Ballast Technology

Ballast Explained

• An electrical ballast is a device that limits the flow of current through an electrical circuit. In the case of a fluorescent lamp, the ballast regulates the current in the lamp's startup phase, during which the current requirements are higher, and also in the subsequent operation of the lamp, during which the negative resistance produced in the lamp's tube would continue to draw more and more unregulated current. Without the limitation of the current provided by the ballast, the lamp would quickly burn itself out.

Magnetic Ballast

• The oldest and least efficient ballasts, called magnetic ballasts, use aluminum or copper wires wrapped around steels coils to regulate current. Copper coils have lower resistance than aluminum coils, so they waste less energy through the production of heat and are thus more efficient than aluminum. Magnetic ballasts are cheaper to produce than ballasts that use newer technologies, but their relative inefficiency offsets the lower manufacturing cost.

Hybrid Ballast

• Lamps require higher voltages at startup than they do after they begin operating, so the most efficient way for the ballast to operate is to lower the voltage after the lamp is started. Hybrid ballasts use an electronic switch to cut off the circuit that supplies the startup voltage once the lamp is operating, thereby lowering the lamp's energy consumption. The basic design of the ballast, however, still employs a wire coil around a steel core.

Electronic Ballast

• An electronic ballast eliminates the magnetic coil from the ballast design and instead uses a solid-state circuit to control the current running through the lamp. Electronic ballasts greatly increase the frequency of the current supplied to the lamp, and the high frequency allows the lamp to operate more efficiently, producing more light while consuming less electricity. These ballasts are more expensive to manufacture than magnetic ballasts, but their operating costs are substantially lower. Another advantage of electronic ballasts is that they tend to decrease the flicker and hum produced by the lamp.