Patent Publication Number: US-8988175-B2

Title: Override device for a circuit breaker and methods of operating circuit breaker

Description:
BACKGROUND OF THE INVENTION 
     The embodiments described herein relate generally to an override device for a circuit breaker, and more particularly, to methods and systems used to activate and de-activate over-current protection in the circuit breaker. 
     A circuit breaker is an automatically operated electrical switch designed to protect an electrical circuit from damage caused by overloaded or shorted circuits. A coupler mechanism of the circuit breaker can be actuated to open and close contacts to which a load is connected. Circuit breakers have an over-current trip unit that provides over-current protection. Conventional over-current trip units use a magnetic yoke that surrounds a current-carrying leader. The magnetic yoke has an anchor that is movable along an axis and a spring that applies a resistive force against movement of the anchor. Current flowing through the leader induces a magnetic force that causes the anchor to apply a force against the resistance of the spring. If the current flowing through the leader exceeds a pre-determined value, the magnetic force acting on the anchor is greater than the force of the spring. Thus, the anchor is pulled toward the magnet which actuates a coupler to interrupt or “trip” the circuit. Some applications may require an override of the over-current trip unit. In these situations, an override device is required to permit current flow through the circuit breaker when the current exceeds the pre-determined value. 
     BRIEF DESCRIPTION OF THE INVENTION 
     In one aspect, an override device is provided for use with a coupler of a circuit breaker. The override device including a cam member coupled to the coupler. The cam member including a slot. The override device also including an actuator coupled to the cam member and configured to move the cam member between an over-current protection position and an over-current relay override position and a push member coupled to the coupler. The slot configured to guide the push member to a first position when the actuator moves the cam member to the over-current protection position. The slot further configured to guide the push member to a second position when the actuator moves the cam member to the over-current relay override position to permit current flow through the circuit breaker. 
     In another aspect, a circuit breaker is provided that includes an over-current trip unit including a trip rod configured to move between a REST position and a TRIPPED position, a coupler removably coupled to the over-current trip unit, and a cam member coupled to the coupler. The over-current trip unit also including an actuator coupled to the cam member and configured to move the cam member between an over-current protection position and an over-current relay override position and a push member coupled to the coupler and to the cam member. The cam member configured to move the push member to a first position such that the trip rod remains spaced from the push member when the trip rod is in the TRIPPED position. 
     In a further aspect, a method of controlling current through a circuit breaker is provided. The method includes positioning a coupler a distance from an over-current trip unit, the over-current trip unit is configured to move between a REST position and a TRIPPED position. The method also includes moving a cam member from an over-current protection position to an over-current relay override position, wherein current is permitted to flow through the circuit breaker when the cam is in the over-current relay override position and the over-current trip unit is in the TRIPPED position. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  illustrates a side view of a circuit breaker in a CLOSED position. 
         FIG. 2  illustrates a partial side view of the circuit breaker shown in  FIG. 1  in an OPENED position and an override device. 
         FIG. 3  illustrates a front view of the override device shown in  FIG. 2  coupled to a coupler of the circuit breaker. 
         FIG. 4  illustrates a rear view of the override device and coupler shown in  FIG. 3 . 
         FIG. 5  illustrates a perspective, exploded view of components of the override device shown in  FIG. 3 . 
         FIG. 6  illustrates a perspective view of components of the override device shown in  FIG. 5  assembled to the circuit breaker. 
         FIG. 7  illustrates a front view of the override device shown in  FIG. 3  coupled to the coupler of the circuit breaker and in an over-current protection position. 
         FIG. 8  illustrates another front view of the override device shown in  FIG. 3  coupled to the coupler and in the over-current protection position. 
         FIG. 9  illustrates a front view of the override device shown in  FIG. 3  coupled to the coupler and in an over-current relay override position. 
         FIG. 10  illustrates another front view of the override device shown in  FIG. 3  coupled to the coupler and in the over-current relay override position. 
