FIELD OF INVENTION
The invention relates to a Junction box adaptable to a plurality type of
Photovoltaic (PV) modules. The invention further relates to a method for rigidly
fixing a junction box capable to accommodate a plurality type of PV modules.
BACKGROUND OF THE INVENTION
PV Modules are manufactured by interconnecting crystalline silicon solar cells in
series configuration to get the required voltage and power output. Generally, 36-
nos. (9*4 configuration) of solar cells are interconnected in series for 12-Volt
application and 72-nos. (12*6 configuration) are connected in series for 24-Volt
application. The interconnected solar cells are laminated in a vacuum laminator
with glass as a super-strate, a back sheet material as substrate and Ethylene
vinyl Acetate (EVA) as lamination material to protect the cells against harsh
environment when deployed. A junction box is required to be fixed on the back
side of the module for terminating the final busbars of the PV module and for
taking out the load connections from the module. Bypass diodes are required to
be incorporated inside the junction box so as to bypass the shadowed solar cell
strings from the array of the PV modules connected in the site and protect the
solar cells against hot spot effect. At least 2-bypass diodes are used in a 36-cell
PV module and 3-bypass diodes in a 72-cell PV module. Cable glands and O-rings
are required to be incorporated to eliminate water and moisture entry inside the
junction box; rusting of the busbars of the PV module, and avoid disconnection
of the module from the array.
A 36-cell contains at least 3-terminals and 2-bypass diodes in the junction box
and a 72-cell module contains 4-terminals and 3-bypass diodes in the junction
box. Prior art is silent on the process to fabricate a common junction box suitable
for both of these (3-terminals and 2-bypass diodes, 4-terminals and 3-bypass
diodes) configurations with a required rigidity in the connection between a
junction box and a PV-module.
US Patent no. 5,280,133 describes a junction box for a solar panel with two
output terminals with body and cover being snap fitted. The structure does not
talk about a common junction box for 3-terminals and 4-terminals.
US Patent no. 7,369,398 B2 discloses a junction box for a solar panel with
provision for discharging the heat dissipated by the bypass diodes. This patent is
also silent about a common junction box for 3/4 terminals.
US Patent no. 6,655,987 B2 describes a junction box for a solar panel with
provision for heat radiation from the bypass diodes by means of lead plates.
OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a common junction box
adaptable to plurality type of PV-modules such as 3-terminal, 2-tybpas diodes,
and 4-terinal, 3-bypass diodes configuration.
Another object of the invention is to to propose a common junction box
adaptable to plurality type of PV-modules such as 3-terminal, 2-tybpas diodes,
and 4-terinal, 3-bypass diodes configuration, which enables to termination of the
busbars from the PV module and solder the busbars on to the tinned terminals of
the junction box.
A still another object of the invention is to propose a common junction box
adaptable to plurality type of PV-modules such as 3-terminal, 2-
bypass diodes, and 4-terinal, 3-bypass diodes configuration, in which cable
glands and O-rings can be provided to protect the PV-modules against water and
moisture entry.
Yet another object of the invention is to propose to propose a common junction
box adaptable to plurality type of PV-modules such as 3-terminal, 2-tybpas
diodes, and 4-terinal, 3-bypass diodes configuration, which is fastened on to the
edge frames of the PV modules to hold the junction box even when the sealant
fail.
A further object of the invention is to propose to propose a common junction box
adaptable to plurality type of PV-modules such as 3-terminal, 2-tybpas diodes,
and 4-terinal, 3-bypass diodes configuration, which is provided with a cover with
at least four corner screws.
SUMMARY OF THE INVENTION
Accordingly, there is provided in a first aspect of the invention a junction box
common to both 3-terminal, 2-bypass diodes and 4-terminal, 3-bypass diodes PV
module configurations. In a second aspect of the invention, there is provided a
method for rigidly fixing a junction box onto a photovoltaic (PV) module.
According to the method, the junction box incorporates tinned terminals for
soldering of the busbars from the PV module. A Plurality of cable glands and 0-
rings are provided to protect the module from water and moisture entry. A
provision for fastening the junction box on to the edge frame, is made, and a
cover over the body of the junction box, is fastened by at least four corner
screws.
The PV-module having a plurality of silicon solar cells connected in series on a
substrate is surrounded by a sheet formed of an insulted material with one each
top and bottom sheet. The PV-module includes a plurality of busbars which
terminate in positive and negative terminals. The busbars extend beyond the PV-
module through the sheet periphery and solderingly connected to the terminals.
Electric cable from external electrical/electronic appliances brought through
openings on the junction box and fastened on to the terminals.
The common junction box includes a body and a cover. The body comprises a
plurality of apertures. The body is positioned to enable disposition of the
terminals within the free-area of the body. The busbars from the PV module are
soldered to the terminals. At least one diode is spanning between two terminals.
The invention further provides a method of rigidly fixing a common junction box
onto a PV-module which junction box is enabled to accommodate a plurality type
of PV-modules for example, 3-terminals, 2-bypass diode, and 4-terminals, 3-
bypass diode configurations.
