Abstract:
A circuit breaker including an adjustable instantaneous trip level. Adjustable instantaneous trip level can be applied to a one-pole and/or two-pole circuit breakers including a thermal and magnetic mechanism, including AFCI, CAFCI, and/or GFCI constructions. The circuit breaker includes a magnet position adjustment mechanism allowing an operator to adjust the instantaneous trip level to a desired setting, such as between about 5 to 10 times the handle rating. The design also allows for alternate magnets to be used for either an increased or decreased instantaneous settings as desired. In two-pole circuit breakers, the instantaneous trip level can be set independently for each mechanism pole. Multi-pole circuit breakers and methods of adjusting instantaneous trip level are provided, as are other aspects.

Description:
RELATED APPLICATION 
       [0001]    This application claims priority to U.S. Provisional Patent Application Ser. No. 62/128,633 filed on Mar. 5, 2015, and entitled “ADJUSTABLE INSTANTANEOUS TRIP FOR A ONE OR TWO-POLE RESIDENTIAL CIRCUIT BREAKER DESIGN,” the disclosure of which is hereby incorporated by reference in its entirety herein. 
     
    
     FIELD 
       [0002]    The present invention relates generally to circuit breakers, and more particularly to adjustability of certain performance parameters of circuit breakers. 
       BACKGROUND 
       [0003]    Conventional residential circuit breakers include a molded case having multiple case pieces (e.g., halves or thirds) forming one or more internal cavities that are configured to accept the various internal circuit breaker components. Some circuit breakers, such as all mechanical single-pole circuit breakers, may include a mechanism pole with a first and second molded case piece housing the internal tripping mechanism components therein. In two-pole electronic circuit breakers, such as ground fault circuit interrupters (GFCIs) type and combination arc fault circuit interrupters (CAFCI) type residential two-pole circuit breakers, an electronic pole may be sandwiched between two mechanism poles. In each case, the mechanism poles may include a moveable contact arm with an attached moveable electrical contact, a stationary electrical contact mounted to the molded case, and a tripping mechanism adapted to separate the stationary and moveable electrical contacts when tripped. 
         [0004]    Conventionally, in one mode of operation, the tripping mechanism allows for manual tripping via throwing a handle of the circuit breaker, but also includes a bi-metal and magnet mechanism that allows for: 1) tripping of the circuit breaker in a thermal mode by motion of the bimetal of a bimetal and magnet mechanism engaging an armature due to internal resistive heating due to a persistent overcurrent situation, and 2) for instantaneous tripping due to high current through the bimetal and magnet mechanism of a magnitude of 5× or more than the rated handle current of the circuit breaker. 
         [0005]    During an instantaneous tripping event, the armature is magnetically attracted to the magnet by magnetic forces generated in the magnet due to the conductance of the high current through the current path including the bimetal. Instantaneous level, as used herein, is the current level at which the circuit breaker will trip due to the abnormally high current (e.g., 5× current) passing through the circuit breaker. As the armature rotates, the latch bite of a latch between the armature and a cradle of the tripping mechanism is decreased. Eventually, when the latch bite gets very small, the cradle is disengaged from the armature and the tripping mechanism will trip. Upon tripping, the moveable and stationary electrical contacts will separate creating an electrical open in the protected branch circuit. 
         [0006]    In existing circuit breaker designs, the magnet is typically welded to the bimetal and the magnet. Because the magnet is welded to the bimetal, the air gap that exists between the magnet and armature is dependent on the bimetal position in the molded case. However, the position of the bimetal may vary due to the welding operations involved in the assembly process. Each time the bimetal is heated to create a welded joint, the bimetal is damaged in the localized areas and may warp and move. Additionally, the bimetal may be welded to connect the load terminal and current braid. Welding processes are controlled by weld parameters for the welding machine, but typically have a relatively large range to work within and thus variations of the bi-metal configuration may occur. 
         [0007]    Because of the possibility of warping, once the welding has been completed, the circuit breaker is thermally calibrated to ensure desired thermal tripping is actually achieved, depending on circuit breaker type. Calibration may be accomplished by adjusting a calibration screw of a thermal calibration mechanism coupled to a portion of the conductive path, such as by adjusting a position of a strap coupled to the bimetal. 
         [0008]    However, calibration of the thermal tripping may inadvertently change the instantaneous level of the circuit breaker. Accordingly, circuit breakers that can achieve more reliable instantaneous trip level are desired. 
       SUMMARY 
