Patent Document

BACKGROUND 
     1. Field 
     The disclosed and claimed concept relates generally to electrical switching equipment and, more particularly, to a switch apparatus for connection with a DC circuit. 
     2. Related Art 
     Numerous types of circuit interrupters are known for use in diverse applications. In certain applications, such as low power situations, the circuit interrupter can be as simple as a mechanical switch, of which many types are known. 
     One type of mechanical switch that is employed in somewhat higher voltage and current applications involves the use of a rotatable shaft upon which an elongated conductor is mounted. The ends of the conductor are electrically connected with a pair of contacts when the switch is in an ON condition. When the switch is moved toward its OFF condition, the shaft is rotated, which causes the elongated conductor to pivot about a pivot axis about the shaft, which causes air gaps to form between the ends of the elongated conductor and the pair of contacts as the conductor is disconnected from the contacts. While such circuit interrupters have been generally effective for their intended purposes, they have not been without limitation. 
     Certain applications involve DC circuits, and it has become desirable in certain applications, such as photovoltaic applications and other application, to increase the voltage and current that flow within a circuit. This increase consequently exacerbates the difficulty of extinguishing the arcs that form at the air gaps when switching a switch from an ON condition to an OFF condition. For example, it has become desirable in photovoltaic applications to increase the number of solar arrays arranged in parallel and in series, which increases current and voltage, respectively, and which must be interrupted by a circuit interrupter such as a switch. Moreover, depending upon the orientation of the contacts in relation to one another and in relation to the movable elongated conductor, it is possible that the arc created at the air gap can tend to move along the elongated conductor toward the pivot axis of the shaft. Movement of the arc toward the pivot axis of the shaft on which the elongated conductor is mounted may tend to shorten the arc and reinforce it, which is undesirable since any arc is preferably extinguished as soon as possible. While efforts have been made to employ magnets and resultant Lorentz forces to extinguish arcs in such circuit interrupters, the result has sometimes been a circuit interrupter that can only interrupt DC power of a given polarity. Moreover, magnets (such as rare earth magnets) are rather costly, and the extensive use of such magnets can undesirably increase the cost of the resultant switching device. It thus would be desirable to provide an improved circuit interrupter that provides improved performance. 
     SUMMARY OF THE INVENTION 
     An improved switch apparatus having a high interruption capability and being usable in a DC circuit employs a rotatable shaft having conductors situated thereon that are removably connected with two or more pairs of contacts that are situated on line conductors and load conductors and that are connectable in parallel by the conductors on the shaft. In rotating the shaft to open the switch, one pair of the contacts is electrically disconnected prior to the electrical disconnection of the other pair of contacts. Further rotation of the shaft causes the other pair of contact to eventually become disconnected. Electrical arcs thus form only at the air gaps between the other pair of contacts and the conductor. Magnetic field elements in the form of permanent magnets are situated in the vicinity of the air gaps of only the other pair of contacts and apply Lorentz forces to the arcs to extinguish them. 
     The pair of magnetic field elements generate magnetic fields that are parallel with an axis of rotation of the shaft and that have their north poles pointed in the same direction and are thus optimized to extinguish an arc at one air gap in a first DC polarity and to extinguish an arc at the other air gap when a second (opposite) DC polarity is applied to the switch apparatus. By electrically disconnecting one pair of contacts prior to electrically disconnecting the other pair of contacts that had been in parallel therewith, electrical arcs are formed only at the other pair of contacts, and the other pair of contacts serve as sacrificial contacts. Moreover, the other pair of contacts are the only contacts where magnets are placed to extinguish arcs, thus resulting in a relatively low magnet cost while providing a high interruption capability. 
     Accordingly, an aspect of the disclosed and claimed concept is to provide an improved switch apparatus that is connectable with a DC circuit, that has a high interruption capability for DC of either polarity, and that has an acceptably low cost. 
     Another aspect of the disclosed and claimed concept is to provide an improved switch apparatus having multiple pairs of contacts that are connected in parallel, with a one pair of the contacts being electrically disconnected prior to another pair of contacts being electrically disconnected in order to cause the other pair of contacts to serve as sacrificial contacts. 
