Abstract:
A circuit breaker ( 10 ) including a terminal barrier system ( 140 ). The terminal barrier system ( 140 ) includes a terminal barrier ( 142 ) attached to a circuit breaker base ( 12 ) at the terminals ( 16, 18 ), line and load, of the breaker ( 10 ) and a terminal connector ( 144 ) mounted in the terminal barrier ( 142 ) to align with a terminal ( 16, 18 ) of the breaker ( 10 ). Several embodiments of the terminal barrier ( 142 ) and terminal connector ( 144 ) are provided which allow flexibility in combining the various terminal barriers and terminal connectors for a given current rating of the breaker ( 10 ). The terminal barrier system ( 140 ) protects the terminals ( 16, 18 ) of the circuit breaker during short circuit condition operations, prevents pole to pole electrification and prevents accidental contact with live electrical wires in the contacts ( 42, 44 ). The circuit breaker ( 10 ) also includes a molded case ( 12 ), a first and second terminal ( 18, 16 ) mounted in the case ( 12 ), the first contact ( 44 ) electrically coupled to the first terminal ( 18 ) and a second contact ( 42 ) electrically coupled to the second terminal ( 16 ). An operating mechanism ( 40 ) having a pivoting member ( 13 ) movable between an ON position, and OFF position and a TRIPPED position is coupled to the second contact ( 44 ). An intermediate latch mechanism ( 52 ) mounted in the housing ( 12 )is coupled to the operating mechanism ( 40 ) and is selectively operated by a trip unit ( 60 ) coupled to the second contact ( 42 ) and the second terminal ( 16 ). An electric arc extinguishing apparatus ( 105 ) is mounted in the housing ( 12 ) and positioned in confronting relation with the first and second contact. ( 42, 44 )

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to a field of circuit breakers, and more particularly to a molded case circuit breaker terminal barrier system. 
     BACKGROUND OF THE INVENTION 
     In general the function of a circuit breaker is to electrically engage and disengage a selected circuit from an electrical power supply. This function occurs by engaging and disengaging a pair of operating contacts for each phase of the circuit breaker. The circuit breaker provides protection against persistent overcurrent conditions and against the very high currents produced by short circuits. Typically, one of each pair of the operating contacts are supported by a pivoting contact arm while the other operating contact is substantially stationary. The contact arm is pivoted by an operating mechanism such that the movable contact supported by the contact arm can be engaged and disengaged from the stationary contact. 
     There are two modes by which the operating mechanism for the circuit breaker can disengage the operating contacts: the circuit breaker operating handle can be used to activate the operating mechanism; or a tripping mechanism, responsive to unacceptable levels of current carried by the circuit breaker, can be used to activate the operating mechanism. For many circuit breakers, the operating handle is coupled to the operating mechanism such that when the tripping mechanism activates the operating mechanism to separate the contacts, the operating handle moves to a fault or tripped position. 
     To engage the operating contacts of the circuit breaker, the circuit breaker operating handle is used to activate the operating mechanism such that the movable contact(s) engage the stationary contact(s). A motor coupled to the circuit breaker operating handle can also be used to engage or disengage the operating contacts. The motor can be remotely operated. 
     A typical industrial circuit breaker will have a continuous current rating ranging from as low as 15 amps to as high as 1600 amps. The tripping mechanism for the breaker usually consists of a thermal overload release and a magnetic short circuit release. The thermal overload release operates by means of a bi-metalic element, in which current flowing through the conducting path of a circuit breaker generates heat in the bi-metal element, which causes the bi-metal to deflect and trip the breaker. The heat generated in the bi-metal is a function of the amount of current flowing through the bi-metal as well as for the period of time that that current is flowing. For a given range of current ratings, the bi-metal cross-section and related elements are specifically selected for such current range resulting in a number of different circuit breakers for each current range. 