       [0009]    In a first aspect, a circuit breaker is provided. The circuit breaker includes a mechanism pole containing a thermal and magnetic mechanism including a bimetal, magnet, and armature, a thermal calibration mechanism configured to adjust thermal tripping of the circuit breaker, and a magnet position adjustment mechanism configured to provide an adjustable instantaneous trip level via moving the magnet to allow adjustment of an air gap between the magnet and the armature. 
         [0010]    In another aspect, a two-pole circuit breaker is provided. The two-pole circuit breaker includes a first mechanism pole containing a first thermal and magnetic mechanism including a first bimetal, first magnet, and first armature, and a first magnet position adjustment mechanism configured to provide an adjustable instantaneous trip level of the first mechanism pole via movement of the first magnet to adjust a first air gap between the first magnet and the first armature; and a second mechanism pole containing a second thermal and magnetic mechanism including a second bimetal, second magnet, and second armature, and a second magnet position adjustment mechanism configured to provide an adjustable instantaneous trip level of the second mechanism pole via movement of the second magnet to adjust a second air gap between the second magnet and the second armature. 
         [0011]    In another aspect, a method of adjusting a circuit breaker is provided. The method includes providing a mechanism pole containing a thermal and magnetic mechanism including a bimetal, magnet, and armature, a thermal calibration mechanism, and a magnet position adjustment mechanism, and adjusting an instantaneous trip level by adjusting a position of the magnet with the magnet position adjustment mechanism to change an air gap between the magnet and the armature. 
         [0012]    Still other aspects, features, and advantages of the present invention may be readily apparent from the following detailed description by illustrating a number of example embodiments and implementations, including the best mode contemplated for carrying out the present invention. The present invention may also be capable of other and different embodiments, and its several details may be modified in various respects, all without departing from the scope of the present invention. Accordingly, the drawings and descriptions are to be regarded as illustrative in nature, and not as restrictive. The invention is to cover all modifications, equivalents, and alternatives falling within the scope of the invention. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0013]    The drawings, described below, are for illustrative purposes only and are not necessarily drawn to scale. The drawings are not intended to limit the scope of the invention in any way. Wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts. 
           [0014]      FIG. 1  illustrates an isometric view of a circuit breaker, such as a two-pole residential circuit breaker (e.g., GFCI or CAFCI), in accordance with one or more embodiments. 
           [0015]      FIG. 2  illustrates a partial top plan view showing an adjustment knob providing external adjustment of an instantaneous trip level of the circuit breaker, such as between a 5× and a 10× handle rating, in accordance with one or more embodiments. 
           [0016]      FIG. 3  illustrates a cross-sectioned top partial view of the adjustment knob interfacing with various parts of the molded case including an adjustment knob block and cover in accordance with one or more embodiments. 
           [0017]      FIG. 4  illustrates a cross-sectioned partial side view of the adjustment knob interfacing with an adjustment knob block, magnet carrier and various other parts of the molded case according to one or more embodiments. 
           [0018]      FIG. 5  illustrates a side view of the mechanism pole (with cover removed) showing the components of a magnet position adjustment mechanism and the components of the tripping assembly according to one or more embodiments. 
           [0019]      FIG. 6  illustrates a side view of the mechanism pole with the components of the magnet position adjustment mechanism shown according to one or more embodiments, with the components of the tripping assembly and other mechanism pole components being removed for clarity. 
           [0020]      FIG. 7A  illustrates an isometric view of some components of a magnet position adjustment mechanism for providing an adjustable instantaneous trip level for a mechanism pole according to one or more embodiments. 
           [0021]      FIG. 7B  illustrates an exploded view of some components of the magnet position adjustment mechanism according to one or more embodiments. 
           [0022]      FIGS. 8A-8C  illustrates various views of an adjustment knob of a magnet position adjustment mechanism according to one or more embodiments. 
           [0023]      FIG. 9  illustrates an isometric view of an adjustment knob block of a magnet position adjustment mechanism according to one or more embodiments. 
           [0024]      FIGS. 10A-10C  illustrates several views with an adjusted small, medium, and large air gap between the armature and the magnet demonstrating the air gap adjustment capability of the magnet position adjustment mechanism according to one or more embodiments. 
           [0025]      FIGS. 11A and 11B  illustrates structural features of a base and cover configured to accept an adjustment knob and an adjustment knob block, respectively, according to one or more embodiments. 
           [0026]      FIG. 12  illustrates a flowchart of a method of adjusting a circuit breaker according to one or more embodiments. 
       
