Electronic ballasts usually change the frequency of the power from the standard mains frequency to 20,000 Hz or higher, substantially eliminating the stroboscopic effect of flicker (100 or 120 Hz, twice the line frequency) associated with fluorescent lighting (see photosensitive epilepsy). In addition, because more gas remains ionized in the arc stream, the lamps actually operate at about 9% higher efficiency above approximately 10 kHz. Lamp efficacy increases sharply to about 10 kHz and continues to improve until approximately 20 kHz*(IES Lighting Handbook 1984). Because of the high frequency of operation, electronic ballasts are generally smaller, lighter, and more efficient (and thus run cooler) than line frequency magnetic ballasts.
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