JPH04351825A - Breaker for wiring - Google Patents

Abstract

PURPOSE:To reduce the size of a breaker for wiring while maintaining large current breaker ability. CONSTITUTION:A PTC resistance device 1 is inserted into am electric pass in an insulating container 13 in series, and is thus connected thereto, namely, it is inserted either between a thermal device 12 and a load side terminal 15 (a), or between a contact 11 of a switching mechanism and the thermal device 12 (b), or between a power source side terminal 13 and the contact (c). Overcurrent at the time of short-circuit accident is thus suppressed, while current breaker value at the time of breaking through the switching mechanism is thus reduced.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a molded case circuit breaker having the function of automatically interrupting an electric circuit in the event of an overload, short circuit, or the like.

0002

[Prior art] AC 600 [V] or less, DC 500 [V]
] In the following electrical systems, a molded case circuit breaker is usually installed between the power supply side and the load side.
It Breaker (hereinafter abbreviated as MCCB) is installed, and if an overload or short circuit accident occurs, this MCCB
By interrupting the overcurrent at B, the system is protected from burnout accidents.

[0003] This type of MCCB generally connects an external connection conductor with a switching mechanism that switches on and off the electrical circuit, an overcurrent tripping device that switches on and off the electrical circuit in response to overcurrent or short-circuit current. The power supply side and load side terminals are assembled together in an insulating container.

[0004] Here, the electric circuit is an electric line between the power supply side terminal and the load side terminal, and the opening/closing mechanism is a mechanism that opens and closes the contacts manually or by a tripping device, and the overcurrent tripping device is a device that detects an overcurrent and opens a contact using a thermal element (eg, bimetal), electromagnetic type, or current transformer.

FIG. 8 shows a three-phase 460[V]/100[A]
Conventional general MCCB with a rating of /25 [kA]
FIG. 9 is a diagram of its circuit configuration.

[0006] In these figures, 30 is MCCB, 3
1 is a contact of the opening/closing mechanism, 32 is a thermal element, 33 is an insulating container, 34 is a power supply side terminal, and 35 is a load side terminal.

[0007] Such an MCCB 30 is used, for example, as a low voltage breaker in a general household, or for protection of electric motors and other power supply systems installed in large numbers in factories and plants.

[0008]

[Problem to be solved by the invention] By the way, the conventional MC
In CB30, in the event of a short circuit accident, overcurrent will
There is a mechanical delay of about 3 to 4 [ms] from when the current flows until it is detected, and then the contact 31 of the opening/closing mechanism begins to open, and the current is finally cut off after 10 to 20 [ms]. During this time, the short circuit current is not limited, so the short circuit breaking current value reaches several [kA] to several tens [kA] even under low voltage circuit conditions. Therefore, the MCCB 30 is required to have the ability to interrupt excessive arc energy that occurs when short-circuit current is interrupted. Especially in factories and plants,
The capacity of the power supply is larger (lower power supply impedance) than in a typical household, and a very large short-circuit current flows.
It is necessary to strengthen the material and structure of MCCB30 and increase the volume of the container.

[0009] Conventionally, therefore, the product price of MCCBs has been high, and in control centers and the like where a large number of MCCBs are installed and used, the volume occupied by MCCBs in one control panel unit is more than one-fourth. There was a problem.

The present invention has been made in view of the above problems, and its purpose is to provide an MCC which has a large current interrupting ability and which can be made smaller and lower in cost.
The goal is to provide B.

[0011]

[Means for Solving the Problems] The structure of the present invention for achieving the above object includes an opening/closing mechanism for opening/closing an electric circuit;
A molded circuit breaker consisting of an overcurrent tripping device that opens and closes the electrical circuit in response to overcurrent or short-circuit current, and power supply side and load side terminals that connect external connection conductors, assembled in an insulating container. In this case, a PTC is applied to the electric circuit in the insulating container.
(Positive Temperature C
oefficient) resistance elements are inserted and connected in series,
The cut-off current value is reduced when the overcurrent or short-circuit current is cut off. Further, a PTC resistance element formed in a thin plate shape or a rod shape was connected to either the power supply side terminal or the load side terminal outside the insulating container.

