Fluorescent lamp ballasts are used to start and operate fluorescent lamps by providing the high voltage required to start the lamps and then limiting the current to a safe value. There are two basic types of fluorescent ballasts: magnetic (low frequency) and electronic (high frequency). Most fluorescent ballasts are now electronic, which are more efficient than magnetic ballasts. Fluorescent ballasts are also distinguished by their starting method: instant start (IS), rapid start (RS), and programmed start (PS). IS ballasts are inherently more efficient than RS and PS ballasts because they rely on a very high initial voltage to initiate the arc rather than electrode heating. However, IS ballasts can result in a significant reduction in lamp lifetime if they are used with occupancy sensors and are frequently switched on and off. PS ballasts, which are advanced versions of RS ballasts, can significantly increase lamp lifetime in occupancy sensor applications.
Efficiency standards for T12 fluorescent ballasts were established by Congress in 1990 and amended by DOE in 2000. T12 fluorescent lamps have a diameter of 1 1/2”; T8 lamps have a 1” diameter; and T5 lamps have a 5/8” diameter. The 2000 rule effectively requires electronic ballasts for new T12 fluorescent fixtures manufactured after July 1, 2005 and effectively requires electronic ballasts for both new T12 fixtures and replacement T12 ballasts after July 1, 2010. DOE published updated standards for fluorescent lamp ballast standards on April 11, 2011 that became effective in November 2014.
The rule significantly expands the scope of coverage to include ballasts that operate T8 and T5 lamps, outdoor sign ballasts, and residential ballasts, among other categories. DOE developed a new efficiency metric, ballast luminous efficiency (BLE), which is the total fluorescent lamp arc power divided by the ballast input power. BLE allows efficiency comparisons to be made across ballasts regardless of the ballast type or the number of lamps the ballast operates.
The NEMA Premium program promotes the use of high-efficiency ballasts.
In commercial and industrial buildings, the most common fixture in the market is four feet long. Technology options for improving the efficiency of fluorescent lamp ballasts include improved components (transformers, diodes, capacitors, and transistors) and improved circuit design.