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Electronic fluorescent ballasts and their proper use
For several years, electronic fluorescent ballasts have been used successfully in many lighting applications, but standard, magnetic ballasts still maintained majority use. But people’s minds and regulations change, and energy savings and environmental protection are again priorities.
Since 2000, an official EU regulation mandates energy-saving ballasts for fluorescent lighting, either by improved magnetic ballasts or electronic ballasts. Electronic ballasts can operate a fluorescent lamp more efficiently than magnetic ballasts because they can convert, via a high frequency switching circuit, line voltage into higher voltage of limited current. These circuits’ characteristics towards the line and the load differ from those of magnetic ballasts (which an installer must consider to prevent future problems).
Magnetic ballasts are very reliable, even in environments that are rough on electronic equipment (high humidity or temperature, or a long distance between the lamp and ballast).
Surge line currents
Electronic ballasts are, almost exclusively, semiconductor circuits that need direct current (DC) for operation, so the alternating line current (AC) must be converted (or rectified) first. A capacitor provides a power reservoir to smooth out the available DC power when the AC voltage is lower than maximum in every 60Hz half cycle.
This capacitor, or reservoir, is completely empty when the ballast is switched on, and this reservoir is filled almost immediately, which creates a huge current demand on the line for a short time. Magnetic ballasts, in contrast, have a delayed and random start time; thus, many paralleled units won’t produce such a high surge current. When multiple ballasts are fed from one branch circuit (this happens in large, lightbox, pole signs, where up to a few hundred fluorescent lamps operate in a small area fed by a long supply line), this high current can trip a fast breaker or RCD switch. Because the capacitor’s charging current flows only when the AC voltage is higher than the capacitor voltage, standard electronic ballasts’ current demand is non-sinusoidal.