0012

[Operation] The MCCB of the present invention does not operate in the same way as conventional MCCBs under normal conditions in which a normal current flows through the electrical circuit, but when an overcurrent flows through the electrical circuit due to a short circuit accident, the Joule heat causes resistance of the PTC resistance element. The value increases, making it difficult for current to flow. The heat generated at this time activates the opening/closing mechanism to cut off the overcurrent.

[0013] Therefore, the operational responsibility of MCCB itself is
Since the current is shared by the TC resistance element and the current cutoff value is reduced, the MC
The structure of the CB can be simplified and the volume can be reduced.

[0014] By forming the PTC resistance element in the form of a thin plate or rod, it is easy to attach it externally to the surface of the insulating container, and the mounting space is also saved.

[0015]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment) FIG. 1 is a circuit diagram of an MCCB according to a first embodiment of the present invention. Referring to this figure, the MCCB 10 of this embodiment has a PTC in the electric line connecting the power supply side terminal 14 and the load side terminal 15 in the insulating container 13.
(Positive Temperature C
(effective) resistance elements 1 are inserted and connected in series.

The insertion and connection points are between the thermal element 12 and the load side terminal 14 as shown in FIG. 1(a), and between the contact 11 of the opening/closing mechanism and the thermal element 12 as shown in FIG. 1(b). , same (c)
It is assumed that the contact point 11 of the opening/closing mechanism is located between the power supply side terminal 13 and the contact point 11 of the opening/closing mechanism. Note that it may be inserted and connected to each location at the same time.

This PTC resistance element 1 has a low resistance value when the current is low, but its resistance value rapidly increases as the current increases.For example, (V1-xCrx)2O3
(However, 0≦x≦0.015) is calcined at 1100°C or higher, Fe is mixed as a sintering aid into this calcined material, and this mixture is further fired at 1535°C or higher. (Patent application No. 198453, filed by the present inventors)
Use.

FIG. 2 is a temperature dependence characteristic diagram of the electrical resistance of this PTC resistance element 1 alone. When the temperature reaches 100° C. or higher, the resistance value increases rapidly, and the current limiting effect due to the temperature increase when a large current is applied. (PTC effect) is shown.

FIG. 3 is a diagram showing short-circuit current, voltage, and resistance changes only in PTC resistance element 1 during a short-circuit test. Referring to FIG. 3, the applied voltage reaches its peak value after an elapsed time of approximately 5 [ms], but the specific resistance of the PTC resistance element 1 is approximately 2.0 ms.
It increases rapidly after 5 [ms]. Accordingly, the relative value of the short-circuit current to the normal current also increases with the elapsed time of 2.5 [ms].
] and then rapidly decreased from a peak of 11. If a short circuit test is performed without inserting and connecting PTC resistance element 1,
Since it has been confirmed that the relative value of the short circuit current exceeds 170, it can be seen that this PTC resistance element 1 can provide a large current suppressing effect.

This PTC resistance element 1 is shown in FIGS.
The MCCB 10 of this embodiment, which is incorporated into the insulating container 13 as shown in (c), does not operate at all like the conventional MCCB during normal operation, but when an overcurrent flows due to a short circuit accident, etc., a resistive element is connected to the PTC. The resistance value of 1 increases rapidly, making it difficult for current to flow. The heat generated at this time or the heat of the thermal element 12 operates the contacts 11 of the opening/closing mechanism to cut off the overcurrent. Therefore, the current cutoff value in the opening/closing mechanism can be reduced, and the specifications of each component of the MCCB can be lowered. Further, the volume of the insulating container 13 can also be reduced accordingly.

FIG. 4 shows a three-phase 460[V]/100[A]/
It is an external structure diagram of MCCB10 of this example which has a rating of 25 [kA]. Referring to FIG. 4, the external dimensions and volume can be significantly reduced compared to the MCCB 30 of the same rating shown in FIG. Moreover, since the PTC resistance element is inexpensive and the prices of other components are also lower, the overall manufacturing cost is significantly reduced.