     In the event of current levels above the normal operating level of the thermal overload release, it is desirable to trip the breaker without any intentional delay, as in the case of a short circuit in the protected circuit, therefore, an electromagnetic trip element is generally used. During the short circuit condition operation of the circuit breaker gas and plasma is generated as the contacts in the circuit breaker move apart. Such gasses are directed into an arc chute for expulsion outside of the circuit breaker. That expulsion usually occurs at or near line terminals which can damage the cable connection, the terminals themselves or cause arcing on a pole-to-pole or pole-to-ground basis as the gas and plasma exit the circuit breaker. In addition, accidental contact with the live connectors of the circuit breaker should be avoided by the operator or installer of the circuit breaker. Further, it is desirable to reduce the likelihood that a small object accidentally dropped, for example a bolt or a nut, could become lodged underneath the breaker terminals in a manner that would reduce electrical clearances. 
     Thus, there is a need for a terminal barrier system that will protect the circuit breaker terminals from the gasses generated during a short circuit operation of the circuit breaker. There is also a need to provided a terminal barrier system that prevents pole to pole electrification. There is a further need to provide a barrier terminal system that prevents accidental contact with the live electrical connections in a circuit breaker. There is a further need for a terminal barrier system that will help prevent small objects from accidentally becoming lodged underneath the breaker terminals. Further, there is a need for a terminal barrier system that has interchangeable parts to accommodate a range of continuous current ratings of circuit breakers. 
     SUMMARY OF THE INVENTION 
     A circuit breaker of the present invention includes a terminal barrier system. The terminal barrier system comprises a terminal barrier attached to the circuit breaker base at the terminals, line and load, of the breaker and a terminal connector mounted in the terminal barrier to align with a terminal of the breaker. Several embodiments of the terminal barrier and terminal connector are provided which allow flexibility in combining the various terminal barriers and terminal connectors for a given current rating of the breaker. The terminal barrier system protects the terminals of the circuit breaker during short circuit condition operations, prevents pole-to-pole and pole-to-ground electrification and prevents accidental contact by persons or small objects with live electrical conductor at the breaker terminal. The circuit breaker also includes a molded case, a first and second terminal mounted in the case, the first contact electrically coupled to the first terminal and a second contact electrically coupled to the second terminal. An operating mechanism having a pivoting member movable between an ON position, and OFF position and a TRIPPED position is coupled to the second contact. An intermediate latch mechanism mounted in the housing is coupled to the operating mechanism and is selectively operated by a trip unit coupled to the second contact and the second terminal. An electric arc extinguishing apparatus is mounted in the housing and positioned in confronting relation with the first and second contact. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a perspective view of a molded case circuit breaker which includes an embodiment of the present terminal barrier system. 
     FIG. 2 is a section view of the circuit breaker shown in FIG. 1 along the lines  2 — 2  and is used to describe the operation of one embodiment of the circuit breaker. 
     FIG.  2   a  is an exploded isometric drawing of the operating mechanism, contact structure and bi-metal trip unit of the circuit breaker shown in FIG.  1 . 
     FIG.  2   b  is an illustration of the circuit breaker cover for the circuit breaker shown in FIG.  1 . 
     FIG.  3   a  is a perspective view of an embodiment of the terminal barrier and a nut plate. 
     FIG.  3   b  is a perspective view of another embodiment of the terminal barrier and a nut plate. 
     FIG.  3   c  is a perspective view of another embodiment of the terminal barrier and a nut plate. 
     FIG. 4 is a perspective view of another embodiment of the terminal barrier with a shield extension and a nut plate. 
     FIG. 5 is an exploded view of another embodiment of the terminal barrier with a shield extension and a connector lug. 
     FIG. 6 is a perspective view of the terminal barrier shown in FIG. 5 with the connector lug mounted in the shield extension. 
     FIG. 7 is a sectional side view of another embodiment of the present circuit breaker having a housing containing the operating mechanism, arc chute, line terminal and an embodiment of the present terminal barrier system and a housing containing an embodiment of a trip unit and load terminal. 
     FIG. 8 is a bottom plan view of the circuit breaker housing shown in FIG. 7 containing the operating mechanism, arc chute, line terminals and an embodiment of the present terminal barrier system illustrating the flow of gas generated during a short-circuit trip condition of the circuit breaker. 
     FIG. 9 is an end plan view of an embodiment of a connector lug. 
