Abstract:
The present disclosure describes an apparatus and method for quenching the arc developed during the interruption of a current carrying path by use of an arc quenching apparatus with a contiguous chamber that shapes and directs the gas pressure and other associated arc components through a set of splitter plates located at the ends of the chamber. The contiguous chamber contains the gas pressure and other associated arc components for the duration of the quenching process.

Description:
BACKGROUND 
       [0001]    The invention relates generally to the field of circuit interrupting devices. More particularly the invention relates to a technique for quenching an arc that results from interruption of a current carrying path between a source of electrical power and a load. 
         [0002]    Various circuit interrupters are currently available and have been developed for interrupting a current carrying path between a source of electrical power and a load. These circuit interrupting devices may take the form of circuit breakers, contactors, relays, motor starters and the like. In general, such devices include one or more moveable contacts and associated one or more stationary contacts. The contacts are joined to complete a current carrying path through the device during normal operation. The contacts may be separated in response to desired events such as turning off a circuit breaker or de-energizing the coil voltage of a relay or contactor in addition to fault conditions such as current overload, thermal protection, or other undesired events. Upon separation of the contacts an electrical arc is generated which results in an increase in temperature and pressure inside the circuit interrupting device. It is desirable to dissipate, extinguish, or quench the arc quickly so as to prevent damage to the contacts of the circuit interrupting device, the device itself, or the load that is being protected. 
         [0003]    There have been various approaches to improve extinguishing an arc in a circuit interrupter. These techniques include lengthening the arc column by increasing the separation of the contacts, constricting the arc so as to increase the pressure resulting in a decreased arc diameter, and introducing ferromagnetic plates which attract the arc and split it into smaller arcs. Additional benefit is gained by the introduction of materials that undergo surface ablation during the arc event which aid in the rapid expansion and extinguishing of the arc. While the various combinations of these techniques are useful in quenching an arc there is a need for further improvement in the containment of the arc pressure generated as a result of the circuit interruption event in order to dissipate an arc more quickly and efficiently 
       BRIEF DESCRIPTION 
       [0004]    The embodiments in the present disclosure provide a novel technique for improved arc extinguishment. The approach may be implemented in a variety of circuit interrupting devices such as circuit breakers, contactors, or relays, with both single and multiple current carrying paths. The operation of these devices may take a variety of mechanical and electromechanical approaches to control the position of the contacts in order to complete and interrupt an electrical circuit. The present disclosure makes reference to a circuit breaker for the purpose of illustration but it is to be understood that this is solely for the purpose of explanation and in no way limits the invention to this particular device. 
         [0005]    An embodiment described provides an improvement in arc quenching by containing the gas generated as a result of the circuit interruption event inside the arc chamber assembly for an increased period of time resulting in an increase in pressure which reduces the time required to extinguish the arc. 
         [0006]    In accordance with a further aspect of the invention the arc chamber framework may be embodied as a single-piece or as a two-piece part for ease of manufacture and assembly. 
