Metal Halide Multi-Vapor MV-400/BD

The first metal halide lamps, invented by GE and announced in 1962, were based on a simple sodium-thallium chemistry. They showed improved efficacy and colour rendering over mercury vapour lamps, however problems with colour stability both during life and between individual lamps were quickly encountered. The life variation was caused by the fact that the orange-radiating sodium chemistry was lost from the arc tube more rapidly than the other elements. The lamp-to-lamp variation resulted from the fact that the arc tubes were formed fairly crudely according to the methods used for mercury lamp production, and the differing shape and temperature profiles resulted in a shift in colour.

The problems were dramatically reduced following Sylvania's invention of the sodium-scandium-thorium lamp chemistry. Scandium and thorium are multi-line radiators and produce a white light on their own. The addition of sodium makes it possible to reduce colour temperature to more favourable levels. However eventual sodium loss and variations in arc tube shape simply cause the colour temperature to increase, but the light colour remains white. GE was quick to embrace these developments and this lamp represents one of the company's earliest sodium-scandium products.

Both ends of the arc tube are sprayed with alumina heat-reflective coatings to increase the vapour pressures of the halide salts. These early lamps were originally separately made for Base Up or Base Down operation. Here the auxiliary ignition electrode is unusually located at the bulb crown end, so that it is on the upper side during the intended base-down operation. A bi-metal strip short-circuits this electrode after reaching operational temperature.
Manufacturer: General Electric U.S.A.
Lamp Power: 400 Watts
Lamp Voltage: 130 Volts
Lamp Current: 3.2 Amperes
Cap Type: E39s Nickel Plated Brass
Bulb Type: BT-120 ED-37 in eighths/inch
Bulb Finish: Clear Leaded Borosilicate
Electrodes: Backwound Tungsten
Arc Length: mm inches
Atmosphere: (Na,Sc)Ix|Hg Argon Outer: Vacuum
Luminous Flux: 34,000lm @ 100h 27,200lm mean
Luminous Efficacy: 85.0lm/W @ 100h 68lm/W mean
Colour Temperature & CRI: CCT: 3500K CRI: Ra 65
Chromaticity Co-ordinates: CCx: 0.407 CCy: 0.397
Rated Lifetime: 10,000 hrs (BD±30°) 6,000 hrs (BD 30°-80°)
Warm-up & Re-strike Time:
Burning Position: BD ±80°  
Overall Length: 287 mm 11 5/16 inches
Light Centre Length: 178 mm 7 inches
Factory: Ravenna Ohio, U.S.A.
Date of Manufacture: October 1973 22
Original / Present Value: US $26.80 (1973) GB £ (2008)
 
References: 1) GE Lamp Catalogue, USA, 1975, p.52
2) GE Lamp Catalogue, USA, 1973, p.49
3) Lamp photometry measurement