     FIG. 10 is a section view of the connector lug shown in FIG. 9 along the line  10 — 10 . 
     FIG. 11 is an end plan view of another embodiment of a connector lug. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     FIG. 1 generally illustrates a three phase molded case circuit breaker  10  of the type which includes an operating mechanism  40  having a pivoting member  13  with a handle  14 . The pivoting member  13  and handle  14  are moveable between an ON position, an OFF position and a TRIPPED position. The exemplary circuit breaker  10  is a three pole breaker having three sets of contacts for interrupting current in each of the three respective electrical transmission phases. In the exemplary embodiment of the invention, each phase includes separate breaker contacts and a separate trip mechanism. The center pole circuit breaker includes an operating mechanism which controls the switching of all three poles of the breaker. Although an embodiment of the present invention is described in the context of the three phase circuit breaker, it is contemplated that it may be practiced in a single phase circuit breaker or in other multi-phase circuit breakers. 
     Referring to FIG. 2., handle  14  is operable between the ON and OFF positions to enable a contact operating mechanism  40  to engage and disengage a moveable contact  42  and a stationary contact  44  for each of the three phases, such that the line terminal  18  and load terminal  16  of each phase can be electrically connected. The circuit breaker housing  12  includes three portions which are molded from an insulating material. These portions include a circuit breaker base  12 , a sub-base  12   a,  a main circuit breaker cover  20  and an accessory cover  28 , with the main breaker cover  20  and the accessory cover  28  having an opening  29  for the handle  14  of the pivoting member  13 . The pivoting member  13  and handle  14  move within the opening  29  during the several operations of the circuit breaker  10 . FIG. 2 is a cut away view of the circuit breaker  10  along the lines  2 — 2  shown in FIG.  1 . As shown in FIG. 2, the main components of the circuit breaker are a fixed line contact arm  46  and a moveable load contact arm  45 . It should be noted that another embodiment of the circuit breaker  10  has a movable line contact arm to facilitate a faster current interruption action. The load contact arms for each of the three phases of the exemplary breaker are mechanically connected together by an insulating cross bar member  55 . This cross bar member  55 , in turn, is mechanically coupled to the operating mechanism  40  so that, by moving the handle  14  from left to right, the cross bar  55  rotates in a clockwise direction and all three load contact arms  45  are concurrently moved to engage their corresponding line contact arms  46 , thereby making electrical contact between moveable contact pad  42  and stationary contact pad  44 . 
     The operating mechanism  40  includes a cradle  41  which engages an intermediate latch  52  to hold the contacts of the circuit breaker in a closed position unless and until an over current condition occurs, which causes the circuit breaker to trip. A portion of the moveable contact arm  45  and the stationary contact bus  46  are contained in an arc chamber  56 . Each pole of the circuit breaker  10  is provided with an arc chamber  56  which is molded from an insulating material and is part of the circuit breaker  10  housing  12 . A plurality of arc plates  58  are maintained in the arc chamber  56 . The arc plates facilitate the extension and cooling of the arc formed when the circuit breaker  10  is opened while under a load and drawing current. The arc chamber  56  and arc plates  58  direct the arc away from the operating mechanism  40 . 
     The exemplary intermediate latch  52  is generally Z-shaped having an upper leg which includes a latch surface that engages the cradle  41  and a lower leg having a latch surface which engages a trip bar  54 . The center portion of the Z-shaped intermediate latch element  52  is angled with respect to the upper and lower legs and includes two tabs which provide a pivot edge for the intermediate latch  52  when it is inserted into the mechanical frame  51 . As shown in FIG. 2, the intermediate latch  52  is coupled to a torsion spring  53  which is retained in the mechanical frame  51  by the mounting tabs of the intermediate latch  52 . The torsion spring  53  biases the upper latch surface of the intermediate latch  52  toward the cradle  41  while at the same time biasing the trip bar  54  into a position which engages the lower latch surface of the intermediate latch  52 . The trip bar  54  pivots in a counter clockwise direction about an axis  54   a,  responsive to a force exerted by a bi-metalic element  62 , during, for example, a long duration over current condition. As the trip bar  54  rotates, in a counter clockwise direction, the latch surface on the upper portion of the trip bar disengages the latch surface on the lower portion of the intermediate latch  52 . When this latch surface of the intermediate latch  52  is disengaged, the intermediate latch  52  rotates in a counter clockwise direction under the force of the operating mechanism  40 , exerted through a cradle  41 . In the exemplary circuit breaker, this force is provided by a tension spring  50 . Tension is applied to the spring when the breaker toggle handle  14  is moved from the open position to the closed position. More than one tension spring  50  may be utilized. 
