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Sylvania Super Metalarc Vertical MS1000/BU |
Convection currents are present in all arcs due to the effects of gravity. For instance a horizontal arc will bow upwards at its centre - the reason why the electric 'arc' is so named. This excessively heats the upper centre of the arc tube wall and the lamp must be run at lower performance levels to prevent overheating here. Curving the arc tube to match the shape of the arc realises improved thermal uniformity, allowing average temperatures to be increased with a benefit in efficiency, such as in the lamp described here.
Matters are somewhat different in the case of vertical arcs. Here it is found that the arc tube convection currents tend to separate into upper and lower patterns. The lower pattern is richer in the metal halide additives and has high efficacy. The upper pattern has a lower halide concentration and is closer to a plain mercury discharge. The total lamp output and efficacy is a combination of these two regions.
By expanding the arc tube diameter in the upper region, the lower halide-rich region is encouraged to fill the arc tube volume with one single convection pattern. The result is a 25% increase in luminous efficacy and better colour uniformity. A coating of heat-reflective zirconium oxide paint behind the lower electrode serves to raise the wall temperature in this region.
| Manufacturer: | GTE Sylvania | |
| Lamp Power: | 1000 Watts | |
| Lamp Current: | 4.3 Amps | |
| Lamp Voltage: | 265 Volts | Min. RMS 340V |
| Cap Type: | E39s/45 | Brass with Vitrite |
| Bulb Finish: | Clear | Lead Borosilicate |
| Bulb Type: | BT-178 | BT-56 (in eighths / inch) |
| Overall Length: | 390 mm | 15 3/8 inches |
| Light Centre Length: | 241 mm | 9 1/2 inches |
| Arc Length: | 90 mm | 3 1/2 inches |
| Electrodes: | Single coil overwind | Thoriated tungsten |
| Inner / Outer Atmosphere: | Ar | Hg, (Na, Sc, Th)Ix | Outer: Nitrogen |
| Luminous Flux: | 125,000 lm @ 100 hours | 100,000 lm mean thro' life |
| Luminous Efficacy: | 125.0 lm/W @ 100 hours | 100.0 lm/W mean thro' life |
| Colour Temperature & CRI: | CCT: 3500K | CRI: Ra 65 |
| Chromaticity Co-ordinates: | CCx: 0.400 | CCx: 0.375 |
| Burning Position: | Base Up ± 15° | |
| Rated Lifetime: | 10,000 hours | To 50% survival |
| Warm-up / Re-strike Time: | 2 minutes to 80% lm | 10 minutes |
| Factory: | Manchester, N.H. | U.S.A. |
| Date of Manufacture: | December 1984 | |
| Original / Present Value: | $145.36 (1991) | £114.77 (2004) |
