Ballast Terms


Electromagnetic (magnetic) ballasts employ a coil and core, and (in some cases) a capacitor. The "coil and core" consists of a core of steel laminations surrounded by one, two or more copper or aluminum coils. This unit provides the conditions for starting and controlling the current flow to the fluorescent lamp.

Prior to the 1980's, the choice of materials in the core and the coils was usually driven by economics to minimize the ballast cost, while meeting performance requirements. These ballasts are usually referred to as standard, or conventional, magnetic ballasts. Many of these ballasts are still in service today.

During the '80's, more efficient designs started to gain some popularity. These designs, commonly referred to as energy efficient magnetic, are optimized for maximum efficiency, using higher grade core and coil materials and costing more. Since 1990, only energy efficient magnetic ballasts have met the U. S. Efficiency regulations for most popular lamp configurations.


This designation refers to ballasts which start like rapid start ballasts but reduce or remove the electrode heating after the lamp is in full operation. They employ an electronic starter. Such products are sometimes referred to as hybrid ballasts.

Electronic (high frequency, solid state):

Electronic ballasts operate lamps at high frequencies, using semi-conductor components to change the frequencies, in combination with small inductive and/or capacitive components to provide the starting and regulating function.

Electromagnetic ballasts operate the lamps at line frequency, usually 60 Hertz (Hz). Electronic ballasts convert this line frequency to operate lamps at frequencies between 20 and 60 Kilo-Hertz (KHz). It is a well established fact that low pressure arcs such as fluorescent lamps, are more efficient when operated from high frequency ballast sources.

Electronic construction weighs less than coil and core magnetic construction, allowing easier handling during installation, lower structural stress on ceiling supports and lower shipping costs.

Ballast Factor:

Ballast factor is a new label for an old index formerly referred to as "relative light output". Ballast factor, expressed as a per cent, is the light output of the lamp(s) operated by a commercial ballast divided by the light output of the same lamp(s) operated by a reference ballast, as determined in accordance with the test procedures specified in ANSI standard C82.2, Method of Measurement.


Pre-heat operation requires use of a starter or manual switch to establish the circuit through the ballast to pre-heat the lamp filaments. When the filaments have heated up, the starter opens and the ballast then provides a suitable voltage to light the lamp and limits the current flow to the proper value. Several seconds may be required to complete the starting operation.

Rapid Start:

Rapid start ballasts provide the proper energy levels to heat the lamp filaments continuously, through small low voltage filament windings. The open circuit voltage of the ballast is adequate to start the lamp only after the filaments have been heated to emission temperature. A grounded reflector close to the lamp, together with a grounded line circuit, is required to provide a capacitive starting aid effect between lamps and fixture and assist ionization in the starting process.

Trigger Start:

Trigger start is a term used for ballasts which operate pre-heat start lamps in a rapid start manner. They supply higher filament voltages to heat the electrodes to start the pre-heat lamps, to simulate the rapid start system. A grounded reflector close to the lamp, together with a grounded line circuit, is required to provide a capacitive starting aid effect between lamps and fixture and assist ionization in the starting process.

Programmed Rapid Start:

Programmed rapid start ballasts apply filament heat initially and delay application of sufficient open circuit voltage to start the lamps until after the filaments have been heated adequately.

Instant Start:

Instant start ballasts deliver an initial high voltage to light the instant start lamp. The arc current heats the filament by bombardment to provide easy electron emission. Instant start lamps are usually identified by the single pin base. No pre-heating of the filament is required for this lamp to light. The starting interval is very short, always less than 200 milliseconds and typically less than 100 milliseconds.

Rapid Start I Instant Start:

Today's popular T8 lamps are bi-pin lamps designed and intended for use interchangeably on magnetic or electronic rapid start ballasts or electronic instant start ballasts. Although electronic instant start systems are more efficient, lamp life is slightly less with instant start operation.

Ballast Lamp Mismatch:

If ballasts and lamp types are mismatched, poor or no performance will result. This may include starting problems as well as shortened lamp and/or ballast life (incidentally, mismatching may void safety listing and ballast or lamp warranty).

Pre-heat, instant start and rapid start lamps have different electrical needs and the matching ballast is designed to supply those needs.

Disclaimer: This information is intended to be general in nature and is not complete regarding ballasts or lighting fixtures. You should consult a qualified electrical engineer for specific applications. See our Terms and Conditions of sale and our warranty which are controlling and supersede this data.