AIR CIRCUIT BREAKER

Abstract

 An air-break circuit interrupter of a large short-time current carrying capacity, in which the movable contact element 6a is prevented from floating and lateral movement to suppress the arcing at the contact surface includes a flexible conductor 7 bent in a substantially U-shape for allowing movements of the movable contact member 6 having the contact element 6a, a lever action pivot shaft 6c for converting an electromagnetic force due to a current flowing through the flexible conductor 7 in the U-shape conductor spreading direction into a pressing force on the movable contact element 6a, and parallel magnetic plates 13 with a magnetic air gap 13a disposed between poles and sides of the U-shape of the conductor for enhancing electromagnetic force. The magnetic plates between each pole may be extended to side portions of the contact elements from side of the U-shape of the flexible conductor.

Description

TECHNICAL FIELD

[0001] This invention relates to an air-break circuit interrupter for interrupting an overcurrent and, particularly, to a multi-pole air-break circuit interrupter for assuring a short-time current carrying capacity at the contact element portion.

BACKGROUND ART

[0002] Fig. 5 is a sectional side view of main portion of a conventional air-break circuit interrupter disclosed in Japanese Patent Laid-Open No. 6-089650, Fig 6 is a perspective view of main portion of the separable contact portion of the conventional air-break circuit interrupter and Fig. 7 is a view illustrating magnetic members disposed around the separable contact portion of the conventional air-break circuit interrupter.

[0003] In the figures, 1 is an outer housing of the air-break circuit interrupter and 2 is a well-known operating mechanism including a toggle link. In such the air-break circuit interrupter, a large dosing force is required, so that the closing is achieved by a spring force charged in a closing spring 2d by a ratchet 2b and an eccentric cam 2c driven by a charge handle 2a or unillustrated motor.

[0004] To a lower link 2e of the operating mechanism 2, a contact arm 4 is connected by a connecting pin 3, and the contact arm 4 is pivotably supported by a contact arm pin 5. 6 is a movable contact member having a movable contact element 6a secured at one end and a flexible conductor 7 made of a thin conductor plates connected at the other end. The other end of the flexible conductor 7 is connected to the lower terminal 8 and the flexible conductor 7 is formed and arranged in a substantially U-shape from the position connected to the lower terminal 8. The movable contact member 6 is rotatably supported by a movable contact member pin 6c inserted into a support hole 6b disposed at the central portion of the movable contact member 6 and a support hole in the contact arm 4. 9 is an upper terminal which has at its one end a stationary contact element 9a to which the movable contact element 6a contacts. 10 is contact pressure spring for urging the flexible conductor 7 at the connection portion with the movable contact member 6 towards the direction in which the U-shape of the flexible conductor 7 is spread. This urging force acts on the movable contact member 6 in the clockwise direction in the figure about the lever fulcrum of the movable contact member pin 6c as the contacting pressure of the movable contact element 6a to the stationary contact element 9a. 11 is an arc extinguisher for extinguishing arcs generated across the separated contacts during the current interruption. 12 are magnetic plates disposed between each pole phase. These magnetic plates 12 are arranged to cover the side portion of the U-shape of the flexible conductor 7 and acts as a magnetic path for enhancing the electromagnetic force for suppressing the floating of the movable contact element 6a upon the flow of an overcurrent which will be described later.

[0005] The description will now be made as to the operation in which the contact member is held against floating upon the fault current in the conventional air-break circuit interrupter. When an excessively large fault current flows through the air-break circuit interrupter, the movable contact element 6a which usually is held on the stationary contact element 9a by the contacting pressure spring 10 tends to separate due to an electromagnetic force. This excessive current flows through the flexible conductor 7, and an electromagnetic force acts on the flexible conductor 7 in the direction of spreading it, so that the movable contact do not separate and no arc generation occurs even when the excessive current flows through U-shaped flexible conductor, thus increasing the short-time current carrying capacity.

