Some systems have a seperate igniter (the coil that provides the 23KV to initiate the arc) from the ballast. Most new ballasts have a built-in igniter.
HID Ignitors
The voltage required to initiate the arc discharge on most High Pressure Sodium lamps and some Metal Halide lamps is greater than the ballast open-circuit voltage. An ignitor is used to provide this additional voltage pulse for a very short period of time (1 to 5 microseconds). In addition, the pulse is timed to occur near the peak of open-circuit voltage so that the necessary current will follow the initial discharge.
The most common ignitors use a portion of the ballast winding as a step-up transformer. When the system is energized, the ignitor provides the required voltage pulse until the lamp is lighted and is then automatically stopped.
Continuous pulsing occurs if a lamp is inoperative or if the socket is empty. While many ignitors have a long-life design, it's preferable to rectify situations that induce continuous pulsing as soon as possible.
Some ignitors are designed with internal high frequency, high voltage transformers so that the output may be applied directly to the lamp. This type of ignitor is often used with Metal Halide lamps for instant (or fast) restrike. Sufficient isolation must be built into an ignitor system of this type to protect the remainder of the ballast circuitry from the high voltage pulse.
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How many of you.. ( HID question)
Linear Mode