     Accordingly, an aspect of the disclosed and claimed concept is to provide an improved switch apparatus that is structured to be connected with a DC circuit. The switch apparatus can be generally stated as including a conduction element comprising a conductor portion and another conductor portion separated from one another, a first pair of contacts, one of which being electrically connected with the conductor portion, and the other of which being electrically connected with the another conductor portion, a second pair of contacts, one of which being electrically connected with the conductor portion, and the other of which being electrically connected with the another conductor portion, a shaft, an elongated first conductor apparatus mounted to the shaft and connectable at its ends with the first pair of contacts, an elongated second conductor apparatus mounted to the shaft and connectable at its ends with the second pair of contacts, and an arc extinction apparatus. The shaft is pivotable about a pivot axis among at least a first position, a second position, and a third position. In the first position, the ends of the first conductor apparatus are electrically connected with the first pair of contacts, and the ends of the second conductor apparatus are electrically connected with the second pair of contacts. In the second position, the ends of the first conductor apparatus are electrically connected with the first pair of contacts, and the ends of the second conductor apparatus are electrically disconnected from the second pair of contacts. In the third position, a pair of air gaps exists between the first conductor apparatus and the first pair of contacts, and the ends of the second conductor apparatus are electrically disconnected from the second pair of contacts. The arc extinction apparatus can be generally stated as including a pair of magnetic field elements, one magnetic field element of the pair of magnetic field elements being situated adjacent one first contact of the first pair of contacts and being structured to generate a magnetic field oriented parallel with the pivot axis, the other magnetic field element of the pair of magnetic field elements being situated adjacent the other first contact of the first pair of contacts and being structured to generate another magnetic field oriented parallel with the pivot axis, the magnetic field and the another magnetic field having their north poles pointed in the same direction. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       A further understanding of the disclosed and claimed concept can be gained from the following Description when read in conjunction with the accompanying drawings in which: 
         FIG. 1  is a perspective view of an improved switch apparatus in accordance with the disclosed and claimed concept; 
         FIG. 2  is another perspective view of the switch apparatus of  FIG. 1 ; 
         FIG. 3A  is a schematic depiction of the switch apparatus in a first position, which is a CLOSED position of the switch apparatus; 
         FIG. 3B  is a schematic depiction of the switch apparatus in a second position; 
         FIG. 3C  is a schematic depiction of the switch apparatus in a third position; 
         FIG. 3D  is a schematic depiction of the switch apparatus in a fourth position, which is an OPEN position of the switch apparatus; 
         FIG. 4  is a further schematic depiction of the switch apparatus in the third position of  FIG. 3C  and depicting Lorentz forces acting on electrical arcs when DC of a first polarity is connected with the switch apparatus; and 
         FIG. 5  is a further schematic depiction of the switch apparatus in the third position of  FIG. 3C  and depicting Lorentz forces acting on electrical arcs when DC of a second polarity is connected with the switch apparatus. 
     
    
    
     Similar numerals refer to similar parts throughout the specification. 
     DESCRIPTION 
     An improved switch apparatus  2  in accordance with the disclosed and claimed concept is depicted generally in  FIGS. 1 and 2  in an OPEN position. The switch apparatus  2  is connectable with a DC circuit  4  which is schematically depicted in  FIG. 1  and which can be of either polarity while still being interruptible by the switch apparatus  2 . 
     As can be understood from  FIGS. 1 and 2 , the switch apparatus  2  includes a line conductor  8  and further includes a load conductor  12  that is depicted in broken lines in  FIGS. 1 and 2  for clarity of illustration. The line and load conductors  8  and  12  are, by themselves, electrically separated but are electrically connectable together to close the DC circuit  4 , as will be set forth in greater detail below. As such, the line and load conductors  8  and  12  can be said to together form a conduction element of the switch apparatus  2 . It is understood that the expressions “line” and “load” in the context of the line and load conductors  8  and  12  or elsewhere are intended merely for purposes of illustration and description and are not intended to be limiting. As such, the line conductor  8  can be connected with either a line or a load, and the load conductor  12  can likewise be connected with either a line or a load without departing from the present concept. 
     The switch apparatus  2  further includes a pair of first contacts  16 A and  16 B (collectively herein referred to with the numeral  16 ) and a pair of second contacts  20 A and  20 B (collectively referred to herein with the numeral  20 ) that are situated on the line and load conductors  8  and  12 . More particularly, the first contact  16 A and the second contact  20 A are both situated on and electrically connected with the line conductor  8 , and the first contact  16 B and the second contact  20 B are situated on and electrically connected with the load conductor  12 . As will be set forth in greater detail below, the first contacts  16  are electrically connectable together, and the second contacts  20  are electrically connectable together in parallel with the first contacts  16 . It is also noted that more than two pairs of contacts can be provided, as necessary, to increase the interruption capability of the switch apparatus  2 . 
