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Methods were investigated to improve the lamp characteristics of inductively coupled electrodeless metal halide lamps to make them practical. First, evaluating lamp efficacy by adjusting the lamp parameters showed that a lamp efficacy of 180 lm/W (Including coil loss: 151lm/W) white color could be attained. Second, the conditions generating free iodine and bulb deterioration, the main factors limiting the life of these lamps, were investigated. For long-life-type lamps, which had 130 lm/W of lamp efficacy, the lamp lumen level did not decrease during 21,000 hours of overload operation (corresponding to 58,000 hours of rated-load operation). These lamps thus have excellent lumen maintenance and life performance compared with conventional electrode metal halide lamps. Third, improving circuit reliability by decreasing the Q value of the resonant circuit was investigated for long-life-tpye lamps which had 145 lm/W of lamp efficacy. The relationship between the Q value and the lamp parameters was analyzed, and the Q value was decreased to 78% its value while maintaining the same lamp performance.

Summary form only given. Inductively coupled electrode-less metal halide lamps were expected to show high efficacy and good life performance and had been studied extensively. At first, at LS6 in 1992, a new inductively coupled HID lighting system was proposed. Since then, improvement of operating circuit efficacy and operation stability of the system has been discussed by using the current limitation of the co-axial cable for impedance matching circuit. On the other hand, dosing tin halides in those arc tubes was tried to extend their life. In this study, to put these systems into practical use, improving lamp efficacy, confirming effect of tin halides on their life performance and improving their operation stability by decreasing Q value, which is resonance constant of their impedance matching circuit, were attempted. As a result, the lamp efficacy reached 180 1m/W with white light and 58% of visible radiation power ratio to the input power was realized by optimizing rare gas pressure, input wattage, a sort of doses and by employing the elliptical-shape outer jacket with uniform temperature distribution on the arc tube surface. Their life performance was confirmed that the lamps with tin halides were abler to survive up to 60000 hours at rated load operation without decreasing lumen output, because tin halides absorb iodine gas generated in the arc tube. Optimizing the distance between the coil and the arc tube, the arc tube diameter and the rare gas pressure, Q value was decreased by 22% without reducing the lamp performance.