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MA Medium Pressure Mercury Vapour
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Updated
23-VIII-2006
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Mercury Vapour lamps operating at medium pressure and with arc tubes of aluminosilicate hard glass are classified as the MA style.This was the first commercial kind of mercury lamp which was mass produced for general lighting. Mercury vapour pressure is typically around five atmospheres and the discharge dissipates between 10 and 100 watts per centimetre of arc length.
MA technology was developed in 1931 by Osram-GEC England, and the first product to be marketed was a 400W rating for vertical cap-up use. The lamp enjoyed tremendous success in factory lighting to replace high wattage incandescent lamps in high bay luminaires, an environment where its cold greenish-blue light was acceptable. Mercury lamps seemed to be an obvious choice for streetlighting as well, but in this application they must burn horizontally to efficiently illuminate the road. In this orientation the convection currents in the discharge tube cause the arc to bow upwards, and before long it can cause the arc tube glass to soften and fail. It was necessary to correct the arc position using a magnetic deflector above the lamp, and once this had been perfected, the first streetlighting installation was set up, just around the corner from Osram's Wembley lamp works on Watford Road, North London. The concept proved tremendously successful and within a year the MA lamp technology had been licensed to GE in America and to its British subsidiary, BTH Mazda.
A 250W lamp later joined the range and was followed in 1936 by a 150W rating as well. But owing to the electrode power losses which become relatively higher as lamp wattage is reduced, it was only marginally more efficient than tungsten filament lamps and was quickly withdrawn. The key to making an efficient lamp of low wattage lies in increasing the mercury pressure to further increase efficacy, and that is the subject of the next page on MB style high pressure mercury technology. Detailed information on the development and fundamentals of the MA lamp can be found by clicking the link to the MA Technical Section. |
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Mazda |
400W |
| MA/V 400W of very early design |
| 1944 |
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Philips |
250W |
| Philora MA/V 250W lamp of first British design |
| 1945 |
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Osram |
265W |
| HgH 1000 of typical German construction |
| 1945 |
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Philips |
450W |
| HO 450 of typical Dutch construction |
| 1956 |
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Mazda |
250W |
| MA/U 250W universal burning lamp |
| 1955 |
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Crompton |
250W |
| MA/V with air-filled outer bulb arrangement |
| 1959 |
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Osram |
400W |
| MA/V lamp of late design for vertical use |
| 1963 |
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Westinghouse |
400W |
| A-H1 Early American style |
| 1942 |
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GE |
400W |
| A-H1 American style medium pressure lamp |
| 1947 |
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GE |
250W |
| H-2 with unusual bare arc tube design |
| 1944 |
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GE |
400W |
| H25-DE Last American style |
| 1959 |
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Siemens |
400W |
| Sieray MA/H coloured lamp for floodlighting |
| c. 1940 |
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Siemens |
400W |
| Sieray MA/H coloured lamp for floodlighting |
| c. 1940 |
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Osram |
400W |
| MAF/V Mercury Cadmium Fluorescent |
| 1963 |
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Siemens |
300W |
| MAT Mercury Blended with tungsten ballast |
| c. 1950 |
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