Metal Halide Ballasts

Like other discharge light sources, high-intensity discharge (HID) metal halide lamps require a ballast to limit current to the electrodes. Ballasts also provide the correct voltage for starting and restarting, and they adjust current to maintain light color and intensity over time. All ballasts suffer internal losses—typically 5 to 30 percent of the lamp wattage—that should be included in any calculation of potential savings, especially when switching from nonballasted sources such as incandescent lamps. Two main types of ballasts are now available: the newer electronic ballasts and the more common magnetic ones.

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