The present disclosure generally relates to a clip fastener for use in grounding photovoltaic modules of a photovoltaic system.
A photovoltaic system (or PV system) is a system which uses one or more photovoltaic modules (or solar panels) to convert sunlight into electricity. The system may include multiple components, including the photovoltaic modules, a racking assembly on which the modules are mounted, mechanical and electrical connections, and devices for regulating and/or modifying the electrical output. Most photovoltaic systems include a photovoltaic array, which is a linked collection of photovoltaic modules. In the case of ground-mounted photovoltaic systems, the photovoltaic modules are mounted on a plurality of racking assemblies assembled in vacant land areas. Such ground-mounted photovoltaic systems may include thousands, if not tens of thousands, photovoltaic modules. Accordingly, the time it takes to assemble each racking assembly and mount the photovoltaic modules on of the photovoltaic modules to the racking assemblies may significantly reduce the overall cost of the photovoltaic system.
In one aspect, a ground lead assembly for use in grounding a photovoltaic module through electrical connection with a racking assembly on which the photovoltaic module is mountable generally comprises a module clip configured for securement to the photovoltaic module. The module clip includes upper and lower clip jaws at least partially defining a press-fit channel for press fitting the module clip onto a lower flange of the photovoltaic module, and a piercing member on at least one of the upper and lower clip jaws for piercing an electrically non-conductive outer layer on the lower flange of the photovoltaic module and contacting an electrically conductive material of the lower flange as the module clip is press fit onto the lower flange. A rail-attachment component is connected electrically to the module clip. The rail-attachment component is configured for securement to and electrical connection with a rail of the racking system.
In another aspect, a module clip for use in grounding a photovoltaic module through electrical connection with a racking assembly on which the photovoltaic module is mountable generally comprises upper and lower clip jaws at least partially defining a press-fit channel for press fitting the module clip onto a lower flange of the photovoltaic module. A piercing member is on at least one of the upper and lower clip jaws for piercing an electrically non-conductive outer layer on the lower flange of the photovoltaic module and contacting an electrically conductive material of the lower flange as the module clip is press fit onto the lower flange. A lead-connecting member is for use in securing a ground wire to the module clip. The piercing member is electrically connected to the lead-connecting member so as to define an electrical path from the piercing member to the lead-connecting member. The module clip has a current-carrying capacity through said electrical path of at least about 750 amps for 4 seconds.
In yet another aspect, a photovoltaic system generally comprises a racking assembly including a rail. A photovoltaic module is mounted on the rail of the racking assembly. The photovoltaic module includes a frame having a lower flange. The frame is constructed from an electrically-conductive material having an electrically non-conductive outer layer disposed over the electrically conductive material. A ground lead assembly grounds the at least one photovoltaic module through electrical connection with the rail on which the photovoltaic module is mounted. The ground lead assembly includes a module clip press fit on the lower flange of the photovoltaic module. The module clip has a piercing member electrically contacting the electrically conductive material. A rail-attachment component is secured to the rail in electrical connection therewith. The rail-attachment component is electrically connected to the module clip to provide an electrical path from the electrically conductive material of the photovoltaic module through the ground lead assembly to the rail.
Other features will be in part apparent and in part pointed out hereinafter.
Corresponding reference characters indicate corresponding parts throughout the drawings.
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As set forth above, the module clip 16 is configured to provide an electrical connection between the module 12 and the rail 14 of the racking assembly to facilitate grounding of the module. As is generally known in the art, the module frame 28 is typically constructed from an electrically-conductive material, such as aluminum or another electrically conductive metal, having an electrically non-conductive outer layer disposed over the electrically conductive material. For example, the module frame 28 may be constructed from anodized aluminum, which has an outer anodic layer that is electrically non-conductive. Accordingly, at least one of the upper and lower clip jaws 34, 36 of the module clip 16 includes one or more piercing members 50 that pierce through (e.g., score, scrape, dig, and/or puncture) the anodic layer, or other electrically non-conductive outer layer, and make electrical contact with the electrically conductive material (e.g., aluminum) as the lower flange 26 of the module frame 28 is press-fit in the press-fit channel 30. In the illustrated embodiment, both the upper and lower clip jaws 34, 36 include piercing members 50 (e.g., teeth). The piercing members 50 on the upper clip jaw 34 extending slightly downward from the terminal end margin 44 of the upper clip jaw and into, or generally adjacent to, the throat 42 of the press-fit channel 30. As shown best in
As the module clip 16 is pressed on, hammered on, or otherwise press fit on the lower flange 26, the piercing members 50 engage the lower flange 26 and score or scrap (i.e., puncture) the anodic layer and contact the electrically-conductive material. Further press fitting of the module clip 16 on the lower flange 26 may cause the piercing members 50 to resiliently deflect (i.e., flatten out), whereby the teeth continue to score the anodized layer, while being urged into contact with the electrically-conductive material, to increase the area of contact between the teeth and the electrically-conductive material. In one embodiment, the module clip (i.e., at least one of the upper and lower jaws 34, 36) may be configured to apply a minimum force of about 30 pound-force to about 70 pound-force to the lower flange 26 to facilitate piercing of the lower flange by the piercing members 50.
