Ceramic metal halide lamp having medium aspect ratio
AssigneeKoninklijke Philips Electronics N.V.
InventorsAndrew D. Jackson, Ray G. Gibson, Sarah Carleton
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Abstract
A metal halide lamp has a ceramic discharge vessel with an inside length L, an inside diameter D, and an aspect ratio L/D of between 3 and 5. The fill gas includes xenon, mercury, sodium halide, and halides of rare earth metals. Hydrogen iodide voltage spikes during start-up are related to product of volume and the cold xenon pressure, which are adjusted to limit the spikes. Voltage crest factor is related to the product of total operating pressure and the square of the inside diameter, which are adjusted to limit the crest factor. The ceramic discharge metal halide (CDM)lamp may have a power rating of 200 W or more and can be used with an existing ballast for a high pressure sodium (HPS) lamp of like power rating.
Claims10
A metal halide lamp comprising
- a ceramic discharge vessel enclosing a discharge space, said discharge vessel having an internal length L, an internal diameter D, an aspect ratio L/D, and an internal volume V=πLD2/4,
- a fill gas comprising xenon, mercury, sodium halide, and halide salts of metals selected from Tl, Dy, Ho, Tm, and Ca, said xenon having a cold fill pressure P, said fill gas having an operating pressure Ptot, and
- a pair of electrodes in said discharge space for sustaining a discharge in said fill gas,
- wherein said aspect ratio lies in a range from 3 to 5.
Dependencies are inferred from the claim text.