Patent Publication Number: US-2016240329-A1

Title: Circuit breaker including current path geometries that increase contact popping level

Description:
BACKGROUND OF THE INVENTION 
     The subject matter disclosed herein relates to the art of circuit breakers and, more particularly, to a circuit breaker including current path geometries that increase contact popping levels. 
     A circuit breaker includes one or more stationary contacts and one or more movable contacts that are connected to close a circuit to pass electrical current. In the event that the electrical current exceeds predetermined parameters, such as during a short circuit event, the movable contact(s) is/are shifted away from the stationary contact(s) to open the circuit. In some cases, the movable contact may chatter or pop at certain current levels. Popping generally results from forces that are generated in a direction of contact opening due to magnetic constriction forces. Popping may create arcing events that reduce an overall service life of the contacts and the circuit breaker. 
     BRIEF DESCRIPTION OF THE INVENTION 
     According to one aspect of an exemplary embodiment, a circuit breaker includes a housing, and a movable contact arm arranged in the housing. The movable contact arm includes a movable contact. A stationary contact assembly is arranged in the housing. The stationary contact assembly includes a base member including a first side and an opposing second side. An anti-popping recess having a wall portion is formed in one of the first and second sides and defines a cantilevered arm portion. A stationary contact member extends from the first side toward the second side. 
     According to another aspect of an exemplary embodiment, a circuit breaker includes a housing, and a first contact assembly arranged in the housing. The first contact assembly includes a first contact member. A second contact assembly is arranged in the housing. The second contact assembly includes a contact portion having a first side and an opposing, second side. An anti-popping recess having a wall portion is formed in one of the first and second sides and defines a cantilevered arm portion. The first contact assembly being attracted to the second contact assembly upon an application of electrical current through the circuit breaker. 
     These and other advantages and features will become more apparent from the following description taken in conjunction with the drawings. 
    
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
       The subject matter, which is regarded as the invention, is particularly pointed out and distinctly claimed in the claims at the conclusion of the specification. The foregoing and other features, and advantages of the invention are apparent from the following detailed description taken in conjunction with the accompanying drawings in which: 
         FIG. 1  depicts a circuit breaker including contacts having a current path geometry that increases a contact popping level shown in an open configuration, in accordance with an exemplary embodiment; 
         FIG. 2  depicts the circuit breaker of  FIG. 1  with the contacts having a current path geometry that increases a contact popping level shown in a closed configuration; 
         FIG. 3  depicts a circuit breaker contact having a current path geometry that increases a contact popping level, in accordance with aspect of an exemplary embodiment; 
         FIG. 4  depicts current flow vectors passing through the circuit breaker contact of  FIG. 2 ; and 
         FIG. 5  depicts current flow vectors passing through a prior art circuit breaker contact. 
     
    
    
