EP1863056A1

EP1863056A1 - Circuit breaker

Info

Publication number: EP1863056A1
Application number: EP07010778A
Authority: EP
Inventors: Masahiro Fushimi; Kenichi Nishina
Original assignee: Mitsubishi Electric Corp
Current assignee: Mitsubishi Electric Corp
Priority date: 2006-06-02
Filing date: 2007-05-31
Publication date: 2007-12-05
Anticipated expiration: 2027-05-31
Also published as: CN101083187A; DE602007000840D1; JP2007324038A; EP1863056B1; CN101083187B

Abstract

A circuit breaker includes a stationary contactor (5), a movable contactor (2) opening/closing with respect to the stationary contactor (5), and a pair of magnetic bodies (10) disposed on the both sides of a switching space (53ps) accommodating these contactors (2,5) and permitting a switching action of the movable contactor (2) so as to move in a direction to come closer relatively with respect to each other. When an interruption current causing: an interruption action of the movable contactor (2) reaches or exceeds a specific value, the magnetic bodies (10) are moved in the direction to come closer relatively with respect to each other by an electromagnetic attraction force acting between the magnetic bodies (10) to narrow the switching space (53ps) within the limits of permitting the switching action of the movable contactor (2), and when the electromagnetic attraction force becomes smaller as the interruption current is made smaller by a current limiting action, the magnetic bodies (10) return to the original positions.

Description

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a circuit breaker with a current limiting capability.

Background Art

In order to provide a function of interrupting a large current, such as a short-circuit current, a circuit breaker in the related art is configured in such a manner that a stationary contactor and a movable contactor form a circuit to cause the movable contactor to act repulsively, and a contact-parting electromagnetic force of the movable contactor and an arc driving force in the grid direction are increased by disposing magnetic bodies covered with an insulation cover on the side surfaces in close proximity to the movable contact of the movable contactor and the stationary contact of the stationary contactor as is disclosed, for example, in JP-A-2002-8508 (see Fig. 1 and the description thereof).
In the circuit breaker in the related art, the insulation covers are provided to guard the magnetic bodies against an arc and to enhance the current limiting capability by raising a pressure nearby the contacts through generation of a cracked gas. By taking into account the withstand voltage capability between the movable contact and the stationary contact at the time of contact parting, the insulation covers are disposed apart from each other by a length of a straight line linking the movable contact and the stationary contact, that is, by a specific distance from an arc occurring at the time of interruption. For the circuit breaker of this kind, it is preferable to further enhance the current limiting capability by securing the withstand voltage capability between the movable contact and the stationary contact.

SUMMARY OF THE INVENTION

The invention was devised in view of the foregoing, and therefore has an advantage to achieve a further enhancement of the current limiting capability by securing the withstand voltage capability between the movable contact and the stationary contact.
According to the invention, the circuit breaker includes the stationary contactor, the movable contactor that opens and closes with respect to the stationary contactor, and a pair of magnetic bodies disposed on the both sides of the switching space that accommodates the stationary contactor and the movable contactor and permits a switching action of the movable contactor so as to be able to move in a direction to come closer relatively with respect to each other, and is configured in such manner that when an interruption current that causes an interruption action of the movable contactor reaches or exceeds a specific value, the both magnetic bodies are moved in the direction to come closer relatively with respect to each other by an electromagnetic attraction force acting between the both magnetic bodies to narrow the switching space within the limits of permitting the switching action of the movable contactor, whereas when the electromagnetic attraction force becomes smaller as the interruption current is made smaller by a current limiting action, the both magnetic bodies return to the original positions. It is thus possible to achieve an advantage that the current limiting capability can be further enhanced by securing the withstand voltage capability between the movable contact of the movable contactor and the stationary contact of the stationary contactor.
The foregoing and other objects, features, aspects, and advantages of the present invention will become more apparent from the following detailed description of the present invention when taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1 is a perspective view showing one example of the overall configuration of a circuit breaker according to a first embodiment of the invention;
Fig. 2 is a perspective view showing one example of the configuration of a major portion of an arc extinction unit in the circuit breaker according to the first embodiment of the invention;
Fig. 3 is a transverse plan view when the cross section of the maj or portion taken along the line A-A in Fig. 1 according to the first embodiment of the invention is viewed in the direction indicated by an arrow, showing a state in the case of a region where a current is relatively small;
Fig. 4 is a transverse plan view when the cross section of the major portion taken along the line A-A in Fig. 1 according to the first embodiment of the invention is viewed in the direction indicated by an arrow, showing a state in the case of a region where a current is relatively large;
Fig. 5 is a perspective view showing an exploded diagram of one example of components in the interior of an arc extinction chamber according to the first embodiment of the invention;
Fig. 6 is a view showing an example of the waveforms of a current at the time of interruption and a pressure nearby the arc according to a second embodiment of the invention; and
Fig. 7 is a view showing the release characteristic of a circuit breaker according to a third embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

