Abstract:
A multi-pole circuit breaker comprising a single main housing containing multiple circuit breakers for protecting multiple branch circuits. Each of the circuit breakers comprises a single line terminal for receiving electrical current from a utility line, a plurality of load terminals for supplying electrical current from the single line terminal to a plurality of branch circuits via load lines, and a plurality of neutral terminals for receiving electrical current returned from the branch circuits via neutral lines Line conductors inside the main housing connect the line terminal to the plurality of load terminals. Sensors inside the main housing generate signals representing characteristics of the electrical current flow in the branch circuits, and a signal processor uses the signals generated by the sensors for detecting abnormal conditions in the branch circuits and generating trip signals in response to the detection of an abnormal condition. A single tripping mechanism between the line terminal and the load terminals receives the trip signals and interrupts the flow of current to the branch circuits in response to a trip signal.

Description:
FIELD OF THE INVENTION 
     The present invention relates to multi-pole circuit breakers that use shared components to reduce cost and size. 
     BACKGROUND 
     Miniature circuit breakers sold today are usually 1 or 2 pole units, in either 15 or 20 amp configurations (although units with additional poles and other amperages also exist), and can include electronics to provide arcing fault (“AFI”) and/or ground fault (“GFI”) protection. These circuit breakers are typically sold and packaged as single units, thus requiring stocking of each individual type or version in stores or in warehouses. There is an increasing need for multi-pole circuit breaker assemblies, particularly for residential applications, and thus there is a need for alternatives to the use of multiple 1-pole and/or 2-pole circuit breakers. 
     BRIEF SUMMARY 
     The present disclosure provides a multi-pole circuit breaker comprising a single main housing containing multiple circuit breakers for protecting multiple branch circuits. Each of the circuit breakers comprises a single line terminal for receiving electrical current from a utility line, a plurality of load terminals for supplying electrical current from the single line terminal to a plurality of branch circuits via load lines, and a plurality of neutral terminals for receiving electrical current returned from the branch circuits via neutral lines. Line conductors inside the main housing connect the line terminal to the plurality of load terminals. Sensors inside the main housing generate signals representing characteristics of the electrical current flow in the branch circuits, and a signal processor uses the signals generated by the sensors for detecting fault conditions in the branch circuits and generating trip signals in response to the detection of fault conditions. A single tripping mechanism between the line terminal and the load terminals receives the trip signals and interrupts the flow of current to the branch circuits in response to a trip signal. 
     As used herein, the term “circuit breaker” refers to a device that uses a single tripping mechanism to control the flow of current to two or more branch circuits. 
     In one implementation, a single ground fault sensor is coupled to conductors located inside the main housing and to the load terminals and neutral terminals for the plurality of branch circuits, for producing a signal representing an imbalance in the current flow in the load and neutral lines for a plurality of branch circuits, and a separate current sensor coupled to each of the branch circuits produces a separate current signal representing characteristics of the current flow in each branch circuit. A single signal processor receives signals from all the ground fault and current sensors to detect the occurrence of a ground fault, overloads or an arcing fault in any of the plurality of branch circuits. If desired, voltages and other operating conditions may also be monitored and used to control the tripping operations. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention may best be understood by reference to the following description taken in conjunction with the accompanying drawings, in which: 
         FIG. 1  is a perspective view of four miniature circuit breakers joined together in a single housing to form an 8-pole circuit breaker assembly. 
         FIG. 2A  is an enlarged vertical section of one embodiment of the miniature circuit breakers used in the housing shown in  FIG. 1 . 
         FIG. 2B  is an enlarged vertical section of a modified embodiment of the miniature circuit breakers used in the housing shown in  FIG. 1 . 
         FIG. 3  is an enlarged side elevation of the tripping solenoid and mechanism in the circuit breakers of  FIGS. 2A and 2B . 
         FIG. 4  is an enlarged perspective of a portion of a modified printed wire assembly for use in the circuit breaker of  FIG. 2B . 
         FIG. 5A  is an exploded perspective of a modified embodiment of an AFI/current sensor for use as an alternative to the sensor shown in  FIG. 4 . 
         FIG. 5B  is a perspective view of a coil to be received in one of the cavities of the housing of  FIG. 5A . 
         FIG. 5C  is a top plan view of the AFI/current sensor of  FIG. 5A  combined with a modified ground fault sensor. 
         FIG. 6  is a sectioned perspective of another modified GFI and AFI/current sensor structure. 
     
    
    
     DETAILED DESCRIPTION 
     Although the invention will be described in connection with certain preferred embodiments, it will be understood that the invention is not limited to those particular embodiments. On the contrary, the invention is intended to cover all alternatives, modifications, and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the claims. 