(Second Embodiment) FIG. 5 is a circuit diagram of an MCCB according to a second embodiment of the present invention.

Referring to FIG. 5, the MCCB of the second embodiment
20 houses the contacts 21 of the opening/closing mechanism, the thermal element 22, a tripping device (not shown), etc., and also houses the power supply side terminal 2.
4 and a load side terminal 25, one end of the PTC resistance element 2 is connected to at least one of the power supply side terminal 24 and the load side terminal 25, and The other end portion is formed so as to be connectable to the power supply side wiring or the load side wiring. As the PTC resistance element 2, for example, the same one as in the first embodiment is used.

[0025] In this way, as in the first embodiment, the external dimensions and volume of the MCCB main body 23 can be reduced;
This has the effect of reducing manufacturing costs.

FIGS. 6(a) and 6(b) show the PT according to this embodiment.
FIG. 2 is a configuration perspective view showing an example of a mounting structure for a C resistance element.

Referring to these figures, for example, a bar-shaped PTC resistance element 2' having a circular cross section is formed, wiring terminals 3a and 3b are provided at both ends thereof, and wiring terminals 3a and 3b are provided at both ends of the rod-shaped PTC resistance element 2'. The PT on other surfaces
Holding members 4a and 4b are provided for holding the C resistance element 2', and one of the wiring terminals 3a and 3b is connected to the power supply side terminal 24 or the load side terminal 25 via the wiring member 5.

FIG. 6(a) is a diagram in which one wiring terminal 3b of the PTC resistance element 2' is connected to the power supply side terminal 24.
The other wiring terminal 3a becomes a new power supply side terminal. On the other hand, FIG. 6(b) is a diagram in which one terminal 3a of the PTC resistance element 2' is connected to the load side terminal 25, and the other wiring terminal 3b becomes a new load side terminal.

The rod-shaped PTC resistance element 2' is integrally molded using, for example, a rubber press, and then fired at a predetermined temperature.

FIGS. 7(a) and 7(b) are perspective views showing other examples of mounting structures.

Referring to these figures, for example, a thin plate-like PTC resistance element 2'' is formed, wiring terminals 3'a and 3'b are provided at both ends thereof, and one of them is directly connected to the power supply side. It is connected to the terminal 24 or the load side terminal 25.

FIG. 7(a) is a diagram in which one wiring terminal 3'b of the PTC resistance element 2'' is connected to the power supply side terminal 24, and the other wiring terminal 3'a is connected to a new power supply side terminal. becomes. On the other hand, FIG. 7(b) is a diagram in which one terminal 3'a of the PTC resistance element 2'' is connected to the load side terminal 25, and the other wiring terminal 3'b becomes a new load side terminal.

The thin plate-shaped PTC resistance element 2'' was formed into a predetermined shape by, for example, cutting out a plate-shaped element from a fired disk-shaped element. Although it may be integrally molded like the rod-shaped PTC resistance element 2', care must be taken since molding unevenness will occur if this is done.

Note that the rod-shaped PTC resistance element 2' and the thin plate-shaped P
When compared with the TC resistance element 2'', the former has the advantage of being easy to process, requires few steps, and can be assembled at low cost, but requires additional installation space. In the latter case, if the cutting method is used instead of the so-called integral molding method, the number of steps will increase accordingly and the cost will be higher, but as is clear from Figures 7(a) and (b), it is possible to realize a significant space saving. .

[0035] The PTC resistance element used in this example is a rod-shaped one with a size of 8 [mm: φ] x 50 [mm: L], and a thin plate-shaped one with a size of 20 [mm: W] x 25 [mm: D] x 50 [mm
:L], but this dimension can be changed depending on the current capacity and other conditions.