First Embodiment

Hereinafter, a first embodiment of the invention will be described with reference to Fig. 1 through Fig. 5. Fig. 1 is a perspective view showing one example of the overall configuration of a circuit breaker. Fig. 2 is a perspective view showing one example of the configuration of a major portion of an arc extinction unit in the circuit breaker. Fig. 3 is a transverse plan view when the cross section of a major portion taken along the line A-A in Fig. 1 is viewed in the direction indicated by an arrow, showing a state in the case of a region where a current is relatively small. Fig. 4 is a transverse plan view when the cross section of the major portion taken along the line A-A in Fig. 1 is viewed in the direction indicated by an arrow, showing a state in the case of a region where a current is relatively large. Fig. 5 is a perspective view showing an exploded diagram of one example of components in the interior of an arc extinction chamber. In the respective drawings, like members are labeled with like reference numerals.
Regarding the overall configuration, as is shown in Fig. 1, the circuit breaker is configured in such a manner that plural arc extinction units 23 are linked to one another with a cross bar 27 extending throughout the arc extinction units 23, and a mechanism portion 25 that opens and closes the contacts described below via the cross bar 27, a relay portion 26 that is provided with a connection terminal 26a to the load side and activates the mechanism portion 25 upon detection of an abnormal current, a handle 29 used to manually operate the mechanism portion 25, and the plural arc extinction units 23 are accommodated in a base 30 and a cover 28 attached above the base 30 in a re-attachable manner.
Each arc extinction unit 23 is provided with an exhaust hole 23b, and a stationary contactor 5 forming the connection terminal 5a is disposed in the interior thereof.
As is described in JP-A-2002-8508 supra, the stationary contactor 5 is provided with a parallel conductor 7 that allows contact parting by causing the movable contactor 3 to act repulsively with an electromagnetic force when a large current flows.
A stationary contact 6 is formed at the end terminal of the parallel conductor 7. A movable contact 2 is disposed to the movable contactor 3 on the surface opposing the stationary contact 6.
The movable contactor 3 is held by a rotor 19 coupled to the cross bar 27, and is configured in such a manner that the movable contact 2 is allowed to move away from and come closer to the stationary contact 6 as the movable contact 2 rotates about the rotational shaft 19a of the rotor 19.
An insulation material 11 is disposed on the top surface of the stationary contactor 5 as a protection against an arc heat. Further, plural magnetic arc extinction plates 16 held by a pair of arc extinction side plates 15 in a space between the arc extinction side plates 15 are disposed on the top of the insulation material 11. In addition, the pair of arc extinction side plates 15 and the plural magnetic arc extinction plates 16 together form an arc extinction plate unit 156.
A pair of magnetic bodies 10 is disposed in close proximity to the contacts inside the arc extinction unit 23. At the occurrence of a large current, these magnetic bodies 10 enhance an electromagnetic force that causes the movable contactor 3 to act repulsively for the movable contact 2 to be opened from the stationary contact 6, and an electromagnetic force that guides an arc between the stationary contactor 5 having the stationary contact 6 and an arc runner 9 and the movable contactor 3 in a direction toward the magnetic arc extinction plates 16.
Each magnetic body 10 is covered with an insulation cover 13 made of an insulation material to protect the magnetic body 10 from the arc. The insulation cover 13 made of an insulation material generates a cracked gas with an arc heat and enhances the current limiting capability by raising a pressure nearby the contacts. In order to keep at least a distance to prevent the occurrence of a dielectric breakdown between the movable contact 2 and the stationary contact 6 at the time of contact parting of the movable contact 2 and the stationary contact 6, the insulation cover 13 is configured in such a manner that springs 14, which push the insulation cover 13 in a direction to move away from the contacts, are disposed in a space between spring bearing portions 13a of the insulation cover 13 and spring bearing portions 23a of the arc extinction unit 23.
In the configuration described above, in the case of a region where a current is relatively small, a force Fb of the spring 14 is stronger than an electromagnetic attraction force Fa induced by a current and acting between the pair of magnetic bodies 10.
Hence, as is shown in Fig. 3, the insulation covers 13 are in a state where they have been moved in a direction to move away from the stationary contactor 5 by the force Fb of the springs 14. The inside width B of the insulation covers 13 is therefore maintained at or greater than a distance not to cause an dielectric breakdown between the movable contact 2 and the stationary contact 6 at the time of contact parting.
Because the inside width of the insulation covers 13 is maintained at the inside width B, in comparison with a case of the inside width C (C < B) described below, a switching space 53ps to permit the switching action of the movable contactor 3 with respect to the stationary contactor 5 is wide.