     
    
     
       DRAWINGS 
         [0007]    These and other features, aspects, and advantages of the present invention will become better understood when the following detailed description is read with reference to the accompanying drawings in which like characters represent like parts throughout the drawings, wherein: 
           [0008]      FIG. 1  is a perspective view of a three phase circuit breaker; 
           [0009]      FIG. 2  is an exploded view of a three phase circuit breaker showing multiple arc chamber assemblies and electrical contact assemblies; 
           [0010]      FIG. 3  is a top view of a three phase circuit breaker illustrating the arc chamber assemblies and contacts; 
           [0011]      FIG. 4  is an end view of a three phase circuit breaker; 
           [0012]      FIG. 5  is a side view with a cutaway of a three phase circuit breaker showing an arc chamber and contacts; 
           [0013]      FIG. 6  is an exploded view of an arc chamber assembly including splitter plates; 
           [0014]      FIG. 7 a    is an assembly view of an embodiment of an arc chamber framework; 
           [0015]      FIG. 7 b    is a top view of an embodiment of an arc chamber framework as a two-piece unit; 
           [0016]      FIG. 7 c    is a top view of an alternate embodiment of an arc chamber framework as an integrally formed unit; 
           [0017]      FIG. 7 d    is top view of another alternate embodiment of an arc chamber framework; 
           [0018]      FIG. 7 e    is top view of another alternate embodiment of an arc chamber framework; 
           [0019]      FIG. 8 a    is perspective view of an embodiment of a splitter plate; 
           [0020]      FIG. 8 b    is perspective view of an alternate embodiment of a splitter plate; 
           [0021]      FIG. 9  is an exploded perspective view of an arc chamber assembly; 
           [0022]      FIG. 9 b    is a side view of an alternate embodiment of the arc chamber assembly with splitter plates; 
           [0023]      FIG. 10 a    is a perspective view of an arc chamber assembly illustrating splitter plate insertion; 
           [0024]      FIG. 10 b    is a detail view of the distal end of the splitter plates in the arc chamber framework showing retention notches; 
           [0025]      FIG. 10 c    is a detail view of the proximal end of the splitter plates in the arc chamber framework; 
           [0026]      FIG. 11 a    is a side view cutaway of a three phase circuit breaker illustrating an arc chamber assembly, contacts, and gas pressure flow; 
           [0027]      FIG. 11 b    is a top view cutaway of a three phase circuit breaker illustrating an arc chamber assembly, contacts, and gas pressure flow; and 
           [0028]      FIG. 12  is a flowchart representing the method of manufacturing and assembly of an arc chamber assembly. 
       
    
    
     DETAILED DESCRIPTION 
       [0029]    Turning now to the drawings, and referring to  FIG. 1 , a circuit interrupting device is illustrated in the form of a three-phase circuit breaker  10  for controlling electrical current carrying paths for three separate phases of electrical power. The circuit breaker  10  of  FIG. 1  includes an upper housing  12  and a lower housing  14  each of which is divided into three electrically isolated phase sections  56 . Each of these electrically isolated phase sections  56  is configured to receive electrical inputs via power input conductors  16  connected to power terminal blocks  72 , one for each phase, and deliver electrical outputs to a load via load output conductors  18  connected to load terminal blocks  74 , one for each phase, when the circuit interrupting device  10  is placed in a state resulting in a completed electrical circuit. 
         [0030]      FIG. 2  illustrates circuit interrupting device  10  in an exploded perspective view with upper housing  12  and lower housing  14  of circuit breaker  10  positioned such that the arc chamber assemblies  24  for each of the three phases in addition to the contact assemblies  100 , and the internal operating or linking member  53 , is shown. In the embodiment illustrated, that of a circuit breaker, the operator for the circuit interrupting device comprises an assembly of an external rotatable operating member  114  and an internal operating or linking member  53  which positions the movable contact arms  49  into relation with the power contact arms  68  and the load contact arms  70  in order to either complete or interrupt the electrical circuit when rotatable operating member  114  is rotated through its range. In other embodiments the external rotatable operating member  114  could take the form of a toggle switch, a push button, a latch, or be replaced by an electromagnetic coil assembly such that the energizing or de-energizing of a coil would cause the internal operating member  53  to position the contacts and control the electrical circuits of the circuit interrupting device  10  as in the case of a relay or contactor. 
         [0031]    As shown in  FIG. 2  and  FIG. 3  lower housing  14  has a generally rectangular base  106  providing a slot  102  therein for receiving a standard DIN rail along the transverse axis generally within the plane of the base  106 . Opposed end walls  60  extend upward from longitudinally opposite sides of the base  106  when the plane of the base  106  is horizontal. Flanking side walls  64  extend upward from the base  106  transversely opposed and perpendicular to the base  106  to span and join to opposite end walls  60  to generally define an interior housing volume between the base  106  and walls  60  and  64 . Two interior walls  108  run from the opposing end walls  60  parallel to and proportionally spaced from side walls  64  to form three electrically isolated chambers into which the arc chamber assemblies  24  are positioned. 
         [0032]    As shown in  FIG. 3  with additional detail in  FIG. 4 , each of the two end walls  60  contain apertures  62  through which gases may be exchanged from the interior housing volume of each of the three chambers defined by side walls  64 , end walls  60 , base interior walls  108 , and base  106 . As shown in  FIG. 2  and  FIG. 4 , above each of the apertures  62  are conductor receiving terminals  72  in the case of the input or power end of circuit breaker  10 , and  74  in the case of the output or load end of circuit breaker  10 , for receiving three conductors at opposite ends, line or power input  16 , or load or power output  18  from longitudinal directions at electrically independent terminals  72  on machine screws or the like. 