     As the intermediate latch  52  rotates responsive to the upward force exerted by the cradle  41 , it releases the latch on the operating mechanism  40 , allowing the cradle  41  to rotate in a clockwise direction. When the cradle  41  rotates, the operating mechanism  40  is released and the cross bar  55  rotates in a counter clockwise direction to move the load contact arms  45  away from the line contact arms  46 . 
     During normal operation of the circuit breaker, current flows from the line terminal  18  through the line contact arm  46  and its stationary contact pad  44  to the load contact arm  45  through its contact pad  42 . From the load contact arm  45 , the current flows through a flexible braid  48  to the bi-metalic element  62  and from the bi-metalic element  62  to the load terminal  16 . (See FIG.  2   a ) When the current flowing through the circuit breaker exceeds the rated current for the breaker, it heats the bi-metalic element  62 , causing the element  62  to bend towards the trip bar  54 . If the over current condition persists, the bi-metalic element  62  bends sufficiently to engage the trip bar surface. As the bi-metalic element engages the trip bar surface and continues to bend, it causes the trip bar  54  to rotate in a counter clockwise direction releasing the intermediate latch  52  and thus unlatching the operating mechanism  40  of the circuit breaker. 
     FIG.  2   a  is an exploded isometric drawing which illustrates the construction of a portion of the circuit breaker shown in FIG.  2 . In FIG.  2   a  only the load contact arm  45  of the center pole of the circuit breaker is shown. This load contact arm  45  as well as the contact arms for the other two poles, are fixed in position in the cross bar element  55 . As mentioned above, additional poles, such as a four pole molded case circuit breaker can utilize the same construction as described herein, with the fourth pole allocated to a neutral. The load contact arm  45  is coupled to the bi-metalic element  62  by a flexible conductor  48  (e.g. braided copper strand). As shown in FIG.  2   a,  current flows from the flexible conductor  48  through the bi-metalic element  62  to a connection at the top of the bi-metalic element  62  which couples the current to the load terminal  16  through the load bus  61 . The load bus  61  is supported by a load bus support  63 . It should be noted that more than one flexible conductor  48  may be utilized. 
     In the exemplary circuit breaker  10 , the cross bar  55  is coupled to the operating mechanism  40 , which is held in place in the base or housing  12  of the molded case circuit breaker  10  by a mechanical frame  51 . The key element of the operating mechanism  40  is the cradle  41 . As shown in FIG.  2   a,  the cradle  41  includes a latch surface  41   a  which engages the upper latch surface in the intermediate latch  52 . The intermediate latch  52  is held in place by its mounting tabs which extend through the respective openings  51   a  on either side of the mechanical frame  51 . In the exemplary embodiment of the circuit breaker, the two side members of the mechanical frame  51  support the operating mechanism  40  of the circuit breaker  10  and retain the operating mechanism  40  in the base  12  of the circuit breaker  10 . 
     FIG.  2   b  illustrates the main breaker cover  20 . The breaker cover  20 , in the preferred embodiment, has two accessory sockets  22  formed in the cover  20 , with one accessory socket  22  on either side of the opening  29  for the pivoting member  13  and handle  14 . The breaker cover  20  with the accessory sockets  22  or compartments can be formed, usually by well known molding techniques, as an integral unit. The accessory socket  22  can also be fabricated separately and attached to the breaker cover  20  by any suitable method such as with fasteners or adhesives. The main breaker cover  20  is sized to cover the operating mechanism  40 , the moveable contact  42  and the stationary contact  44 , as well as the trip mechanism  60  of the circuit breaker  10 . The breaker cover has an opening  29  to accommodate the handle  14 . 