     Turning now to the drawings and referring first to  FIG. 1 , four miniature circuit breakers are integrated in a single housing  10  to form an 8-pole circuit breaker assembly. The housing  10  includes four apertures  11   a - 11   d  that receive four handles  12   a - 12   d  for opening and closing the four circuit breakers inside the housing. In addition, the housing  10  includes four line terminals  13   a - 13   d  for receiving power from the utility lines, and four push-to-test buttons  14   a - 14   d  for testing the four circuit breakers. On the load side, the housing  10  includes eight load terminals  15   a - 15   h  for supplying power to eight branch circuits, i.e., two branch circuits per circuit breaker, and eight neutral terminals  16   a - 16   h  for receiving the neutral return lines from the eight branch circuits. Although the illustrative embodiment uses four circuit breakers to control the current flow in eight branch circuits, it will be understood that other configurations may be used with different numbers of circuit breakers and/or branch circuits, and different numbers of branch circuits controlled by each circuit breaker. 
     Inside the housing  10 , the two neutral lines associated with each circuit breaker are joined to a single neutral conductor  17  (see  FIG. 2A ) that is passed through a single ground fault sensor (discussed in more detail below), and then connected internally to a neutral conductor  18  that is common to all the circuit breakers in the housing  10 . This common neutral conductor  18  exits the housing  10  and forms a neutral pigtail  20  for connection to a neutral bar (not shown) in a load center. Any of the other standard connectors may be used in place of the pigtail. 
     The front of the housing  10  forms a pair of shallow recesses for receiving a pair of face plate labels  21  and  22 . Included in the face plate labels are circuit traces and electronic components such as the push-to-test (PTT) buttons  14   a - 14   d  and LEDs  24   a - 24   d , which may be used to indicate the trip status of each of the four circuit breakers. The labels  21  and/or  22  may include a dome switch (not shown) for each pole position. The LEDs  24   a - 24   d  may be illuminated to show the cause of a breaker trip (e.g., overload, ground fault, arcing fault, or the use of a PTT button) or to indicate which of the branch circuits associated with a common breaker caused the tripping of that breaker. For example, an LED may be illuminated continuously or intermittently in one or more colors to indicate which branch circuit caused the tripping of a given breaker. 
       FIG. 2A  illustrates the internal structure of one of the circuit breakers inside the housing  10 , e.g., the circuit breaker having the handle  12   a . Power is routed through the circuit breaker via the line terminal  13   a  and the load terminals  15   a  and  15   b . As depicted in  FIG. 2A , the circuit breaker is in a closed position, enabling current to flow through the circuit breaker. The current path through the circuit breaker extends from the line terminal  13   a , formed by a stationary contact carrier  30 , to the load terminals  15   a  and  15   b . In the closed position, current flows from the line terminal  13   a  to the movable contact carrier  31  via stationary and movable contacts  32  and  33 , respectively. From the movable contact carrier  31 , a line conductor  34  having bifurcated load-end portions  34   a ,  34   b  (see  FIG. 5 ) conducts current to the load terminals  15   a  and  15   b . Current flows out of the load end of the circuit breaker via the load terminal  15   a  and  15   b , through a pair of branch circuits, and returns through a pair of neutral lines to the neutral terminals  16   a  and  16   b.    
     From the movable contact carrier  31 , the line conductor  34  conducts the current through a single ground fault sensor  40  that is common to both branch circuits, and then the bifurcated portions  34   a  and  34   b  conduct current through a pair of parallel arcing fault or current sensors  41  and  42  to the two load terminals  15   a  and  15   b . The current path them proceeds from the load terminals  15   a  and  15   b  to the field loads by means of field wiring (not shown). 
     After the current has gone through the field loads, it returns to the circuit breaker via neutral wires (not shown) which are connected to the neutral terminals  16   a ,  16   b , and is then carried by the single neutral conductor  17  through the ground fault sensor  40  to the common neutral conductor  18  for all the neutral wires in the housing  10 . The conductor  18  exits the housing  10  and forms the neutral pigtail  20 . Since multiple poles are combined into one housing, only the one common neutral pigtail  20  (or other standard connector) is needed outside the housing, which further reduces the cost of the assembly. 
     The illustrative circuit breaker includes an actuating mechanism that opens and closes the contacts  32  and  33 . For the open position, the movable contact carrier  31  is rotated away from the stationary contact  32 , causing the movable contact  33  to separate from the stationary contact  32 . When the contacts  32  and  33  separate, current no longer flows from the line terminal  13   a  to the load terminals  15   a  and  15   b . The circuit breaker may be tripped open in any of several ways, including manual control or in response to an abnormal condition such as a short circuit, an overload, arcing fault or ground fault. 