BRIEF DESCRIPTION OF THE ACCOMPANYING DRAWINGS
Figure 1 - shows a schematic illustration of a PV Module with 36-cell (3-
terminals, d-bypass diodes)
Figure 2 - shows a sketch of a PV Module with 72-cells (4-terminals, 3-bypass
- diodes)
Figure 3 - shows a junction box body for 3-terminals and 2-bypass diodes
Figure 4 - shows a junction box body for 4-terminals and 3-bypass diodes
Figure 5 - shows the junctions box cover with four corner screws
Figure 6 - shows a provision for fastening the junction box on to the module
frame
Figure 7 - shows a provision for cable glands and O-Rings
DETAILED DESCRIPTION OF THE INVENTION
According to this invention there is provided a method for terminating the
busbars (3TBB, 4TBB) of a PV Module (1) for both 3-terminals (3TBB), 2-bypass
diodes (2) and 4-terminals (4TBB), 3-bypass diodes (2) configurations. The
junction box (3) is suitable for both 75-watts (36-cells) and 170-watts (72-celss)
PV Modules (1). The invention further provides a junction box common to both
3-terminas, 2-bypass diodes, and 4-terminals 3-bypass diodes configurations of
PV-module.
The junction box (3) incorporates tinned terminals for soldering the busbars
(TBB) from the PV Module (1) and provided with means for fixing the bypass
diodes (2) across the terminals (TBB), glands (6a) and O-ring (6b), including
means for fixing the junction box (3) on to the module (1) frames and cover (5)
with at least four corner screws (7).
As shown in Figures 1 to 2, the PV module busbars (3TBB, 4TBB) are terminated.
It is taken out from the backside of the module (1) for soldering on to the
junction box terminals (4) as shown in Figure-3 and Figure-4 for 3-terminal and
4-terminal configuration respectively.
As shown in figure-5 a cover is provided with four corner screws (7) so as to
close the body of the junction box (2). The junction box (2) is fixed rigidly on to
the frame (1) as shown in Figure-6. Cable glands (6a) and O-Rings (6b) as
shown in Figure-7 ensures protection of the modules (1) against water and
moisture.
A hinge (9). is provided between the cover (5) and the junction box (3). A
plurality of fastening screws (8) are provided to fix the frame of the PV module
(1) to the junction box (3).
ADVANTAGES
Major advantages of this Junctions Box are as follows:-
- The junction box is suitable for both 3-terminal and 4-termianl configuration
i.e. 36-celss and 72-cells configuration.
- Cable glands and O-rings protect the modules from water and moisture.
- The fixing of the junction box on to the module frames ensures rigidness and
prevent from failing off.
- The procedure of taking out and soldering of the final busbars ensures
adequate connection between the electrical/electronic devices with the PV-
module.
WE CLAIM
1. A common junction box adaptable to photovoltaic (PV) modules to terminate
the busbars of the PV-modules, the PV-modules having an enclosing member
a plurality of output terminals capable of being solderingly connected at one
edge to an electric cable of electronic devices via the junction box; a plurality
of by pass diodes acting as rectifying means releasably disposed between the
terminals, the junction box comprising:
- a front part accommodating a frame portion and disposed in such a way that
the output terminals of the PV-niodule remain substantially encompassed;
- a terminal disposed against an opposite face of the frame member of the PV-
module;
- a back part positioned against said opposite face of the enclosing member of
the PV-moduie and attached to the front part so that the edge of the PV-
module being interposed; and
- a passage configured on the front and back part to allow the electric cable of
the electronic device to pass through from an external location of the junction
box to a position within said frame portion.
2. The junction box as claimed in claim 1, comprising a cover to close the front
part and the back part by means of a plurality of corner screws.
3. The junction box as claimed in claim 1, wherein a plurality of cable glands
and O-ring are provided to eliminate ingress of water through openings on
the enclosing member of the PV-module.
4. A common junction box adaptable to photovoltaic (PV) modules to terminate
the busbars of the PV-modules, as substantially described and illustrated
herein with reference to the accompanying drawings.

The invention relates to a common junction box adaptable to photovoltaic (PV)
modules to terminate the busbars of the PV-modules, the PV-modules having an
enclosing member a plurality of output terminals capable of being solderingly
connected at one edge to an electric cable of electronic devices via the junction
box; a plurality of by pass diodes acting as rectifying means releasably disposed
between the terminals, the junction box comprising a front part accommodating
a frame portion and disposed in such a way that the output terminals of the PV-
module remain substantially encompassed; a terminal disposed against an
opposite face of the frame member of the PV-module; a back part positioned
against said opposite face of the enclosing member of the PV-module and
attached to the front part so that the edge of the PV-module being interposed;
and a passage configured on the front and back part to allow the electric cable
of the electronic device to pass through from an external location of the junction
box to a position within said frame portion.