Patent Publication Number: US-6714108-B1

Title: Circuit breaker including mechanism for breaking tack weld

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application is related to commonly assigned, concurrently filed U.S. patent application Ser. No. 10/405,739, filed Apr. 2, 2003, entitled “Remotely Controllable Circuit Breaker Including Bypass Magnet Circuit”. 
    
    
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to circuit breakers for protecting electric power circuits and, more particularly, to such circuit breakers including a mechanism for breaking a tack weld between separable contacts. 
     2. Background Information 
     Circuit breakers used in residential and light commercial applications are commonly referred to as miniature circuit breakers because of their limited size. Such circuit breakers typically have a set of separable contacts opened and closed by a spring powered operating mechanism. A thermal-magnetic trip device actuates the operating mechanism to open the separable contacts in response to persistent overcurrent conditions and to short circuit conditions. 
     When a movable contact arm of a circuit breaker, electrical contactor or electrical relay is actuated, for example, by a solenoid or motor, it is necessary, under certain circumstances, to be able to open a relatively small tack weld that has formed on the faces of the separable contacts. In some circumstances, the actuating mechanism is not able to generate enough force on the movable contact arm to break the tack weld and open the separable contacts. 
     There is room for improvement in circuit breakers including a mechanism for breaking a tack weld between separable contacts. 
     SUMMARY OF THE INVENTION 
     These needs and others are met by the present invention, which provides improvements in rocking separable contacts, in order to achieve a peeling action on the separable contact faces, in combination with increasing the force of an actuator, such as a solenoid, in order to assist in breaking a relatively light tack weld. 
     Whenever an actuator, such as a solenoid, opens the separable contacts, the plunger of the solenoid freely moves a pivot of a movable contact arm to one end of a pivot opening. This accomplishes two purposes: (1) a peeling action is provided on the faces of the separable contacts, thereby reducing the force needed to break the tack weld; and (2) a gap within the solenoid between the solenoid core and the solenoid plunger is reduced, thereby increasing the opening force of the solenoid plunger. These synergistic actions reduce the force needed to break the tack weld and, also, increase the opening force as provided by the solenoid plunger, in order to break such tack weld. 
     In accordance with the invention, an electrical switching apparatus comprises: a housing comprising a pivot opening having a first end and a second end; a movable arm including a first portion having a pivot pivotally mounted in the pivot opening and a second portion, the pivot opening being substantially larger than the pivot; a fixed contact mounted in the housing; a movable contact mounted on the second portion of the movable arm, the fixed contact, the movable contact and the movable arm cooperating.to provide a closed state, a pivot state and an open state; an actuator mounted in the housing, the actuator including a member coupled to the movable arm, the actuator moving the member between a first position and a second position to provide the open state and the closed state, respectively, the member having a third position between the first position and the second position; and means for biasing the movable arm toward the fixed contact to maintain the closed state; wherein the closed state is defined by the second position of the member of the actuator, with the pivot engaging the second end of the pivot opening and being apart from the first end of the pivot opening, wherein the pivot engages the first end of the pivot opening and is apart from the second end of the pivot opening in the pivot state, wherein the open state is defined by the first position of the member of the actuator, with the pivot engaging the first end of the pivot opening and being apart from the second end of the pivot opening, and wherein when the fixed contact and the movable contact are welded closed, the actuator provides insufficient force to move the member of the actuator to the first position until after the pivot moves apart from the second end of the pivot opening and at least substantially toward the first end of the pivot opening. 
     The actuator may be a solenoid having a core and at least one coil wound on the core, and the member may be a plunger of the solenoid. The plunger may engage the core in the first position, be set apart from the core with a first gap in the third position, and be further set apart from the core with a larger second gap in the second position. The at least one coil may include a closing coil and an opening coil, and the opening coil may energize the core to attract the plunger with a first force in the third position, and a second smaller force in the second position. 
     The pivot may have a size within the pivot opening. A distance between the first end and the second end of the pivot opening may be about twice the size of the pivot. 