[0006] However, an excessive fault current upon the load short circuiting to be interrupted by the air-break circuit interrupter is a three-phase alternating current that flows simultaneously through three poles. Therefore, three magnetic fluxes phase-shifted by 120 degrees pass through the magnetic plates 12 disposed between the phases. Therefore, when the interruption current is large, the magnetic plate 12 is magnetically saturated in the area of the same phase as the adjacent pole of the current and the magnetic flux is off set in the area of the opposite phase, so that the electromagnetic force (contact depressing force) for spreading the U-shaped flexible conductor 7 does not increase as compared to the increase in the current and the separating electromagnetic repulsive force between the stationary contact element 9a and the movable contact element 6a becomes greater, tending to the contact element floating. Even when the thickness of the magnetic plates 12 is increased, a contact floating prevention effect as expected cannot be obtained.

[0007] Also, since the magnetic plates 12 are disposed only around the flexible conductor 7, the movable contact 6 is subjected to the effect of the magnetic field of the adjacent pole which, together with the current flowing through itself, generates a lateral electromagnetic force. This lateral force moves the the movable contact element 6a in the lateral direction and causes an electric arc to be generated across the movable contact element 6a and the stationary contact element 9a and generates damages in the contact surfaces, resulting in a less higher short-time current carrying capacity.

[0008] This invention has been made in order to solve the above problems and has as its object the provision of an air-break circuit interrupter in which the stationary contact element 9a and the movable contact element 6a are prevented from separating and lateral movement is prevented to suppress the arcing at the contact surface, thereby providing a large short-time current carrying capacity.

DISCLOSURE OF INVENTION

[0009] An air-break circuit interrupter of the present invention includes a flexible conductor arranged in a substantially U-shaped configuration flexible in the direction of opening and closing for allowing contact opening and closing movements of the movable contact member having the movable contact element, a pivot shaft of a lever action for converting an electromagnetic force due to a current flowing through the flexible conductor in the direction of spreading the U-shape of the flexible conductor into a pressing force on the movable contact member, and a plurality of magnetic plates disposed between poles and side faces of the U-shape of the flexible conductor for enhancing the electromagnetic force, the magnetic plates being arranged in parallel and having a magnetic air gap defined between them.

[0010] Also, the magnetic plates are arranged to extend to a space defined between the contact elements in each pole.

[0011] Also, a housing of an insulating resin defining an outer housing of the air-break circuit interrupter is provided with an inter-phase partition wall for isolating the contact elements in each pole, and that the inter-phase partition wall has formed therein insertion slots, with an air gap corresponding to the magnetic air gap, in which the magnetic plates are inserted.

[0012] Also, the inter-phase partition wall has separate insertion slots for the magnetic plates disposed at the side of the U-shape of the flexible conductor and a magnetic shield plate for the separable contact portion including the movable contact member.

[0013] Also, the magnetic plates and each the magnetic shield plate includes a lamination of magnetic thin plates.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014] The present invention will become more readily apparent from the following detailed description of the preferred embodiments of the present invention taken in conjunction with the accompanying drawings, in which:

Fig. 1 is a sectional side view of main portion of the air-break circuit interrupter of the first embodiment of the present invention;

Fig. 2 is a view illustrating the mounting arrangement of the magnetic plates to the housing according to the first embodiment;

Fig. 3 is a view showing the arrangement of the magnetic plates disposed around the separable contact portion of the second embodiment of the present invention;

Fig. 4 is a view showing the arrangement of the magnetic plates and the shields according to the third embodiment of the present invention;

Fig. 5 is a sectional side view of main portion of a conventional air-break circuit interrupter;

Fig. 6 is a perspective view of main portion of the separable contact portion of the conventional air-break circuit interrupter; and

Fig. 7 is a view showing the arrangement of the magnetic member disposed around the separable contact portion of the conventional air-break circuit interrupter.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1

[0015] Fig. 1 is a sectional side view of main portion of the air-break circuit interrupter of the first embodiment of the present invention, and Fig. 2 is a view illustrating the mounting arrangement of the magnetic plates to the housing according to the first embodiment.

[0016] In the figures, 1 - 11 are components similar to those of the already described conventional device, so that their explanation will be omitted. 13 are magnetic plates, which are disposed at the side portion of the U-shape of the flexible conductor 7.

[0017] These magnetic plates 13 are disposed between each poles of the multi-pole contact portion and magnetic air gap 13a is provided between the magnetic plates.

