Ageing effects on the stability performance of small wattage metal-halide (MH) lamps

It is widely perceived that the ageing process of a MH lamp shifts the distribution of the acoustic resonance eigenfrequencies. However, there is no detailed research result so far to show how and to what extent the acoustic resonance frequency band shifts. The purpose of this paper is to carry out a study on the influence of operating time on the stability of small wattage MH lamps. Experimental results show that the ages of lamps do not affect the fundamental acoustic eigenfrequency values. The upper limit of highest acoustic resonance frequency bands where arc will become unstable is not affected by the ages of lamps. However, the ages of lamps do increase the instability inside the lamps. It makes lamp voltage increases significantly.