Sõlarc 3W Metal Halide Lamp

Welch Allyn's Sõlarc series of metal halide lamps represents the ultimate achievement in reducing the size, and wattage of metal halide light source technology. The lamp illustrated here is an experimental 3 Watt rating of incredibly small dimensions - surpassed only by a still smaller 2W prototype.

The arc tube is AC driven and of course requires a specially developed electronic ballast for stable operation. An ignition peak of 6.0kV is applied, hot restrike then being possible with the aid of a starting antenna alongside the arc tube.

The lamps achieve an unusually high efficacy, and although the precise operating characteristics of this lamp are unknown, the larger and commercially available 10W version is capable of around 53 lm/W. This results partly from heavy doping with thallium and indium iodides, and consequently the lamp produces a strongly blue coloured output. The wall loading is of the order of 25-35 W/cm² and the strong re-absorption of the indium peak is evident in the spectrum.

The principal market for the 10W-plus lamps is as alternatives to halogen lamps in professional battery-powered applications. Its strongest feature is the low wattage compared to equivalent output halogen lamps, which offers important potential to extend battery life. It has found applications in bicycle headlamps, underwater diving lights, fibre optics and professional torches and flashlights.

The arc tubes rated below 10W, such as this 3W sample were never commercialised, in view of the fact that their efficacy, lifetime, size and cost are were all surpassed by competing developments with LED technologies.
Manufacturer: Welch Allyn
Lamp Power: 3 Watts
Lamp Current: Unknown
Lamp Voltage: Unknown
Cap Type: Wires
Bulb Finish: Clear Quartz
Bulb Type: BTT-3 mm BTT-1 eighths/inch
Overall Length: 25mm 1 inches
Light Centre Length: N/A
Arc Length: 1mm 1/25 inch
Electrodes: Thoriated tungsten rod
Atmosphere: Ar | Hg, (Sc,Na,In,Tl) Ix
Luminous Flux: Unknown
Luminous Efficacy: Unknown
Colour Temperature & CRI: CCT: c. 8000 CRI: Ra c.80
Chromaticity Co-ordinates: CCx: CCy:
Burning Position: Horizontal ± 45°
Rated Lifetime: Not published
Warm-up & Re-strike Time: 10 seconds Instant
Factory: Skaneateles Falls, NY U.S.A.
Date of Manufacture: c. 1990
Original & Present Value: N/A
References: 1) Welch Allyn Technical Data Sheet
2) Miniature Metal Halide Lamps Part I, D.E. Brabham, 10th International Symposium on the Science & Technology of Light Sources, Toulouse, France, 2004