     The switch apparatus  2  further includes a shaft  24  that is pivotable about a pivot axis  28 , and also includes a first conductor apparatus  32  and a second conductor apparatus  36  that are situated on the shaft  24 . The first and second conductor apparatuses  32  and  36  are each elongated and extend radially from the shaft  24 . The first and second conductor apparatuses  32  and  36  are electrically in parallel with one another when connected together with the pairs of first and second contacts  16  and  20 . Moreover, the first and second conductor apparatuses  32  and  36  can be said to be physically oriented parallel with one another and to extend generally in a common plane  38  that extends through the pivot axis  28 . 
     The first conductor apparatus  32  in the depicted exemplary embodiment comprises two conductors, i.e., a pair of first conductors  40  and  41 . The second conductor apparatus  36  in the depicted exemplary embodiment likewise comprises two conductors, i.e., a pair of second conductors  44  and  45 . Depending upon the rotational position of the shaft  24  about the pivot axis  28 , the first conductors  40  and  41  may be electrically connected at opposite ends thereof with the first contact  16 . Further depending upon the rotational position of the shaft  24  about the pivot axis  28 , the second conductors  44  and  45  may be electrically connected at opposite ends thereof with the second contact  20 . As will be set forth in greater detail below, the first and second contacts  16  and  20  and the first and second conductors  40 ,  41 ,  44  and  45  are together arranged such that the second contacts  20  are electrically connectable together only if the first contacts  16  are electrically connected together. However, the first contacts  16  are electrically connectable together even if the second contacts  20  are electrically disconnected. 
     The switch apparatus  2  can further be said to include a support  46  upon which the line and load conductors  8  and  12 , the pairs of first and second contacts  16  and  20 , the shaft  24 , and the first and second conductor apparatuses  32  and  36  are disposed. Although not expressly depicted herein, it is understood that the switch apparatus  2  is intended to further be disposed within an enclosure or to have an enclosure mounted on the support  46  in order to electrically isolate the aforementioned components that are situated on the support  46  from exposure to the environment. 
     The switch apparatus  2  further and advantageously includes an arc extinction apparatus  48  that is situated on the support  46  and that is positioned generally in the vicinity of the first contacts  16 . The arc extinction apparatus  48  can be said to include two magnetic field elements  52 A and  52 B (collectively referred to herein with the numeral  52 ) which each generate a magnetic field  56 A and  56 B, respectively, (collectively referred to herein with the numeral  56 ) that are parallel to one another and parallel with the pivot axis  28 . As will be set forth in greater detail below, the north poles of the magnetic field elements  56  point in the same direction. 
     In the depicted exemplary embodiment, the magnetic field element  52 A includes an outboard magnet  60 A and an inboard magnet  64 A that are situated at alternate sides of the first contact  16 A and which have north poles  68 A and  72 A, respectively, that are oriented in the same direction. Likewise, the magnetic field element  52 B includes an outboard magnet  60 B and an inboard magnet  64 B that are situated at alternate sides of the first contact  16 B and which have north poles  68 B and  72 B, respectively, that are oriented in the same direction, which is the same direction as that in which the north poles  68 A and  72 A are oriented. 
     The switch apparatus  2  is schematically depicted in  FIGS. 3A-3D  as being movable between a first position that is depicted generally in  FIG. 3A , a second position that is depicted generally in  FIG. 3B , a third position that is depicted generally in  FIG. 3C , and a fourth position that is depicted generally in  FIG. 3D . Upon rotation of the shaft  24  in the counter-clockwise direction from the perspective of  FIGS. 3A-3D , the switch apparatus  2  is sequentially movable from the first position ( FIG. 3A ) to the second position ( FIG. 3B ) to the third position ( FIG. 3C ) and to the fourth position ( FIG. 3D ). It is likewise understood that if the shaft  24  is pivoted in the clockwise direction from the perspective of  FIGS. 3A-3D , the switch apparatus  2  is sequentially movable from the fourth position ( FIG. 3D ), to the third position ( FIG. 3C ), to the second position ( FIG. 3B ), and to the first position ( FIG. 3A ). 