         FIG. 11  is an exemplary flowchart illustrating a method of controlling current through the circuit breaker shown in  FIG. 1 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  illustrates a side view of a circuit breaker  10  shown in a CLOSED position  14 .  FIG. 2  illustrates a partial side view of circuit breaker  10  shown in an OPENED position  16  and an override device  12 . Circuit breaker  10  includes a housing  18  having a base  20  for mounting components thereon. Circuit breaker  10  further includes a first terminal  22 , a second terminal  24 , a movable contact  26 , a stationary contact  28 , an over-current trip unit  30 , a flexible connection  32  and a coupler  34 . 
     In use, current enters circuit breaker  10  through one of terminals  22  and  24  and exits circuit breaker  10  through the other of terminals  22  and  24 . The current also passes through movable contact  26  and stationary contact  28 . When circuit breaker  10  is in CLOSED position  14 , current flows unrestricted through circuit breaker  10  and, therefore, through an electrical device or circuit (not shown) that circuit breaker  10  is designed to protect. When circuit breaker  10  is in OPENED position  16 , current flow is interrupted through circuit breaker  10  and, consequently, through the electrical device or circuit that circuit breaker  10  is designed to protect. 
     During the presence of a higher current value than the assigned current for circuit breaker  10 , over a specified period of time, circuit breaker  10  moves to OPENED position  16 . The exposure of circuit breaker  10  to the higher current value activates over-current trip unit  30  which causes coupler  34  to release a latch  42  and to facilitate movement of a lever arm  36  with flexible connection  32  to interrupt the current flow through circuit breaker  10 . 
     Movable contact  26  is coupled to and carried by flexible connection  32  on lever arm  36  and stationary contact  28  is coupled to first terminal  22 . Contact  26  is movable between CLOSED position  14  and OPENED position  16  with respect to first terminal  22 . Movable contact  26  is coupled to stationary contact  28  in CLOSED position  14 , and movable contact  26  is de-coupled from stationary contact  28  in OPENED position  16 . 
     Flexible connection  32  is configured to electrically connect terminals  22  and  24 . Flexible connection  32  is mounted on lever arm  36  and is rotatably coupled to base  20 . Flexible connection  32  includes a first end  38  coupled to movable contact  26  and a second end  40  coupled to second terminal  24 . Lever arm  36  is configured to rotate movable contact  26  between CLOSED position  14  and OPENED position  16  with respect to first terminal  22 . Second end  40  remains coupled to second terminal  24  as first end  38  rotates movable contact  26 . Latch  42  is coupled to lever arm  36  and is configured to release lever arm  36  when acted upon by coupler  34  as described herein. 
     Over-current trip unit  30  is coupled to second terminal  24  and is configured to detect current from second terminal  24 . When current exceeds a pre-determined value, i.e., an over current event, over-current trip unit  30  interrupts or breaks current flow through circuit breaker  10 . Over-current trip unit  30  includes a magnetic yoke  44 , a trip rod  46 , an anchor  48 , and a spring  50 . Trip rod  46  is positioned perpendicular to magnetic yoke  44  and is coupled to anchor  48 . 
     Spring  50  is configured to resist downward movement of anchor  48 . As current flows through terminals  22  and  24 , a magnetic flux is created within magnetic yoke  44  that attracts anchor  48  against the force of spring  50 . Movement of anchor  48  causes trip rod  46  to move and to contact and push coupler  34 . 
       FIG. 3  illustrates a front view of override device  12  coupled to coupler  34 .  FIG. 4  illustrates a rear view of override device  12  and coupler  34 . Coupler  34  is configured to rotate latch  42  when acted upon by trip rod  46  (shown in  FIG. 2 ) as described herein. Coupler  34  includes a flange  54  and a rocker assembly  56  rotatably coupled to flange  54 . Flange  54  includes a first leg  58  which is configured to couple to base  20  and a second leg  60  extending substantially perpendicular from first leg  58 . 
     Rocker assembly  56  includes a front link  62 , a rear link  64 , and a trip block  66 . Each link  62  and  64  has opposing ends  68  and  70 , and a body  72  therebetween. A pivot pin  74  rotatably couples front link  62  to a front side  76  of second leg  60  and rotatably couples rear link  64  to a rear side  78  of second leg  60 . A coupling pin  80  couples trip block  66  to ends  70  of links  62  and  64 . In the exemplary embodiment, trip block  66  is coupled between links  62  and  64 . Links  62 ,  64  are configured to move trip block  66  up and down with respect to flange  54 . When links  62  and  64  move trip block  66  upward, trip block  66  is configured to contact and rotate carrier latch  42 . 
