Abstract:
There is provided an arc extinguishing unit of a molded case circuit breaker (MCCB) having a structure in which grids and side plates forming an arc chamber are coupled in an inserted manner, facilitating an operation, and intervals of grids are uniformly maintained and a configuration of the grids is not damaged, thus maintaining stable performance and allowing for maintenance.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2013-0054563, filed on May 14, 2013, the contents of which is incorporated by reference herein in its entirety. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The present disclosure relates to an arc extinguishing unit of a molded case circuit breaker (MCCB), and more particularly, to an arc extinguishing unit of an MCCB having a structure in which grids and side plates forming an arc chamber are coupled in an inserted manner, facilitating an operation, and intervals of grids are uniformly maintained and a configuration of the grids is not damaged, thus maintaining stable performance and allowing for maintenance. 
     2. Background of the Invention 
     In general, an MCCB is an electric device for automatically breaking a circuit in an electrically overloaded or in the event of a short-circuit accident to protect circuits and a load. An MCCB includes a terminal unit allowing for connection between a power source side and a load side, a mechanism unit opening and closing a stator and a mover to be mechanically brought into contact, a trip unit sensing an overcurrent or a short circuit current flowing from a power source and inducing the mechanism unit to perform trip operation, and an arc extinguishing unit for extinguishing an arc generated when a fault current is interrupted. 
     A short circuit current intended to be interrupted in an MCCB is a current greater by tens of times than a rated current of the MCCB, and a short circuit current sufficient for the MCCB to interrupt is an interrupting capacity. An MCCB limits a short circuit current to a current level lower than a predetermined current to interrupt a current, and this is called current limitation interruption. In general, an MCCB has current limitation performance in proportion to arc extinguishing capability of an arc extinguishing unit and in inverse proportion to an operating time of a mechanism unit. 
     Performing tripping in the event of a fault current and extinguishing an arc and discharging it are the main functions of an MCCB to interrupt a fault current to protect a product, a load, and a line and are directly connected with performance of the MCCB. An arc chamber of an arc extinguishing plays a key role in the performance, and an assembled state of the component, maintaining an assembled configuration, a position thereof, and the like, significantly affect performance of the MCCB. 
     Korean Utility Model Registration No. 20-0462420 entitled “Arc extinguishing unit of Small MCCB” and Korean Utility Model Registration No. 20-0393296 entitled “Arc extinguishing unit of MCCB” may be referred to as related art arc extinguishing mechanisms. 
       FIGS. 1 through 5  illustrate an example of a related art.  FIG. 1  is a cross-sectional view illustrating a single pole breaking unit of an MCCB including an arc extinguishing unit according to a related art,  FIG. 2  is a perspective view illustrating a part of the arc extinguishing unit in the single pole breaking unit of  FIG. 1 ,  FIG. 3  is a partially exploded perspective view of the arc extinguishing unit of  FIG. 1 ,  FIG. 4  is an assembled view of the arc extinguishing unit of  FIG. 1 , and  FIG. 5  is a perspective view of a grid of  FIG. 4 . 
     When a rate current flows in an arc extinguishing mechanism, a stator  102  and a mover  103  are maintained in a contact state, but when a fault current such as an overcurrent or a short circuit current is generated, the mover  103  is separated from the stator  102  by electrodynamic repulsion force generated between a fixed contact of the stator  102  and a movable contact of the mover  103 , interrupting the current. 
     The moment the mover  103  is separated, an arc is generated between the fixed contact and the movable contact, and the generated arc is induced by an arc runner to be moved to an arc chamber  121 . In this case, the arc is divided by a grid  122  of the arc chamber  121  to allow an arc voltage to be increased to be higher than a source voltage, thus limiting the short circuit current to extinguish the arc. 
     As for a configuration of the arc chamber  121  in the related art, the arc chamber  121  includes a plurality of grids  122  arranged at predetermined intervals in an outer side of a casing  101  from a rotary trace of the mover  103 , a pair of side plates  123   a  coupled to both sides of the grids  122 , hybrid fixing plates  123  extending from the side plates  123   a , and lateral magnets  128  coupled to rear surfaces of the hybrid fixing plates  123 . 
     Here, the hybrid fixing plates  123  are fixed to the grids  122  such that protrusions  122   a  of the grids  122  are respectively inserted into holes  123   b  of the side plates  123   a , so as to be fixed in a caulking manner. 
