Energy Balance of Low Wattage Single-Ended Metal Halide Lamps and the Method of Calculation of Discharge Capsule Size

Abstract

A new approach to design of low wattage metal halide lamps has been used in order to minimize the end losses and to make the wall temperature more uniform. Using the method suggested by Elenbaas, the lamp's absolute total radiation was measured as a function of input power for discharge capsules of different sizes filled with mercury and sodium-scandium iodides. From this experimental data, the discharge thermal losses, i.e., that part of the lamp imput power which goes into heating the quartz capsule, were determined and applied in a thermal balance equation from which the quartz capsule dimensions were found for single-ended lamps of different wattages at a given wall temperature. The described method can be successfully used with only slight modifications for engineering calculations of other lamp types.