     The detailed description explains embodiments of the invention, together with advantages and features, by way of example with reference to the drawings. 
     DETAILED DESCRIPTION OF THE INVENTION 
     A circuit breaker, in accordance with an exemplary embodiment, is indicated generally at  2 , in  FIG. 1 . Circuit breaker  2  includes a housing  4  that encloses a first or movable contact assembly)  6  and a second or stationary contact assembly  8 . Movable contact assembly  6  includes a movable contact arm  12  that supports a movable contact  14  which, in accordance with an aspect of an exemplary embodiment, may be formed from silver, a silver alloy, or other electrically conductive materials. 
     In accordance with an exemplary embodiment, stationary contact assembly  8  includes a contact portion  19  having a base member  20  that is electrically coupled to a lug or connection strap  22 . Connection strap  22  may provide a connection point for an electrical load (not shown). Connection strap  22  may also provide a connection point for a source of electricity or line connection (also not shown). Base member  20  includes a first side  24  and an opposing, second side  25 . Base member  20  may also include a third side (not separately labeled) and an opposing fourth side (also not separately labeled). Second side  25  includes an anti-popping recess  28  having a wall portion  30  that is off-set relative to first and second sides  24  and  25 . Anti-popping recess  28  establishes a cantilevered arm portion  32  on contact portion  19 . Wall portion  30 , in accordance with the exemplary embodiment shown, extends substantially parallel to first and second sides  24  and  25  and substantially aligns with second end portion  16  of movable contact  14  when circuit breaker  2  is in a closed or electrically conducting configuration such as shown in  FIG. 2 . 
     Anti-popping recess  28  promotes magnetic flux lines that establish an attractive force which draws movable contact  14  toward contact portion  19 . In addition, contact portion  19  may also include a stationary contact member  34  coupled to base member  20 . Stationary contact member  34  may be formed from silver, a silver alloy, or other electrically conductive materials and includes an end portion  38  that may be co-extensive or substantially align with second side  25  of base member  20 . Stationary contact member  34  promotes forward loop attraction forces that reduce repulsion forces and further draw movable contact  14  toward stationary contact member  34 . In accordance with another aspect of an exemplary embodiment illustrated in  FIG. 3 , a stationary contact member  46  may include an end portion  48  that may be co-extensive or substantially align with wall portion  30 . 
     In accordance with an aspect of an exemplary embodiment, anti-popping recess  28  includes a desired depth and a desired height. The desired depth is represented by a distance between second side  25  and wall portion  30 . The desired height, e.g., a length of wall portion  30 , establishes a desired thickness of cantilevered arm portion  32 . The desired thickness of cantilevered arm portion  32 , in accordance with an exemplary aspect, should be understood to include a thickness of stationary contact member  34 . In this manner, anti-popping recess  28  and cantilevered arm portion  32  influence magnetic flux through movable contact  14  and stationary contact member  34 . In accordance with an aspect of an exemplary embodiment, a desired ratio of a depth of anti-popping recess  28  verses a thickness of cantilevered arm portion  32  is about 2:7. In accordance with another aspect of an exemplary embodiment, the desired ratio is about 4:6. In accordance with yet another aspect of an exemplary embodiment, the desired ratio is about 3:5. Of course, it should be understood that the desired ratio may vary depending upon contact geometries, current, and material properties of movable contact assembly  6  and stationary contact assembly  8 . Further, it should be understood that the desired height will also affect the desired thickness of cantilevered arm portion  32  and stationary contact member  34  and thus play a role in establishing the desired ratio. 
     In further accordance with an exemplary embodiment, anti-popping recess  28  establishes desired current flow vectors through stationary contact member  34  and movable contact  14 . More specifically, current flow vectors flux lines that pass through stationary contact member  34  are substantially parallel to current flow vectors passing through movable contact  14  thereby generating an attraction force, as shown in  FIG. 4 . More specifically, the current flow vectors flow substantially in one direction generating an attraction force. In contrast, prior art flux lines diverge from one another forming a reverse loop, such as shown at  80  in  FIG. 5 , creating a repulsion force that may lead to popping at lower current levels. More specifically, in prior art systems, the current flow vectors flow in opposite directions causing popping or chatter at lower current levels. 
     At this point, it should be understood that the anti-popping recess shapes magnetic flux field lines and current density fields flowing through contact portion  19  causing a reduction in reverse loop forces that may reduce the repulsion of movable contact  14  away from base member  20 . In addition, base member  20  may include a stationary contact member having a geometry, e.g., a position of an end portion relative to base member, that further promotes magnetic flux field lines that enhance forward loop attraction forces. In this manner, the anti-popping recess and the stationary contact member cooperate to establish an attraction force between the stationary contact portion and movable contact. The attraction force opposes repulsion forces that may be created between the stationary contact and the movable contact thereby increasing contact popping level and enhancing performance at higher currents and an overall operational life increase of the circuit breaker. The phrase “popping level” should be understood to describe a condition in which a particular current level causes a popping, chatter and/or vibration of the moveable contact relative to the stationary contact. Increasing the popping level should be understood to mean that the geometry of the stationary contact member increases the level of current that could lead to popping, chatter and/or vibration of the moveable contact relative to the stationary contact. Further, exemplary embodiments increase popping level without a need for additional heavy springs, longer movable contact lever arms, and the like that may be employed to hold contacts together 
     While the invention has been described in detail in connection with only a limited number of embodiments, it should be readily understood that the invention is not limited to such disclosed embodiments. Rather, the invention can be modified to incorporate any number of variations, alterations, substitutions or equivalent arrangements not heretofore described, but which are commensurate with the spirit and scope of the invention. Additionally, while various embodiments of the invention have been described, it is to be understood that aspects of the invention may include only some of the described embodiments. Accordingly, the invention is not to be seen as limited by the foregoing description, but is only limited by the scope of the appended claims.