     As another aspect of the invention, a remotely controllable circuit breaker comprises: a housing comprising a pivot opening having a first end and a second end; a first terminal; a second terminal; a set of first contacts mounted in the housing; an operating mechanism mounted in the housing and coupled to the set of first contacts for opening and closing the set of first contacts; a movable arm including a first portion having a pivot pivotally mounted in the pivot opening and a second portion, the pivot opening being substantially larger than the pivot; a set of second contacts comprising a fixed contact mounted in the housing and a movable contact mounted on the second portion of the movable arm, the fixed contact, the movable contact and the movable arm cooperating to provide a closed state, a pivot state and an open state, the set of second contacts being electrically interconnected with the set of first contacts between the first and second terminals; a remotely controllable solenoid including a member coupled to the movable arm, the remotely controllable solenoid moving the member between a first position and a second position to provide the open state and the closed state, respectively, the member having a third position between the first position and the second position; and means for biasing the movable arm toward the fixed contact to maintain the closed state, wherein the closed state is defined by the second position of the member of the actuator, with the pivot engaging the second end of the pivot opening and being apart from the first end of the pivot opening, wherein the pivot engages the first end of the pivot opening and is apart from the second end of the pivot opening in the pivot state, wherein the open state is defined by the first position of the member of the actuator, with the pivot engaging the first end of the pivot opening and being apart from the second end of the pivot opening, and wherein when the fixed contact and the movable contact are welded closed, the actuator provides insufficient force to move the member of the actuator to the first position until after the pivot moves apart from the second end of the pivot opening and at least substantially toward the first end of the pivot opening. 
     The fixed contact and the movable contact may include opposing faces, which are engaged in the closed state and are disengaged in the open state. When the opposing faces are welded closed, the pivot state separates a portion of the opposing face of the movable contact from the opposing face of the fixed contact. 
     As another aspect of the invention, an electrical switching apparatus comprises: a housing; a movable arm including a first portion and a second portion; means for mounting the first portion of the movable arm for pivotal movement and longitudinal movement with respect to the housing; a fixed contact mounted in the housing; a movable contact mounted on the second portion of the movable arm, the fixed contact, the movable contact and the movable arm cooperating to provide a closed state, a pivot state and an open state; and an actuator mounted in the housing, the actuator including a member coupled to the movable arm, the actuator moving the member between a deactuating position and an actuating position to provide the open state and the closed state, respectively, the member having a pivot position between the deactuating position and the actuating position, wherein the closed state is defined by the actuating position of the member of the actuator, wherein the first portion of the movable arm moves to a first longitudinal position in the pivot state and in the open state, wherein the first portion of the movable arm moves to a second longitudinal position in the closed state, and wherein when the fixed contact and the movable contact are welded closed, the actuator provides insufficient force to move the member of the actuator to the deactuating position until after the first portion of the movable arm moves at least substantially toward the first longitudinal position in the pivot state. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     A full understanding of the invention can be gained from the following description of the preferred embodiments when read in conjunction with the accompanying drawings in which: 
     FIG. 1 is an elevational view of a remotely controllable circuit breaker shown with the cover removed and with the main contacts and secondary contacts closed. 
     FIG. 2 is a view similar to that of FIG. 1 with the secondary contacts open. 
     FIG. 3 is an elevational view of a remotely controllable circuit breaker in accordance with the invention shown with the cover removed and with the main contacts and secondary contacts closed. 
     FIG. 4 is a view similar to that of FIG. 3 with the main contacts open. 
     FIG. 5 is a simplified elevational view of the secondary contact arm and secondary contacts of FIG.  3 . 
     FIG. 6 is a view similar to that of FIG. 5, but also including the fixed and movable armatures of FIG.  3 . 
     FIG. 7 is a view similar to that of FIG. 6, but also showing the current path of the primary circuit of FIG.  3 . 
     FIG. 8 is a simplified elevational view of the secondary contact arm and secondary contacts of FIG. 3 in the closed state. 
     FIG. 9 is a simplified elevational view of the secondary contact arm and secondary contacts of FIG. 3 in the pivot state. 
     FIG. 10 is a simplified elevational view of the secondary contact arm and secondary contacts of FIG. 3 in the open state. 
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     As employed herein, the statement that two or more parts are “coupled” together shall mean that the parts are joined together either directly or joined through one or more intermediate parts. Further, as employed herein, the statement that two or more parts are “attached” shall mean that the parts are joined together directly. 
