FIELD OF INVENTION
This invention relates to inspection of a Solar PV Module adoptable at the final
inspection stage in a PV module manufacturing plant. More particularly, the
invention relates to a device for inspecting a PV module at the final stage.
BACKGROUND OF THE INVENTION:
PV modules are manufactured using solar cells of 125mm x 125mm or 156mm x
156mm size mono / multi crystalline silicon wafers. Typically, each 125-mm solar
cell generates a power output of 2.2 to 2.3 watts. According to prior art, thirtysix
numbers of these 125mm cells are interconnected in series to get a PV Module of
75 to 85-watts power output (12-V application), and seventytwo numbers of
cells of said silicon wafers of said size are interconnected in series, the PV
Module of 150 to 170-watts power output (24-V application) can be obtained.
Similarly sixty number of 156x156mm cells when interconnected in series a PV
Module of 220 to 240 watts power output (20-V application) can be obtained and
seventytwo numbers of such cells when interconnected in series PV Module of
270 to 300 watts power output (24-V application), can be configured.

Solar cells are basically produced from raw Silicon material through various
critical process like melting, crystal pulling, slicing etc. The sliced silicon is called
wafer which is the input for cell processing.
In Solar Cell Production, as shown in figure 1(a) the 'wafers' go through a series
of processes for example, pre-cleaning, texturisation, chemical cleaning,
diffusion, junction removal, etching, anti reflection coating, printing, drying, firing
and testing. Metalisation on solar cells is carried out by means of screen and
printing metal paste on them. Screen printing is carried out in three stages i.e. i)
Silver-aluminium bus bar on back surface ii) Aluminium paste in rest of the area
super-imposing the bus bars on the back surface and iii) Fine-line grid pattern
using silver material on the front surface. After completion of all the process, a
solar cell is produced, which is enabled to produce electrical power when
exposed to light.
The cells are inter-connected in series to produce more power output in a
modular form called PV module. The various sub processes of module making is
shown in figure 1(b).

Front tabbing: In PV module production the solar cells are soldered with an
interconnect (tin plated copper strip of 0.15x1.2mm size) having twice the length
of the solar cell. This process is called front tabbing.
Stringing: The front tabbed cells are inter connected by soldering in series
(front to back of adjacent cells) using a layup jig in a particular matrix as per
required pattern for the particular power and voltage of the module. For
example, a 20Vx220W module shall be made of 156mm size solar cells
connected in series in a matrix of 6 columns by 10 rows. Each columns are
connected to an adjacent column by bus bars (tin plated copper, size 0.2x5mm).
Finally, all the cells for example, sixty numbers are connected in three branches
of each twenty cells and terminated with four leads (one is common for both
branch). This configuration is made for by-passing of a failed cell during
exposure to sunlight. Otherwise, the failed cells may block the power generated
by other operating cells. A cell may fail to generate power due to various reasons
namely shadow, de-soldering of the joint, breakage of cells and interalia affects
the power output of the module. The said three branches are interconnected
through three by-pass diodes and finally two leads are taken out as positive and
negative terminal of the module. This process is called as stringing.

Lavup: The stringed cells are transferred on a glass having EVA spread over
it. EVA (ethyl vinyl acetate) is a jell forming sheet which is heated to a higher
temperature. Another EVA is spread over the stringed cells. A special back sheet
is placed on the assembly. The four terminal leads are taken out of the back
sheet by carefully cutting and pulling out.
Inspection: The entire assembly is inspected for any defective cell, defective
soldered joint, broken cell, any inclusion.
Lamination: The assembly is placed in a laminator chamber. The laminator
chamber is evacuated, heated and the layup is pressed uniformly. After the cycle
of operation, the laminate is taken out from the laminator. The laminate is
inspected for any air bubble, cell breakage, wrinkles or any other defect.
Testing: The laminate is tested in a sun simulator. Power output and other
electrical parameters are recorded.
Framing: The electrically accepted modules are taken for framing. The excess
projection of EVA and back sheet are trimmed out. Sealant is applied on the
trimmed edges, and aluminum frames are fixed at the edges. All the four frames
are firmly held by on the laminate either by screwing or crimping.
Junction Box fixing: Junction box made up of a UV resistant plastic material,
consisting of at least three diodes, and corresponding clips for inserting the
terminal leads of the laminate. Two leads with quick connecting ends come out

of the Terminal Box for inter connecting to make a PV power system. This
junction box (JB) is fixed on the back side of the module. The four leads from
the laminate are inserted in the clips provided in the JB. Sealant is applied in the
groove of the JB to prevent moisture ingress. The finished module with circuit
diagram is shown in fig 2.
Cleaning: After curing of the sealant, the module is cleaned by removing
unwanted adhesives dirt.
Inspection by OS: QS inspects the PV module against any visual defect. The
electrical parameters are also inspected to clear the acceptable modules for
supply to the end-users.
As explained hereinabove, a module is tested for electrical power output at the
laminate stage only. It may be noted that after testing of the electrical power
output, the laminate undergoes further operations for example, trimming, frame
fixing, JB fixing, lead fixing. Thus, a possibility always exists for the P.V. module,
of loosening of leads in the clips, loosening of diodes from its position, defective
diodes, improper connectivity of lead wire with the terminal box, which can not be
detected by prior art visual inspection. The present inventors through extensive
search on prior art recognized that the prior art fails to provide a system or
device enabled to inspect the healthiness of the module at the final stage.

