Abstract:
A disconnect switch includes a case having a movable contact, a stationary contact and a plurality of magnets. The movable contact is adapted to move from a first closed position where it is in physical contact with the stationary contact to a second open position. The magnets are located at predefined locations and in predefined orientations about the axis of movement of the movable contact, whereby upon the movement of the movable contact from the first position to the second open position, a current arc created by the movable contact is extinguished.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application claims the benefit of U.S. Provisional Patent Application Nos. 61/303,123, filed on Feb. 10, 2010 and 61/314,805, filed on Mar. 17, 2010, both of which are incorporated by reference herein as if fully set forth. 
    
    
     FIELD OF INVENTION 
     This application is related to disconnect switches. 
     BACKGROUND 
     A disconnect switch is utilized to disconnect power sources from an electrical system. In a direct current (DC) system, for example, a photovoltaic disconnect switch may be used to disconnect multiple DC power sources from the electric system that is supplied by photovoltaic cells in one or more photovoltaic modules. The Underwriters Laboratory (UL) standard requirement for certification of a photovoltaic disconnect switch are for the device to operate at an overload of 200 percent of the rated current of the switch and to pass an endurance test at the rated current. 
     However, opening the contacts of a disconnect switch under a DC load creates an arc between the stationary contact, (e.g., line side), and movable contact, (e.g., load side), of the switch. Current industry devices attempt to suppress this arc by connecting two poles of a three pole disconnect switch in series and by using arc grids (e.g., deion plates) to suppress the arc. This series connection creates additional break points in the circuit when the switch is opened, which add to the overall resistance of the circuit, thereby causing the arc to be rapidly extinguished. Additionally, arc grids in some cases break the arc into smaller arcs and cool the arc, which raises the arc voltage and aids in extinguishing the arc. 
     However, the current devices allow only one line/load combination to be wired through a three pole disconnect switch. When wiring the current devices in a three (3) line/load configuration with no additional series connection, they are not able to meet the necessary number of operations under overload and endurance conditions as required by the UL rating body. 
     Additionally, arc grids alone work well only when they remain relatively cool. The arc in general rises with natural convection into the arc grids. When the temperature of the arc grids increase during endurance, the heat of the grids begin to repel the arc. This repulsion acts to constrain and shorten the path of the arc. The increase in arc voltage is not achieved and the arc remains active after the disconnect switch is completely open. This failure to rapidly extinguish the arc results in additional heat being built up in the system and the eventual melting of the disconnect switch, since the arc itself may be at a temperature of 20,000 Degrees Kelvin. 
     It would therefore be beneficial to provide a disconnect switch that does not use arc grids to extinguish the arc. 
     SUMMARY 
     A disconnect switch is disclosed. The disconnect switch includes a case having a movable contact, a stationary contact and a plurality of magnets. The movable contact is adapted to move from a first closed position where it is in physical contact with the stationary contact to a second open position. The magnets are located at predefined locations and in predefined orientations about the axis of movement of the movable contact, whereby upon the movement of the movable contact from the first position to the second open position, a current arc created by the movable contact is extinguished. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is an exploded perspective view of a disconnect switch in accordance with an embodiment; 
         FIG. 2  is a plan view of the disconnect switch of  FIG. 1 ; 
         FIG. 3  is a side elevation of the disconnect switch of  FIG. 2  viewed along the lines  3 - 3 ; 
         FIG. 4  is a plan view of a disconnect switch in accordance with an alternative embodiment; and 
         FIG. 5  is a side elevation of the disconnect switch of  FIG. 4  viewed along the lines  5 - 5 . 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     By utilizing a combination of magnets to extinguish an arc, instead of utilizing an arc grid, space is opened up for the arc to lengthen and cool. 
     Referring now to the drawings, wherein like reference numerals refer to similar components across the several views,  FIG. 1  is an exploded perspective view of a disconnect switch  100  in accordance with an embodiment. The disconnect switch  100  includes a cover  110  and a base  120 . Disposed within the base  120  are movable contacts  130  and stationary contacts  140 . For purposes of example, a three pole switch  100  is shown, which may have a current rating of 30 amps. Accordingly, three movable contacts  130  are depicted as well as 3 sets of stationary contacts  140 . However, it should be noted that an additional number of contacts  130  and  140 , or less contacts, may be utilized depending on the desired application. Additionally, it should be noted that although the disconnect switch  100  is depicted as a “double-break” switch, where the movable contact  130  makes/breaks contact at two physical locations with two respective stationary contacts  140 , the disconnect switch could also be a “single-break” switch where there is only one physical connection between the movable contact  130  and one respective stationary contact  140 . 
