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MBIL/H Linear Metal Halide Floodlight |
The principal reason for the long arc was to enable the lamp to be used in floodlighting luminaires of a similar type to the very successful design which had been created for linear halogen lamps, and were popular for the floodlighting of sports fields and buildings. There was a strong desire to achieve the same kind of optical control from a discharge lamp to realise their significant energy saving possibilities.
Prior to this time nearly all discharge lamps required an outer jacket to provide thermal insulation and prevent the end seals from oxidation. The large dimensions of the outer bulb made it impossible to locate such lamps at the focus of a small reflector, as was possible with linear halogen. So from the outset of MBIL development it was decided to dispense with the outer jacket, thermal insulation and protection from the environment being provided by the sealed fitting it was designed to be used with.
Early MBIL lamps were made in clear quartz but owing to the long arc, colour inhomogeneities can occur due to demixing of the halides. Externally frosting the arc tube successfully resolved these issues. Special coloured lamps were also made. Today the MBIL lamp continues to be popular in some applications on account of its remarkably good colour stability, but it has been largely superseded by shorter arc types which can achieve better efficacy in newly designed luminaires.
| Manufacturer: | Thorn Lighting Ltd. (Lamp No. 91-7473) | |
| Lamp Power: | 1500 Watts | |
| Lamp Current: | 6.7 Amps | |
| Lamp Voltage: | 250 Volts | |
| Cap: | Rx7s | |
| Bulb Finish: | Frosted quartz | |
| Bulb Type: | T-20.1 (pinches 21.3 wide) | |
| Overall Length: | 254 mm | |
| Light Centre Length: | 127 mm | |
| Electrodes: | Backwound tungsten with thoriated shank | |
| Atmosphere: | Ar | Hg (Na,Sc)Ix | |
| Luminous Flux (100 hrs): | 120,000lm (100hrs) | 110,000lm (2000hrs) |
| Luminous Efficacy (100 hrs): | 80 lm/W (100hrs) | 73 lm/W (2000hrs) |
| Colour Temperature & CRI: | CCT: 5200K | CRI: Ra 65 |
| Chromaticity Co-ordinates: | CCx: 0.340 | CCy: 0.360 |
| Burning Position: | Horizontal ± 45° | |
| Rated Life: | 6000 hours (to 50% survival) | |
| Warm Up / Re-strike Time: | 2 minutes | 15-20 minutes |
| Factory: | Leicester, England | |
| Date of Manufacture: | July 1988 | |
| Original / Present Value: | £88.00 (1988) | £145.04 (2002) |
