Ballast:
Ballast is a type of transformer that is used to increase the voltage for florescent lamps as well as control the electrical current. The basic kind of ballast is magnetic ballast, and these are used in older fluorescent lamps. These ballasts have a low cycle rate that causes vibrations that account for the humming sound you might hear in an older light.

Different kinds of ballasts:

 Electronic ballast:

a) Electrical connection is by direct wiring to a quick connecting terminal block
b) Metal housing
c) Earth connected
d) Low power consumption
e) Glare-free and no noise
f) Power factor (pf) as high as 0.99 due to power factory correction

T5 electronic ballast:

a) Electrical connection is by direct wiring to a quick connecting terminal block.
b) Metal or plastic housing; earth connected; low power consumption; glare-free and no noise.

T8 electronic ballast:

a) Modification of high power factor: 0.99C.
b)  Total harmonic distortion THD: 10%.
c)  Lamp current wave crest ratio: 1.5.

 Electronic hid ballast:

a) Modification of high power factor: 0.99C.
b) Total harmonic distortion THD: 10%.
c)  Lamp current wave crest ratio: 1.5.

Florescent lighting ballasts and schools:
Many schools in the U.S. have fluorescent light ballasts containing polychlorinated biphenyls (PCBs). The PCBs are contained within the light ballasts capacitors and in the ballasts' potting material, which is used for insulation. PCBs are very stable chemical compounds that do not readily break down. Because of this, they may remain in the body, causing long-lasting toxic effects over many years.
As these fixtures age, they may be prone to leaking or catching on fire. A ballast leak or fire could happen at any time, without warning. If it happens in a busy classroom in the middle of the day, a school could be looking at long-term health impacts on many students and staff. Even a small, isolated leak may pose health issues for the staff or students who discover it. Schools also face potentially huge costs to clean up after a ballast leak or fire.
To avoid these problems, EPA recommends removing PCB-containing ballasts as part of a complete lighting retrofit. A complete lighting retrofit includes removing old fluorescent tubes as well as ballasts and replacing the entire lighting fixture with more energy-efficient fixtures. New fixtures reduce energy costs and improve lighting quality.



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