         [0033]    As shown in  FIG. 1 , a top wall  112  covers the upper housing  12  which in turn covers and substantially encloses the lower housing  14  and provides an external rotatable operating member  114  extending upward there through. Upper housing  12  hosts three sets of electrically isolated contact assemblies  100  as illustrated in  FIG. 2 , one for each phase. These assemblies consist of a power contact arm  68  to which a power stationary contact  48  is attached and a load contact arm  70  to which a load stationary contact  50  is attached. Each power contact arm  68  is connected to a conductor receiving terminal  72  configured to receive a conductor  16  on machine screws  98  or the like which provides electrical power to the device. Each load contact arm  70  is connected to a conductor receiving terminal  74  configured to receive a conductor  18  on machine screws  98  or the like which provides an electrical connection to the load that is controlled and protected by the device. 
         [0034]    Referring to  FIG. 2  and  FIG. 3 , contained within each arc chamber assembly or arc dissipating structure are a set of electrical contacts for each phase. Each set of contacts is comprised of a power moveable contact  52  and a load moveable contact  54 , and a power stationary contact  48  and a load stationary contact  50 . A power stationary contact  48  is attached to a power contact arm  68  that is connected to a power terminal block  72  for each phase. A load stationary contact  50  is connected to a load contact arm  70  that is connected to a load terminal block  74  for each phase. A power moveable contact  52  is connected to a load moveable contact  54  with a moveable contact arm  66  for each phase. As illustrated in  FIG. 5  the power stationary contact  48  and the load stationary contact  50  for each phase are positioned towards the top of the arc chamber assembly  24  and the moveable contact arm  66  with the power moveable contact  52  and the load moveable contact  54  for each phase are positioned towards the middle portion of the arc chamber assembly  24 . All of the contacts are contained within the arc chamber assembly  24  in both the energized and de-energized states. 
         [0035]    When the circuit breaker  10  is actuated to an energized state the moveable contact arm  66  for each phase is moved into a position such that the power movable contact  52  comes into contact with the power stationary contact  48  and the load moveable contact  54  comes into contact with the load stationary contact  50  thus forming an electric circuit with electric current flowing through the moveable contact arm  66 . Conversely, when the circuit breaker  10  is actuated to a de-energized state the moveable contact arm  66  moves to a position where the power movable contact  52  and the load moveable contact  54  are no longer in contact with their corresponding contacts, the power stationary contact  48  and the load stationary contact  50 , causing the interruption of the electric current flow which in turn generates an electrical arc, the quenching of which is the interest of the present disclosure. 
         [0036]    As shown in  FIG. 2  with additional detail in  FIG. 5  each set of contacts for each phase is contained within an arc chamber assembly  24 . Referring to  FIG. 6 , each arc chamber assembly  24  comprises an arc chamber framework  22  and two splitter plate groups  28  located at opposite ends of the arc chamber framework  22 . Each splitter plate group  28  is comprised of a plurality of splitter plates  26 . 
         [0037]    One embodiment of the arc chamber framework  22  is depicted in  FIG. 7 a    as a left arc chamber framework panel  30  and a right arc chamber framework panel  32 . In the embodiment that is illustrated in  FIG. 7 a    and  FIG. 7 b    the two panels are comprised of left axial extensions  78 , center walls  82 , and right axial extensions  80 . Other embodiments may include asymmetric body halves. Left axial extensions  78  and right axial extensions  80  contain apertures  34  which are in a spaced relation and generally parallel to one another for the purpose of engaging, spacing, and retaining a plurality of arc splitter plates  26 . The left arc chamber framework panel  30  and a right arc chamber framework panel  32  join to form the center body portion  76  as shown in  FIG. 7 b   . The left arc chamber framework panel  30  and the right arc chamber framework panel  32  are joined by integral, molded connecting structures. Left arc chamber framework panel female connector  38  mates with right arc chamber framework panel male connector  44  and right arc chamber framework panel female connector  42  mates with left arc chamber framework panel male connector  40  to form the arc chamber framework  22  as depicted in  FIG. 7 b   . Alternate embodiments of arc chamber framework  22  may include those where connectors  38 ,  40 ,  42 , and  44  are absent and the arc chamber framework panels  30  and  32  are connected only by the arc splitter plates  26 . The left arc chamber framework panel  30  and a right arc chamber framework panel  32  are molded of a resin comprised of gas evolving materials such that the heat of the arc causes the material to emit a gas with arc quenching properties in addition to raising the pressure in the arc chamber assembly both of which have a positive effect on extinguishing of the arc. 