     Each accessory socket or compartment  22  is provided with a plurality of openings  24 . The accessory socket openings  24  are positioned in the socket  22  to facilitate coupling of an accessory  80  with the operating mechanism  40  mounted in the housing  12 . The accessory socket openings  24  also facilitate simultaneous coupling of an accessory  80  with different parts of the operating mechanism  40 . Various accessories  80  can be mounted in the accessory compartment  22  to perform various functions. Some accessories, such as a shunt trip, will trip the circuit breaker  10 , upon receiving a remote signal, by pushing the trip bar  54  in a counter clockwise direction causing release of the mechanism latch  52  of the operating mechanism  40 . The shunt trip has a member protruding through one of the openings in the accessory socket  22  and engages the operating mechanism  40 . Another accessory, such as an auxiliary switch, provides a signal indicating the status of the circuit breaker  10 , e.g. “on” or “off”. When the auxiliary switch is nested in the accessory socket  22 , a member on the switch assembly protrudes through one of the openings  24  in the socket  22  and is in engagement with the operating mechanism  40 , typically the cross bar  55 . Multiple switches can be nested in one accessory socket  22  and each switch can engage the operating mechanism through a different opening  24  in the socket  22 . 
     In normal operation and especially in operation under a short circuit condition, the circuit breaker  10  generates gasses in the arc chamber  56 . These gasses, are expelled from the breaker  10  through the arc chute assembly  105  in each of the poles of the circuit breaker  10 . FIG. 8 illustrates a typical gas flow from the arc chute assemblies  105  past the line terminals  18  of the circuit breaker  10 . A terminal barrier system  140  is provided for each terminal  16 ,  18 . Although, in typical circuit breaker operation gasses are expelled usually only from the line terminal  18  side of the circuit breaker  10 , the terminal barrier system  140  is also used on the load side of the breaker since there are other functions of the terminal barrier system  140  disclosed herein and will be described below. 
     There are several embodiments for the terminal barrier system  140  with interchangeable parts to provide a range of protection and electrical clearances for various operating current ratings of the circuit breakers. The terminal barrier system  140  generally comprises the terminal barrier  142  which attaches to the circuit breaker base  12  at the line terminal  18  and load terminal  16  and a terminal connector  144  which is mounted in the terminal barrier  142  and aligns with the terminal  16 ,  18  of the circuit breaker  10 . FIGS.  3   a,    3   b,    3   c,    4 ,  5  and  7  illustrate several embodiments of the present terminal barrier system  140 . 
     One embodiment of the terminal barrier system  140  is provided with a nut plate  146  type terminal connector  144 . The nut plate  146  has a mounting portion  148  which is provided with a substantially central hole. See FIG.  4 . The mounting nut  146  also has aligned at a substantially right angle to the mounting portion  148  a terminal hole portion  150 . The terminal hole portion  150  is provided with a substantially central hole  152  that is threaded to receive a mounting fastener  170 . The mounting fastener can be used to attach the terminal barrier system  140  directly to the circuit breaker terminal  16  or  18 , or can be used to mount a connector lug  166  (as will be described below) or can be used to attach a cable connector or bus strap to the terminals,  16  or  18 . The nut plate is attached to the terminal barrier  142  by staking the mounting portion  148  to a mounting post  143 . The attachment can be done by ultra-sound or by heating. It could also be accomplished with a rivet or threaded fastener. When the nut plate is mounted in the terminal barrier  142 , the terminal hole portion  150  of the terminal connector  144  is offset, that is not touching the terminal portion  154  (FIG.  3   a,    3   b,    3   c ) as explained below, from the terminal barrier  142 . The right angle feature of the nut plate  146  formed by the mounting portion  148  and the terminal hole portion  150  improves electrical creepage and through-air clearances for applicable electrical ratings and standards. When so mounted as shown in FIGS.  3   a,    3   b,    3   c  and  7 , the cantilevered terminal hole portion  150  of the terminal connector  144  does not touch the sidewalls  160  of the terminal barrier  142 . The terminal barrier  142  has a terminal connection portion  154  and a shield portion  156 . The nut plate  146  installation described above places the nut plate  146  in the terminal connection portion  154  of the terminal barrier  142 . The shield portion  156  can be of a size and shape that encloses the lower side of the circuit breaker base  12  and depends on the particular design of the molded circuit breaker housing  12 . FIGS. 2 and 7 illustrate two embodiments of the shield portion  156  mounted into two embodiments of the present circuit breaker  10 . 