[0018] The magnetic plates 13 are held at predetermined positions by inserting them into insertion slots 1b formed in the inter-phase partition wall 1a of the box-shaped base made of an insulating resin material which is for the outer housing 1 of the air-break circuit interrupter as illustrated in Fig. 2. The insertion slots 1b are disposed in parallel to each other with a magnetic air gap 13a defined in the central portion of the inter-phase partition wall 1a made of the insulating resin material which is the material for the base so that the plurality of magnetic plates 13 are mounted in parallel with the magnetic air gap 13a therebetween.

[0019] In the air-break circuit interrupter having such structure, since the magnetic saturation and the magnetic flux cancellation between the magnetic flux by the current in a particular pole and the magnetic flux by the current in the adjacent pole are alleviated by the plurality of the magnetic plates 13 even when the current has phase differences between the poles, so that the electromagnetic force (contact depressing force) for spreading the U-shape of the flexible conductor 7 can be easily increased in proportion to the intensity of the current, enabling the separating of the contacts due to the electromagnetic repulsive force between the contacts to be suppressed.

[0020] Therefore, the separating or the floating of the contact upon the occurrence of an excessive current can be prevented and the short-time current carrying capacity can be increased.

Embodiment 2

[0021] Fig. 3 is a view showing the arrangement of the magnetic plates disposed around the separable contact portion of the second embodiment of the present invention. In the figure, 1 and 6 - 9 are the components similar to those in the above first embodiment. 14 are a plurality of magnetic plates. In the second embodiment, each of the magnetic plates 14 is made extended to the side portion of the separable contacts from the side portion of the U-shape of the flexible conductor 7. The plurality of the magnetic plates 14 are mounted in place by inserting them into the parallel insertion slots (no reference numeral assigned in the figure) having the magnetic air gap 13a intervening therebetween and disposed in the inter-phase partition wall 1a.

[0022] Thus, by providing the extended magnetic plates 14 to the side portion of the separable contacts including the movable contact member 6, the magnetic plates 14 shields the magnetic flux due to the current in the adjacent pole, so that the lateral movement of the movable contact member 6 due to the electromagnetic force generated by the current flowing through the contact member itself and the magnetic flux from the adjacent pole can be prevented.

[0023] Therefore, in addition to the prevention of the separating or the floating of the contact due to increase of the electromagnetic force (contact depression force) for spreading the U-shape of the flexible conductor 7 as explained in the first embodiment, the lateral shift of the movable contact member 6 can be alleviated and the short-time current carrying capacity can be further increased.

Embodiment 3

[0024] Fig. 4 is a view showing the arrangement of the magnetic plates and the shields according to the third embodiment of the present invention;

[0025] Fig. 4 is a view showing the arrangement of the magnetic plates and the shields according to the third embodiment of the present invention. In the figure, 1, 6 - 9 and 13 are the components similar to those of the previously-described first embodiment. 15 are magnetic shield plates, which are disposed between each pole phase at the side portions of the movable contact member 6 and the contact separating portion of the movable contact element 6a and the stationary contact element 9a. Reinforcing portions 1c are provided between the magnetic plates 13 and the shield plates 15.

[0026] In the second embodiment, the inter-phase partition wall 1a is provided with elongated slots extending between the side portion of the U-shape of the flexible conductor 7 and the side portion of the contact separating portion, in which the magnetic plates 14 are inserted and held therein. Therefore, the side wall of the insertion slots may have cracks due to a massive electromagnetic force acting on the magnetic plates 14. Making the inter-phase partition wall 1a thicker in to cope with the cracks is not desirable because it makes the volume of the air-break circuit interrupter large. Under the circumstances, the arrangement was made such that the magnetic plates 13 and the shield plates 15 are divided so that they have functions of providing the magnetic path magnetic shield against the adjacent pole, respectively, then the current interruption was achieved with no decrease in the short-time current carrying capacity, and that the inter-phase partition walls 1a have the same thickness before and insertion slots for the magnetic plates 13 and the shield plates 15 are made independent from each other with the reinforcing portion 1c therebetween, then the cracks in the inter-phase partition walls 1a can be prevented. The housing 1 may be molded integrally with the inter-phase partition walls 1a with an electrically insulating resin within mold dies. When the housing 1 is to be taken out form the mold dies, the above reinforcing portion 1c may be effectively used as the position at which the ejector pin is brought into contact.

