Patent Abstract:
A junction box adapted to provide an electrical connection to an electrical wire attached to a photovoltaic panel. The junction box has a lower portion which has an entry slot to allow entry of the wire into the junction box and a raised protrusion over which the wire is bent and formed to be substantially in the same shape as the raised protrusion. The junction box also has a clamp adapted to be attachable to said lower portion, whereby the clamp holds the wire in place for providing the electrical connection. The wire is preferably bus ribbon. The lower portion preferably has an elastic polymeric element disposed between the raised portion and the wire. The raised protrusion may have an elastic polymeric element.

Full Description:
BACKGROUND 
     1. Technical Field 
     The present invention relates to electrical connections to photovoltaic panels and more particularly to a junction box with upper and lower portions which snap together to achieve the electrical connection. 
     2. Description of Related Art 
     A photovoltaic module or photovoltaic panel is a packaged interconnected assembly of photovoltaic cells, also known as solar cells. Since a single photovoltaic module can only produce a limited amount of power, commercial installations include several modules or panels interconnected in serial and in parallel into a photovoltaic array. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired amount of current source capability. A photovoltaic installation typically includes the array of photovoltaic modules, an inverter, batteries and interconnection wiring. Electronic modules may be integrated with the photovoltaic modules which perform electrical conversion, e.g. direct current (DC) to direct current conversion, electrical inversion, e.g. micro-inverter, or other functions such as monitoring of performance and/or protection against theft. 
     Bus ribbon is a common interconnect that is used to connect photovoltaic modules. Bus ribbon is made up of a copper ribbon, or flat wire, that is coated in solder. The solder protects the surface of the copper from oxidation and provides a layer of solder to form the solder joint. Bus ribbon is generally 5 mm-6 mm wide, although some applications require bus ribbon to be more than twice as wide. Bus ribbon may serve as an input/output to a conventional junction box typically mounted on the back side of the photovoltaic module. 
     When part of a photovoltaic module is shaded, the shaded cells do not produce as much current as the unshaded cells. Since photovoltaic cells are connected in series, the same amount of current must flow through every serially connected cell. The unshaded cells force the shaded cells to pass more current. The only way the shaded cells can operate at a higher current is to operate in a region of negative voltage that is to cause a net voltage loss to the system. The current times this negative voltage gives the negative power produced by the shaded cells. The shaded cells dissipate power as heat and cause “hot spots”. Bypass diodes are therefore integrated with the photovoltaic modules to avoid overheating of cells in case of partial shading of the photovoltaic module. 
     Blocking diodes may be placed in series with cells or modules to block reverse leakage current backwards through the modules such as to block reverse flow of current from a battery through the module at night or to block reverse flow down damaged modules from parallel-connected modules during the day. 
     The term “wire” or “electrical wire” as used herein is a piece of metal or other electrically conductive material of any cross-sectional shape used for carrying electrical currents or signals. Bus ribbon is an example of an electrical wire used to electrically connect to photovoltaic panels. 
     The term “cable gland” as used herein refers to a device used for the entry of electrical cables or cords into electrical equipment and is used to firmly secure an electrical cable entering a piece of electrical equipment. 
     BRIEF SUMMARY 
     According to embodiments of the present invention there is provided a junction box adapted to provide an electrical connection to an electrical wire attached to a photovoltaic panel. The junction box has a lower portion which has an entry slot to allow entry of the wire into the junction box and a raised protrusion over which the wire is bent and formed to be substantially in the same shape as the raised protrusion. The junction box may have a clamp attachable to the lower portion. The clamp holds the wire in place for providing the electrical connection. The wire is typically bus ribbon. The lower portion may have an elastic polymeric element disposed between the raised protrusion and the wire and or the raised protrusion may have an elastic polymeric element. 
     The junction box may have an upper portion including a terminal. The terminal connects to an electrical load. The terminal is adapted to be applied under pressure onto the wire, thereby conforming the terminal to be of substantially the same shape as the raised protrusion. The upper portion typically has a fastener which closes the upper portion to the lower portion under pressure. The terminal is typically spring loaded. The electrical load may be a direct current (DC) to DC converter, a DC to alternating current (AC) inverter, a DC motor or a battery. The upper portion preferably has a seal which is positioned between the upper and the lower portions. The seal is adapted to seal under the same pressure which effects the electrical connection between the terminal and the wire. The upper portion typically includes a diode connected to the terminal. The diode may be either a bypass diode or a blocking diode. The upper portion may be an electronic module connected to the terminal. The upper portion preferably has a cable gland. 