     The invention will be described as applied to a miniature circuit breaker, although it will become apparent that it could be applied to other types of circuit breakers as well. An example of a miniature remotely controllable circuit breaker is disclosed in U.S. Pat. No. 6,259,339, which is incorporated by reference herein. Referring to FIG. 1, a miniature circuit breaker  1  includes a molded housing  3  with the cover of the housing removed. The basic components of the circuit breaker  1  are a set of main contacts  5 , an operating mechanism  7  for opening such main contacts, and a thermal-magnetic trip device  9 , which actuates such operating mechanism to trip the set of main contacts  5  open in response to certain overcurrent conditions. Further included arc a set of secondary contacts  11  and an actuator  13  in the form of a magnetically latchable solenoid  13 , which is remotely controllable to control the open and closed states of the set of secondary contacts  11 . Finally, the circuit breaker  1  includes an operating member/indicator member  101 , to be described, for manually closing the set of secondary contacts  11  and which also serves as a position indicator to provide a visual indication external to the molded housing  3  of the open/closed state of the set of secondary contacts  11 . 
     The set of main contacts  5  includes a fixed contact  15  secured to a line terminal  17  and a movable main contact  19  affixed to an arcuate movable contact arm  21 , which forms part of the operating mechanism  7 , for opening and closing such main contacts. The operating mechanism  7  is a well-known device, which includes a pivotally mounted operator  23  with an integrally molded handle  25 . The operating mechanism  7  also includes a cradle  27  pivotally mounted on a support  29  molded in the housing  3 . With the handle  25  in the closed position, as shown in FIG. 1, a spring  31  connected to a hook  33  on the movable contact arm  21  and a tab  35  on the cradle  27  holds the main contacts  5  closed. The spring  31  also applies a force with the set of main contacts  5  closed, as shown, to the cradle  27  which force tends to rotate such cradle in a clockwise (with respect to FIG. 1) direction about the support  29 . However, the cradle  27  has a finger  37 , which is engaged by the thermal-magnetic trip device  9  to prevent this clockwise rotation of such cradle under normal operating conditions. Otherwise, as is well-known, the trip device  9  pivots counter-clockwise (with respect to FIG. 1) to unlatch the finger  37  and, thus, the cradle  27 , in order to trip open the set of main contacts  5 . 
     The set of secondary contacts  11  includes a fixed secondary contact  55  secured on a load conductor  57 , which leads to a load terminal  59 . The set of secondary contacts  11  also includes a movable secondary contact  61  fixed to a secondary movable contact arm  63 , which at its opposite end is seated in a molded pocket  65  in the molded housing  3 . The movable contact arm  63  is electrically connected in series with the set of main contacts  5  by a flexible braided conductor  67  connected to the upper (with respect to FIG. 1) or fixed end of the bimetal  39 . The free end of the bimetal  39  is electrically connected to the main movable contact arm  21  by a flexible braided conductor  51 . Thus, a circuit for load current is established from the line terminal  17  through the set of main contacts  5 , the main movable contact arm  21 , the flexible braided conductor  51 , the bimetal  39 , the flexible braided conductor  67 , the secondary movable contact arm  63 , the set of secondary contacts  11 , and the load conductor  57  to the load terminal  59 . 
     The set of secondary contacts  11  is biased to the closed state of FIG. 1 by a helical compression spring  69  seated on a projection  71  on an offset  73  in the secondary movable contact arm  63 . The spring  69  is oriented such that the force that it applies to the movable contact arm  63 , which tends to close the set of secondary contacts  11 , is relaxed to a degree with such secondary contacts in the open position. This serves the dual purpose of providing the force needed to close the set of secondary contacts  11  against rated current in the protected circuit and, also, reducing the force that must be generated by the magnetically latching solenoid  13  to hold such secondary contacts in the open state. In order for the set of secondary contacts  11  to withstand short circuit currents and allow the set of main contacts  5  to perform the circuit interruption, the magnet force generated by the short circuit current causes a movable armature  75  mounted on the secondary movable contact arm  63  to be attracted to a fixed pole piece  77  seated in the molded housing  3 , thereby clamping the set of secondary contacts  11  closed. 
     The actuator/solenoid  13  includes a first or close coil  79  and a second or open coil  81  concentrically wound on a steel core  83  supported by a steel frame  85 . A plunger  87  moves rectilinearly within the coils  79  and  81 . A permanent magnet  89  is seated between the steel core  83  and the steel frame  85 . 