     Override device  12  includes a cam member  82 , an actuator  84  and a push member  86 . Cam member  82  includes a body  88  having a pair of pin apertures  90  and a fastener aperture  92  which extend through body  88 . Body  88  further includes a slot  96  extending at least partially therethrough. In one embodiment, slot  96  extends entirely through body  88 . Slot  96  includes a first portion  98 , a second portion  100  and a third portion  102 . In one embodiment, second portion  100  is angled in a first direction with respect to first portion  98  and third portion  102  is angled in a second direction with respect to first portion  98  that is opposite the first direction. 
     Push member  86  is spaced from trip rod  46  (shown in  FIG. 2 ) and is configured to rotatably couple to coupler  34 . In one embodiment, push member  86  is configured to have two positions. In the first position, trip rod  46  contacts push member  86  during an over current event to activate coupler  34 . In the second position, push member  86  remains spaced from trip rod  46  in an over current event such that coupler  34  is not activated during the over current event. Push member  86  includes a first end  110 , a second end  112  and a body  114  therebetween. A pivot pin  116  rotatably couples second end  112  to link ends  68  of coupler  34 . Push member  86  is configured to rotate about pivot pin  116  and between link ends  68 . Push member  86  further includes a drive pin  118  coupled to first end  110  and extending outward toward cam member  82 . In one embodiment, drive pin  118  extends through slot  96 . In an alternative embodiment, drive pin  118  extends at least partially into slot  96 . 
       FIG. 5  illustrates a perspective, exploded view of components of override device  12 .  FIG. 6  illustrates a perspective view of components of override device  12  shown in  FIG. 5  assembled to circuit breaker  10 . Actuator  84  is configured to couple with cam member  82  at pin apertures  90 . When acted upon by a force, actuator  84  is configured to reciprocally move cam member  82 . As illustrated, actuator  84  includes a lever  120 , a handle  122 , and a coupler member  124 . Lever  120  has a first portion  126  and a second portion  128 . Handle  122  couples to first portion  126  and coupler member  124  couples to second portion  128 . A pair of coupling pins  130  extend outward from coupler member  124  and extend into apertures  90 . A pivot pin  132  extends from lever  120  proximate the intersection of first portion  126  and second portion  128  and couples to a protective housing  133 . In one embodiment, actuator  84  includes an electrically driven device (not shown). 
       FIG. 7  is a front view of override device  12  coupled to coupler  34 . Override device  12  is shown in an over-current protection position  134  that facilitates interrupting or breaking current flow through circuit breaker  10  when current through override device  12  exceeds a pre-determined value, i.e., during an over current event. 
     To position circuit breaker  10  in over-current protection position  134 , a user moves handle  122  and rotates lever  120  (shown in  FIGS. 5 and 6 ) which rotates cam member  82  to over-current protection position  134 . In over-current protection position  134 , push member  86  is positioned such that end  110  is spaced from trip rod  46  and drive pin  118  extends within slot  96  at slot third portion  102 . As shown in  FIG. 7 , trip rod  46  is positioned in a REST position  138  that is spaced away from push member  86 . 
       FIG. 8  is another front view of override device  12  shown in over-current protection position  134  with trip rod  46  positioned in the TRIPPED position. When current flowing through circuit breaker  10  exceeds a pre-determined value, trip rod  46  moves from REST position  138  to a TRIPPED position  140 . During this movement, trip rod  46  contacts push member end  110  and moves push member  86 . In response, links  62  and  64  rotate about pivot pin  74  with respect to coupler flange  54 . In the exemplary embodiment, link ends  70  rotate in a first direction about pivot pin  74  and link ends  68  rotate in a second, opposite direction about pivot pin  74  while drive pin  118  moves within slot third portion  102 . By moving within slot third portion  102 , drive pin  118  prevents cam member  82  from moving out of over-current protection position  134  and maintains circuit breaker  10  in OPENED position  16  (shown in  FIG. 2 ). 
