The lamps are 75W halogen bulbs with a wide-angle dichroic reflector such as are used in shop displays etc. The lamps are placed approximately lm from the test plane so that the light from each illuminates a circular area of 0.3m dia. The lamps are arranged in a triangular tessalation and are electrically con­nected so that each three adjacent lamps are powered from the three seperate phases.

The output from a single lamp is of the form shown in fig. 1. The ripple is of the order of ±10%. When the output from three lamps on seperate phases are superimposed the ripple is reduced to less than ±0.5%.

At the edges of the array of lamps a highly reflective polished aluminium sheet is used so that the reflected radiation gives an image of an infinite field of lamps at the test plane. A unifor­mity of ±3% is measured, but improved uniformity may be achieved with individual lamp output adjustment. A simple prototype using 6 lamps was built to demonstrate the principle (Fig. 2) and a large array of 99 lamps is under construction.

A reference cell is used to set the illumination level although spectral mismatch is such that errors are not excessive if a pyranometer is used to measure radiation. A straightforward electronic load or switched resistors may be used to obtain the I-V curve. This technique is particularly useful in an in­dustrial environment where a check of short circuit current may be made using a meter. I-V curve measurements made using this equipment compare well with outdoor tests for both crystalline and amorphous cells.


Lamp 1 Lamp 2 Lamp 3 Mean Output

Fig, 1. A C Lamp Output

3 — Phase Overlap

Irradiance (W/m2)/l00


Fia. 2. Prototype unit



Faeka M. H. Khater

ERI, National Research Center, Dokkі
Cairo, Egypt

Updated: August 22, 2015 — 10:26 pm