The ballast is the electrical component which starts and regulates voltage and current to a flourescent lamp.
- L - Ballast gives you the “least necessary” light but you save on energy bill
- N - Normal energy and light
- H - High Power. It uses lots of energy but in return gives you lots of light
- HO - Stands for High Output. It gives you the most light but uses the most energy
A magnetic ballast is a simple device that uses a core and coil assembly transformer to perform the minimum functions required to start and operate a lamp. Magnetic ballasts are often found in HID systems, as well as older fluorescent systems.
An electronic ballast uses solid state circuitry to start and operate a lamp.
RAPID START BALLASTS
Rapid start ballasts ignite lamps by providing cathode voltage (heat) and voltage across the lamp simultaneously. As the cathodes heat, the voltage required to ignite the lamp is reduced. At some time after both voltages are applied, the cathodes reach a temperature sufficient for the applied voltage to ignite the lamps. During this starting scenario, voltage across the lamps creates a glow current that damages the lamp by sputtering off the cathode’s emissive material. The sputtering results in end blackening and a reduction in lamp life. After all of this material is depleted from the cathode, the lamp ultimately fails.
INSTANT START BALLASTS
Instant start ballasts ignite lamps by applying a significant voltage across the lamp during starting. However, no cathode heating is applied before or after the lamps are ignited. The high voltage applied across the lamps typically ignites them within 50 milliseconds. Since the cathodes are not heated with instant start ballasts, emissive material is also released during this type of scenario.
PROGRAMMED START BALLASTS
Programmed start ballasts incorporate a precise starting scenario which breaks the process into unique and well-defined steps that eliminate the pitfalls of the other starting methods.
The first step in the series is the application of cathode heat. While this heat is being applied (preheat interval), voltage across the lamp is reduced to a level that reduces damaging glow current. Glow current is actual lamp current that flows during this preheat interval and causes end blackening and degradation in lamp life. It is important during this step that sufficient voltage is applied to the cathodes for a long enough duration so the cathode’s temperature is at least 700°C. The duration of this step is pre-programmed into the ballast circuitry. Since the lamp voltage is kept very low, the lamps cannot ignite until the cathodes are heated to optimal temperature and the ballast program moves to the second step.
The second step of the starting process is the application of lamp voltage. After the programmed time of step one has been reached, a voltage is applied across the lamps, igniting them with minimal loss of the emissive material. Minimal loss of the emissive material equates to gentle treatment of and prolonged life for the lamp.