MEI/H Coolseal with Supercool Leads

GEC made its entry into the business of manufacturing MEI lamps in 1977 under direction of Angus Dixon, who made many contributions to the development of this light source. Also of value was the invention of Dr. Alan Prest, in 1982, which gave these lamps their "Coolseal" brand name.

MEI lamps dissipate immense power in a small volume and the quartz-to-molybdenum seals at either end of the arc tube easily overheat, oxidise, and cause the lamp to fail by splitting the seals open. A great deal of energy is carried into the seals by the light pipe effect, in which radiation from the arc tube travels along the seals as though it was a large optical fibre. This energy is concentrated at the ends where it can cause overheating and premature failure.

Dr. Prest's invention was to etch the surface of the seals, thus destroying the light pipe effect and dissipating much of the radiant energy out the side of the lamp. The Coolseal principle was most effective in increasing lamp life, while also eliminating the need for cooling fins in the luminaire.

A further breakthrough came in 1987 when the Supercool principle was invented, also by GEC. To further reduce seal temperatures the usual metal end caps were dispensed with, and replaced with flexible leads, thus eliminating the heat build-up found in the old bases. Electrical connections were made at the end of heavy duty leads, thus displacing them to a lower temperature region away from the lamp. Ceramic baffle plates protect the connections from the radiant heat of the arc, and also serve as the lamp mounting. By suspending them between springs, as illustrated, the lamp was better protected from mechanical shocks in service.
Manufacturer: The General Electric Company of England PLC
Lamp Power: 2500 Watts
Lamp Current: 14.9 Amps (Magnetic) 13.5 Amps (Electronic)
Lamp Voltage: 190 Volts (Magnetic) 180 Volts (Electronic)
Cap Type: Supercool Leads Female 8mm screw thread
Bulb Finish: Clear Quartz Sandblasted end seals
Bulb Type: BTT-30 BTT-14 in eighths/inch
Overall Length: 303 mm 11 15/16 inches
Light Centre Length: N/A N/A
Arc Length: 25.0 mm 0.98 inches
Electrodes: Solid Tungsten
Atmosphere: Ar | (Dy,Ho,Tm)Ix, Hg
Luminous Flux: 240,000 lm
Luminous Efficacy: 96.0 lm/W
Colour Temperature & CRI: CCT:5600K CRI:Ra 90-95
Chromaticity Co-ordinates: CCx:0.335 CCx:0.335
Burning Position: Horizontal
Rated Lifetime: 500 hours To 50% survival
Warm-up / Re-strike Time: 2 minutes Instantaneous
Factory: Shaw, Oldham England
Date of Manufacture: June 1988 Date Code VF2
Original / Present Value: £518.67 (1989) £840.59 (2004)
 
References: 1) Osram-GEC Lamp Catalogue, UK, 1985/86, p.234
2) GEC "MEI" Lamps brochure, c. 1980.
3) GEC "Studio, Theatre & Location Lamps" brochure, c. 1988.
4) US Patent 4677338, GEC Lamps & Lighting 1985.
5) Osram-GEC UK Price List April 1989.