High Intensity Discharge Headlamps - 300M Special
High Intensity Discharge Headlamps (HID) rely on an electrical charge to ignite xenon gas contained in a sealed beam lamp. The HID lamps are similar in operation to common vapor filled street (halogen) lamps. Instead of using a filament to produce light, the gas inside the lamp is ignited by creating an arc between two electrodes.
The color of the light source is classified as its color temperature. As the color temperature increases, the color of the light moves from yellow to white to blue-white. The light produced by the HID lamps appears as a white color as opposed to the yellow color of the standard (halogen) lamps. HID lamps provide light as a higher color temperature than standard halogen lamps.
For the color temperature of different lamp types, refer to the COLOR TEMPERATURE table. As a point of reference, typical sunlight at noon has a color temperature of 4977°C (8990°F)
| LAMP | TEMPERATURE |
|---|---|
| INCANDESCENT LAMPS | 2527° C (4580° F) |
| HALOGEN LAMPS | 2927° C (5300° F) |
| HID LAMPS | 3827° C (6920° F) |
There are three components to each of the HID headlamps (Figure ):
- Ballast Module - The 12 volt Direct Current (DC) power supplied by the low beam relay is converted to Alternating Current (AC) power by the ballast module (Fig 1 ). Each lamp requires its own ballast. The ballast converts and steps up the low beam relay output to 800 volts AC, and supplies the lamp assembly via a cable connected to the igniter.
- Igniter - The lamp assembly contains an igniter (Fig 2 ) that controls the voltage applied to the lamp electrodes. The igniter uses the voltage supplied by the ballast and momentarily steps up the voltage to 25,000 volts to start the lamp. Once ignited, it will reduce the voltage to 85 volts.
- Lamp - The lamp (Fig 2 ) contains electrodes and xenon gas. The lamp takes about 10-15 seconds of warm-up time to reach full operation. The light appears blue during warm-up and then turns to white.