    
    
     DESCRIPTION 
       [0027]    Reference will now be made in detail to the example embodiments of this disclosure, which are illustrated in the accompanying drawings. 
         [0028]    In existing residential circuit breakers, the instantaneous level is not readily adjustable. Moreover, the inventors have recognized that the air gap between the magnet and armature dictates the instantaneous trip level and that the air gap may be quite variable from breaker-to-breaker for various reasons. Variability may arise in existing circuit breaker designs because, as discussed above, the welding operations that have taken place on the bimetal cause a bimetal position relative to the armature to be relatively inconsistent. This positional inconsistency can affect the air gap and therefore the instantaneous level of the circuit breaker. 
         [0029]    For example, in existing CAFCI and/or GFCI 1-pole and/or 2-pole circuit breaker designs, the air gap between the magnet and armature is even more inconsistent because of the thermal calibration adjustment. The thermal calibration mechanism adjustment occurs in order to adjust the trip level of the circuit breaker due to low current causing heating of the bimetal to desired limits. Thus, the air gap is dependent on the bimetal position after this thermal calibration, which can result in an instantaneous trip level that is not consistent from circuit breaker to circuit breaker. 
         [0030]    Additional embodiments of a circuit breaker including an adjustable trip level, various components thereof, and methods of adjusting an instantaneous trip level of a circuit breaker are described with reference to  FIGS. 1-12  herein. 
         [0031]    In one or more embodiments, the adjustment of instantaneous trip level is provided by a mechanism pole that includes a magnet position adjustment mechanism. The magnet position adjustment mechanism may include a rotating knob, rotating magnet carrier, and a magnet. The magnet position adjustment mechanism interfaces with other mechanism module components, such as an armature, and adjustment of the position of the magnet by the magnet position adjustment mechanism changes an air gap between the magnet and the armature. This changes the instantaneous trip level of the circuit breaker. 
         [0032]    Embodiments of the invention may be used on one-pole or two-pole circuit breakers having thermal and magnetic mechanism and thermal/magnetic tripping capability. One or more embodiments of the invention allow independent adjustment, and thus influence over, the instantaneous level of each mechanism pole that are independent of thermal calibration. 
         [0033]    Further details of embodiments of the circuit breaker including adjustable instantaneous trip level and components thereof are described with reference to  FIGS. 1-12  herein. 
         [0034]    Referring now to  FIGS. 1-9 , an embodiment of a two-pole circuit breaker  100  embodied as a GFCI or CAFCI and components thereof are shown and described. The circuit breaker  100  includes a molded case  102  including multiple poles, such as first mechanism pole  104 , second mechanism pole  106 , and an electronic pole  108 . Each pole may be made up of multiple molded case pieces, which may be a polymer, such as a thermoplastic material. The various mechanism and electronic poles  104 ,  106 ,  108  may be assembled together using fasteners  110 , such as rivets, screws, or the like. 
         [0035]    The circuit breaker  100  may further include other conventional components, such as handles  109  and handle interconnector  111  on the front  100 F of the circuit breaker  100 , line side connectors  100 C (e.g., c-clips) on the line side  100 A, and a neutral conductor  100 N (only a portion shown) on the load side  100 B. 
         [0036]    The circuit breaker  100  further includes adjustment of an instantaneous trip level thereof. Instantaneous trip level adjustment may be accomplished for one or both of the first mechanism pole  104  and the second mechanism pole  106 . When used on both, instantaneous trip level adjustments may be made independently of one another. However, it should be apparent that instantaneous trip level adjustment in accordance with one or more embodiments may be advantageously incorporated on one-pole electronic circuit breakers, as well as on all mechanical one-pole and two-pole circuit breakers. 
         [0037]    In one or more embodiments, adjustment of instantaneous trip level of the circuit breaker  100  may be accomplished by one or more magnet position adjustment mechanisms  112 . Each of the magnet position adjustment mechanisms  112  in each respective mechanism pole  104 ,  106  are configured to provide an adjustable instantaneous trip level via moving a magnet  520  ( FIG. 5 ) to allow adjustment of an air gap between a magnet  520  and an armature  522 , as will be explained in detail herein. 