     According to embodiments of the present invention there is provided a method to provide a connection to a photovoltaic panel. A wire, e.g. bus ribbon, which connects electrical to the photovoltaic panel is passed through an entry slot of a lower portion of a junction box. The bus ribbon is bent over a raised protrusion provided in the lower portion of the junction box. The bus ribbon is formed to be substantially the same shape as the raised protrusion. The bus ribbon is typically clamped onto the protrusion of the lower portion of the junction box. 
     An upper portion of the junction box is inserted into the lower portion of the junction box and while inserting a terminal is loaded compressively onto the bus ribbon. The compressive loading may include spring loading. Additionally while inserting, the upper portion is sealed to the lower portion of the junction box. The terminal is typically conformed to the shape of the protrusion while electrically connecting to the bus ribbon between the terminal and the protrusion. An elastic polymeric material is typically inserted between the protrusion and the wire. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is herein described, by way of example only, with reference to the accompanying drawings, wherein: 
         FIG. 1  shows a partial view of the back side (i.e. non photovoltaic side) of a photovoltaic panel according to an embodiment of the present invention. 
         FIG. 2  shows a lower half of a junction box assembly according to an embodiment of the present invention. 
         FIG. 3   a  which shows a junction box assembly with clamp according to an embodiment of the present invention. 
         FIG. 3   b  shows a partial cross sectional view of a wire ribbon mounted in a lower junction box assembly with a clamp according to an embodiment of the present invention. 
         FIG. 4  shows a method according to an embodiment of the present invention. 
         FIGS. 5   a  and  5   b  show isometric views of upper an junction box assembly connected/inserted into a lower junction box assembly according to an embodiment of the present invention. 
         FIGS. 5   c  and  5   d  show isometric views of the underside of an upper junction box assembly according to an embodiment of the present invention. 
         FIG. 5   e  shows a cross section view of an upper junction box assembly inserted into a lower junction box assembly according to an embodiment of the present invention. 
         FIG. 5   f  shows area A shown in  FIG. 5   e  in greater detail according to an embodiment of the present invention. 
         FIG. 5   g  shows a method according to an embodiment of the present invention. 
         FIGS. 6   a  and  6   b  show an upper junction box assembly inserted into a lower junction box assembly according to another embodiment of the present invention. 
         FIG. 6   c  shows an underside isometric view of an upper assembly according to an embodiment of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like reference numerals refer to the like elements throughout. The embodiments are described below to explain the present invention by referring to the figures. 
     Before explaining embodiments of the invention in detail, it is to be understood that the invention is not limited in its application to the details of design and the arrangement of the components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments or of being practiced or carried out in various ways. Also, it is to be understood that the phraseology and terminology employed herein is for the purpose of description and should not be regarded as limiting. 
     By way of introduction, embodiments of the present invention are directed to enable an interconnection of photovoltaic panels with cables and/or photovoltaic panels with electronic modules such as alternating current (AC) inverters or direct current (DC) to DC converters with a minimal use of hand tools while providing electrical isolation and hermeticity. 
     Reference is now made to the drawings.  FIG. 1  shows a partial view of the back side  104  (i.e. non photovoltaic side) of a photovoltaic panel  100  according to an embodiment of the present invention. bus ribbons are  102  located on back side  104  of panel  100  and provide electrical connections to internal photovoltaic cells of panel  100 . 
     Reference is now made to  FIG. 2  which shows a lower half of a junction box assembly  218  according to an embodiment of the present invention. Assembly  218  is typically attached to back side  104  of panel  100  at the time of manufacture/assembly of panel  100 . Assembly  218  may be made or cast as one piece, in the form of a plastic injection molding. Assembly  218  has support rails  216 , retainer clip  214  and lower part  210  of junction box. 
     Reference is now also made to  FIGS. 5   a  and  5   b  which shows isometric views of upper junction box assembly  500  connected/inserted into lower junction box assembly  218  according to an embodiment of the present invention. Assembly  500  has a lid  504  which when removed shows an upper terminal assembly  528  fixed into lower assembly  218  using screws  530 . Upper terminal assembly  528  after being inserted into lower assembly  218  provides complete electrical isolation of the electrical connection of upper assembly  528  with the lower assembly  218 . Lid  504  provides a cosmetic appearance and/or further level of isolation. Attached mechanically and electrically to upper terminal assembly  528  is electronic module  524 . Electronic module  524  is attached mechanically to panel  100  using support rails  216  and retainer clip  214 . Electronic module  524  has cable glands  526  which allow a cable entry into electronic module  524  where the cable may be terminated inside electronic module  524 . 
     Referring back to  FIG. 2 , support rails  216  may be made from one piece of plastic as part of an injection molding process or as separate parts. Support rails  216  may be made from spring metal which may be plastic coated. Support rails  216  provide the correct distance between module  524  and backside  104  of panel  100 . Support rails  216  also provide support for module  524  along with retainer clip  214 . Retainer clip  214  may also be made from spring metal which may be plastic coated or made from one piece of plastic as part of an injection molding process. 
