circuit breaker, and an overheat detection unit provided on the support member for outputting an electric signal in response to abnormal overheating of the terminal are provided. A circuit breaker with an overheat prevention device having a structure. 2. The first cover according to claim 1, wherein the support member is a terminal cover for covering a terminal for connecting an electric wire.
A circuit breaker with an overheat prevention device according to the item. 3. The circuit breaker with an overheat prevention device according to claim 1, wherein the support member is an insulating support for mounting an inter-electrode barrier of a terminal for connecting an electric wire.