When the electromagnetic attraction force Fa acting on the magnetic bodies 10 becomes larger due to a large current to the extent that the electromagnetic attraction force Fa acting on the magnetic bodies 10 exceeds the spring force Fb, as is shown in Fig. 4, the magnetic bodies 10 and the insulation covers 13 are moved in a direction to come closer to the stationary contactor 5 by the electromagnetic attraction force Fa. The inside width of the insulation covers 13 therefore reaches the inside width C that secures a smaller distance than the inside width B. In other words, the switching space 53ps that permits the switching action of the movable contactor 3 with respect to the stationary contactor 5 is in a narrower state than in the state (see Fig. 3) where the inside width of the insulation covers 13 is maintained at the inside width B.
When the magnetic bodies 10 and the insulation covers 13 have moved in a direction to come closer to the stationary contactor 5 and the inside width of the insulation covers 13 reaches the inside width C, a distance from the insulation covers 13 to an arc occurring between the contacts is so short that the switching space 53ps becomes narrower than in the case of the inside width B and a cracked gas generated when the arc is exposed to the insulation covers 13 is generated in a large volume. Consequently, a pressure nearby the contacts rises abruptly and the arc is narrowed, which makes it possible to enhance the current limiting capability markedly.
When the interruption of a current is completed, the magnetic bodies 10 and the insulation covers 13 are returned by the spring force Fb to the positions at which the inside width B is maintained.
When a sum of the spring force Fb and a pressing force Fc by the pressure nearby the contacts exceeds the electromagnetic attraction force Fa, that is, when Fa < Fb + Fc, even when a large current keeps flowing, the magnetic bodies 10 and the insulation covers 13 move in a direction to reach the inside width B from the position at which they reach the inside width C. In this case, because an effect of suppressing the generation of an excessive pressure due to the generation of a cracked gas is expected, it is possible to use inexpensive materials by lowering the strength of materials forming the arc extinction units 23.
To be more specific, the circuit breaker according to the first embodiment as described above includes a stationary contactor, a movable contactor that opens and closes with respect to the stationary contactor, and a pair of magnetic bodies disposed on the both sides of a switching space that accommodates the stationary contactor and the movable contactor and permits a switching action of the movable contactor so as to be able to move in a direction to come closer relatively with respect to each other. The circuit breaker is configured in such a manner that when an interruption current that causes an interruption action of the movable contactor reaches or exceeds a specific value, the both magnetic bodies are moved in the direction to come closer relatively with respect to each other by an electromagnetic attraction force acting between the both magnetic bodies to narrow the switching space within the limits of permitting the switching action of the movable contactor, and when the electromagnetic attraction force becomes smaller as the interruption current is made smaller by a current limiting action, the both magnetic bodies return to the original positions.
It can be said that the insulation materials 13 that generate a cracked gas with an arc heat are interposed between the respective magnetic bodies 10 and the switching space 53ps.
Also, it can be said that the stationary contactor 5, the movable contactor 3, and the switching space 53ps are housed in the arc extinction unit 23 and the magnetic bodies 10 are disposed on the both side walls of the arc extinction unit 23.
It can be said that the magnetic bodies 10 are incorporated into magnetic body incorporation holes 23sr made in the both side walls of the arc extinction unit 23 so as not to stick out to the outside from the both side wall surfaces 23ss.
Herein, the accident current is equal to or greater than the specific value, and the overload current is lower than the specific value. More specifically, the respective magnetic bodies 10 and the insulation materials 13 move when the accident current flows between the two contacts 3 and 5 so that the current is limited effectively, whereas they do not move when the overload current flows so that a sufficient withstand voltage is maintained.
As has been described, the first embodiment of the invention achieves a circuit breaker with an excellent current limiting capability by raising a pressure nearby the contacts abruptly when a large current is interrupted.
Also, as has been described, the first embodiment of the invention makes it possible to enhance the current limiting capability markedly by moving the insulation covers close to the arc only when the circuit breaker interrupts a relatively large current.
Further, as has been described, the first embodiment of the invention is configured in such a manner that the insulation covers covering the magnetic bodies are attached to the arc extinction unit in such a manner so as to allow the magnetic bodies and the insulation covers to move as one piece. Hence, not only is it possible to achieve a satisfactory current limiting capability by raising a pressure nearby the contacts abruptly by forcing the insulation covers to come closer to an arc through the use of an electromagnetic attraction force induced by the magnetic bodies when a large current is interrupted, but it is also possible to secure a necessary distance between the insulation covers and the arc with a spring force in a region where the current is small.
Furthermore, because the insulation covers covering the magnetic bodies in the circuit breaker are able to come closer to an arc when a large current is interrupted, the current limiting capability can be enhanced markedly. Also, because a sufficient distance can be secured from the insulation covers to an arc in other cases, a sufficient withstand voltage capability can be achieved.