     Reference is now also made to  FIG. 3   a  which shows junction box assembly  218  with clamp  300  according to an embodiment of the present invention. Clamp  300  is preferably attached to the bottom side  210   a  of junction box  210  with an adhesive, by screws through hole pillars  212  or by the insertion of upper junction box assembly  500  ( FIG. 5   b ) and the tightening of screws  530  into threaded pillars  212 . 
     Referring back to  FIG. 2 , junction box  210  has gland apertures  220  to accommodate embodiment  600  and through hole pillars  212 . Through hole pillars  212  are typically used to attach junction box  210  to backside  104  of panel  100 . Through hole pillars  212  may also be used to attach clamp plate  300  to the bottom side  210   a  of junction box  210 . 
     Junction box  210  has a slot  210   b  where bus ribbons  102  are passed through and are placed into the inside of junction box  210 . Bus ribbons  102  are typically bent and formed over raised protrusion  208 . Raised protrusion  208  may have additionally a rubber or elastic material  206  placed in-between protrusion  208  and bus ribbon  102 . 
     Reference is now made to  FIG. 3   b  which shows a partial cross sectional view  302  of wire ribbon  102  mounted in lower junction box assembly  218  with clamp  300  according to an embodiment of the present invention. Cross sectional view  302  shows bus ribbon  102  clamped by clamp  300  over elastic material  206  and protrusion  208 . One of two gaskets  310  (for example an “O” ring), is shown between bottom side  210   a  of junction box  210  and clamp  300 . Gasket  310  provides a level of sealing against the ingress of water and/or dust into panel  100 . Additionally the underside of clamp  300  may be coated with an elastic material to provide sealing between the elastic material and bus ribbon  102 . bus ribbon  102  passes through slot  210   b  of junction box  210 . bus ribbon  102  continues through a hole in backside  204  of solar panel  100  and is connected to the photovoltaic cells inside panel  100 . Protrusion  208  is typically formed by an indentation on bottom side  210   a  of junction box  210 . Bottom side  210   a  of junction box  210  is located and may be attached on backside  204  of solar panel  100 . 
     Reference is now made to  FIG. 4  which shows a method  401  according to an embodiment of the present invention. Typically, assembly  218  is attached to backside  104  of panel  100  at the time of manufacture/assembly of panel  100  whilst ensuring bus ribbon  102  is passed through entry slot  210   b  of junction box  210  (step  403 ). With bus ribbon  102  located inside junction box  210  as a result of step  403 , bus ribbon  102  is bent over elasticated material  206  and protrusion  208  (step  405 ). After being bent, bus ribbon is then formed (step  407 ) to take substantially the shape of protrusion  208  and/or elasticated material  206 . The bending (step  405 ) and forming (step  407 ) of bus ribbon  102  is then held firm and clamped into place (step  409 ) in junction box  210  using clamping plate  300 . Clamp  300  is preferably attached to the bottom side  210   a  of junction box  210  with an adhesive, by screws through hole pillars  212  or by the insertion of upper junction box assemblies  500  and  600  (not shown) and the tightening of screws  530   
     Reference is now made to  FIGS. 5   c  and  5   d  which show isometric views of the underside of upper junction box assembly  500  according to an embodiment of the present invention. Upper junction box assembly  500  has electronic module  524  with lid  532 , when lid  532  is removed the component side of electronic circuit board  542  is shown. Circuit board  542  is typically a direct current (DC) to DC converter or a DC to alternating current (AC) inverter. Termination of interconnecting cables on circuit board  542  is provided by insertion of interconnecting cables into cable entry glands  526 . Upper terminal assembly  528  has mounting through holes  540  which along with screws  530  (not shown) are used as part of the insertion and retention of assembly  500  into lower junction box assembly  218 . Upper terminal assembly  528  also has terminals  536  which provide an electrical connection between circuit board  542  and the curved portions  536   a  of terminals  536 . An indented portion of assembly  528  houses curved portions  536   a  of terminals  536  and typically there may be an elastic material placed between assembly  528  and curved portions  536   a . Sufficient flexibility and movement of curved portions  536   a  typically allows curved portions  536   a  to conform around the bent and formed portion wire ribbon  102  when upper junction box assembly  500  inserted into lower junction box assembly  218 . 