OBJECTS OF THE INVENTION
It is therefore an object of the invention to propose a device for inspecting a PV
module at the final stage.
Another object of the invention is to propose a device for inspecting a PV module
at the final stage, which is enabled to determine the electrical integrity of a PV
module.
A further object of the invention is to propose a device for inspecting a PV
module at the final stage which is cost-effective and easy to use.
SUMMARY OF THE INVENTION
Accordingly, there is provided a device for inspecting a PV module at the final
stage. The device uses 230V power supply for illuminating a lamp. A voltmeter is
connected in the circuit. The module output voltage is indicated in the voltmeter.
The lamp is connected through a foot switch. Voltmeter inputs can be easily
connected with the module output leads. A circuit diagram is shown in the fig 3.
BRIEF DESCRIPTION OF THE ACCOMPAYING DRAWINGS
Figure 1(a) - Shows a process flow for producing photovoltaic (PV) cell.
Figure 1(b) - Shows a process flow for fabricating a photovoltaic module.
Figure 2 - Shows interconnectivity of a PV module.

Figure 3 - Shows a circuitory of a device for inspecting a PV module at the final
stage of the invention.
Figure 4 - Shows a block diagram of a device for inspecting a PV module at the
final stage of the invention.
DETAILED DESCRIPTION OF THE INVENTION
The inventive device is applicable for final inspection of all interconnections in
the PV modules after fixing the junction box. Accordingly light is directed on the
module covering all three branches of strings widthwise, but not on entire the
surface of the module. There is no recording of data envisaged in this device. As
shown in figure 4, the device consists of :
- at least one digital voltmeter for measuring DC input;
- a neon lamp;
- a foot operated pedal switch;
- an input power supply and cables;
- a mechanical enclosure for the device; and the lamp;
- a support for the device; and
- an inspection strand for inspection of the PV module by the device

OPERATION OF THE TESTING DEVICE:
The device comprises a digital voltmeter capable to measure DC input at the
range from 0 to 999V, input supply for the voltmeter being AC, 230V. A neon
lamp for example 1KW power, 230V, AC input provided as a source of light.
These components are assembled in an enclosure and kept on a stand. Power
supply cables, pedal switch are connected to the device. At least two cables are
connected to the device to connect with the PV module power output cable. The
module DC output is fed to the voltmeter for showing voltage produced by the
module.
Operating procedure:
• The module under inspection is placed on the inspection stand facing the
cell side down.
• The device is placed below the module within the four legs of the
inspection stand.
• AC input is connected to the device through an input cable.
• Check the functioning of the voltmeter. The voltmeter shall be on and
shows 0 volt.
• Press the pedal switch and check the light glows.

• Connect the module power cables with the device using a matching cable
provided in the device.
• Observe the voltage.
• Press the pedal switch and observe the voltage shown by the voltmeter.
• If all the connections are perfect, the voltmeter shows a voltage about
20V. If any loose connection or defect on any branch of the strings, a
voltage less than is exhibited by the voltmeter. It indicates that there is
some problem in the module and not fit for dispatching to customer.
• Repeating the above steps for subsequent modules.

WE CLAIM :
1. A device for inspecting a PV module at the final stage, comprising :
a digital voltmeter enabled to measure D.C. input at the range of 0 to 999
volt;
a power source for supplying 230V, AC to the voltmeter;
a neon lamp operable under 230V, AC input connectable to the voltmeter,
the neon lamp acting as a source of light;
a supporting structure accommodating a metal enclosure, the metal
enclosure including the voltmeter, the neon lamp, and the connecting
cables;
a PV module to be tested disposed above an inspection bay with the
output cables of the module for insertion into the device during testing;
and
a foot operated pedal switch connectable to the device to check glowing
of the neon lamp.
2. A method for testing of an assembly of a PV-module and a junction box,
the method comprising the steps of :-
placing the assembly on an inspection bay with the PV cells positioned
downwards;

- placing the testing device on a supporting structure, the supporting
structure being located within four legs of the inspection bay;
- providing the device with 230V AC supply from a power source;
- connecting the PV-module assembly with the device by joining the output
cables of the assembly and the device;
- recording the voltage exhibiting on the voltmeter, after pressing the pedal
switch;
- repeating the steps and recording an average value exhibited by the
voltmeter; and
- allowing the module assembly to pass the test which records an average
voltage about 20 volt.

ABSTRACT

The invention relates to a device for inspecting a PV module at the final stage,
comprising: a digital voltmeter enabled to measure D.C. input at the range of 0
to 999 volt; a power source for supplying 230V, AC to the voltmeter; a neon
lamp operable under 230V, AC input connectable to the voltmeter, the neon
lamp acting as a source of light; a supporting structure accommodating a metal
enclosure, the metal enclosure including the voltmeter, the neon lamp, and the
connecting cables; a PV module to be tested disposed above an inspection bay
with the output cables of the module for insertion into the device during testing;
and a foot operated pedal switch connectable to the device to check glowing of
the neon lamp.