         [0038]    Magnet position adjustment mechanism  112  includes an adjustment knob  114  that is externally accessible and adjustable for each mechanism pole  104 ,  106 . For example, as shown in  FIGS. 1 and 2 , each adjustment knob  114  is provided on a front  100 F of the circuit breaker  100 . As best shown in  FIGS. 4, 6 and 8 , the adjustment knob  114  includes a cam  116 . Any suitable structure may be used for the cam  116  may be used, such as a post offset from a physical centerline of the adjustment knob  114 . For example, the engaging surface  823  of the cam  116  that engages the magnet carrier  415  may be offset from the centerline  824  (the rotational axis) of the adjustment knob  114  by an offset distance “d.” The offset distance “d” may be greater than about 0.50 mm, or even greater than about 0.58 mm, or even between about 0.50 mm and about 0.64 mm in some embodiments, for example. The adjustment knob  114  may include a turning feature  114 F, such as Phillips head slot shown, or the like, that may be used to make the adjustment of instantaneous trip level. Other types of turning features  114 F, such as slot head, hex head or socket, torx, or the like may be used. Adjustment knob  114  may be made of a suitably rigid material, such as a glass-filled polyester or nylon. 
         [0039]    The magnet position adjustment mechanism  112  further includes a magnet carrier  415  including a pivot joint  628  and a first end  615 A engageable with the cam  116  and a second end  615 B opposite the first end  615 A. Magnet carrier  415  may be made of a suitably rigid material, such as a glass-filled polyester or nylon. The second end  615 B may include mounting features  726  that are configured to mount the magnet  520  onto the magnet carrier  415 . Mounting features  726  may comprise one or more magnet carrier posts. However other fastening means, such as fasteners (screws or adhesive or combinations thereof) may be used. 
         [0040]    The magnet  520  may include one or more holes  734  that may be received over the one or more mounting features  726  (e.g., magnet carrier posts). Magnet  520  may be attached to the magnet carrier  415  by press fit of the holes  734  onto the magnet carrier posts. Adhesive may be applied to the back side of the magnet  520  and a mating surface of the magnet carrier  415 . Magnet may be U-shaped member manufactured from a magnetically-permeable material, such as cold-rolled steel. The magnet  520  may include a raised feature  520 R for the armature  522  to contact. 
         [0041]    In the depicted embodiment of  FIG. 6 , the magnet carrier  415  is mounted inside the mechanism pole  104  and is pivotable about a pivot joint  628 . The pivot joint  628  may include a post  630  that may be formed integrally with the molded case  102 , such as on the base  346 , and that is configured to engage with an aperture  732  ( FIG. 7B ) formed in the magnet carrier  415 . The post  630  and aperture  732  are appropriately sized to allow a close slip fit allowing the magnet carrier  415  to freely pivot on the post  630  relative to the molded case  102 . Other types of pivot joints  628  may be used. A retaining member  637  may be received over and lock onto the post  630  to retain a lateral location of the magnet carrier  415  inside of the mechanism pole  104 . 
         [0042]    As shown in  FIGS. 6 through 7B , the magnet carrier  415  includes the first end  615 A on a first side of the pivot joint  628  and a second end  615 B on a second side of the pivot joint  628 , wherein the magnet  520  may be mounted on the second end  615 B. A distance to a center of the magnet  520  from the pivot joint  628  may be between about 11.6 mm and 17.7 mm, for example. A distance between the pivot joint  628  and a portion of the first end  615 A engaging the cam  116  may be between about 11 mm and 13 mm. Other dimensions may be used. 
         [0043]    A return spring  636  may be provided, and may be configured to bias the first end  615 A of the magnet carrier  415  into engagement with the cam  116 . Any suitable return spring  636  may be used, such as the leaf spring shown. Other types of return spring  636  may be adapted to perform the biasing function, such as a coil spring, wave spring, torsion spring, or the like. Furthermore, although shown engaging the first end  615 A, the return spring  636  may be located at any location along the magnet carrier  415  that will provide the biasing contact between the cam  116  and the magnet carrier  415 . 
         [0044]    As discussed above, a retaining member  637 , such as a retaining ring, may be used to secure the magnet carrier  415  onto post  630 . Retaining member  637  may fit in countersink  739  formed in the magnet carrier  415 . The retaining member  637  may include teeth to deform the post  630  when installed, and may be further secured in place with an adhesive, for example. Alternatively, a push-on type or other fastener could be used. 
