Dimming Characteristics of Large-scale High-Intensity-Discharge (HID) Lamp Lighting Networks using a Central Energy-Saving System

This paper summarizes the test results on several large-scale lighting systems based on a range of high-intensity-discharge (HID) lamps. The study focuses on the energy-saving, energy efficiency and dimming characteristics of magnetic-ballast-driven HID lamp systems that are suitable for public lighting networks. A central energy-saving unit that can change the input mains voltage of 220V to a variable voltage within 220V to 170V is used to control a large lighting network. This central dimming unit offers a new freedom for users to use lighting energy when and where it is needed and to an appropriate power level. Lamp characteristics under full and reduced voltage operation for 6 types of high-intensity-discharge (HID) lamps have been measured. Six large-scaled networks of ballast-lamp sets have been set up and dimmed with a central energy-saving unit with a rated power of 13.2kVA per phase. The full load current under test was set at about 40A per phase. The loss of the energy-saving unit on a per-lamp-set basis was measured at different voltage levels. It is found that the energy-saving unit can reduce overall system power at least 40% without causing lamp flickering. Through the controllable voltage range, there is no obvious change in color temperature. The lamp power and light output decrease almost linearly with input voltage within the range from 170V to 220V, and the power loss of the energy-saving unit is less than 2.4% of the full power in all tests. For these large-scaled lighting networks, it is envisaged a 25%-35% of energy-saving can be achieved in large public lighting applications