     In this case, however, the caulking operation may cause the grids  122  to be deformed, broken, twisted, or the like, and the grids  122  may be released due to a defective caulking operation or omission during transportation or when an end product is assembled. In addition, since the caulking operation is performed a plurality of times, a processing time is lengthened, productivity is degraded, grid intervals of the grids  122  are poorly maintained, and the like, and production costs are increased. In addition, maintenance is not possible. 
     SUMMARY OF THE INVENTION 
     Therefore, an aspect of the detailed description is to provide an arc extinguishing unit of a molded case circuit breaker (MCCB) having a structure in which grids and side plates forming an arc chamber are coupled in an inserted manner, facilitating an operation, and intervals of grids are uniformly maintained and a configuration of the grids is not damaged, thus maintaining stable performance and allowing for maintenance. 
     To achieve these and other advantages and in accordance with the purpose of this specification, as embodied and broadly described herein, an arc extinguishing unit of a molded case circuit breaker (MCCB) including a casing, a stator connected to a load or a power source, and a mover rotatably installed within the casing such that it is brought into contact with or separated from the stator, including: a plurality of grids arranged at predetermined intervals in an outer side of a movement trace of the mover; a pair of side plates including two-stage flat plates having a step cross-section and including a first flat plate fixing one end portions of the grids to form an arc chute and a second flat plate forming an arc chamber together with a lower surface of the grids; and a pair of lateral magnets fixedly installed on rear surfaces of the second plates. 
     Here, an intermediate protrusion formed on a lateral surface of each of the grids has a first stop projection formed on one side thereof, a second stop projection is formed on a lower surface of each grid, a first installation hole is formed on the first plate to allow the intermediate protrusion to be inserted therein, and a connection portion formed between the first flat plate and the second flat plate has a second installation hole to which the second projection is inserted. 
     An upper protrusion and a lower protrusion may be formed above and below the intermediate protrusion, respectively, on both sides of the grids. 
     A third installation hole may be formed in the first flat plate to allow the lower protrusion to be insertedly coupled therein. 
     A support protrusion is formed between the third installation recesses to provide bearing power by virtue of shear force and frictional contact when the grids are coupled to the side plates and to serve to separate the respective grids at predetermined intervals. 
     The first stop projection and the second stop projection may be formed in an outer side based on a contact point between the first flat plate and the connection portion. 
     In the case of the arc extinguishing unit of an MCCB according to exemplary embodiments of the present disclosure, since the grids and the side plates forming an arc chamber are formed to be coupled in an inserting manner, an operation may be facilitated. 
     Also, since the grids are maintained at uniform intervals and a shape thereof is not damaged, stable performance may be maintained. 
     In addition, since the grids and the side plates are separable, maintenance may be facilitated. 
     Further scope of applicability of the present application will become more apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from the detailed description. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this specification, illustrate exemplary embodiments and together with the description serve to explain the principles of the invention. 
       In the drawings: 
         FIG. 1  is a cross-sectional view illustrating a single pole breaking unit of a molded case circuit breaker (MCCB) including an arc extinguishing unit according to a related art. 
         FIG. 2  is a perspective view illustrating a part of the arc extinguishing unit in the single pole breaking unit of  FIG. 1 . 
         FIG. 3  is a partially exploded perspective view of the arc extinguishing unit of  FIG. 1 . 
         FIG. 4  is an assembled view of the arc extinguishing unit of  FIG. 1 . 
         FIG. 5  is a perspective view of a grid of  FIG. 4 . 
         FIG. 6  is a perspective view illustrating an arc extinguishing unit of an MCCB according to an exemplary embodiment of the present disclosure. 
         FIG. 7  is a perspective view of grids of  FIG. 6 . 
         FIG. 8  is a view illustrating an operation of the arc extinguishing unit of an MCCB according to an exemplary embodiment of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     Description will now be given in detail of the exemplary embodiments, with reference to the accompanying drawings. For the sake of brief description with reference to the drawings, the same or equivalent components will be provided with the same reference numbers, and description thereof will not be repeated. 