         [0045]    The return spring  636  may have a suitable shape so that it may be press fit, or otherwise slip onto, a securement member  641  located in the base  346 , as shown in  FIG. 6 . The return spring  636  may be made from a spring steel material, and may include a free end  636 F that may engage with a side of the magnet carrier  415  and may function to interface with and maintain contact and spring bias between the cam  116  of the adjustment knob  114  and an end (e.g., first end  615 A) of the magnet carrier  415 . Return spring  636  may have a spring rate of about 40 to 45 pounds per inch, for example. Other spring rates may be used depending upon the distance from the pivot joint  628 . In the depicted embodiment, a distance between the pivot joint  628  and a portion of the first end  615 A being engaged by the In the depicted embodiment, a distance between the pivot joint  628  and a portion of the first end  615 A being engaged by the return spring  636  may be between about 8.0 mm and 9.0 mm. Other dimensions may be used. 
         [0046]    Referring now to  FIGS. 3, 4, 8, and 9  the adjustment knob  114  may include a first stop feature  338  that is engageable with second stop features  340 A,  340 B. Second stop features  340 A,  340 B may be formed in an adjustment knob block  242  or elsewhere in the molded case  102 . The adjustment knob block  242  may contain a cavity  343  in which the first stop feature  338  may rotate and stop, as needed. The engagement of the first stop feature  338  with second stop features  340 A,  340 B functions to limit a rotational excursion of the adjustment knob  114  in either direction within rotational limits. The separation between the second stop features  340 A,  340 B limits the maximum rotation in either direction. Limits may be a rotational excursion of between about 20 degrees and about 30 degrees, for example. Other rotational limits may be used. Adjustment knob  114  may be inserted into, and be rotatable in, a recess  335  of a cover  344  of the mechanism pole  104  in some embodiments, as shown in  FIG. 3 . Likewise, the adjustment knob block  242  may be inserted into a pocket  345  formed in the base  346  of the molded case  102  of the mechanism pole  104 . 
         [0047]    In one or more embodiments, the adjustment knob  114  may include an indexing feature  348  that may be engageable with detent features  350  to provide for an incremental adjustment of the instantaneous trip level between two or more values. The indexing feature  348  and detent features  350  interact and engage to lock the adjustment knob  114  into multiple preset positions. For example, the incremental adjustment may include at least increments of five times (5×) and ten times (10×) of the handle rating of the circuit breaker  100 . Other increments may be provided as well including, for example, one or more of 6×, 7×, 7.5×, 8×, and 9×. Other increments may be used. 
         [0048]    As shown in  FIGS. 2 and 8A-8C , a top of the adjustment knob  114  may include an indicator feature  252 , such as a mark or other indicia, configured to align the adjustment knob  114  with the setting indicators  253  (e.g., 5× or 10×) provided on the adjustment knob block  242  (or optionally on the base  346 ). 
         [0049]    The rotation of the adjustment knob  114  may be accomplished by inserting a screw driver or other implement into the turning feature  114 F located on the top of the adjustment knob  114 . Rotating the adjustment knob  114  between the limits (e.g., 5× and 10× settings) will increase or decrease the air gap “G” between the magnet  520  and armature  522  as shown in  FIGS. 10A-10C . 
         [0050]    As the adjustment knob  114  is rotated, detent features  350  formed or provided in the cover (or optionally, the base  346 ) interface with the indexing feature  348 . As best shown in  FIGS. 3 and 4 , the adjustment knob  114  is held in place by the surrounding geometry and the interaction of the indexing feature  348  and the detent features  350 . In particular, retention features of the base  346  (e.g., grooves) and cover  344  (e.g., grooves) may secure the adjustment knob  114  in position, as well as the adjustment knob block  242 . 
         [0051]    The adjustment knob block  242  may include a first retention feature  453 , such as a rib, that interfaces with a second retention feature  454 , such as a groove or grooves formed in the base  346  and/or cover  344 , for example. The adjustment knob  114  may include, for example, a rib as the first retention feature  453  that extends entirely or part way around the body of the adjustment knob  114 . Rib may interface with the second retention features  454  on the cover  344  and even third features  455  (e.g., a groove) formed on the adjustment knob block  242 . This rib located on the adjustment knob  114  engages with the grooves on the cover  344  and the adjustment knob block  242  to secure the adjustment knob  114  in place after assembly. Likewise, the adjustment knob block  242  may include fourth retention features  456  (e.g., ribs) that interface with fifth retention features  457  (e.g., grooves) to retain the adjustment knob block  242  in the molded case  102  (e.g., in the base  346 ). 