[0027] While the magnetic shield plates 15 has been described above as a plurality of plates having a magnetic air gap 13a therebetween, in view of the maintaining strength of the inter-phase partition walls 1a, the arrangement may be such that the magnetic plates 13 comprise a plurality of plates but the magnetic shield plate 15 comprises only a single plate.

Embodiment 4.

[0028] When the magnetic plates 13 and 14 as well as the magnetic shield plates 15 are arranged to have a plurality of plates with magnetic air gaps 13a therebetween, while the effect of the adjacent pole can be eliminated, the eddy current due to the circulating magnetic flux in the same pole is greater than that when a single magnetic plate and a single shield plate without any magnetic air gap, and the heat generation at the magnetic plates 13 and 14 and the magnetic shield plate 15 due to the eddy current loss within a normal rated current range is a cause of the loss of energy and the temperature rise of the air-break circuit interrupter

[0029] To cope with this, the magnetic plates 13 and 14 as well as the magnetic shield plates 15 can be made of a lamination of magnetic thin plates having a weak insulating treatment on the surface, whereby the eddy current loss can be alleviated to suppress the heat generation.

INDUSTRIAL APPLICABILITY

[0030] As has been described, in the air-break circuit interrupter having such structure, since the magnetic saturation and the magnetic flux cancellation between the magnetic flux by the current in a particular pole and the magnetic flux by the current in the adjacent pole are alleviated by the plurality of the magnetic plates 13 even when the current has phase differences between the poles, so that the electromagnetic force (contact depressing force) for spreading the U-shape of the flexible conductor 7 is increased in proportion to the intensity of the current, enabling the separating of the contacts due to the electromagnetic repulsive force between the contacts to be suppressed. Also, the extended magnetic plates 14 disposed between the poles at the contact opening and closing portion of the movable contact element 6a and the stationary contact element 9a shields the magnetic flux due to the current in the adjacent pole, so that the lateral movement of the movable contact member 6 due to the electromagnetic force generated by the current flowing through the contact member itself and the magnetic flux from the adjacent pole can be prevented.

[0031] Therefore, the separating or the floating and the lateral movement of the contact upon the occurrence of an excessive current can be prevented and the short-time current carrying capacity can be increased.

Claims

1. An air-break circuit interrupter comprising;

a multi-pole contact members including a stationary contact element and a movable contact element;

a flexible conductor arranged in a substantially U-shaped configuration flexible in the direction of opening and closing for allowing contact opening and closing movements of said movable contact member having the movable contact element;

a pivot shaft of a lever action for converting an electromagnetic force due to a current flowing through said flexible conductor in the direction of spreading the U-shape of said flexible conductor into a pressing force on said movable contact member; and

a plurality of magnetic plates disposed between poles and side faces of the U-shape of said flexible conductor for enhancing the electromagnetic force, said magnetic plates being arranged in parallel and having a magnetic air gap defined therebetween.

2. An air-break circuit interrupter as claimed in claim 1, characterized in that said magnetic plates extend to a space defined between the contact elements in each pole.

3. An air-break circuit interrupter as claimed in claim 1 or 2, characterized in that a housing of an insulating resin defining an outer housing of the air-break circuit interrupter is provided with an inter-phase partition wall for isolating the contact elements in each pole, and that said inter-phase partition wall has formed therein insertion slots, with an air gap corresponding to the magnetic air gap, in which the magnetic plates are inserted.

4. An air-break circuit interrupter as claimed in claim 2 or 3, characterized in that said inter-phase partition wall has separate insertion slots for the magnetic plates disposed at the side of the U-shape of said flexible conductor and a magnetic shield plate for the separable contact portion including the movable contact member.

5. An air-break circuit interrupter as claimed in any one of claims 1 to 4, characterized in that said magnetic plates and each said magnetic shield plate comprises a lamination of magnetic thin plates.

Drawing