The Phillips 250 Watt or
400 Watt Ceramic Metal Halide bulbs run on either an HPS ballast
or Life Light digital ballast. The 400 Watt ceramic metal halide is Philips' first
commercially available grow light, developed to suit
growing plants indoor.
The high pressure
sodium lamp is frequently employed in open high bay style luminaires in
the USA, and in this indoor application there is considerable interest in
changing over to a white light source if the high luminous efficacy can be
maintained. For several years before the introduction of this lamp,
Venture Lighting had enjoyed success in marketing a quartz metal halide
lamp which operates directly on the HPS control gear. Luminous efficacy
was of course reduced. This lamp was created as a higher performance
retrofit which delivers still higher colour rendering but also at high
efficacy.
It will instantly be recognised that its arc tube is of
quite a different aspect ratio than the short, large diameter types found
in the smaller CDM lamps. This is advantageous for a high luminous
efficacy and to permit similar optical control to the sodium arc tube it
replaces. The problems were minimised by choosing an alternative chemistry based
on the halides of cerium.
Since ceramic arc tubes rarely fail with the
violence of their quartz counterparts, the fragments can be contained here
by a simple wire spiral around the arc tube.
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