NaT 200W-3 German Linear Sodium

Within 3 years of AEI-Mazda's 1959 invention of the linear sodium concept, the first lamp to break the 100 lm/W barrier, German Osram usurped that feat with its 118 lm/W Na 220W lamp. This was achieved by increasing both the length and diameter of the arc tube to reduce current density. It was a 1200mm long lamp in a 40mm outer jacket having grooves of about the same aspect ratio as the British lamps. Between 1962 and 1965 the diameter was increased to 45mm to accommodate a heat-reflection glass sleeve.

Like other high power sodium lamps, it had a high arc voltage which limited system efficacy owing to the need for inefficient transformer ballasts. Osram tried to overcome this by running its lamps on cross-phase 380V mains with a choke ballast plus thermal starter-switch, but that was not very convenient. In 1966, work commenced on a low voltage lamp that could maintain the same output but run direct on 220V mains with ignition by a simple glow-starter. The result was this NaT 200W-3, introduced in 1966-67.

The low voltage was attained by widening the arc tube to 38mm, plus a novel Krypton-Argon-Neon fill which produces an unusual blue-white colour before the lamp has warmed up. The aspect ratio of the grooves is shorter than normal, this raising surface area and efficacy. The first lamp had a heat reflection coating of tin oxide and achieved 29,000lm at 145lm/W, upgraded in 1968 to 31,000lm at 155lm/W thans to a superior indium-tin oxide film. Note the gaps in the coating near the lamp ends, to prevent it from becoming electrified and drawing sodium out of the arc tube. Despite the high performance sodium lamps never became popular in Germany, and this model was discontinued in 1985.
´╗┐Manufacturer: Osram GmbH
Lamp Power: 200 Watts
Lamp Current: 2.3 Amps
Lamp Voltage: 90 Volts
Cap Type: 2x G13 Ni plated brass
Bulb Type: T-45 T-14.7 in eighths/inch
Bulb Finish: Indium-tin oxide film Soda-lime glass
Electrodes: Triple Coil Black W + BCT emitter
Arc Length: 1444 mm Electrode Gap: 1000 mm
Atmosphere: Na | KrArNe Outer: Hard Vacuum
Luminous Flux: 31,000 lm (@ 100 hrs)
Luminous Efficacy: 155 lm/W (@ 100 hrs)
Colour Temperature & CRI: CCT: 1700K CRI: Ra -44
Chromaticity Co-ordinates: CCx: 0.574 CCy: 0.425
Rated Lifetime: 7,500 hours
Warm-up & Re-strike time: Approx. 20 minutes Instantaneous
Burning Position: Horizontal ┬▒ 20┬░
Overall Length: 1200 mm 48 inches
Insertion Length:
Factory: Berlin Charlottenburg Germany
Date of Manufacture: July 1978 Date Code: nFX
Original Value:
References: 1) Osram GmbH Catalogue, 1962 DE.
2) Osram GmbH Catalogue, 1965 DE.
3) Osram GmbH Catalogue, 1984 DE.
4) Untersuchungen an Na-Dampflampen, J.Pfaue & H.Schirrwitz, Technisch-wissenschaftliche Abhandlungen der Osram-Gesellschaft v9 (1967) p.79-110
5) Osram Neuheiten, April 1968.
6) Osram Lebensdauern Entladungslampen 1968.