| HID lamps are wide used in lighting systems, also in indoor and outdoor applications. The ballasts necessary for their normal operation could be magnetic or electronic and in the last decade we assist to a debate on which is a better option, the dimming capabilities being one of the most claimed advantages of the electronic ballasts. But, in the last years, several lower cost solutions for getting dimmability with magnetic ballasts have been reconsidered. In this paper, the possibility to dim lamps trough the classical voltage amplitude modulation by means an autotransformer is explored. This solution can be cheaper, robust and most suited for the low budget Africa’s lighting systems. To understand the context, two lighting systems from Antananarivo, capital of Madagascar, and Dakar, capital of Senegal, have been depicted. Experimental tests have been performed on 250 W HID lamps, a High Pressure Sodium (HPS) and a Metal Halide (MH), operated by Very Low Loss magnetic ballast. The range of the voltage modulation has been from 160 V to 250 V and the power consumption, the light output and the harmonics content have been recorded. The energy saving per lamp by dimming to 160V is about 50 to 55% for the considered lamps. |
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