     An arc extinguishing unit of a molded case circuit breaker (MCCB) including a casing, a stator connected to a load or a power source, and a mover rotatably installed within the casing such that it is brought into contact with the stator or separated therefrom according to an exemplary embodiment of the present disclosure includes a plurality of grids  10  arranged at predetermined intervals outside of a movement trace of the mover; a pair of side plates  20  including two-stage flat plates having a step cross-section and including a first flat plate  21  fixing one end portions of the grids  10  to form an arc chute and a second flat plate  27  forming an arc chamber together with a lower surface of the grids  10 ; and a pair of lateral magnets  30  fixedly installed on rear surfaces of the second plates  27 . 
     Here, an intermediate protrusion  12  formed on a lateral surface of each of the grids  10  has a first stop projection  12   a  formed on one side thereof. A second stop projection  14  is formed on a lower surface of each grid  10 . A first installation hole  22  is formed on the first plate  21  to allow the intermediate protrusion  12  to be inserted therein. A connection portion  25  formed between the first flat plate  21  and the second flat plate  27  has a second installation hole  26  to which the second projection  14  is inserted. 
       FIG. 6  is a perspective view illustrating an arc extinguishing unit of an MCCB according to an exemplary embodiment of the present disclosure.  FIG. 7  is a perspective view of grids of  FIG. 6 .  FIG. 8  is a view illustrating an operation of the arc extinguishing unit of an MCCB according to an exemplary embodiment of the present disclosure. 
     An arc extinguishing unit of an MCCB according to an exemplary embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. 
     In the arc extinguishing unit of an MCCB according to an exemplary embodiment of the present disclosure, components such as a casing, a stator connected to a load and a power source, a mover rotatably installed within the casing such that it is brought into contact with or separated from the stator, and the like are identical to those of the related art, so a description and illustration thereof will be omitted. 
     The grids  10  are configured as flat plates formed of a ferromagnetic metal. A plurality of protrusions are formed on lateral surfaces of the grids  10 . In an exemplary embodiment, upper protrusions  11 , intermediate protrusions  12 , and lower protrusions  13  may be formed to be protruded from the respective lateral surfaces of the grids  10 . Each intermediate protrusion  12  has the first stop projection  12   a  formed to be protruded from an upper end portion thereof. The second stop projection  14  is formed to be protruded from a lower surface of each grid  10  having the lower protrusion  13  inwardly. The second stop projection  14  may be formed to have a size equal to that of the first stop projection  12   a  and be symmetrical to the first stop projection  12   a . When viewed based on a lower corner of the lower protrusion  13 , the first stop projection  12   a  and the second stop projection  14  are formed to face outwardly, so, when the side plates  20  are coupled to the grids  10 , the first stop projection  12   a  and the second stop projection  14  serve to provide force pulling the both ends such that the side plates  20  and the grids  10  may not be easily separated. 
     A lower surface of each grid  10  has a deep and wide recess, forming one surface of the arc chamber. 
     A plurality of grids  10  are integrally laminated at predetermined intervals, and serve to divide arc generated when the movable contactor is separated from the fixed contactor. 
     The side plates  20  include two-stage flat plates having a step cross-section. A lower plate of each cap side magnet  20  formed to have a step will be referred to as a first flat plate  21 , a portion vertically bent from the lower plate will be referred to as a connection portion  25 , and an upper plate of the cap side magnet  20  vertically bent again from the connection portion  25  such that it is parallel to the lower plate will be referred to as a second flat plate  27 . 
     First and third installation recesses  22  and  23  are formed in the first flat plate  21  of the cap side magnet  20  to allow the intermediate protrusion  12  and the lower protrusion  13  of the grid  10  are inserted. Here, a length of the first installation hole  22  may be equal to or slightly smaller than a length of the inner side of the intermediate protrusion  12 , namely, a length excluding the first stop projection  12   a . A length of the third installation hole  23  may be equal to or slightly smaller than a length of the lower protrusion  13 . This is designed in consideration of inserting type coupling or force inserting type coupling. The number of the first and third installation recesses  22  and  23  may be equal to the number of the intermediate and lower protrusions  12  and  13  in a corresponding manner. 
     A support protrusion  24  is formed between the third installation recesses  23  to provide bearing power by virtue of shear force and frictional contact when the first flat plate  21  is coupled to the grids  10 . Also, the grids  10  may be coupled by means of the support protrusions  24  with a predetermined interval maintained therebetween. 
     The first flat plate  21  may be coupled to the grids  10  to form an arc chute. 
