Acoustic resonance (AR) occurs in metal halide (MH) lamps and could cause light flicker, lamp arc bending and rotation, lamp extinction and arc tube explosion in the worst situations. This study takes place in the context of developing electronic ballasts with a low-cost and robust AR detection and avoidance mechanism. In this case, a lock-in amplifier is used to obtain the variations of lamp voltage envelope. A mathematical criterion is proposed to classify AR presence and severity. This criterion is based upon the short-term standard variation of voltage envelope and it was tested over a set of MH lamps with different powers and manufacturers. By varying the operation frequency of the high-frequency ballast, it was experimentally possible to control the average electrical power and the level of AR occurrence in the lamps. A data set consisting of healthy (without AR or AR-free) and faulty (with AR) cases was constructed by varying these parameters. The proposed criterion permitted to classify the observed waveforms in a two-dimensional (2D) plane. It was observed that AR-free and AR cases are separated. The results of this study show that the voltage envelope variations and the defined criterion are significantly correlated with AR presence whatever the lamp of the operation power.
['Fang Lei', 'Pascal Dupuis', 'Olivier Durrieu', 'Georges Zissis', 'Pascal Maussion']
Acoustic resonance detection using statistical methods of voltage envelope characterization in metal halide lamps