     The movable contact carrier  31  may be moved between the open and closed positions by a user manually moving the handle  12   a  to the right or left, respectively, causing corresponding movement of the upper end of the movable contact carrier  31  to the left or right of a pivot point. A spring  35  is connected at one end to trip lever  50  and at another end to the bottom of the movable contact carrier  31 . When the upper end of the movable contact carrier  31  is left of the pivot point, the spring  35  biases the bottom of the movable contact carrier  31  to the open position. Conversely, when the upper end of the movable contact carrier  31  is right of the pivot point, the spring  35  biases the bottom of the movable contact carrier  31  to the closed position. 
     In the closed position, the trip lever  50  is latched by engagement with an armature  51 . The trip lever  50  is pivotally mounted about a pivot at one end. The other end of the trip lever  50  is seated in a latched position on the armature  51 . The spring  35  connects the trip lever  50  to the movable contact carrier  31 , and biases the movable contact  33  against the stationary contact  32 . To trip the breaker, a solenoid  52  is energized to move the armature  51  to unlatch the trip lever  50 . The trip lever  50  then swings clockwise to its tripped position, carrying the upper end of the spring  35  to the opposite side of its dead center position. The spring  35  rotates the movable contact carrier  31  from the closed circuit position to the open circuit position, separating the movable contact  33  from the stationary contact  32 . 
     The circuit breaker is provided with circuitry  53  to trip the breaker in response to an arcing fault, ground fault or overload. The trip circuitry  53 , which typically includes signal processing circuitry (usually in the form of a signal processor), is formed on a printed wiring assembly (PWA, which is a printed circuit board having multiple components mounted on it)  54  mounted within the housing  10 . When the circuitry detects any of these abnormal conditions, it generates a trip signal to energize the solenoid  52 . 
     To detect the occurrence of a ground fault when the contacts  32  and  33  are closed, the ground fault sensor  40  detects any difference between the currents in the line conductor  34  and the neutral conductor  17  and provides a signal representing any such difference to the trip circuitry  53 . The neutral conductor  17  and the line conductor  34  are both routed through the ground fault sensor  40  to permit sensing of any such imbalance of current flow in the line and neutral conductors. If the imbalance exceeds the trip level of the ground fault detection circuitry, the trip circuitry  53  sends a trip signal to energize the solenoid  52  to trip the circuit breaker. 
     One example of a ground fault detection circuit is described in U.S. Pat. No. 7,193,827, and an improved sensor utilizing that circuit is described in copending application Ser. No. 12/267,750 filed Nov. 10, 2008, both of which are assigned to the assignee of the present invention and are incorporated herein by reference in their entirety. The detection circuit described in U.S. Pat. No. 7,193,827 detects both ground faults and grounded neutrals with only a single current sensor. 
     To detect the occurrence of an arcing fault when the contacts  32  and  33  are closed, the bifurcated portions  34   a  and  34   b  of the line conductor  34  pass through the arcing fault or current sensors  41  and  42  to monitor the currents supplied to the two branch circuits via the load terminals  15   a  and  15   b . Signals from the sensors  41  and  42 , preferably representing the respective rates-of-change of the currents, are supplied to the trip circuitry  53  mounted on the printed circuit board. The arcing fault detection circuitry in the trip circuitry  53  analyzes the signal for characteristics of an arcing fault. If the arcing fault detection circuitry detects the presence of an arcing fault, it sends a trip signal to energize the solenoid  52  to trip the circuit breaker. 
     The patterns of the fluctuations in the signals produced by the arcing fault or current sensors  41  and  42  indicate whether the associated branch circuits are in normal operating condition or an arcing fault condition. Examples of suitable arcing fault sensors and arcing fault detection circuitry or signal processors are described in U.S. Pat. Nos. 6,259,996, 7,151,656, 7,068,480, 7,136,265, 7,253,637 and 7,345,860, owned by the assignee of the present invention, which are incorporated herein by reference in their entirety. 
     To detect the occurrence of an overload when the contacts  32  and  33  are closed, an overload detection portion of the trip circuitry  53  samples the current flowing through the line conductor  34 . The overload detection circuitry analyzes the current samples for characteristics of an overload, and if an overload is detected, the trip circuitry  53  sends a trip signal to energize the solenoid  52  to trip the circuit breaker in the same fashion as described above. Overload detection circuitry typically simulates the bimetal deflection of traditional circuit breakers, as described in U.S. Pat. No. 5,136,457, assigned to the assignee of the present invention and incorporated herein by reference in its entirety. To simulate bimetal deflection, the overload circuitry accumulates the squared values of current samples taken from the line conductor  34 . The sum of the squared values of that current is proportional to the accumulated heat in the tripping system. The overcurrent circuitry decrements logarithmically the accumulated square of the current to account for the rate of heat lost due to the temperature of the power system conductors being above ambient temperature. When the accumulating value exceeds a predetermined threshold representing the maximum allowed heat content of the system, the trip circuitry  53  sends a trip signal to energize the solenoid  52  to trip the circuit breaker. 
