MBI Metal Halide - Ceramic Style

Updated
15-II-2006
The possibility of employing ceramic arc tubes for metal halide lamps is not a new idea - indeed their use was proposed in the earliest patents on metal halide lamps back in the 1960's. Their potential advantages were recognised even at that time, in that they are more resistant than quartz to the corrosive nature of the metal halide salts within the arc tube. In addition they can operate at temperatures beyond which quartz begins to soften. Ceramics thus offer the possibility to increase the loading in the arc tube, bringing about an increase in wall temperature, which in turn increases colour rendering properties and luminous efficacy.

However while the ceramic arc tube itself is more resistant to halide corrosion, the same cannot be said of the end seals where the metal lead wires pass through the ceramic. The end seals must be kept at low enough temperatures to reduce the rate of corrosion, and traditional metals known for ceramic to metal seals cannot be exposed to the halides.

The first practical solution to this problem was developed by Thorn Lighting in England during the early 1980s, and in 1981 that company exhibited the world's first Ceramic Metal Halide lamp at the Hannover World Light Fair. This so-called 'TSH' lamp is illustrated below, and employs electrically conductive cermet caps to close the ends of the arc tube and make a halide-resistant seal. The unique molecular spectrum of the tin chloride dose also resulted in rather good colour properties for its time. But the marketing division did not take the idea further, since this lamp required a special kind ballast that was not available.

The commercial introduction of ceramic lamps had to wait until 1994 when Philips unveiled its 'CDM' range having the 'Protruding Plug' kind of end seal. In this approach the seal is displaced some distance away from the heat of the arc tube, thus bringing its temperature down to safe limits. An ingenious arrangement of different metallic conductors is contained within the seal both to ensure halide resistance and prevent cracking of these delicate seals. All subsequent lamps are based on this and later variants of the protruding plug seal.

Thorn

150W

TSH Tin Sodium Halide with Cermet seals
1981

Thorn

150W

TSH Tin Sodium Halide with Corstar arc tube
1981

Thorn

70W

CMH 70W for use on standard ballast
~1983

Philips

35W

CDM-T Single Ended with 5-part arc tube
1994

Philips

150W

CDM-TD Double Ended with 5-Part arc tube
1997

GE

20W

CMH-TC Compact with 3-Part arc tube
2001

Philips

70W

CDM-E Ellipsoidal Fluorescent for U.S.A.
1994

Philips

35W

Mastercolour CDM-R PAR30 Reflector
1997

Philips

35W

Mastercolour CDM-R111 Aluminium Reflector
2003

Iwasaki

150W

Ceralux MT150-CEW with Cermet end seals
2002

G.S.

230W

Lamp of Japan Storage Battery Company
2001

Philips

400W

HPS Retro-White High Wattage CDM
2001

Osram

250W

HCI-T Poweball 2-Part elliptical arc tube
2002

GE

250W

CMH-TT 250W / 830 Single Piece Arc Tube
2003

Wujin Lijia

150W

First Chinese Ceramic Metal Halide
2002

Toto

70W

CMI-T with Transparent YAG ceramic arc tube
1999

Philips

25W

CDMR-i Self Ballasted Reflector Format
2005

GE

20W

CMH ConstantColour MR16 Spot Reflector
2005