Second Embodiment

Fig. 6 shows an example of the waveforms of a current at the time of interruption and a pressure nearby the arc, indicating that a large current starts to flow at the time T0, and the pressure in close proximity to the arc starts to rise at the time T1 due to a cracked gas generated from the insulation covers 13 with the arc. When the time at which the magnetic bodies 10 and the insulation covers 13 start to operate is later than the time T1, the magnetic bodies 10 and the insulation covers 13 operate slower or they fail to move as the pressing force Fc by the pressure nearby the contacts increases abruptly. Given these circumstances, by setting the spring force Fb and the electromagnetic attraction force Fa to allow the magnetic bodies 10 and the insulation covers 13 to move to reach the inside width C between the time T0 and the time T1, that is, to establish Fb < Fa between T0 and T1, the actions described above can be performed in a reliable manner.

Third Embodiment

Fig. 7 shows the release characteristic of the circuit breaker. The abscissa is used for a current and the ordinate is used for a release action time. The springs 14 that push the magnetic bodies 10 and the insulation covers 13 in a direction to move way from the contacts need to be appropriately strong so as not to lose their own function by a molten material produced at the time of interruption and lodged therein. It is at least a region exceeding the instantaneous release of the circuit breaker specified in Fig. 7 where the current limiting capability is susceptible to a pressure nearby the arc. Hence, by setting the spring force Fb and the electromagnetic attraction force Fa in such a manner that the magnetic bodies 10 and the insulation covers 13 will not operate within the instantaneous release region, that is, to establish Fb < Fa when the current has increased to exceed the instantaneous release region, it is possible to achieve a spring with a relatively strong spring force against a large current. A configuration with a high operation reliability can be therefore achieved.