     Disposed within the cover  110  are magnets  150 , (designated  150   1 ,  150   2 , and  150   3 ). Additionally, the cover  110  includes vents to release heat. Again, for purposes of example, three magnets  150  are shown, however, it should be noted that a greater or lower number of magnets may be included, depending on the desired application. 
       FIG. 2  is a plan view of the disconnect switch  100  of  FIG. 1 , and  FIG. 3  is a side elevation of the disconnect switch  100  of  FIG. 2  viewed along the lines  3 - 3 . 
     Referring now collectively to  FIGS. 2 and 3 , the operation of the disconnect switch  100  is shown during the opening of the switch. The magnets  150  are shown in a particular orientation with respect to the path and axes of the movable contacts  130 . For example, as shown, magnet  150   1  is disposed substantially parallel to the axis of the paths of the movable contacts  130 , having its north pole facing to the center of the disconnect switch  100  and the south pole facing to the outer wall of the disconnect switch  100  in the view of  FIG. 2 . Magnet  150   2  is disposed substantially parallel to the axis of the paths of the movable contacts  130 , having its north pole facing to the left and the south pole facing to the right in the view of  FIG. 2 . Magnet  150   3  is disposed at an angled orientation, (e.g., 45 degrees), with respect to the axes and paths of the movable contacts  130 , and having the south pole facing substantially the center of the disconnect switch  100  and the north pole facing toward the outside of the disconnect switch  100 . Each of the magnets  150  produces a magnetic field M m  proceeding from the north pole of the magnet to the south pole of the magnet. 
     As each movable contact  130  rotates about its axis from a first position where it is in physical contact with its respective stationary contact  140  to a second, open, position, an arc “A” is formed along the path of the movable contact  130  in breaking its physical contact with its respective stationary contact  140 . A magnetic field M A  is generated by the current flow of each arc. As the arc A proceeds along its path, it is first attracted by the magnetic fields M m  produced by magnets  150 , stretching and lengthening the path of the arc by acting on the Arc&#39;s magnetic field. That is, the magnetic fields M m  of magnets  150   1 ,  150   2  and  150   3  first attract the arc A, stretching and lengthening the path of the arc by acting on the Arc&#39;s magnetic field. As the movable contact  130  moves past the magnets  150   1  and  150   3 , the arc A is repelled. The combination of attracting and repelling the arc A increases its voltage above the system voltage, (e.g., 600V and higher), which aids in extinguishing the arc. In addition, the magnetic fields of the magnets deflect the arc plasma, which causes an additional increase in the arc voltage. This effect may be referred to as the “Hall” effect. Since ions may be many times heavier than electrons, (e.g., 10,000 times heavier), as the electrons are pushed out of the plasma stream, the stream ceases to be a good conductor and extinguishes. The arc is also cooled through the vents of the cover  110  through convection. 
       FIG. 4  is a plan view of a disconnect switch  1000  in accordance with an alternative embodiment, and  FIG. 5  is a side elevation of the disconnect switch  1000  of  FIG. 4  viewed along the lines  5 - 5 . The disconnect switch  1000  includes a cover  1010  and a base  1020 . Disposed within the base  1020  are movable contacts  1030  and stationary contacts  1040 . For purposes of example, a three pole switch  1000  is shown, which may have a current rating of 60 or 100 amps. Accordingly, three movable contacts  1030  are depicted as well as 3 sets of stationary contacts  1040 . However, it should be noted that an additional number of contacts  1030  and  1040 , or less contacts, may be utilized depending on the desired application. Additionally, it should be noted that although the disconnect switch  1000  is depicted as a “double-break” switch, where the movable contact  1030  makes/breaks contact at two physical locations with two respective stationary contacts  1040 , the disconnect switch could also be a “single-break” switch where there is only one physical connection between the movable contact  1030  and one respective stationary contact  1040 . 
     In this embodiment, disposed within the base  1020  are three magnets ( 1050   1 ,  1050   2 , and  1050   3 ), while disposed within the cover  1010  are five magnets ( 1050   4 ,  1050   5 ,  1050   6 ,  1050   7 , and  1050   8 ). Additionally, the cover  1010  includes vents to release heat. Again, for purposes of example, eight magnets  1050  are shown, however, it should be noted that a greater or lower number of magnets may be included, depending on the desired application. 