     The plunger  87  engages the secondary contact arm  63  to cooperatively form a closing member. When the close coil  79  is energized, a magnetic field is produced to drive the plunger  87  downward to a first position, which rotates the secondary movable contact arm  63  clockwise (with respect to FIG. 1) and thereby moves the set of secondary contacts  11  to the closed state. The set of secondary contacts  11  is maintained in the closed state by the spring  69 . When it is desired to open the set of secondary contacts  11 , the open coil  81  is energized, which lifts the plunger  87  and with it the secondary movable contact arm  63  to open such secondary contacts. With the plunger  87  in the full upward position of FIG. 2, it contacts the steel core  83  and is retained in this second position by the permanent magnet  89 . Subsequently, when the close coil  79  is energized, the magnetic field generated is stronger than the field of the permanent magnet  89  and, therefore, overrides the latter and moves the plunger  87  back to the first, or closed position. A projection  91  on the plunger  87  engages an actuating lever  93  on a microswitch  95 , which controls remote operation of the solenoid  13  by signals provided over a remotely operable control circuit represented by control leads  97 . As the set of secondary contacts  11  are held closed by the spring  69  and held open by the magnetic latching provided by the permanent magnet  89 , only momentary signals are needed to operate such secondary contacts to the open and closed states. 
     With the set of secondary contacts  11  open, as shown in FIG. 2, an extension  115  can be pushed to the right (with respect to FIG. 2) as shown by the arrow  123 , to rotate the operating member/indicator member  101  clockwise (with respect to FIG.  2 ), thereby depressing a coupling pin  107  and driving the plunger  87  downward to open a gap  125  (as shown in FIG. 1) between the core  83  and the plunger  87 , in order that the set of secondary contacts  11  is closed and held closed by the spring  69 . 
     Referring to FIG. 3, a remotely controllable circuit breaker  200  in accordance with the present invention is shown. For convenience of disclosure, the circuit breaker  200  includes some of the features of the circuit breaker  1  of FIGS. 1 and 2, which features are shown with common reference numerals, such as, for example, the line terminal  17 , the set of main contacts  5 , the operating mechanism  7 , the bimetal  39 , the solenoid  13 , and the load terminal  59 . 
     As best shown in FIG. 5, the circuit breaker  200  of FIG. 3 includes a secondary movable contact arm  202  having a T-shaped pivot end  204  with two pivot legs  206  (only one is shown) mounted in two corresponding oversized openings  208  (only one is shown) in a molded housing  210 . The pivot opening  208  has a first or upper (with respect to FIG. 5) end  207  and a second or lower (with respect to FIG. 5) end  209 . Although pivot legs on a movable contact arm and a pivot opening in a molded housing are shown, the invention is applicable to any suitable mechanism for mounting one portion of a movable contact arm, such as  202 , for pivotal movement and longitudinal movement with respect to a housing, such as  210 . For example, the housing  210  could provide one or more pivot points (not shown) and the movable contact arm  202  could provide an elongated pivot opening (not shown), which receives such pivot points. 
     The opening force for the secondary movable contact arm  202  is provided by the plunger  87  of the solenoid  13  of FIG. 3 or by any suitable electric solenoid or motor. The closing force for the secondary movable contact arm  202  may be provided by the plunger  87 , and is preferably also provided by spring  69 ′. An actuator assembly  211  includes the actuator/solenoid  13  and its plunger  87  along with the secondary movable contact arm  202  and the helical compression spring  69 ′, which cooperate to selectively move the set of secondary contacts  228  between the open and closed states. 
     As best shown in FIG. 6, a magnetic armature assembly  212  includes a first or movable magnetic armature  214  coupled to (e.g., suitably mounted on) the secondary movable contact arm  202 , and a second or fixed magnetic armature (e.g., pole piece)  216  seated in the molded housing  210  of FIGS. 3 and 4. The secondary movable contact arm  202  includes a first portion  218 , an intermediate second portion  220  and a third portion  222 . As best shown in FIG. 7, near the first portion  218 , the movable contact arm  202  is electrically connected to a flexible braided conductor  224  (and, in turn, to a current loop  234 ). The second portion  220  of such arm is positioned between the first and second magnetic armatures  214 , 216 , and the third portion  222  is fixed to and carries a movable secondary contact  226 . A set of secondary contacts  228  includes the movable secondary contact  226  and a fixed secondary contact  230  secured on a load conductor  232 , which leads to the load terminal  59  (FIGS.  3  and  4 ). 