         [0052]    According to one or more embodiments, a circuit breaker  100  (e.g., a residential circuit breaker) including a mechanism pole (e.g., mechanism pole  104 ) containing, as shown in  FIG. 5 , a thermal and magnetic mechanism  516  is provided. Thermal and magnetic mechanism  516  is configured to adjust thermal tripping of the circuit breaker  100 . Thermal and magnetic mechanism  516  includes a bimetal  518 , magnet  520 , and armature  522  as is conventional, except that in embodiments of the present invention, the bimetal  518  is not attached to the magnet  520 . Bimetal  518  is disconnected from the magnet  520 . The ramifications of this construction will become apparent below. The mechanism pole (e.g.,  104  and/or  106 ) and the thermal and magnetic mechanism  516  may be part of an electronic circuit breaker including an electronic pole  108  (either one-pol or two-pole). In one or more embodiment, the circuit breaker  100  may be a two-pole circuit breaker and may comprise the mechanism pole  104  and a second mechanism pole  106  containing a second thermal and magnetic mechanism (identical to thermal and magnetic mechanism  516 ) that is independently adjustable. 
         [0053]    In one or more embodiments, magnet position adjustment mechanisms may be provided in a two-pole circuit breaker  100  as shown in  FIG. 1 . In this embodiment, the first mechanism pole  104  contains the first thermal and magnetic mechanism  516  including a bimetal  518 , magnet  520 , and armature  522 , and a magnet position adjustment mechanism  112  configured to provide an adjustable instantaneous trip level of the first mechanism pole  104  via movement the magnet  520  to adjust a first air gap between the magnet  520  and the armature  522 . Two-pole circuit breaker also includes a second mechanism pole  106  containing a second thermal and magnetic mechanism (identical to first thermal and magnetic mechanism  516 ) including a second bimetal, second magnet, and second armature (each identical to bimetal  518 , magnet  520 , and armature  522 ), and a second magnet position adjustment mechanism that may be identical to the magnet position adjustment mechanism  112  or a mirror image thereof. Second magnet position adjustment mechanism may be configured to provide an adjustable instantaneous trip level of the second mechanism pole  106  via movement of the second magnet to adjust a second air gap between the second magnet and the second armature 
         [0054]    In one tripping sequence, i.e., thermal tripping, the thermal and magnetic mechanism  516  is adapted to trip the circuit breaker  100  when the bimetal  518  heats to a certain heating level due to a persistent electrical overcurrent condition. The heating (resistive heating) causes bending of the bimetal  518  due to differential coefficients of expansion of the metal strips making up the bimetal  518 , and causes the end of the bimetal  518  to engage with the armature  522 . After sufficient heating and bending, a tripping mechanism  525  will be released. Tripping mechanism  525  includes conventional components such as cradle  527  pivotable about cradle pivot  527 P, moveable contact arm  529  including moveable electrical contact  529 M, and cradle spring  531  connecting cradle  527  and moveable contact arm  529 . Also shown is a thermal calibration mechanism  528  which is operable to adjust the thermal tripping of the circuit breaker  100 . Thermal calibration mechanism  528  includes an adjustment screw  528 S which threads into strap  533 . Adjustment of the adjustment screw bends the strap  533  between points on then housing  102  and calibrates the thermal trip level to a desired value, such as between a range of values. 
         [0055]    The present thermal and magnetic mechanism  516  is configured to adjust thermal tripping of the circuit breaker  100 , as was the case in the prior art. However, as discussed above, in prior art circuit breakers including conventional structure, a thermal calibration mechanism adjustment not only adjusts the thermal trip point, but also may affect the instantaneous trip level of the circuit breaker. This is not the case with embodiments of the invention. In the instant thermal and magnetic mechanism  516  of the circuit breaker  100 , the bimetal  518  is not connected to the magnet  520  and the position of the magnet  520  may move relative to the bimetal  518 . This has the advantageous effect of making the instantaneous trip level insensitive to thermal calibration mechanism adjustments. 
         [0056]      FIGS. 10A-10C  illustrates the magnet position adjustment mechanism  112  with a small air gap G 1 , a medium air gap G 2 , and a large air gap G 3 . During an instantaneous trip condition or event in one mechanism pole (e.g., mechanism pole  104  or  106 ), the armature  522  is attracted to the magnet  520  by a magnetic force that is generated in the magnet  520  as current flows thru the current path including the bimetal  518  of the circuit breaker  100 . This attraction varies depending on the air gap G between the armature  522  and magnet  520 . Rotating the adjustment knob  114  of the magnet position adjustment mechanism  112  can increase or decrease this air gap G as shown in table 1 below. This changes the instantaneous trip level. 
         [0000]    
       
