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IEC 60904-9:2020 © IEC 2020
b) Move the irradiance detector across the entire designated
test area and take
simultaneously recordings with the stationary cell. The recommended minimum step
widths for both spatial directions are the detector dimensions. The maximum step width for
both spatial directions results from the detector dimensions and to 80 % coverage
requirement as defined in 5.3.2.2 . For an array detector the step
width shall correspond to
the spacing of detector cells.
c) Shift the reference point defined in step a) by half dimensions of the detector cell in both
directions and repeat the uniformity measurement as described in step b). This step is
only necessary when the associated positions have not already been covered in step b).
d) Determine spatial non-uniformity using formula (1) for both measured irradiance patterns.
e) The class of the simulator for non-uniformity is determined by the irradiance pattern with
highest value of non-uniformity:
Class A+: Spatial non-uniformity of irradiance
≤
1 %, as specified in Table 3. This
classification can be only assigned if spectral match
evaluation is performed
according to Table 2.
Class A: Spatial non-uniformity of irradiance >1 % and
≤
2 %, as specified in Table 3.
Class B: Spatial non-uniformity of irradiance >2 % and
≤
5 %, as specified in Table 3.
Class C: Spatial non-uniformity of irradiance >5 % and
≤
10 %, as specified in Table 3.
A table of the measured irradiance pattern should be supplied with the classification report
to assist the user in testing and to clearly define different areas with different
classifications and find the optimum test positions for different module/cell sizes.
f) If the irradiance patterns measured in steps b) and c) differ in spatial non-uniformity by
more than 0,5 % (class A+) / 1 % (class A) / 1,5 % (class B) / 2 % (class C) , a more
detailed assessment of the uniformity should
be undertaken, tailored to the intended use
of the simulator. For example, a higher resolution measurement with
a smaller detector
(size-matched to the cell dimensions of the devices to be tested) would provide more
useful data for the calculation of non-uniformity contribution to
final measurement
uncertainty, especially in cases where thin-film technologies of strip-like cell aspect ratio
are to be measured. In such cases, the resulting additional non-uniformity information is
for the benefit of the system operator and will not affect solar simulator classification.
For the verification of spatial non-uniformity (periodical maintenance work or onsite
acceptance testing) a reduced number of measurement points is permitted. The details and
best practice recommendations for different types of light source (single lamp, multi-lamp,
lamps with
integrated optics, etc.) are given in IEC TR 60904-14. The whole grid shall be
measured if the difference of non-uniformity values, calculated from the restricted number of
measurement points, and the previous or factory measurement is larger than: 0,5 % (class A+)
/ 1 % (class A) / 1,5 % (class B) / 2 % (class C) or if the non-uniformity value
measured with
the restricted number of measurement points falls outside the original classification.
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