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SON-I Solarcolour High Pressure Sodium |
Having the same dimensions as a 125W MBF mercury lamp, it was ideally suited to introduce SON technology to Group B street lighting, as well as any areas where low luminaire heights ruled out the use of higher wattage SON lamps. A diffuse elliptical lamp was made to work with the optics of existing mercury lanterns, as well as this clear format for new luminaires which achieved better optical control. All lamps incorporated an internal ignitor so that no extra gear space was required in the standard mercury lanterns.
The ignitor takes the form of the GEC's classic snap-switch design. A tempered bi-metal strip with silver contacts passes a current to a nearby heater coil, all mounted on a small ceramic block. At switch-on the heater becomes incandescent and draws full current from the ballast, around which a magnetic field develops. After a minute or so, the bi-metal strip flexes and instantly breaks the whole circuit. The collapsing field around the ballast windings induces a high voltage which is usually successful in striking the arc at the first attempt. The hot restrike time is rather long though, with 15-20 minutes being required for the bi-metal to cool.
Also of interest in this lamp are the early disc-type niobium seals at either end of the arc tube. One end is blind, while the other contains sodium amalgam within the exhaust tube.
| Manufacturer: | The General Electric Company of England PLC | |
| Lamp Power: | 120 Watts | |
| Lamp Current: | 1.4 Amps | |
| Lamp Voltage: | 100 Volts | |
| Cap Type: | E27s/27 | Ni plated brass + vitrite |
| Bulb Finish: | Clear | Soft glass |
| Bulb Type: | ED-75 | ED-23½ in eighths/inch |
| Overall Length: | 178 mm | 7 inches |
| Light Centre Length: | 112 mm | 4½ inches |
| Arc Length: | ||
| Electrodes: | Backwound Tungsten | Barium Calcium Tungstate |
| Atmosphere: | Na,Hg | Xe | Outer: Hard Vacuum |
| Luminous Flux: | 8,600 lm (@ 100 hrs) | 8,000 lm (@ 2,000hrs) |
| Luminous Efficacy: | 71.7 lm/W (@ 100 hrs) | 66.6 lm/W (@ 2,000hrs) |
| Colour Temperature & CRI: | CCT: 2100K | CRI: Ra 23 |
| Chromaticity Co-ordinates: | CCx: 0.526 | CCy: 0.418 |
| Burning Position: | Universal | |
| Rated Lifetime: | 10,000 hours | 80% survival, 90% lumens |
| Warm-up & Re-strike Time: | 5 minutes | 15 minutes |
| Factory: | Shaw, Oldham | England |
| Date of Manufacture: | May 1976 | |
| Original & Present Value: | £28.89 (1988) | £51.89 (2005) |
