MA Medium Pressure Mercury Vapour

Updated
15-IV-2017
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higher as lamp wattage is reduced, it was only marginally more efficient than tungsten filament lamps and was quickly withdrawn.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.

Standard Lamps

Westinghouse

400W

A-H1 Early American style
1942

Mazda

400W

MA/V 400W Early British design
1944

GE

400W

A-H1 Early American style
1947

GE

250W

H-2 with unusual bare arc tube design
1944

Osram

265W

HgH 1000 of typical German construction
1945

Philips

250W

Philora MA/V 250W lamp of first British design
1945

Philips

450W

HO 450 of typical Dutch construction
1956

Mazda

250W

MA/U 250W universal burning lamp
1955

Crompton

250W

MA/V with air-filled outer bulb arrangement
1959

GE

400W

H25-DE Final American version
1959

Osram

400W

MA/V lamp of late design for vertical use
1963

Mazda

1000W

MA/H horizontal floodlighting lamp
1952

Coloured Lamps

Siemens

400W

Sieray MA/H coloured lamp for floodlighting
c. 1940

Siemens

400W

Sieray MA/H coloured lamp for floodlighting
c. 1940

Osram

400W

MAF/V Mercury Cadmium Fluorescent
1952

Self-Ballasted Lamps

Siemens

300W

Sieray "Dual" MAT/V First Self-Ballasted Lamp
1940

Mazda

300W

MAT Mercury Blended with tungsten ballast
c. 1955