     Another embodiment of the terminal barrier system  140  provides the shield portion  156  with a shield extension  158 , see FIGS. 4,  5 ,  6  and  7 . The shield extension  158  comprises of a pair of spaced apart parallel sidewalls  160  and a cross piece  162  connecting the two sidewalls  160  at one end. The length of the sidewalls  160  can be of any convenient dimension depending on the size and rating of the circuit breaker to which it is mounted. FIG. 7 illustrates an embodiment of the terminal barrier system  140  having a shield extension  158 . The cross piece  162  connects the two sidewalls  158  but also provides a protection of a clamp screw  165  and protects the terminal during gas expulsion on the line side of the circuit breaker  10  (see FIG.  8 ). The shape and dimensions of the cross piece  162  can be selected in accord with the specific application and current rating of the circuit breaker  10 . 
     Another embodiment of the terminal barrier system  140  provides that each sidewall  160  has a mounting rib  164  with a terminal connector  144  being a connector lug  166  mounted in the shield extension  158  shield portion  156  of the terminal barrier  142 . The connector lug  166  is provided with a slot  168  corresponding to the mounting rib  164  for securing the lug  166  in the shield extension  158  shield portion  156 . See FIG.  5 . The mounting rib  164  can be molded into the sidewall  160  of the shield extension  158 . The mounting rib  164  fitting into a slot  168  in the terminal connector  144  provides a snap fit retention so that the terminal barrier  142  and the terminal connector  144  can be assembled as a unit. The slots  168  in the terminal connector  144  are longer than the mounting rib  164  and allow the connector  144  to slide vertically with respect to the shield extension  158 . This allows the connector dowel  167  to enter the terminal hole  152 . Prior to tightening the cable clamp  165  to the terminal,  16 ,  18 , a resilient member  155  retains the connector lug  166  in place. (See FIG. 5) Further, after the load or line cable is installed and the cable clamp  165  is tightened, the connector  144  is secured to the terminal  16 ,  18 . The rib  164  engaged in the slot  168  prevents the shield extension  158  of the shield portion  156  of the terminal barrier  142  of the present terminal barrier system  140  from becoming separated from the circuit breaker  10  during a short circuit interruption. The gasses generated during the breaker operation outgassing from the arc chamber  56  tends to blow against the terminal barrier  142 . The mounting ribs  164  assist in keeping the terminal barrier  142  installed in the circuit breaker. 
     Another embodiment of the terminal barrier system  140  provides a connector lug  166  type of terminal connector  144  mounted in the shield portion  156  and connected to the circuit breaker terminal  16 ,  18  with the fastener  170 . See FIG.  7 . The connector lug can be fabricated from steel or aluminum and fits within the sidewalls  160  of the shield portion  156  and specifically within the shield extension  158  portion of the terminal barrier  142  of the terminal barrier system  140 . The lug may be coated with an appropriate electrical conducting corrosion resistant plating. 
     The various embodiments described above provide a system in which the various parts such as the terminal barrier  142  of the type illustrated in FIGS.  3   a,    3   b  and  3   c  or the type illustrated in FIG. 4, or  6  or  7  can be assembled with several embodiments of the terminal connector  144 . The nut plate  146  can be fabricated in steel or aluminum or copper and can have different cross sectional thicknesses depending upon the current rating for the circuit breaker  10  application. The nut plate  146  may be coated with an electrical conductive, corrosion resistant plating. 