     Reference is now made to  FIG. 5   e  which shows a cross section view of upper junction box assembly  500  inserted into lower junction box assembly  218  according to an embodiment of the present invention. Area A shows an electrical connection between upper junction box assembly  500  inserted into lower junction box assembly  218 . Upper junction box assembly  500  includes further; electronic module  524  with lid  532  and electronic circuit board  542 . Lid  532  rests and is held by support rails  216  along with module  524  held by retainer clip  214 . Terminal  536  provides the electrical connection between circuit board  542  and connection to photovoltaic cells in panel  100  (not shown) via the electrical connection between upper assembly  500  inserted into lower assembly  218 . 
     Reference is now made to  FIG. 5   f  and  FIG. 5   g  which show area A shown in  FIG. 5   e  in greater detail and a method  501  respectively according to an embodiment of the present invention. Area A shows details of the insertion (step  505 ) of upper junction box assembly  500  inserted into lower junction box assembly  218  to form an electrical connection between circuit board  542  and connection to photovoltaic cells in panel  100  (not shown). The electrical connection is formed between curved portion  536   a  which may be spring loaded and bus ribbon  102 . Curved portion  536   a  is held by assembly  528 . Curved portion  536   a  is connected to circuit board  542  via terminal  536 . Sealing of lower assembly  218  is provided by gaskets  310  which provide a level of sealing against the ingression of water and/or dust into aperture  210   b  by using clamp  300 . Sealing between upper assembly  500  and lower assembly  218  is provided by gaskets  534 . Further sealing of upper and lower assemblies by lid  504 . Protrusion  208  is formed as a part of the bottom side  210   a  of junction box  210 . In between protrusion  208  and bus ribbon  102  is elastic material  206 . 
     Reference is now made to  FIGS. 6   a  and  6   b  which show upper junction box assembly  600  inserted into lower junction box assembly  218  according to another embodiment of the present invention. Upper junction box assembly  600  inserted into lower junction box assembly  218  does not make use of support rails  216  and retainer clip  214  only junction box  210  of lower assembly  218 . Clamp  300  in junction box  210  is preferably attached to the bottom side  210   a  of junction box  210  with an adhesive, by screws through hole pillars  212  or by the insertion of upper junction box assembly  600  and the tightening of screws  630  into threaded pillars  212 . Upper assembly  600  after being inserted into lower assembly  218  provides complete electrical isolation of the electrical connection of upper assembly  600  with the lower assembly  218 . Lid  602  provides a cosmetic appearance and/or further level of electrical isolation and sealing. Assembly  600  has cable glands  626  which allow a cable entry into assembly  600  where the cable may be terminated inside assembly  600 . 
     Reference is now made to  FIG. 6   c  which shows an underside isometric view of upper assembly  600  according to an embodiment of the present invention. Curved portions  636   a  are typically held by an indented portion of assembly  600 . An elastic material may be placed between assembly  600  and curved portions  636   a . Sufficient flexibility and movement of curved portions  636   a  typically allows curved portions  636   a  to conform around the bent and formed portion of wire ribbon  102  when upper junction box assembly  600  is inserted into lower junction box assembly  218 . Curved portions  636   a  are connected to one end of a bypass diode  642  via terminal  636 . Bypass diodes  642  are typically connected between terminals  636 . Sealing between upper assembly  600  and lower assembly  218  is provided by gasket  634 . Further sealing of upper and lower assemblies may be by lid  602 . Upper assembly  600  after being inserted into lower assembly  218  is held in place by screws  630  (not shown) which go through holes  640 . Cables are typically passed through and are held by glands  626  and terminated in clamp  638 . Clamp  638  is typically spring loaded and is moved by an insertion of a screwdriver to reveal an aperture. The aperture receives an insertion of a conductor provided by a cable which is inserted into gland  626 . The removal of the screwdriver causes the aperture to close which clamps the conductor in clamp  638  and a connection of the conductor with terminal  636  is established. 
     Reference is now made again method  501  shown in  FIG. 5   g  with respect to upper assembly  600  according to an embodiment of the present invention. Upper assembly  600  inserted (step  505 ) into lower junction box assembly  218  to form an electrical connection between cables terminated in clamp  638  and connection to photovoltaic cells in panel  100  (not shown). The electrical connection is formed between curved portion  636   a  (which may be spring loaded) and bus ribbon  102 . Insertion of upper assembly  600  into lower assembly  218  further provides sealing between upper assembly  600  and lower assembly  218  by gasket  634 . Further sealing between upper  600  and lower  218  assemblies is provided by lid  602 . 
     The definite articles “a”, “an” is used herein, such as “a terminal”, “a junction box” have the meaning of “one or more” that is “one or more terminals s” or “one or more junction boxes”. 
     Although selected embodiments of the present invention have been shown and described, it is to be understood the present invention is not limited to the described embodiments. Instead, it is to be appreciated that changes may be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the claims and the equivalents thereof.

Technology Classification (CPC): 7