     Link ends  70  rotate about pivot pin  74  to move trip block  66  toward carrier latch  42  and rotates carrier latch  42  to release and thus enable rotation of lever arm  36 . Lever arm  36  rotates movable contact  26  (shown in  FIG. 2 ) away from first terminal  22  (shown in  FIG. 2 ) and positions circuit breaker  10  in OPENED position  16  (shown in  FIG. 2 ). 
       FIGS. 9 and 10  are front views of override device  12  in over-current relay override position  136 .  FIG. 9  illustrates trip rod  46  in REST position  138  and  FIG. 10  illustrates trip rod  46  in TRIPPED position  140 . Override position  136  permits current flow through circuit breaker  10  during an over current event and trip rod  46  is moved from REST position  138  to TRIPPED position  140 . 
     To position circuit breaker  10  in over-current relay override position  136 , a user moves handle  122  and rotates lever  120  (shown in  FIGS. 5 and 6 ) which rotates cam member  82  to over-current relay override position  136 . Rotation of cam member  82  moves slot  96 . In the exemplary embodiment, slot  96  guides drive pin  118  away from slot third portion  102 , through slot first portion  98  and to slot second portion  100 . Slot first portion  98  is sized and shaped to guide drive pin  118  to slot second portion  100  upon rotation of lever  120 . Drive pin  118  rotates push member  86  about pivot pin  116  and away from trip rod  46 . 
     As shown in  FIG. 10 , when trip rod  46  moves to TRIPPED position  140 , trip rod  46  does not contact push member  86 . Consequently, push member  86  does not actuate coupler  34  and current continues to flow through circuit breaker  10  even though current exceeds the pre-determined trip value. 
       FIG. 11  is an exemplary flowchart  200  illustrating a method of controlling current through a circuit breaker, for example circuit breaker  10  (shown in  FIG. 1 ) by an override device, such as override device  12  (shown in  FIG. 2 ). The method includes positioning  210  a coupler, such as coupler  34  (shown in  FIG. 2 ), in a spaced position from an over-current trip unit, for example over-current trip unit  30  (shown in  FIG. 2 ). The over-current trip unit is configured to move between a REST position and a TRIPPED position. A cam member, such as cam member  82  (shown in  FIG. 3 ), is coupled  220  to the coupler. The method also includes coupling  230  an actuator, for example actuator  84  (shown in  FIG. 3 ), to the cam member. The actuator is moved  240  to rotate the cam member to a over-current relay override position, for example over-current relay override position  136  (shown in  FIGS. 9 and 10 ). The coupler is rotated or cammed  250  away from the over-current trip unit before the over-current trip unit moves to the TRIPPED position to permit current flow through the circuit breaker even during an over current event. The method also includes rotating  260  the cam member to an over-current protection position, such as over-current protection position  134  (shown in  FIGS. 7 and 8 ) and rotating the coupler toward the over-current trip unit to interrupt or prevent current flow through the circuit breaker during an over current event. 
     The embodiments described herein provide a over-current relay override device for a circuit breaker. The override device can be used for new manufacture of circuit breakers or can be retro-fit with existing circuit breakers. In one embodiment, the override device includes a cam member configured to move between an over-current protection position and an over-current relay override position. The cam member reciprocates between the over-current protection position and the over-current relay override position to facilitate current flow through the circuit breaker when the circuit breaker is in a CLOSED position and an OPENED position. The override device provides effective circuit breaker designs to override any current controller to facilitate current flow when current exceeds a pre-determined value. 
     A technical effect of the system described herein is that the override device includes a cam member configured to move between an over-current protection position and an over-current relay override position. A further technical effect is that the cam member reciprocates between the over-current protection position and the override position to facilitate current flow through the circuit breaker when current exceeds a pre-determined value. 
     Exemplary embodiments of the override device and methods of controlling current flow are described above in detail. The override device and methods are not limited to the specific embodiments described herein, but rather, components of the override device and/or the circuit breaker and/or steps of the method may be utilized independently and separately from other components and/or steps described herein. For example, the override device and methods may also be used in combination with other electrical systems and methods, and are not limited to practice with only the circuit breaker as described herein. 
     Although specific features of various embodiments of the invention may be shown in some drawings and not in others, this is for convenience only. In accordance with the principles of the invention, any feature of a drawing may be referenced and/or claimed in combination with any feature of any other drawing. 
     This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any layers or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.