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Philips SOX-E (Economy) 26W, 1st Generation |
Lamp current is a little over half that of the traditional SOX range, to lower discharge current density and raise efficacy. Lower power requires improved thermal insulation to keep the discharge tube at the temperature required for optimum efficacy. This is achieved by an increased tin : indium ratio in the IR film, improving reflectivity without reducing transmission of sodium light. This coating is characterised by a reddish colour of surface reflections. Thermal insulation at the U-bend has been improved by changing the shape of the outer envelope, and installing the heat-reflector of the 18W lamp together with a small metal spacer to ensure that the IR film extends further past the bend. The more uniform sodium vapour pressure in this region leads to a reduction in lamp voltage. Finally to reduce conduction and convection losses, a platinum catalyst pellet is clipped into the bend support - this cracks hydrocarbon impurities to yield hydrogen, which is then eliminated by the barium getter.
SOX-E lamps should be used on low-current SOX-E ballasts for optimum efficacy, but can also deliver energy savings and improved efficacy on standard SOX gear. Thanks to the lower voltage there is a small power drop, and the improved insulation delivers increased efficacy. There is always a drop in lumens vs standard SOX, but this is often acceptable as many installations became overlit when SOX replaced SOI.
| Manufacturer: | Philips Gloeilampenfabrieken | |
| Lamp Power: | 25 Watts (SOX-E gear) | 31W (SOX gear) |
| Lamp Current: | 0.37 Amps (SOX-E gear) | 0.6 Amps (SOX gear) |
| Lamp Voltage: | 59 Volts (SOX-E gear) | 59 Volts (SOX-E gear) |
| Cap Type: | BY22d | Black Alkyde Insulator |
| Bulb Type: | T-50 | T-16 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: | 3,500lm (100h SOX-E gear) | 4,060lm (100h SOX gear) |
| Luminous Efficacy: | 140lm/W (100h SOX-E gear) | 131lm/W (100h SOX gear) |
| Colour Temperature & CRI: | CCT: 1700K | CRI: Ra -44 |
| Chromaticity Co-ordinates: | CCx: 0.574 | CCy: 0.425 |
| Rated Lifetime: | 12,000 hours | 50% survival |
| Warm-up & Re-strike time: | 7 minutes | Instantaneous |
| Burning Position: | Horizontal ± 110° | |
| Overall Length: | 310 mm | 12¼ inches |
| Light Centre Length: | 183 mm | 7¼ inches |
| Factory: | Turnhout | Belgium |
| Date of Manufacture: | December 1984 | |
| Original / Present Value: | GB £14.74 (1988) | GB £35.30 (2014) |