[0036]

[Effects of the Invention] As detailed above, in the present invention, MC
Insert and connect a PTC resistance element in series with the electric circuit in the CB, that is, between the contacts of the switching mechanism and the power supply terminal, between the contacts and the thermal element, or between the thermal element and the load terminal, or
Since I attached a PTC resistance element externally to the B main body,
Under normal conditions, it has no effect on the electrical system, but when a short circuit accident occurs, the overcurrent is immediately suppressed, and the MCC
This has the effect of significantly reducing the current interrupting ability (responsibility) of B. Thereby, the structure of the MCCB can be simplified and its volume can be significantly reduced. in particular,
Conventional MCCBs with the same rating could only be installed in 8-tier control panel spaces, but now 12-tiers can be stacked in multiple stacks, saving resources (materials) and space. When externally attaching a PTC resistance element, the shape can be changed to, for example, a thin plate shape to further save space.

Furthermore, since overcurrent is suppressed by the PTC resistance element, the conductor wired from the control panel to the load circuit can be made thinner, and inspection and maintenance of the MCCB, load circuit, etc. can be performed safely and easily. became.

[0038] Furthermore, the time required to shut off the circuit in the event of a short circuit is shorter than that of the conventional system, and can now be set to 5 [ms] or less.

Furthermore, the PTC resistance element itself is inexpensive;
Since the component parts of the MCCB can also be made inexpensive, the manufacturing cost of the entire product can be significantly reduced.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a molded circuit breaker according to a first embodiment of the present invention, and (a), (b), and (c) show a PTC resistance element between a load side terminal and a thermal element. These are inserted and connected between the element and the contact, and between the contact and the power supply side terminal.

FIG. 2 is a temperature-dependent characteristic diagram of the electrical resistance of a single PTC resistance element used in the present invention.

FIG. 3 is a diagram of changes in voltage, current, and specific resistance during a short circuit test of the PTC resistance element used in the present invention.

FIG. 4 is an external structural diagram of the molded circuit breaker according to the first embodiment of the present invention, and is a three-phase 460[V]/100[A]/25
The dimensions are shown for a rating of [kA].

FIG. 5 is a circuit configuration diagram of a molded circuit breaker according to a second embodiment of the present invention, in which (a) a PTC resistance element is externally attached to the load side terminal, and (b) is an externally attached PTC resistance element to the power supply side terminal. It is attached.

FIG. 6 is a configuration perspective view showing an example of the mounting structure of the PTC resistance element according to the second embodiment of the present invention;
The C resistance element is connected to the power supply side terminal, and (b) is connected to the load side terminal.

FIG. 7 is a configuration perspective view showing another example of the mounting structure of the PTC resistance element according to the second embodiment of the present invention, in which (a) a thin plate-like PTC resistance element is connected to a power supply side terminal;
b) is connected to the load side terminal.

FIG. 8 is an external structural diagram of a conventional molded circuit breaker, showing dimensions in the case of a three-phase rating of 460 [V]/100 [A]/25 [kA].

FIG. 9 is a circuit diagram of a conventional molded circuit breaker.

[Explanation of symbols]

1, 2, 2', 2''...PTC resistance element, 11, 21,
31... Contact of opening/closing mechanism, 13, 23, 33... Insulating container,
14, 24, 34... Power supply side terminal, 15, 25, 35... Load side terminal, 3a, 3b, 3'a, 3'b... Wiring terminal,
4a, 4b...holding member, 5...wiring member.

Claims (3)

[Claims] Claim 1: An opening/closing mechanism that opens and breaks an electric circuit, an overcurrent tripping device that opens and closes an electric circuit in response to overcurrent or short-circuit current, and power supply side and load side terminals that connect external connection conductors. and a molded circuit breaker integrally assembled in an insulating container, in which a PTC resistance element is inserted and connected in series to the electrical path in the insulating container to reduce the breaking current value when interrupting the overcurrent or short-circuit current. A hardwired circuit breaker characterized by: [Claim 2] An opening/closing mechanism for opening and closing an electric circuit, an overcurrent tripping device for opening and closing an electric circuit in response to overcurrent or short-circuit current, and power supply side and load side terminals for connecting external connection conductors. and a wiring breaker integrally assembled in an insulating container, characterized in that a PTC resistance element is connected to either the power supply side terminal or the load side terminal outside the insulating container. vessel. 3. The molded circuit breaker according to claim 2, wherein the PTC resistance element is formed into a thin plate shape or a rod shape.