     To produce a faster trip when the current in the load line increases significantly, such as in the case of a short circuit, the line conductor  34  is wrapped around (two turns) the frame  54  of the tripping solenoid  52  to induce a magnetic loop (see  FIGS. 2A ,  2 B and  3 ). In the event of a short circuit, this loop causes the plunger  55  of the tripping solenoid  52  to quickly retract into the body of the solenoid, thereby producing an immediate trip. The plunger  55  pulls on the end of the armature  51 , thus releasing the trip lever  50 , causing the mechanism to trip and open the contacts  32  and  33 . Two turns of the conductor are wrapped around the frame  54  in  FIGS. 2A ,  2 B and  3 , but any number of turns may be utilized. 
       FIG. 2B  illustrates a modified embodiment in which the line conductor  34  is routed from the solenoid frame  54  to a stamped conductor  60  that extends through the ground fault sensor  40 . On the load side of the sensor  40 , the stamped conductor  60  splits to form a pair of resistive sensors that are attached to the PWA at  71   a ,  71   b  and  72   a ,  72   b  before being connected to the load terminals  15   a ,  15   b , respectively. 
       FIG. 4  illustrates the stamped conductor  60  in more detail, connecting the line conductor  34  to the load terminals  15   a  and  15   b . The conductor  60  passes through the ground fault sensor  40  and is then split into two branches for connection to the two load terminals  15   a  and  15   b . Between the sensor  40  and the terminals  15   a ,  15   b , the bifurcated portion of the stamped conductor  60  is connected to the PWA  54  at  71   a ,  71   b  and  72   a ,  72   b  and loops upwardly from the PWA between the two connection points  71  and  72  to provide a desired length of material, i.e., a desired resistance, in the space available between the sensor  40  and the terminals  15   a  and  15   b . During an overload condition in one of the branch circuits, the current flow through the corresponding branch of the conductor  60  increases, which increases the voltage drop across that portion of the conductor. When the voltage drop exceeds a predetermined threshold, the trip circuitry  53  sends a trip signal to energize the solenoid  52  to trip the circuit breaker. 
     The neutral wires from the branch circuits are connected to the neutral terminals  16   a  and  16   b  that have a common connector plate  75  connected to the neutral conductor  17  that passes through the ground fault sensor  40  to a common neutral bar  70  that receives the neutral wires from all the branch circuits. 
       FIGS. 5A ,  5 B and  5 C illustrate an arrangement of four ground fault sensors  40   a - 40   d  and eight arcing fault/current sensors  41   a - 41   d  and  42   a - 42   d  for all four of the circuit breakers in the housing  10 . The coils C of the four ground fault sensors  40   a - 40   d  are contained in cavities formed by a unitary molded plastic housing  80  that has hollow posts aligned with the centers of four coils C for passing the four line conductors  34   a - 34   n  and the corresponding neutral conductors (not shown). The coils C of the eight arcing fault/current sensors  41   a - 41   d  and  42   a - 42   d  are contained in two sets of four cavities formed in opposite sides of a unitary molded plastic housing  81  that has hollow posts  82   a - 82   h  aligned with the centers of eight coils C for passing the bifurcated end portions of the four line conductors  34   a - 34   d . The two sets of cavities formed by the housing  81  are offset from each other so that the conductors that pass between the coils C in the first set of cavities are positioned to pass through the centers of the coils C in the second set of cavities. 
       FIG. 6  illustrates a modified embodiment of that portion of a line conductor  34  that passes through a single ground fault sensor  40  and a pair of arcing fault/current sensors  41  and  42 . The portion of the conductor  34  that passes through the ground fault sensor  40  is formed by a flat T-shaped plate  90 , and the bifurcated portion of the conductor that passes through the two arcing fault/current sensors  41  and  42  is formed by a pair of insulated flat plates  91  and  92  that are connected at one end to the two arms of the T-shaped plate  90  and are connected at the other end to a pair of lugs  93  and  94 . 
     While particular embodiments and applications of the present invention have been illustrated and described, it is to be understood that the invention is not limited to the precise construction and compositions disclosed herein and that various modifications, changes, and variations may be apparent from the foregoing descriptions without departing from the spirit and scope of the invention as defined in the appended claims.