     As best shown in FIG. 5, the first portion  218  of the movable contact arm  202  has the pivot legs  206  pivotally mounted in the pivot opening  208 , which is substantially larger than the pivot legs  206 . For example, the pivot legs  206  have a size  205  within the pivot opening  208 , and the distance  203  between the first end  207  and the second end  209  of the pivot opening  208  is about twice the size  205  of the pivot legs  206 . 
     As discussed below in connection with FIGS. 8-10, the fixed contact  230 , the movable contact  226  and the movable contact arm  202  cooperate to provide a closed state (FIG.  8 ), a pivot state (FIG. 9) and an open state (FIG.  10 ). The fixed contact  230  and the movable contact  226  include opposing faces  229 , 227  (FIG.  10 ), respectively, which are engaged in the closed state and are disengaged in the open state. As shown in FIG. 9, when the opposing faces  227 , 229  are welded closed at  231 , the pivot state separates a portion of the opposing face  227  of the movable contact  226  from the opposing face  229  of the fixed contact  230 . Preferably, the opposing faces  227 , 229  have arcuate cross-sections. 
     Referring again to FIG. 6, the set of magnetic armatures  214 , 216  is preferably employed to clamp the set of secondary contacts  228  closed during relatively high current conditions, such as a short circuit. These magnetic armatures are U-shaped forms, which wrap around the secondary movable contact arm  202 . In addition to the magnetic armatures  214 , 216 , the spring  69 ′ (FIG. 3) may bias the movable contact arm  202  toward the fixed contact  230  to maintain the closed state. The spring  69 ′ is oriented such that the force that it applies to the movable contact arm  202  tending to close the set of secondary contacts  228  is relaxed to a degree with such secondary contacts in the contact welded position (FIG.  9 ), and is further relaxed to a degree with such secondary contacts in the open position (FIG.  10 ). Hence, the spring  69 ′ reduces a force applied to the movable contact arm  202  and toward the fixed contact  230  as the solenoid  13  (FIG. 3) moves the plunger  87  from its closed or lower (with respect to FIGS. 3 and 4) position at least substantially toward its intermediate position (FIG.  9 ), which moves the pivot legs  206  from the second or lower end  209  of the pivot opening  208  at least substantially toward the first or upper end  207  of such pivot opening. 
     Referring to FIG. 7, the exemplary current loop  234  is a solid conductor form (e.g., copper), which raps around the fixed magnetic armature  216 . The loop  234  is U-shaped and includes a first leg  236  having a foot  237 , which is electrically interconnected with the bimetal  39  (FIGS. 3 and 4) and, thus, with the set of main contacts  5  by a flexible braided conductor  238 . The loop  234  also includes a second leg  240 , which is electrically interconnected with the secondary movable contact arm  202  and, thus, with the set of secondary contacts  228  by the flexible braided conductor  224 . The first leg  236  passes between the first and second magnetic armatures  214 , 216 . Preferably, an insulating or molded barrier  242  insulates the current loop  234  from the magnetic armatures  214 , 216 . 
     Referring again to FIG. 3, a primary circuit  243  for load current is established from the line terminal  17  through the set of main contacts  5 , the main movable contact arm  21 , the flexible braided conductor  51 , the bimetal  39 , the flexible braided conductor  238 , the current loop  234 , the flexible braided conductor  224 , the secondary movable contact arm  202 , the set of secondary contacts  228 , and the load conductor  232  to the load terminal  59 . This primary circuit  243  electrically connects the set of main contacts  5  to the set of secondary contacts  228  between the line and load terminals  17 , 59 . Through the first leg  236  of the current loop  234  and the intermediate second portion  220  of the secondary movable contact arm  202 , the primary circuit  243  passes between the first and second magnetic armatures  214 , 216 , which are responsive to a first predetermined condition (e.g., a short circuit or other fault condition) of current flowing therein. Hence, these two turns (i.e., the first current loop leg  236  and the intermediate second portion  220  of the secondary movable contact arm  202 ) of the primary circuit  243  cooperate with the armatures  214 , 216  to hold the set of secondary contacts  228  in the closed state during that condition of current, thereby clamping such secondary contacts closed. 