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The module clip 16 is electrically conductive so as to define an electrical path from the electrically-conductive material of the module frame 28, through the piercing members 50, the jaws 34, 36, and the lead-connecting member 54, to the ground wire 20. In one example, the module clip 16 is capable of electrically conducting current through the electrical path as required by UL 467 and/or UL2703, to effectively ground the module through the rail 14. In one non-limiting example, the module clip 16 is constructed to have a current-carrying capacity through the electrical path of at least 750 amps for four seconds to satisfy the requirement of UL 467. In another non-limiting example, the module clip 16 may be wired in series with an applicable fuse (e.g., a 60 amp fuse) and connected to a 5,000 amp source. In this example, the module clip 16 has a current-carrying capacity of at least 135% current (e.g., 81 amperes, where the fuse is a 60 am fuse) for sixty minutes and at least 200% current (e.g., 120 amperes, where the fuse is a 60 am fuse) for four minutes. It is understood that the module clip 16 may have other current-carrying capacities without departing from the scope of the present invention. It has been found that for the clip to have a desired current-carrying capacity, such as that of a 10 gauge wire, three features may need to be present for the clip to function as desired. First, the lead-connecting member 54 must be of sufficient cross-sectional area to carry the specified current from at least one of the clip jaws 34, 36 to the ground wire 50 without getting so hot as to fail and no longer have continuity with at least one of the clip jaws 34, 36. Second, the portion of the clip jaws 34, 36 that carry current from the piercing member(s) 50 to the lead-connecting member 54 should have a collective cross-sectional area suitable for collectively carrying the desired current. And third, the piercing member(s) 50 should be configured such that when the clip 16 is pressed onto the frame 26 of the solar module 12, the piercing members “plow” or cut into the frame to a suitable depth such that the collective area of the piercing members in direct contact with the conductive material disposed under the non-conductive layer is sufficient to carry the desired current.
In the illustrated embodiment, the module clip 16 is integrally formed as a unitary, one-piece construction. Thus, the lead-connecting member 54 is formed integrally with the upper and lower jaws 34, 36, respectively, and the channel base 32. For example, the upper and lower jaws, 34, 36, respectively, the channel base 32, and the lead-connecting member 54 may be fabricated from a single sheet of metal, such as spring steel. In such an embodiment, the single sheet of metal may be bent to form the upper and lower clip jaws 34, 36, respectively, and the sheet may be lanced to form the piercing members 50 and the lead-connecting member 54. In one embodiment, the piercing members 50 may have a hardness from about 46 Rockwell C scale to about 50 Rockwell C scale to facilitate piercing of the lower flange 26. In one example, the module clip 16 may be formed from a sheet of metal (e.g., spring steel) having a thickness from about 18 gauge to about 20 gauge or from about 0.035 in to about 0.048 in, and in one example, about 16 gauge or from about 0.053 in to about 0.065 in. Other ways of making the module clip 16 do not depart from the scope of the present invention.
In the illustrated embodiment, where the lead-connecting member 54 is formed integrally with the upper and lower jaws 34, 36, respectively, and the channel base 32, the lead-connecting member 54 has a substantially uniform width W along substantially its entire length L from the juncture of the lead-connecting member and the channel base 32 to the terminal end 54a of the lead-connecting member. The lead-connecting member 54 has a substantially uniform width along substantially its entire length L to avoid a region of weakness in the lead-connecting member 54 where the chance of failure (e.g., melting), due to the amount of current flowing through the module clip, is reduced. It has been found, through testing, that a device including a lead-connecting member having a necked-down portion with a width of 0.35 in and a thickness of 0.044 in (i.e., a cross-sectional area of 0.0154 in2) at the juncture of the lead-connecting member and the channel base 32 is not suitable for directing an electrical current of 750 amps for 4 seconds (instead, it was capable of directing an electrical current of 400 amps for 4 seconds). However, a module clip constructed from the same sheet metal with the same thickness of 0.044 in and including a lead-connecting member having a width of 0.50 in (i.e., a cross-sectional area of 0.022 in2) along substantially its entire length is suitable for directing an electrical current of 750 amps for 4 seconds. As can be seen from this testing, the cross-sectional area of the necked-down portion of the first device was not sufficient to carry the desired capacity, while the cross-sectional area of the lead-connecting member of the second device, which was constructed according to the teachings of the present disclosure, was sufficient to carry the desired capacity. The second device was also found to carry 5000 amps for a sufficient amount of time to allow a 60 amp fuse to short the circuit.
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In one embodiment, each of the modules 12 of the photovoltaic system is grounded through one of the rails 14 of the racking assembly using one or more ground lead assemblies 10. The module 12 is quickly and easily grounded through one of the rails 14 by press fitting the module clip 16 onto the lower flange 26 of the module, such as by using a hammer or other tool, whereby the piercing members 50 of the module clip pierce through (e.g., score, scrape, dig, and/or puncture) the anodic layer—or other electrically non-conductive outer layer—of the flange 26, and make electrical contact with the electrically conductive material (e.g., aluminum). The rail-attachment component 18 is connected to the rail 14 by snapping the rail-attachment component onto one of the lips of the rail.
Having described embodiments of the invention in detail, it will be apparent that modifications and variations are possible without departing from the scope of the invention defined in the appended claims.
When introducing elements of the present invention or the preferred embodiments(s) thereof, the articles “a”, “an”, “the” and “said” are intended to mean that there are one or more of the elements. The terms “comprising”, “including” and “having” are intended to be inclusive and mean that there may be additional elements other than the listed elements.\
As various changes could be made in the above constructions, products, and methods without departing from the scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense.
Number | Date | Country | |
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Parent | 13545602 | Jul 2012 | US |
Child | 14942439 | US |