Double Envelope Halogèna BTT Mini

The original Halogèna family of mains voltage incandescent retrofit lamps launched by Philips France in 1987 included models rated 75W, 100W and 150W. Although this made them suitable for replacing the higher wattage GLS lamps used in residential lighting it failed to address the largest incandescent lamp market, served by the 60W rating and below. That situation was rectified with the world premiere of the first 60W high voltage mains halogen lamps at Hanover Messe 1991, and later that year the range was extended with this miniature lamp having an E14 cap. It features double the lifetime and about 15% increase in luminous flux vs conventional 60W incandescent lamps.

Part of the reason for the delay in realising this 60W model is that lower power lamps require finer filament wires, and especially at high mains voltages the filament must be still thinner. While Bromine-cycle halogen lamps are successful in redepositing lost tungsten back to the incandescent part of the filament, they can suffer problems of the halogen actually eroding the filament away at the colder filament ends, leading to premature failure. Many years of research into balancing lamp chemistry and thermodynamics was needed before this 60W model became feasible.

Soon after the launch it was realised that the smaller E14-capped lamps are often used in decorative luminaires where the lamp is on show, and success of this BT-shaped version was limited owing to its more technical appearance which didn't match classical luminaires using candle-shape lamps. Also it is too long to replace the small E14 globe lamps. In 1992 it was superseded by a decorative candle shaped version and the BT model quickly disappeared.
Manufacturer: NV Philips Gloeilampenfabrieken
Lamp Power: 60 Watts
Lamp Voltage: 220-230 Volts
Lamp Current: 0.267 Amperes
Cap Type: E14/25x17 Brass + vitrite
Bulb Type: BT-40 BT-12.5 in eighths/inch
Bulb Finish: Clear Soda-Lime
Filament Type: CC-8 Axial Coiled Coil
Atmosphere: Bromine in Kr Outer: Nitrogen
Luminous Flux: 810 lm
Luminous Efficacy: 13.5 lm/W
Peak Intensity: N/A
Beam Distribution: N/A
Colour Temperature & CRI: CCT: 2850K CRI: Ra 100
Chromaticity Co-ordinates: CCx: 0.444 CCy: 0.406
Rated Lifetime: 2000 hours to 50% survival
Burning Position: Universal
Max. Overall Length: 104.5 ± 3.0 mm
Light Centre Length:
Factory: Pont-à-Mousson France
Date of Manufacture: October 1991 Date Code 1K
Original / Present Value:
References: 1) Philips Licht - Hanover Messeschwerpunkte 1992.
2) Philips Lighting News - Hanover Highlights April 1992.
3) Philips Licht GmbH - Produktionforationblatt HalogenA E14 Lampen, März 1993.