Driving Waveform Effects On Acoustic Resonance, Electrode Temperature And Dimming Of HID Lamps

Compared to other lamps, HID lamps have the advantages of high luminous efficacy, high color rendering index, and long lifetime. Due to their negative voltage-current characteristics, HID lamps have to work with certain ballasts. In order to study the influence of driving waveform on the parameters of HID lamps, we did some experiments to investigate the acoustic resonance characteristic, electrode temperature and dimming feature of HID lamps.Chapter1mainly introduced the fundamental knowledge of HID lamps and experimental content and objectives.Chapter2described the acoustic resonance experiment of HID lamps. We measured the electrical parameters (such as current, voltage and equivalent impedance) and photometric parameters (such as color temperature, color rendering index, luminous flux and luminous efficacy) at different working frequencies, then got the acoustic resonance frequencies from the variation of these parameters. The experimental results show that the lamps have acoustic resonance at30kHz and45kHz, and close to these two frequencies, the color temperature and color rendering index have substantial changes. However, the luminous flux and luminous efficacy have no such sudden changes at acoustic resonance frequencies.Chapter3described the experiment of electrode temperature measurement of HID lamps. We measured the electrode temperature of a quartz mental halide lamp at different working frequencies, different electrode position and different working current. The experimental results show that the electrode temperature changes periodically with time. When the electrode is in cathode phase, its temperature drops, and rises in anode phase. When the frequencies rise, the variation amplitude of the electrode temperature drops, and so as the average temperature of the electrode. The electrode temperatures at different electrode positions are different, the temperature is the highest near the electrode tip. Away from the tip, the average temperature and its fluctuation drop gradually. When the working current goes down from the rated value, the electrode drops faster and faster. Under a certain current value, the electrode temperature is too low, which may cause the arc to be unstable or even extinguish.Chapter4described the dimming experiment of a UHP lamp with rated power250W. In the experiment, we measured the lamp electrical parameters of current, voltage etc. and color parameters of luminous flux, color rendering index, color temperature etc. at different power input. The results show that the UHP lamp voltage rises with higher power input except a small drop at170W which results a reverse Z curve. The luminous flux, color rendering index and luminous efficiency rises with higher power input, but the color temperature has a sudden rise and then drops slowly. At last, with the measured full width of half maximum of Hg546nm spectral line, lamp voltage and lamp current, we calculated the mercury pressure at different input power。Chapter5summarized the above three chapters and got the final conclusions.