Solarcolour Plus SONP-T 310W

Osram-GEC was one of the first companies to manufacture the "Plus" range of HPS lamps having significantly improved luminous efficacy and lifetime. The range was introduced in 1981, starting first with a 250W rating and followed soon after by 150W, 400W and this 310W version.

The performance boost was achieved by increasing the xenon pressure in the arc tube. Since Xenon is a poor heat conductor, it lowers thermal losses from the arc. The increased pressure also preserves the electrodes for longer, slowing the rate of evaporation of tungsten and emissive materials. Since the primary failure mechanism of HPS lamps is voltage increase during life, and this is partly caused by arc tube temperature rising as it is progressively blackened, lamp life and lumen maintenance are both extended.

Ignition of standard HPS lamps can easily be achieved with the pulse from a standard ignitor. However the arc tubes with increased xenon pressure require a higher voltage. To enable starting on standard ignitors, breakdown voltage is lowered by a capacitively coupled molybdenum antenna mounted alongside the arc tube, which is connected via the support frame to one electrode. To prevent sodium ions being drawn out of the arc tube by this external conductor, it is mounted on a pair of bi-metal strips which cause it to move away from the arc tube when hot.

The arc tube is GEC's later design, with a 3-part construction and monolithic end seals to niobium tubes. One end is blind whereas the other is an open tube, used for evacuating and dosing the arc tube. It has been sealed by pinching the end closed and arc welding the outer end of the tube.
Manufacturer: The General Electric Company of England PLC
Lamp Power: 310 Watts
Lamp Current: 3.2 Amps 4.8A during starting
Lamp Voltage: 110 ±15 Volts 1000V ignition
Cap Type: E40s/45 Ni plated brass + vitrite
Bulb Type: TD-51 TD-16 in eighths/inch
Bulb Finish: Clear Borosilicate glass
Electrodes: Backwound Tungsten BCT Emitter
Arc Length: 90 mm 31/2 inches
Atmosphere: Inner: Na,Hg | Xe Outer: Hard Vacuum
Luminous Flux: 41,000 lm (@ 100 hrs) 40,000 lm (average)
Luminous Efficacy: 132.3 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 95% survival, 95% lumens
Warm-up & Re-strike Time: 5 minutes 15 minutes
Burning Position: Universal
Overall Length: 285 mm 111/4 inches
Light Centre Length: 175 mm 67/8 inches
Factory: Shaw, Oldham England
Date of Manufacture: November 1987 Date Code UL
Original / Present Value: GB £48.11 (1988) GB £115.20 (2014)
References: 1) Osram-GEC Lamp Catalogue, UK, 1985/86, p.223
2) Osram-GEC Solarcolour Brochure, 1981
3) Osram-GEC Solarcolour Brochure, c.1985
4) Osram-GEC Price List, Apri 1988