A lighting ballast controls the starting and operating voltages of gas discharge lights. Small lights use passive components, while high-power lights require more complex ballasts. Electromagnetic ballasts cause flickering, while electronic ballasts can reduce or eliminate it. Electronic ballasts are more efficient and popular, but some applications require electromagnetic ballasts.
A lighting ballast is equipment required to control the starting and operating voltages of gas discharge electric lights. Examples of gas-discharge light sources include fluorescent and neon lights and high-intensity discharge (HID) lamps. The term lighting ballast can refer to any circuit component intended to limit the flow of current through light, from a single resistor to more complex devices.
A lighting ballast is needed to operate discharge lights because they have negative resistance, which means they are unable to regulate the amount of current flowing through them. A lighting ballast must be used to control the current flow; otherwise the light may fail. Small light sources can use passive components, which don’t require additional power to operate, such as ballasts. An example would be a series resistor that limits the flow of current through its terminals. For high-power lights, however, a resistor would waste a great deal of electricity, so a more complex lighting ballast is needed.
An electromagnetic lighting ballast uses electromagnetic induction to provide the starting and operating voltages of a gas discharge light. Inside each is a coil of wire and an electromagnetic field that together transform voltage. Some also include an igniter for high power applications.
Electromagnetic ballasts limit the flow of current to light but do not change the frequency of the input power. The lamp then turns on with every half-cycle of the power source. This is why many fluorescent and neon lights flicker visibly. Since the light glows in half cycles, the flicker frequency is twice the frequency of the power source, which means the light will flicker at 100Hz or 120Hz. A lead-lag lighting ballast can minimize flicker when connected to two lamps by alternating the flow of current to them: one carrying the frequency of the input power and the other following it.
A more modern type of lighting ballast is electronic rather than electromagnetic. An electronic ballast for lighting uses solid-state circuitry to transform voltage, but unlike electromagnetic ballasts, it can also alter the frequency of the power supply. This means that an electronic lighting ballast can greatly reduce or eliminate any flickering in lamps. Because it uses solid-state circuitry instead of magnetic coils, it’s also more efficient and therefore runs cooler.
Due to their higher efficiency and ability to reduce flicker, electronic ballasts are more popular than electromagnetic ballasts and are often used to replace them. However, some applications require an electromagnetic lighting ballast, such as ballasts that need to preheat or extremely high-power lamp ballasts.
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