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Philips SOX Compact 18W |
A key feature is its very narrow diameter discharge tube, measuring just 7mm internally. This allowed a reduction in lamp current, and hence discharge current density, with a knock-on benefit for luminous efficacy. To achieve a given power dissipation with such low current density, it was of course necessary to increase the length of the discharge tube. Keeping such a large discharge tube of low power dissipation warm enough for the sodium vapour pressure to build up to the level required for optimum efficacy meant that thermal insulation of this lamp had to be maximised.
That has been achieved by a specially enhanced indium-tin oxide coating having an electrical resistance of about 5 ohms per square, similar to that employed on SOX-E lamps. A nickel plated steel heat-reflection disc provides additional insulation at the U-bend, and this supports a small platinum catalyst pellet which breaks down hyrdocarbon vapours in the outer bulb such that they can be removed by the barium getter near the cap, thereby limiting thermal conduction and convection losses.
The lamp is unusually equipped with an E27 screw cap. Philips experimented with various designs having powers from about 8W to 25W, but the concept was never commercialised - perhaps because of the relatively small energy saving vs traditional SOX lamps.
| Manufacturer: | Philips Gloeilampenfabrieken | |
| Lamp Power: | 18 Watts | |
| Lamp Current: | 0.25 Amps | |
| Lamp Voltage: | 75 Volts | 300V ignition |
| Cap Type: | E27s | Brass + Vitrite |
| Bulb Type: | TD-38 | TD-12 in eighths/inch |
| Bulb Finish: | Indium-tin oxide film | Soda-lime glass |
| Electrodes: | CCC-4 Beehive | Black W + BCT emitter |
| Arc Length: | ||
| Atmosphere: | Na | 99% Ne, 1% Ar | Outer: Hard Vacuum |
| Luminous Flux: | 2,160 lm (@ 100 hrs) | |
| Luminous Efficacy: | 120 lm/W (@ 100 hrs) | |
| Colour Temperature & CRI: | CCT: 1700K | CRI: Ra -44 |
| Chromaticity Co-ordinates: | CCx: 0.574 | CCy: 0.425 |
| Rated Lifetime: | Not Published | |
| Warm-up & Re-strike time: | 15 minutes | Instantaneous |
| Burning Position: | Not Published | |
| Overall Length: | ||
| Light Centre Length: | ||
| Factory: | Eindhoven | Netherlands |
| Date of Manufacture: | Approx 1985 | |
| Original / Present Value: | Engineering Sample | No commercial value |
