Sylvania Unalux Penning-Start Mercury Retrofit

Over time two HID lamp ballast families have emerged - the originals being designed to operate mercury lamps, with a second group tailored for high pressure sodium. This was necessary because the primary failure mechanism of HPS lamps is voltage rise during life, whereas mercury lamps stay fairly constant. Additionally, thermal losses to the arc tube wall are higher than in mercury lamps. This leads to higher reignition voltages on each half-cycle. These problems are compounded such that when the reignition peaks exceed the available supply voltage, the lamp will extinguish, cool, then cycle on and off. To achieve suitably long lifetimes, HPS lamps are therefore designed to have an arc voltage about 25% lower than mercury lamps.

This requires an increased lamp current for each wattage rating, hence the need for different ballasts. Coupled with the fact that the xenon gas filling requires a high voltage pulse to strike the arc, the first HPS lamps were electrically excluded from the millions of sockets for mercury lamps.

In 1973 Sylvania invented this so-called Penning-Start lamp to make a simple retrofit possible. The gas is changed to a neon-argon Penning mixture, combined with a third auxiliary electrode coiled around the arc tube to allow breakdown at ordinary open circuit voltages. A bi-metal switch disconnects the coil when the lamp is hot to minimise sodium loss during life. The amalgam ratio is also adjusted to suit the higher voltage for a mercury ballast. Efficacy is about 15% less than ordinary lamps because thermal losses are higher with Ne:Ar than Xe fills, and life is also reduced due to the higher initial voltage. However a 10% energy saving and 75% increase in luminous flux is still possible vs mercury lamps.
Manufacturer: GTE Sylvania
Lamp Power: 360 Watts
Lamp Current: 3.3 Amps
Lamp Voltage: 125 Volts
Cap Type: E39s Brass + vitrite
Bulb Type: BT-116 BT-37 in eighths/inch
Bulb Finish: Clear Leaded Borosilicate
Electrodes: Backwound tungsten BCT emitter
Arc Length: 86.9 mm 3.42 inches
Atmosphere: NaHg | 98.5% Ne, 1.5% Ar Outer: Hard vacuum
Luminous Flux: 38,000 lm @ 100h 34,960 lm average
Luminous Efficacy: 105.7 lm/W @ 100h 97.1 lm/W average
Colour Temperature & CRI: CCT: 2060K CRI:
Chromaticity Co-ordinates: CCx: 0.516 CCy: 0.408
Rated Lifetime: 16,000 hours 50% suvival & 80% flux
Warm-up & Re-strike time: 4 minutes 3 minutes
Burning Position: Universal
Overall Length: 292.1mm 111/2 inches
Light Centre Length: 177.8mm 7 inches
Factory: Manchester, NH U.S.A.
Date of Manufacture: November 1982 Date Code 023
Original / Present Value:
References: 1) GTE Sylvania Brochure - Unalux Lamps - 1979
2) GTE Sylvania Product Information Bulletin - Unalux 360W Lamps - 1979
3) GTE Sylvania Large Lamp Catalog (USA) - 1982.