     Referring now collectively to  FIGS. 4 and 5 , the operation of the disconnect switch  1000  is shown during the opening of the switch. The magnets  1050  are shown in a particular orientation with respect to the path and axes of the movable contacts  1030 . For example, as shown, magnets  1050   1 ,  1050   2 , and  1050   3  are disposed substantially parallel to the axis of the paths of the movable contacts  1030 , having their north pole facing to the left of the disconnect switch  1000  and their south poles facing to the right of the disconnect switch  1000  in the view of  FIG. 4 . In addition, the magnets  1050   1 ,  1050   2 , and  1050   3  are oriented at an angle, (e.g., 45 degrees), with respect to the bottom plane of the base  1020 . 
     Disposed within the cover  1010  are magnets  1050   4 ,  1050   5 ,  1050   6 ,  1050   7 , and  1050   8  substantially parallel to the axis of the paths of the movable contacts  1030 . Magnets  1050   5  and  1050   8  each have their north poles facing to the left and the south poles facing to the right in the view of  FIG. 4 . Magnets  1050   4 ,  1050   6 , and  1050   7  each have their north poles facing to the right and the south poles facing to the left in the view of  FIG. 4 , (i.e., the opposite to the pole orientations of magnets  1050   5  and  1050   8 ). Each of the magnets  1050  produces a magnetic field M m  proceeding from the north pole of the magnet to the south pole of the magnet. 
     As each movable contact  1030  rotates about its axis from a first position where it is in physical contact with its respective stationary contact  1040  to a second, open, position, an arc “A” is formed along the path of the movable contact  1030  in breaking its physical contact with its respective stationary contact  1040 . A magnetic field M A  is generated by the current flow of each arc. As the arc A proceeds along its path, it is attracted immediately upon creation by the magnetic fields M m  produced by magnets  1050   5  and  1050   8 , stretching and lengthening the path of the arc by acting on the Arc&#39;s magnetic field, due to the magnets&#39; locations proximate to the stationary contacts  1040 . 
     Also, as the arc A proceeds along its path, it is first attracted by the magnetic fields M m  produced by magnets  1050   1 ,  1050   2 ,  1050   3 ,  1050   4 ,  1050   6 , and  1050   7 , stretching and lengthening the path of the arc by acting on the Arc&#39;s magnetic field, and then repelled by their magnetic fields as the movable contact  1030  moves past the magnets  1050   1 ,  1050   2 ,  1050   3 ,  1050   4 ,  1050   6 , and  1050   7 . The combination of attracting and repelling the arc A increases its voltage above the system voltage, (e.g., 600V and higher), which aids in extinguishing the arc. In addition, the magnetic fields of the magnets deflect the arc plasma, which causes an additional increase in the arc voltage. This effect may be referred to as the “Hall” effect. Again, since the ions may be many times heavier than the electrons, as the electrons are pushed out of the plasma stream, the stream ceases to be a good conductor and extinguishes. The arc is also cooled through the vents of the cover  1010  through convection. In addition, the magnets  1050   1 ,  1050   2 ,  1050   3 ,  1050   4 ,  1050   6 , and  1050   7  twist the arc to further aid in the extinguishing of the arc. 
     The above embodiments provide a disconnect switch, for example a photovoltaic disconnect switch, that rapidly stretch, attract, repel, and twist an arc generated during the breaking of contact between a movable contact in the switch with a stationary contact in order to extinguish the arc. The arc is thereby extinguished before the contacts are fully open allowing the disconnect switch to operate at higher voltages, such as 600V and higher, and break current higher than rated current, (e.g., twice rated current), at that voltage. Additionally, the above embodiments provide for the breaking of multiple independent sources in a single disconnect switch. Although the disconnect switches  100  and  1000  are described as including a separate cover and base portion, it should be noted that the switches  100  and  1000  may be formed as a single case unit. In addition, example magnets  150  may be formed of a material such as a grade 35 Neodymium-Iron-Boron (NdFeB), having a coating in accordance with the American Society for Testing and Materials (ASTM) standard B689-97, although other types of magnets may be used. 
     The foregoing embodiments have been shown and described for the purposes of illustrating the structural and functional principles of the embodiments, as well as illustrating the methods of employing the embodiments and are subject to change without departing from such principles. All modifications to the embodiments are therefore encompassed within the spirit of the following claims.