     An alternate or bypass magnetic circuit  244  is provided for arcing current. As shown in FIG. 4, the set of main contacts  5  has just been opened by the operating mechanism  7  in response to a short circuit condition or other fault condition. The alternate circuit  244  includes a flexible braided conductor  246 , which is electrically connected between an arc plate  248  and the load conductor  232  and, thus, to the load terminal  59 . Preferably, the conductor  246  is insulated by a suitable insulator  242 . As is well-known, the arc plate  248  draws an arc  249  from the main fixed contact  15  when the main movable contact arm  21  opens the set of main contacts  5  under short circuit or other fault conditions. An arc chute (not shown) may be employed in the vicinity of the arc  249  and arc plate  248 . A small percentage of current may still conduct through the primary circuit  243  until the arc  249  is extinguished. The alternate circuit  244  passes between the first and second magnetic armatures  214 , 216 , which are responsive to the arcing condition of current flowing in that circuit and which cooperate to hold the set of secondary contacts  228  in the closed state during that arcing condition of current. 
     In the alternate circuit  244 , the arcing current is established from the line terminal  17  through the main fixed contact  15 , the arc  249 , the arc plate  248 , the flexible braided conductor  246 , and the load conductor  232  to the load terminal  59 . At least initially, the arcing current is about equal to the fault current, although the arcing current is quickly reduced as the arc  249  is quenched. Nevertheless, the corresponding force, as provided by the magnetic armatures  214 , 216  in response to the arcing current in the alternate circuit  244 , continues after the time that the other force, as provided by the magnetic armatures  214 , 216  in response to the fault current in the primary circuit  243  has ceased as a result of the interruption of that fault current by the separation of the set of main contacts  5 . 
     When the exemplary bypass magnetic circuit  244  is used with the set of main circuit breaker contacts  5 , the bypass energy advantageously increases and/or lengthens the duration of the clamping power of the magnetic armatures  214 , 216 . As shown in FIGS. 3 and 4, due to the nature of the alternate circuit  244 , a majority of the energy that was passing through the circuit breaker  200  in the primary circuit  243  (FIG. 3) is now redirected from the movable main contact  19 , in order to limit the damage under fault current conditions. As the energy decreases in the two turns of the primary circuit  243  (i.e., the first current loop leg  236  and the intermediate second portion  220  of the secondary movable contact arm  202 ), the corresponding magnetic hold down force on the set of secondary contacts  228  is also decreased. To help minimize that loss, the current path from the bypass magnetic circuit  244  is directed through the magnetic armatures  214 , 216  as shown in FIG.  4 . This increases the magnetic holding force and, at the same time, provides an alternate path for current. This further limits the amount of damage incurred by the set of secondary contacts  228 . 
     Although the flexible braided conductor  246  is shown as being electrically connected to one end of the load conductor  232  and, thus, indirectly to the fixed secondary contact  230 , it may alternatively be electrically connected directly to the load terminal  59  or at about the fixed secondary contact  230 . For example, in order to increase the clamping force of the magnetic armatures  214 , 216 , the primary current path may be routed by one or more loops (not shown) to provide more “amp-turns”. The increased amp-turns increase the magnetic force that the movable armature  214  places on the secondary movable contact arm  202 . This force, in turn, increases the contact force of the set of separable contacts  228 . As another example, a flexible braided conductor (not shown) may be electrically connected between the bimetal  39  (FIG. 3) and the secondary movable contact arm  202 , and pass between the first and second magnetic armatures  214 , 216  for one or more turns, before being electrically connected to that arm  202 . Preferably, a suitable insulating barrier (not shown) is disposed between such conductor and the first and second magnetic armatures  214 , 216 . 
