IESNA Definition: a device used with an electric-discharge lamp to obtain the necessary circuit conditions (voltage, current and waveform) for starting and operating.

The operation of discharge light sources, such as fluorescent and high intensity discharge (HID) lamps, relies on an electric arc passing between two electrodes. The electrical characteristics are controlled by a ballast.

The ballast:

  • provides proper electrical conditions to establish an arc between the two electrodes
  • regulates the electric current flowing through the lamp to stabilize light output
  • supplies the correct voltage for proper lamp operation and may compensate for voltage variations in the electrical current

Ballasts for fluorescent lamps have traditionally been of the electromagnetic type, operating at a voltage frequency of 60 Hz. Since the early 1980's, electronic ballasts have become increasingly popular, operating at frequencies of 20,000 - 60,000 Hz. This high frequency operation causes lighting systems to convert electric power to light more efficiently than systems run by standard electromagnetic ballasts.

Adapted from Specifier Reports: Electronic Ballasts

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Glossary Terms: arc, electrodes, IESNA, light output