     The second flat plate  27  forms an arc chamber together with a lower surface of the grids  10 . An inner surface of the second flat plate  27  may be formed to be smooth. Also, an insulating material such as nylon, or the like, may be provided on the inner surface of the second flat plate  27  so as to be decomposed by a high temperature to generate an arc extinguishing gas when an arc is generated. 
     The lateral magnet  30  is coupled to a rear surface of the second flat plate  27 . To this end, the second flat plate  27  is formed to be thicker than the first flat plate, and an accommodation recess  28  having a shape corresponding to that of the lateral magnet  30  may be formed in the rear surface of the second flat plate  27 . Also, a fixing hook  29  may be formed to be protruded from the accommodation recess  28  to allow the lateral magnet  30  to be easily fastened and receive bearing power. 
     The connection portion  25  is formed between the first flat plate  21  and the second flat plate  27  such that the connection portion  25  is perpendicular to the respective flat plates. The connection portion  25  may be formed to have a plate shape. The connection portion  25  may have the second installation hole  26  formed in a position corresponding to the second stop projection  14  when the grids  10  are coupled. As the second stop projection  14  is insertedly coupled into the second installation hole  26  and the first stop projection  12   a  is insertedly coupled into the first installation hole  22 , the grids  10  and the cap side magnet  20  are fixedly coupled. A step may be formed in the corner where the connection portion  25  and the second flat plate  27  are contiguous, in a length direction. 
     Preferably, the first flat plate  21 , the connection portion  25 , and the second flat plate  27  may be integrally formed through a molding operation, or the like. 
     Hereinafter, a coupling process of the arc extinguishing unit of the MCCB according to the exemplary embodiment of the present disclosure will be described.  FIG. 8  is a view illustrating an operation of the arc extinguishing unit of an MCCB according to an exemplary embodiment of the present disclosure. 
     The first installation hole  22  of the cap side magnet  20  is inserted into the intermediate protrusion  12  of the grid  10 . Here, in a state in which the cap side magnet  20  is sloped to the outside downwardly, the first installation hole  22  is inserted into and caught in the first stop projection  12   a  of the intermediate protrusion  12 . As the cap side magnet  12  is pressurized downwardly and pressed inwardly, the second stop projection  14  of the grid  10  is inserted into the second installation hole  26  formed in the connection portion  25 . 
     As the first installation hole  22  of the cap side magnet  20  is caught by the first stop projection  12   a  of the grid  10 , the cap side magnet  20  is pressed in an outer direction on one side thereof, and as the second installation hole  26  of the cap side magnet  20  is caught by the second stop projection  14  of the grid  10 , the cap side magnet  20  is pressed in an inward direction on the other side thereof. Thus, the cap side magnet  20  is stably maintained in a coupled state, without being released from the grids  20 . 
     The operation of the arc extinguishing unit of an MCCB according to the exemplary embodiment of the present disclosure may be summed up as follows. As described above, the fixed contact of the stator and the movable contact of the mover are maintained in a contact state at a rated current, and when a fault current such as an overcurrent or a short circuit current occurs, the mover is separated from the stator due to electrodynamic repulsion force exerted between the fixed contact and the movable contact, interrupting the current. When the mover is separated, an arc is generated between the fixed contact and the movable contact, and the generated arc moves to the arc chute. The arc is divided by the grids  10  of the arc chute to increase an arc voltage to be higher than a source voltage to thus limit the short circuit current to extinguish the arc. Meanwhile, an arc extinguishing effect is also obtained by an arc extinguishing gas generated by the second flat plate  27  of the cap side magnet  20 . 
     The foregoing embodiments and advantages are merely exemplary and are not to be considered as limiting the present disclosure. The present teachings can be readily applied to other types of apparatuses. This description is intended to be illustrative, and not to limit the scope of the claims. Many alternatives, modifications, and variations will be apparent to those skilled in the art. The features, structures, methods, and other characteristics of the exemplary embodiments described herein may be combined in various ways to obtain additional and/or alternative exemplary embodiments. 
     As the present features may be embodied in several forms without departing from the characteristics thereof, it should also be understood that the above-described embodiments are not limited by any of the details of the foregoing description, unless otherwise specified, but rather should be considered broadly within its scope as defined in the appended claims, and therefore all changes and modifications that fall within the metes and bounds of the claims, or equivalents of such metes and bounds are therefore intended to be embraced by the appended claims.