Polamp WLS 400W 1st Generation
This lamp is representative of the earliest style of high pressure sodium lamp to have been manufactured in Poland, by that country's state-run lampmaker, Polamp. Dating to 1978, its construction bears many similarities to the early HPS lamps as first developed by General Electric of America. That company formed an early technical agreement with Tungsram of Hungary, and many features of its design were adopted by the other East-European lampmakers.

Seals have been formed to cups pressed from niobium metal, and are believed to have been sealed to the ceramic arc tube with a glass frit material. At the cap end the niobium sealing disc is depressed inwards at its centre, an unusual feature which has only been observed on early Polish lamps. Possibly this was in an effort to reduce stresses within the metal-to-ceramic seals, which can lead to cracking. At the other end of the arc tube the end cap is brazed to a long piece of niobium tube. This is consistent with GE's method of dosing and sealing HPS arc tubes, in which the sodium amalgam is located within this tube and the lamp is sealed off from the exhaust machinery by cold fusion to crimp the tube closed. As with lamps of the British Osram-GEC which also follow this early American arc tube sealing technique, the end of the crimped niobium tube has been arc-fused to reduce risk of leaks. The length of this tube is unusually long, and as a result sodium vapour pressure in this lamp is rather low.

The arc tube is sealed into a narrow ellipsoidal outer jacket of hard glass, whose shape is typical of Tungsram's influence on the other East European lampmakers. A barium getter is provided to maintain high vacuum during lamp life.
Manufacturer: Polamp
Lamp Power: 400 Watts
Lamp Current: 4.6 Amps
Lamp Voltage: 105 Volts
Cap Type: E40s/45 Ni plated brass + vitrite
Bulb Type: ED-58 ED-18 in eighths/inch
Bulb Finish: Clear Borosilicate glass
Electrodes: Backwound Tungsten BCT Emitter
Arc Length:
Atmosphere: Inner: Na,Hg | Xe Outer: Hard Vacuum
Luminous Flux: 44,000 lm (@ 100 hrs)
Luminous Efficacy: 110 lm/W (@ 100 hrs)
Colour Temperature & CRI: CCT: 2050K CRI: Ra 25
Chromaticity Co-ordinates: CCx: 0.534 CCy: 0.431
Rated Lifetime: 10,000 hours
Warm-up & Re-strike Time: 5 minutes 1 minute
Burning Position: Vertical Cap Up ± 110°
Overall Length: 257 mm 101/8 inches
Light Centre Length: 175 mm 7 inches
Factory: Poland
Date of Manufacture: March 1978 Date Code: 03.78
Original / Present Value: Unknown