Due to the very high life of LED lamps, amounting to tens of thousands of hours, the life declared by the manufacturer is most often life determined on the basis of the method of forecasting the long term lumen maintenance. Life forecasting is based on operational measurements of the luminous flux drop over a period of at least up to 6000 h every 1000 h and extrapolation of the obtained results with an appropriate exponential curve. The article presents the results of measurements of luminous flux changes in the range of 0 to 9000 h of operation of light sources. The analysis of the obtained results was carried out and the life of the tested lamps was estimated.

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