Friday, August 31, 2007

Magnetic vs. Electronic Ballasts

If an existing lighting system is to be evaluated for changes it will be important to determine if the system is utilizing magnetic or electronic ballasts.

The full output electronic ballast is a high frequency version of the conventional magnetic "core-and coil" ballast. The electronic ballast operates fluorescent lamps more efficiently at frequencies greater than 20,000 Hz.

The full output electronic ballast is rated with a ballast factor of at least .85. This factor actually identifies the output of light from the ballast-lamp combination. The ballast factor is simply that percentage of the lamp's rated lumens actually produced by the ballast lamp combination.

Magnetic ballasts normally have a ballast factor of between .90 to .95. The electronic ballast however can be purchased in a large range of ballast factors. You can purchase an electronic ballast that may range from 1.00 to 1.30 which acts as a booster with the lamp and actually lets the lamp produce a greater amount of lumens then the lamp is actually rated for.

On the other hand, you could purchase an electronic ballast with a range of .45 to .85, which shows that some ballasts can be utilized to actually reduce the amount of light put out by the fixture. If the ballast is a full output type, it would have a ballast factor that would exceed .85.

A partial output electronic ballast is utilized to have a lighting fixture put out less light than that which it is rated. This can be useful for several different types of installations.

A simple way to determine if the installed ballast is electronic or magnetic is to utilize a "strobe top". Some ballast manufacturers supply these free of charge to designers and installers. The top is simply spun directly under the fixture in question. If you see pattern lines, the lights are operating at 60 Hz and therefore are utilizing magnetic ballasts. If the pattern turns out to be a smooth pattern with no lines, the fixtures are utilizing high-frequency electronic ballasts.