RLOD#6 (2020.05.10) 2011 Panasonic MT150C-LW-SPD

In 2010 Matsushita of Japan released its “Cerameta Premier SPD” family of HID lamps with an improved lumen maintenance (no more than 15 % of flux depreciation through life). In this range there were some remarkable lamps designed for maximum lumen efficacy, the MT150C-LW-SPD shown here is one of them. Characterized by a lumen output of 18.0 klm, the lamp and its electronic control gear was intended for the replacement of 400 W mercury lamp systems, enabling an impressive energy saving of 60 % at system level (165 vs. 415 W) with a 50 % longer useful lamp life (18 vs. 12 kh). An efficacy of 125 lm/W is achieved via the use of an efficient sodium-cerium iodide fill chemistry in an unusually long and slim ceramic burner. The latter is of a single-piece slip-cast type and features alumina-molybdenum cermet end seals that are electrically connected to wire leads via a tiny metal cup retainer. An active wire antenna is attached to the burner and is coupled to the frame via a high-impedance resistor whose purpose is to prevent a destructive flashover in case of burner rupture or leakage at end of life.

The design of the discharge vessel enables an optimum discharge operation at low power density, which minimizes heat losses from the cooler plasma. Moreover, the long electrode gap distance enables a reduction of the mercury pressure to a sub-atmospheric level, which reduces the plasma's infrared output in a significant way. The fill chemistry is balanced for the production of warm white light at 2800 K, however the dominance of sodium on the emitted spectrum results in an orangish light color, which lowers the color rendering to 50 Ra8. This is a direct consequence of an efficacy optimization done at the expense of light color quality. Interestingly, the lamp can be operated at all positions without causing significant color segregation in the discharge tube, but changes in salt vapor pressure cause the light output and color temperature to drop slightly in the vertical position.