         [0038]    An alternate embodiment of the arc chamber framework  22  is shown in  FIG. 7 c   . In this embodiment the framework is molded as a single integral piece. Additional embodiments of the arc chamber framework  22  are shown in  FIG. 7 d    and  FIG. 7 e   . As illustrated in  FIG. 7 d    the walls form a convergent to a divergent chamber shape and in  FIG. 7 e    the walls form a divergent to a convergent chamber shape. The shape of the chamber is optimized so as to influence the pressure flow of the arc in order to quench the arc most efficiently. It should be understood by someone skilled in the art that the embodiments of the present disclosure as described may be further modified without departing from the spirit and scope of the present disclosure. 
         [0039]      FIG. 8 a    is a detailed view of a splitter plate  26 . The splitter plate  26  is a planar member have parallel major faces constructed of ferromagnetic material sized to fit within the periphery defined by the walls of the arc chamber  22  and of a thickness which is determined by the number of splitter plates  26  required for the splitter plate groups  28  which are comprised of a plurality of splitter plates  26  in spaced relation and generally parallel to one another in the illustrated embodiment. The number of splitter plates  26  in a splitter plate group  28  will vary depending upon the electrical parameters of the circuit interrupting device. 
         [0040]    The splitter plate  26  includes a generally V-shaped recess  92  with a generally declining width as it progresses from the proximal to the distal end of the plate. The internal volume of the recess is defined by the internal edges  96  of the opposing splitter plate arms  90  and culminating in the splitter plate center notch  86 . The general shape of the recess  92  including its contour and overall width and depth is configured so as to increase the amount of magnetic material in proximity to the power stationary contact  48 , the power moveable contact  52 , the load stationary contact  50 , and the load moveable contact  54  such that when an electrical arc occurs at the moment that the circuit interrupting device is de-energized the attractive forces on the arc are maximized for most effective quenching. 
         [0041]    An alternate embodiment of a splitter plate  26  with a varying recess contour is shown in  FIG. 8 b   . It should be understood by someone skilled in the art that the embodiments of splitter plates in the present disclosure as described may be further modified without departing from the spirit and scope of the present disclosure. 
         [0042]      FIG. 9  provides another perspective of an embodiment of the arc chamber assembly  24  and the splitter plate groups  28  which are comprised of a plurality of splitter plates  26  in spaced relation and generally parallel to one another. Other embodiments of arc chamber assembly  24  may be a fanned arrangement of the splitter plates  26  in the arc chamber framework  22  as illustrated in  FIG. 9B . It should be understood by someone skilled in the art that the embodiments of the arrangement of the splitter plates in the present disclosure as described may be further modified without departing from the spirit and scope of the present disclosure 
         [0043]    Turning to  FIG. 10 a   , the insertion of the splitter plates  26  into the arc chamber framework  22  to form the arc chamber assembly  24  is shown. As each splitter plate  26  is inserted into a splitter plate aperture  34  the axial extensions of the left arc chamber framework panel  30  and right arc chamber framework panel  32  flex slightly to allow each splitter plate to enter the splitter plate aperture  34 . Upon the complete insertion of a splitter plate  26  the axial extensions of the left arc chamber framework panel  30  and right arc chamber framework panel  32  return to their original positions and a splitter plate  26  is retained by the splitter plate retainer  36  that is molded into each splitter plate aperture  34  as depicted in  FIG. 10 b   . Additionally, the splitter plate arms  90  of each splitter plate  26 , when completely inserted into splitter plate aperture  34  provide lateral strength to the left arc chamber framework panel  30  and the right arc chamber framework panel  32  opposing arc side pressure  94  as shown in  FIG. 10   c.    