       FIG. 3D  is intended to depict the shaft  24  and the first and second conductor apparatuses  32  and  36  as being in the same position as is depicted generally in  FIGS. 1 and 2 , i.e., the fourth position of the switch apparatus  2 , which is an OPEN position. In such position, the line and load conductors  8  and  12  are electrically disconnected from one another since the first conductor apparatus  32  is disconnected from the first contacts  16  and the second conductor apparatus  36  is disconnected from the second contacts  20 . As will be understood from the following description, the first, second, and third positions of the switch apparatus  2  correspond with a CLOSED position of the switch apparatus  2 . 
     When the shaft  24  is in the first position of  FIG. 3A , the first contacts  16  are electrically connected together via the first conductor apparatus  32 , and the second contacts  20  are electrically connected together via the second conductor apparatus  36 , with the second contacts  20  being electrically connected in parallel with the first contacts  16 . By providing both the first contacts  16  and the second contacts  20  electrically in parallel, the switch apparatus  2  can possess a relatively higher current carrying capability than would be generally possible with only the first contacts  16  or the second contacts  20 . 
     When the shaft  24  is rotated in the counter-clockwise direction from the first position of  FIG. 3A  toward the second position of  FIG. 3B , the second pair of contacts  20  become electrically disconnected ( FIG. 3B ) while the first pair of contacts  16  remain electrically and physically connected together. That is, upon rotation of the shaft  24  from the first position of the switch apparatus  2 , as is depicted generally in  FIG. 3A , to the second position of the switch apparatus  2 , as is depicted generally in  FIG. 3B , the second contacts  20  become electrically disconnected. However, the first contacts  16  remain electrically and physically connected together in the second position since the first conductor apparatus  32  remains electrically connected with the first contacts  16 . This is because the first contacts  16  are relatively taller in the vertical direction from the perspective of  FIGS. 3A-3D  than the second contacts  20 . That is, and as can be seen in  FIG. 3D , the first contacts  16  can be said to be of a relatively taller dimension  78  in a direction extending away from the conduction element, and the second contacts  20  can be said to be of a relatively shorter dimension  82  in the direction extending away from the conduction element. 
     Upon further rotation of the shaft  24  in the counter-clockwise direction from the second position of  FIG. 3B  to the third position of  FIG. 3C , the pair of first conductors  40  and  41  become physically disconnected from the pair of first contacts ( FIG. 3C ). However,  FIG. 3C  also depicts the pair of first conductors  40  and  41  being in sufficiently close physical proximity to the first contacts  16  that a pair of arcs  80 A and  80 B (collectively referred to herein with the numeral  80 ) are formed at a pair of air gaps  76 A and  76 B, respectively, (collectively referred to herein with the numeral  76 ) which are disposed between the first contacts  16  and the first conductors  40  and  41 , in which situation a certain level of DC current flows through the switch apparatus  2 . As will be set forth in greater detail below, however, the arcs  80  are desirably extinguished by the arc extinction apparatus  48 . Nevertheless, the mere possibility of current flow through the switch  2  in the third position of the switch apparatus  2  ( FIG. 3C ) causes the third position of the switch apparatus  2  to be considered a CLOSED position. 
     Since the first and second conductor apparatuses  32  and  36  are oriented parallel with one another in a common plane along the common axis  38 , a rotation of the shaft  24  in the counter-clockwise direction with respect to  FIGS. 3A-3D  will result in the second contacts  20  being electrically disconnected from the second conductor apparatus  36  ( FIG. 3B ) prior to the first contacts  16  being physically disconnected from the first conductor apparatus  32  ( FIG. 3C ). Since in the second position of  FIG. 3B  the first contacts  16  remain electrically connected together, and since the second contacts  20  had been electrically connected together in parallel with the first contacts  16 , electrical arcs generally do not form at air gaps between the second contacts  20  and the second conductor apparatus  36 . 
     It is understood that other configurations of contacts and conductors can be employed without departing from the present concept. For example, if the first and second conductor apparatuses did not both lie in a common plane, the pairs of contacts that might be employed may be of the same height but at different positions to cause one pair of contacts to be connected at a different rotational position of the shaft than the connection of another pair of contacts. Other variations will be apparent to one of ordinary skill in the art within the scope of the disclosed and claimed concept. 
     As can be understood from the foregoing, therefore, upon rotation of the shaft  24  from the first position of  FIG. 3A  and the second position of  FIG. 3B , no arcs are formed between the second contacts  20  and the second conductor apparatus  36  when they become physically and electrically disconnected. This is because the first contacts  16  remain electrically connected together at the point when the second contacts  20  become electrically disconnected. However, when moving from the second position of  FIG. 3B  to the third position of  FIG. 3C , at which point the first conductor apparatus  32  becomes physically disconnected from the first contacts  16 , the arcs  80  are formed at the air gaps  76 . 