         
               
             
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Air gap adjustment 
               
             
          
           
               
                   
                   
                 Factor of 
               
               
                   
                   
                 Breaker 
               
               
                   
                   
                 Handle 
               
               
                 Knob Position 
                 Air gap (G) 
                 Rating 
               
               
                   
               
               
                 1 
                 0.020 inch 
                     5X 
               
               
                 2 
                 0.052 inch 
                 7.5X 
               
               
                 3 
                 0.096 inch 
                  10X 
               
               
                   
               
             
          
         
       
     
         [0057]    As shown, due to the magnetic attraction, the armature  522  rotates in a counterclockwise direction and touches the magnet raised features  520 R. The small area of contact between the magnet  520  and armature  522  reduces the magnetic attraction force once the current is broken. This armature rotation decreases the cradle  527  to armature  522  latch bite. When the latching surface becomes too small to maintain, the cradle  527  is released and rotates clockwise and the tripping mechanism  525  will open the contacts and break the circuit. 
         [0058]      FIGS. 11A and 11B  illustrate partial isometric views of the cover  344  and base  346 , respectively, of the molded case  102  ( FIGS. 3 and 4 ). Illustrated are the pocket  345  in the base  346  that accepts the adjustment knob block  242  ( FIG. 9 ) and the recess  335  that accepts the adjustment knob  114 . 
         [0059]    Referring now to  FIG. 12 , a method of adjusting a circuit breaker  100  is provided. The method  1200  includes, in  1202 , providing a mechanism pole (e.g., mechanism pole  104  or  106 ) containing a thermal and magnetic mechanism (e.g., thermal and magnetic mechanism  516 ) including a bimetal (e.g., bimetal  518 ), magnet (e.g., magnet  520 ), and armature (e.g., armature  522 ), a thermal calibration mechanism (e.g., thermal calibration mechanism), and a magnet position adjustment mechanism (e.g., magnet position adjustment mechanism  112 ). 
         [0060]    The method  1200  includes, in  1204 , adjusting an instantaneous trip level by adjusting a position of the magnet (e.g., magnet  520 ) with the magnet position adjustment mechanism (e.g., magnet position adjustment mechanism  112 ) to change an air gap (e.g., air gap G) between the magnet (e.g., magnet  520 ) and the armature (e.g., armature  522 ). 
         [0061]    While the invention is susceptible to various modifications and alternative forms, specific embodiments and methods thereof have been shown by way of example in the drawings and are described in detail herein. It should be understood, however, that it is not intended to limit the invention to the particular apparatus, systems or methods disclosed, but, to the contrary, the intention is to cover all modifications, equivalents and alternatives falling within the scope of the invention.