Lighting : Lighting February 2015 - Vol 35 Issue 1
34 LIGHTING MAGAZINE | February/March 2015 Figure 3. The normalised luminous flux as a function of time for 4 (colour/dot coded) series of directional LED lamps. 48 LED products have been tested in the maintenance test procedure. The light sources were measured in an integrating sphere spectrometer at 500, 1000, 2000, 3000, 4000, 5000, 6000, 11000 and 19000 hours of powered operation. Three of the light sources failed completely within the 3000-7500 hour time span and 10 failed during the remaining time. Examples of the results can be seen in Figure 3. The study was done in an effort to help consumers in making informed decisions, to avoid products with performance characteristics below what should be expected. The study was concentrated on the energy efficiency, spectral light quality and service life of the products, as these characteristics are essential to long term satisfaction and thereby the likely adoption of new technology by consumers. The study supports the notion that the market for consumer grade lighting products has a high variation in efficacy and light quality. Many products available did not meet the criteria of the EU Quality Charter. Without proper education of, or information to the consumer about CRI and light quality, it is possible that consumers will find these products to have a light quality that does not meet their expectations. However, it has been found that most of products tested had a CRI above 80 in accordance with both the EUQC and widely applied European regulation of work places5. With regard to efficacy, there was a large spread in the values, for similar light quality. In the long-term maintenance study we saw a high degree of stability over time for directional sources. Depreciation is evident after 19000 hours with values from 90% to 60%. This outcome is to be expected even though some of these light sources do not reach the useful life of 50000 hours, which is widely quoted. The study was concentrated on the energy efficiency, spectral light quality and service life of the products, as these characteristics are essential to long term satisfaction and thereby the likely adoption of new technology by consumers.
Lighting December 2014 - Vol 34 Issue 6
Lighting April 2015 - Vol 35 Issue 2