An electrical ballast is a device intended to limit the amount of current an electric circuit. For example, as a series resistor used commonly with a small light emitting diodes.
Ballasts are used where a electrical load cannot effectively regulate its current. These are most often used in the fluorescent lamp to provides a positive resistance or reactance that limits the ultimate current to an appropriate level. In this way, the ballast provides for the proper operation of the negative-resistance device by appearing to be a legitimate, stable resistance in the circuit. Ballasts can also be used simply to deliberately reduce the current in an ordinary, positive-resistance circuit.
A ballast is an indicator common in line-frequency to provide the proper starting and operating electrical condition to power a fluorescent lamp or high intensity discharge lamp. Because of the use of the inductor, such ballasts are usually called magnetic ballasts. The inductor has two benefits:
Its reactance limits the power available to the lamp with only minimal power losses in the inductor
The voltage spike produced when current through the inductor is rapidly interrupted is used in some circuits to first strike the arc in the lamp.
A disadvantage of the inductor is that current is shifted out of phase with the voltage, producing a poor power factor therefore a capacitor is often paired with the inductor to correct the power factor.
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Ballasts
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