Fourth Embodiment

In the embodiments above, the configuration to make plural springs 14 to have different spring forces has not been described. However, for example, by making the spring force on the contact terminal 5a side stronger than the spring force on the rotational shaft 19a of the rotor 19 side, the insulation covers 13 on the side maintained at the inside width D operate on a smaller current in comparison with those maintained at the inside width E, thereby establishing the relation, inside width D < inside width E. The exhaust efficiency toward the exhaust hole 23b is therefore hardly impaired, and the strength of the arc extinction unit 23 can be lower. Conversely, by making the spring force on the rotational shaft 19a of the rotor 19 side stronger than the spring force on the connection terminal 5a side, the insulation covers 13 on the side maintained at the inside width E operate on a smaller current in comparison with those maintained at the inside width D, thereby establishing the relation, inside width D > inside width E. A pressure nearby the contacts can be therefore maintained high, which in turn makes it possible to achieve a high current limiting capability.
Various modifications and alterations of this invention will be apparent to those skilled in the art without departing from the scope and sprit of this invention, and it should be understood that this is not limited to the illustrative embodiments set forth herein.

Claims

A circuit breaker provided with a stationary contactor and a movable contactor that opens and closes with respect to the stationary contactor, characterized by comprising:
a pair of magnetic bodies 10 disposed on both sides of a switching space 53ps that accommodates the stationary contactor 5 and the movable contactor 2 and permits a switching action of the movable contactor 2 so as to be able to move in a direction to come closer relatively with respect to each other,
wherein when an interruption current that causes an interruption action of the movable contactor 2 reaches or exceeds a specific value, the both magnetic bodies 10, 10 are moved in the direction to come closer relatively with respect to each other by an electromagnetic attraction force acting between the both magnetic bodies 10, 10 to narrow the switching space 53ps within limits of permitting the switching action of the movable contactor 2, and when the electromagnetic attraction force becomes smaller as the interruption current is made smaller by a current limiting action, the both magnetic bodies 10, 10 return to original positions.
The circuit breaker according to Claim 1, characterized in that the both magnetic bodies 10, 10 move in the direction to come closer relatively with respect to each other before an arc occurs between the stationary contactor 5 and the movable contactor 2.
The circuit breaker according to Claim 1 or 2, characterized in that the both magnetic bodies 10, 10 move in the direction to come closer relatively with respect to each other when a current flowing through the stationary contactor 5 and the movable contactor 2 exceeds an instantaneous release region of the circuit breaker.
The circuit breaker according to any of Claims 1 to 3, characterized in that a quantity of relative movements of the both magnetic bodies 10, 10 differs on an arc initiation point side and on an arc elongation side.
The circuit breaker according to any of Claims 1 to 4, characterized in that an insulation material 13, 13 that generates a cracked gas with an arc heat is interposed between the both magnetic bodies 10, 10 and the switching space 53ps.
The circuit breaker according to any one of Claims 1 through 5, characterized in that the stationary contactor 5, the movable contactor 2, and the switching space 53ps are housed in an arc extinction unit 23, and the magnetic bodies 10, 10 are disposed on both side walls of the arc extinction unit 23.
The circuit breaker according to Claim 6, characterized in that the magnetic bodies 10, 10 are incorporated into magnetic body incorporation holes 23sr made in the both side walls of the arc extinction unit 23 so as not to stick out to an outside from both side wall surfaces 23ss.
The circuit breaker according to any of Claims 1 to 7, characterized in that an accident current is equal to or greater than the specific value, and an overload current is lower than the specific value.