     The terminal barrier system  140  is installed in the circuit breaker housing base  12  by inserting the terminal barrier system  140  within a separate molded pole area for each pole of the circuit breaker  10 . The same arrangement for the line side  18  and the load side  16  terminals of the circuit breaker can be utilized or different terminal barrier  142 /terminal connector  144  combinations can be utilized. One embodiment of the terminal barrier system  140  provides the terminal barrier  142  with a plurality of protrusions  141  that correspond to a plurality of slots  145  in the housing base  12  of the circuit breaker  10  to attach the terminal barrier  142  to the circuit breaker  10 . It should be understood that it is also possible that the terminal barrier  142  is provided with a plurality of slots that correspond to a plurality of protrusions in the housing base  12  of the circuit breaker  10  to attach the terminal barrier  142  to the circuit breaker  10 . 
     The line terminal  18  and load terminal  16  of a typical circuit breaker is provided with a hole for purposes of mounting the cable from the line source to the load device. The hole in the terminal is aligned with the hole  152  in the nut plate  146  and the two are fastened together with an appropriate fastener such as a screw, bolt or a rivet. If the connector lug  166  type terminal connector  144  is utilized, a fastener  170  can be used to attach the terminal barrier system  140  to each circuit breaker terminal  16 ,  18  in a manner similar to that used with the nut plate  146  or with a dowel  167  formed in one side of the connector lug  166  that engages the hole in the circuit breaker terminal  16 ,  18 . Such arrangement fixes the connector lug  166  in the terminal barrier  142  in position when the clamping screw  165  of the connector lug  166  is tightened against a cable inserted into the connector lug  166 . Several types of connector lugs are illustrated in FIGS. 7,  9 ,  10  and  11  which are configured to mate with the several embodiments of the terminal barrier  142  of the present terminal barrier system  140 . 
     In another embodiment, as shown in FIG. 2, the terminal barriers  142  without extensions as shown in FIG.  3   a,    3   b,  and  3   c  provide for the retention of the terminal connectors shown in FIGS. 9,  10 , and  11 . In this embodiment the nut plate  146  is omitted. The terminal barrier  142  retains the connector lug  166  in engagement with the terminal prior to installation of the cable. Either the formed sheet metal lug in FIG. 9 or the extruded metal lug shown in FIG. 11 may be used. The embossed rib  169  in FIG. 9 is dimensioned similarly to feature  169  in the extruded lug in FIG.  11 . This allows either of the two lugs to be retained by the same plastic terminal barriers  142 . 
     The terminal barrier system  140  in addition to the function of protecting the terminal during outgassing operation of the circuit breaker  10 , also functions to retain the terminal connector  144  and prevents accidental contact with live terminals by an operator and installer of the circuit breaker  10 . The terminal barrier can be formed or fabricated from any suitable electrical insulating material such as plastic or similar composition. 
     Another embodiment of the terminal barrier system  140  provides for a terminal barrier  142  that engages a cable bus connector. The cable bus connector is inserted into the terminal barrier  142  and fastened to the terminal barrier  142  by either a pin or threaded fastener. The cable bus connector has a flattened portion which connects to the line or load cable. The terminal barrier  142  mounts to the circuit breaker terminal  16 ,  18  with a mounting fastener  170 . Such arrangement allows the line and load cables to be attached to the circuit breaker  10  from underneath or rear of the circuit breaker  10  rather than from the side of the circuit breaker. FIGS. 1,  2  and  7  illustrate the circuit breaker  10  orientated for a side connection of the line or load cables. 
     While the embodiments illustrated in the figures and described above are presently preferred, it should be understood that these embodiments are offered by way of example only. Invention is not intended to be limited to any particular embodiment, but it is intended to extend to various modifications that nevertheless fall within the scope of the intended claims. For example, other types of electrical conducting material can be utilized in the connector lugs or nut plates and different shapes can be utilized for the terminal connector. Although an individual terminal barrier system is utilized at each pole of the circuit breaker, it is contemplated that a multiple pole terminal barrier system can also be utilized. It is also contemplated tht an electronic trip unit can be used. Additionally, it is also contemplated that the trip mechanism having a bi-metal trip unit or an electronic trip unit with a load terminal be housed in a separate housing capable of mechanically and electrically connecting to another housing containing the operating mechanism and line terminal thereby providing for a quick and easy change of current readings for an application of the circuit breaker contemplated herein. Other modifications will be evident to those with ordinary skill in the art.