     The arc extinction apparatus  48  is thus advantageously provided to rapidly extinguish the arcs  80  at the air gaps  76  when the switch apparatus  2  is moved from its second position to its third position. The arc extinction apparatus  48  rapidly extinguishes the arcs  80  via the application of Lorentz forces to the arcs  80 . 
     The first conductor apparatus  32  is depicted in  FIG. 4  as being in the third position with respect to the first contacts  16  and as having DC of a first polarity being connected between the line and load conductors  8  and  12 . In this regard, the direction of the current flow through the first conductor apparatus  32  is indicated generally with the numeral  84 , and the direction of the current flow at the air gaps  76  as a result of the arcs  80  is depicted at the numerals  88 A and  88 B (collectively referred to herein with the numeral  88 ) at the air gaps  76 A and  76 B, respectively. 
     When the DC of the first polarity is applied, as is depicted generally in  FIG. 4 , the action of the magnetic fields  56 A and  56 B on the arcs  80 A and  80 B results in the application of Lorentz forces  90 A and  90 B (collectively referred to herein with the numeral  90 ) on the arcs  80 A and  80 B, respectively, according to the well understood Right Hand Rule. As can be understood from  FIG. 4 , the Lorentz force  90 A causes the arc  80 A to be pushed in a direction generally away from the pivot axis  28 , whereas the Lorentz force  90 B causes the arc  80 B to be pushed in a direction generally toward the pivot axis  28 . While it is understood that the pushing of the arc  80 B toward the pivot axis  28  would typically cause the arc  80 B to become shortened and thereby reinforced and strengthened, it can be understood that the extinction of either the arc  80 A or the arc  80 B will result in the extinction of both arcs  80 . As such, the Lorentz force  90 A applied to the arc  80 A, which is in a direction generally away from the pivot axis  28 , causes both arcs  80  to be extinguished very rapidly. 
       FIG. 5  depicts an instance wherein DC of an opposite polarity (i.e., opposite that of  FIG. 4 ) is applied to the switch apparatus  2  in the third position. The direction of the current flow in the first conductor apparatus  32  is indicated generally at the numeral  92 , and the direction of the current flow at the air gaps  76 A and  76 B is represented generally at the numerals  94 A and  94 B (collectively referred to herein at the numeral  94 ) and which take the form of electrical arcs  96 A and  96 B (collectively referred to herein at the numeral  96 ). The magnetic fields  56  cause Lorentz forces  98 A and  98 B (collectively referred to herein at the numeral  98 ) to act on the arcs  96  in directions generally opposite those of the Lorentz forces  90 A and  90 B, respectively. 
     That is, whereas the Lorentz force  90 A caused the arc  80 A to move in a direction generally away from the pivot axis  28 , the Lorentz force  98 A causes the arc  96 A to move in a direction generally toward the pivot axis  28 . Likewise, the Lorentz force  98 B acting on the arc  96 B causes the arc  96 B to move in a direction generally away from the pivot axis  28 , which is an opposite direction from that of  FIG. 4 . The arc  96 B is expected to be extinguished prior to the extinction of the arc  96 A since the arc  96 B is being pushed by the Lorentz force  98 B in a direction generally away from the pivot axis  28  and, as before, the extinction of either arc  96  will result in the extinction of both arcs  96 . 
     It thus can be seen that the magnetic field elements  52  applied to the first contacts  16  results in rapid extinction of the arcs  80  and  96  regardless of the polarity of the DC applied to the switch apparatus  2 . By causing the first contacts  16  to remain electrically connected together via the first conductor apparatus  32  subsequent to the second contacts  20  becoming electrically disconnected from the second conductor apparatus  36 , the arcs  80  and  96  advantageously occur only at the first contacts  16  and not at the second contacts  20 , with the advantageous result that the arc extinction apparatus  48  need provide only the magnetic field elements  52  in the vicinity of the first contacts  16 . This reduces costs by avoiding the need for such additional magnetic field elements to be placed in the vicinity of the second contacts  20 . The switch apparatus  2  thus advantageously is configured to interrupt high current levels of DC of either polarity at an acceptably low cost. 
     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 invention which is to be given the full breadth of the claims appended and any and all equivalents thereof.

Technology Category: h