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Solarstream Linear Sodium SON-L 250W |
By switching the bulb material from glass to heat-resistant quartz, it could be brought closer to the arc without risk of melting. Additionally the outer is filled with high pressure argon, instead of the vacuum atmosphere of other sodium lamps. This permits a higher loading with increased output, the gas pressure restraining the rate of alumina evaporation and lumen depreciation. However it is imperative that luminaires be sealed, otherwise air draughts will cool the lamp, this cooling being conducted via the gas filling to the arc tube. Lamp voltage is about 20% lower in free air.
The SON-L range comprised 250, 310, 400 & 1000W types. The R12.5s cap was introduced with silver plated copper pins to ensure reliable electrical contact at the high current and temperature. Competitors were fast to offer their own variants - Thorn's SON-TD becoming the market leader as its length and contact type matched that of linear halogen lamps. An identical product was offered by Sylvania until quite recently. German Osram's lamps are characterised by their very short length and the Fc2 end contacts.
Linear SON has remained a small part of the market, owing to the high lamp cost, and because standard lamps are usually good enough. It is used only where optical precision is demanded. The SON-L range was discontinued in 1994.
| Manufacturer: | The General Electric Company of England PLC | |
| Lamp Power: | 250 Watts | |
| Lamp Current: | 3.0 Amps | 4.1A Starting current |
| Lamp Voltage: | 100 Volts (in luminaire) | 80 Volts (in free air) |
| Cap Type: | R12.5s | Silver plated copper pin |
| Bulb Finish: | Clear | Quartz |
| Bulb Type: | T-20 | T-6 in eighths/inch |
| Overall Length: | 273 mm | 10¾ inches |
| Contact Length: | 265 mm | 10½ inches |
| Arc Length: | 88 mm | 3½ inches |
| Electrodes: | Backwound Tungsten | Barium Calcium Tungstate |
| Atmosphere: | Na,Hg | Xe | Outer: Argon high pressure |
| Luminous Flux: | 29,000 lm @ 100 hours | 28,500 lm @ 2,000 hours |
| Luminous Efficacy: | 116.0 lm/W @ 100 hours | 114 lm/W @ 2,000 hours |
| Colour Temperature & CRI: | CCT: 2100K | CRI: Ra 23 |
| Chromaticity Co-ordinates: | CCx: 0.526 | CCy: 0.418 |
| Burning Position: | Horizontal ± 20° | |
| Rated Lifetime: | 10,000 hours | 80% survival, 90% lumens |
| Warm-up & Re-strike Time: | 3 mins to 80% light | 30-60 seconds restrike |
| Factory: | Shaw, Oldham | England |
| Date of Manufacture: | May 1992 | Date Code Z5 |
| Original & Present Value: | £75.07 (1992) | £104.07 (2005) |
