Lighting Research Center Lighting Research Center
    Volume 7 Issue 4
June 2003    
ballast - A device required by electric-discharge light sources such as fluorescent or HID lamps to regulate voltage and current supplied to the lamp during start and throughout operation. ballast factor (BF) - The ratio of the light output of a fluorescent lamp or lamps operated on a ballast to the light output of the lamp(s) operated on a standard (reference) ballast. Ballast factor depends on both the ballast and the lamp type; a single ballast can have several ballast factors depending on lamp type. compact fluorescent lamp (CFL) - A family of single-ended fluorescent-discharge light sources with small-diameter [16-millimeter (5/8-inch) or less] tubes. electrodes - The structure that serves as the electric terminals at each end of electric discharge lamps. high-intensity discharge (HID) - An electric lamp that produces light directly from an arc discharge under high pressure. Metal halide, high-pressure sodium, and mercury vapor are types of HID lamps. luminaire - A complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply. (Also referred to as fixture.) load shedding - The practice of turning off electrical devices during peak energy demand hours to reduce building energy use. rated lamp life - The number of hours at which half of a group of product samples fail. The rated life is a median value of life expectancy; any lamp or group of lamps may vary from the published rated life. Rated life is based on standard test conditions. rated light output - The sum of the initial rated lamp lumens of the lamp(s) that were supplied with the luminaire.
What is an adaptable ballast?

“Adaptable ballast” is a term NLPIP uses to describe an electronic ballast with special circuitry that enables it to operate multiple lamp types, operate different quantities of lamps, and/or operate on multiple input voltages. They are sometimes referred to by manufacturers and distributors as universal ballasts, universal voltage ballasts, generic ballasts, or flexible ballasts, although none of these terms is an industry standard. Some products are adaptable only in one or two of these options (e.g., they can operate different lamp types at different voltages, but can only operate a single lamp). Products that are adaptable in all three specifications (lamp type, lamp quantity, input voltage) are becoming more common.

Lamp type. Most ballasts for linear fluorescent lamps can now operate different lengths of lamps, provided the total lamp current is fairly constant. An adaptable ballast can accommodate not only different lengths, but different lamp shapes or different lamp wattages. Figure 1 shows an example of the variety of compact fluorescent lamp (CFL) combinations that a single adaptable ballast can operate.

Figure 1. An adaptable ballast and the different CFL lamp combinations it can operate

Lamp quantity. Luminaires typically contain one to four fluorescent lamps, so most ballasts are designed to operate exactly 1, 2, 3, or 4 lamps. An adaptable ballast may be able to operate either 1, 2, 3, or 4 lamps, although more likely it will operate two lamp quantities (e.g., 1 or 2 lamps, or 3 or 4 lamps).

Input voltage. In the United States, lighting loads are typically within 110- or 277-volt electrical systems. Some Canadian lighting systems use 347 volts (Canadian Standards Assoc., 1999). Most ballasts will operate on only one voltage. Ballasts are now available that can handle any voltage within a wide range (such as 108 volts to 305 volts) and can operate on either 50 hertz or 60 hertz systems for compatibility with both North American and European electrical systems. Regulatory requirements in Europe differ from North America’s, so these ballasts may not necessarily meet European requirements for radio interference unless specifically labeled as such. Ballasts operating on 347-volt electrical systems require higher voltage-rated components, and thus are still typically dedicated to that one voltage (Wigglesworth, 2002).

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