     FIG. 8 shows the closed state of the secondary separable contacts  228  in which an opening force is induced on the secondary movable contact arm  202  through the plunger  87  of the solenoid  13  of FIG.  3 . When a relatively light tack weld (e.g.,  231  of FIG. 9) is present (e.g., arising from electrical operations) between the contact faces  227 , 229 , the solenoid  13 , when energized by the open coil  81 , may not be capable of opening such weld. In order to assist the solenoid  13 , the pivot opening  208  for the pivot legs  206  of the secondary movable contact arm  202  is opened up or elongated, in order to permit sufficient movement. As shown in FIG. 8, the closed state is defined by the lower or second or actuating position (FIG. 3) of the solenoid plunger  87 , with the pivot legs  206  engaging the lower or second end  209  of the pivot opening  208  and being apart from the upper or first end  207  of such pivot opening. When the secondary separable contacts  228  are welded closed, the solenoid  13  may provide insufficient force to move the solenoid plunger  87  to the upper or first or deactuating position until after the pivot legs  206  move apart from the lower or second end  209  of the pivot opening  208  and at least substantially toward the upper or first end  207  of such pivot opening. 
     As shown in FIG. 9, the solenoid plunger  87  has a pivot position intermediate the deactuating position (FIG. 10) and the actuating position (FIG.  8 ). The movement of the plunger  87  from the actuating position to the pivot position (FIG. 9) moves the pivot legs  206  of the secondary movable contact arm  202  to the upper (with respect to FIG. 9) end  207  of the pivot opening  208 , thereby allowing the secondary movable contact  226  to perform a peeling action with respect to the secondary fixed contact  230 . This action helps to tear open the light tack weld  231 . When the pivot legs  206  engage the first or upper end  207  of the pivot opening  208  and are apart from the second or lower end  209  of such pivot opening  208 , the pivot state is provided. Thus, the first portion  218  of the movable contact arm  202  moves to that upper longitudinal position in the pivot state (FIG. 9) and remains there in the open state (FIG.  10 ). 
     After the light tack weld  231  is broken, the set of secondary contacts  228  open to the fully open state of the solenoid  13  of FIG.  3  and the secondary movable contact arm  202 , as shown in FIG.  10 . This open state is defined by the first or upper position of the solenoid plunger  87 , with the pivot legs  206  engaging the first or upper end  207  of the pivot opening  208  and being apart from the second or lower end  209  of such pivot opening. 
     With the set of secondary contacts  228  closed, as best shown in FIG. 3, the coupling pin  107  is depressed, thereby driving the plunger  87  downward to open a gap  125  between the core  83  and the plunger  87 , in order that such set of secondary contacts is closed and held closed by the spring  69 ′. However, with the set of secondary contacts  228  open, as shown in FIG. 10, the plunger  87  engages the core  83  in the first or upper position. In accordance with an important aspect of the present invention, the plunger  87  is set apart from the core  83  with a relatively smaller gap  125 ′ in the third or pivot position of FIG.  9 . In contrast, the plunger  87  is further set apart from the core  83  with the larger gap  125  in the closed position of FIG.  8 . As a result, when the opening coil  81  is energized, the solenoid core  83  attracts the plunger  87  with a relatively greater force in the pivot position (FIG.  9 ), and with a relatively smaller force in the closed position (FIG.  8 ). Hence, the elongated pivot opening  208  permits the plunger  87  to freely move the secondary movable contact arm  202  to the pivot state of FIG. 9, even in the presence of a relatively light tack weld  231  on the separable contact faces  227 , 229 . Then, in the pivot position (FIG.  9 ), the solenoid gap is reduced (e.g., from gap  125  to gap  125 ′), thereby providing greater solenoid force to break the relatively light tack weld  231  as the secondary movable contact arm  202  moves from the pivot position of FIG. 9 to the open position of FIG.  10 . 
     Although the invention has been disclosed in connection with the circuit breaker  200  including the exemplary operating mechanism  7  and thermal-magnetic trip device  9 , the invention is applicable to a wide range of circuit breakers, with or without circuits  243 , 244 , employing a wide range of operating mechanisms and/or one, two or more sets of separable contacts, with or without an operating member/indicator member, such as  101 , and/or trip mechanisms, with or without bimetal conductors, such as  39 . 
     Although a remote controlled circuit breaker having sets of main and secondary contacts is shown, the invention is applicable to a wide range of electrical switching apparatus, such as other circuit breakers, electrical contactors and electrical relays, whether actuated by a solenoid or motor, where a moving conductor or movable contact arm is actuated by an actuator mechanism, which does not generate sufficient force to break a light tack weld between the faces of one or more sets of separable contacts. 
     While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the claims appended and any and all equivalents thereof