         [0044]    A representation of the arc event is depicted in  FIG. 11 a    and  FIG. 11 b   .  FIG. 11 a    is a side view of the circuit breaker  10  with a cutaway showing the internals of the lower housing  14  including the relation of the power movable contact  52  to the power stationary contact  48  and the load moveable contact  54  to the load stationary contact  50 .  FIG. 11 b    provides a top view of lower housing  14  illustrating the flow of the gas pressure at the time of the arc event. When the circuit breaker  10  is energized the power movable contact  52  comes into contact with the power stationary contact  48  and the load moveable contact  54  comes into contact with the load stationary contact  50  thus forming an electric circuit with electric current flowing through the moveable contact arm  66 . Conversely, when the circuit breaker  10  is actuated to a de-energized state the interruption of the electric current flow generates an electrical arc, the quenching of which is the interest of the present disclosure. 
         [0045]    When the circuit breaker  10  is actuated to an energized state the moveable contact arm  66  for each phase is moved such that the power movable contact  52  comes into contact with the power stationary contact  48  and the load moveable contact  54  comes into contact with the load stationary contact  50  thus forming an electric circuit with electric current flowing through the moveable contact arm  66 . Conversely, when the circuit breaker  10  is actuated to a de-energized state the interruption of the electric current flow generates an electrical arc. The generation of an electric arc results in a rapid increase in temperature and pressure internal to each arc chamber assembly  24 . Experimentation has shown that containing the pressure inside each arc chamber assembly  24  will significantly decrease the time required to quench the arc. The nature of the arc chamber assembly  24  is such that the gas produced as a result of the electrical arc  46  is restricted to the interior of the arc chamber assembly  24  and cools as it flows through the splitter plate groups  28  and is substantially only allowed to exit the circuit breaker  10  through the lower housing apertures  62  as illustrated in  FIG. 4 . As previously discussed, the shape of the walls of the arc chamber framework  22  can improve the rapid quenching of the electrical arc. The shape of the sides may be such that the arc chamber framework  22  has a generally convergent profile from the center body portion  76  to the distal end of the arc chamber framework  22 , a generally divergent profile over the same length, a divergent and then convergent profile, or a convergent to divergent profile over the length of the arc chamber framework  22  as illustrated in  FIG. 7 c   ,  FIG. 7 d   , and  FIG. 7   e.    
         [0046]    Each splitter plate  26  as part of the splitter plate groups  28  attracts the electromagnetic portion of the arc and splits the arc in order to quickly raise the arc voltage which results in the arc being extinguished more quickly. Placing the splitter plate groups  28  in close proximity to the location of the initiation of the arc, that being the power movable contact  52  and the power stationary contact  48  and the load moveable contact  54  and the load stationary contact  50  results in improved arc quenching. The shape of the splitter plates  26 , specifically the V-shaped recess  92  may be optimized in order to improve the arc quenching ability of the arc chamber assembly  24 . An alternate embodiment of the splitter plate  26  is shown in  FIG. 8   b.    
         [0047]    Referring to  FIG. 12 , a flowchart representing the method of manufacturing and assembly of an arc chamber assembly is presented. The first step,  116  is the manufacture of the arc chamber panels. As illustrated in  FIG. 7 a    a left arc chamber framework panel  30  and a right arc chamber framework panel  32  are manufactured from an ablating source material. In a preferred embodiment left arc chamber framework panel  30  and right arc chamber framework panel  32  are assembled  118  by inserting right arc chamber framework panel male connector  44  into left arc chamber framework panel female connector  38  and inserting left arc chamber framework panel male connector  40  into right arc chamber framework panel female connector  42  to form an arc chamber framework  22  of  FIG. 6 . As depicted in  FIG. 10 a    splitter plates  26  are inserted  120  into arc chamber assembly  22  to form arc chamber assembly  24 . Finally, each arc chamber assembly  24  is inserted  122  into the lower housing  14  as illustrated in  FIG. 2 . 
         [0048]    While only certain features of the invention have been illustrated and described herein, many modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.