China manufacturer of magnetic ballasts for metal halide flood lights & hps flood lights

A fluorescent lamp ballast is an electrical transformer. Fluorescent lamps require different voltages at different places in the lamp in a standard rapid start system. There are small filaments at the end of the lamp that require low voltage (approx. 4 volts) to aid in starting the lamp, this is called cathode voltage. The lamp also requires a higher voltage (200 volts or higher depending on lamp type) from end to end on the lamp to operate, this is called arc voltage. The ballast transforms line voltage 120 volts to these requirements. The ballast limits the amount of current that the lamp can draw. This prevents the lamp from drawing too much current and failing.