Metal halide ballast how does it works

Often a phosphor coat is used to both diffuse the light and change the lamp's color properties. Volume 7 Issue 1. January revised March How do metal halide lamps work? This includes an iron core inductor. The inductor provides an impedance to AC current.

If the current through the lamp increases, the inductance decreases to maintain the current-limited voltage. Electronic ballasts-these are lighter and more compact. They consist of an electronic oscillator which generates high frequency current to drive the lamp. Because they have lower resistance losses than magnetic ballasts, they are more energy efficient.

However, high frequency operation does not increase lamp efficiency as a fluorescent lamp. The pulse-started metal halide bulb does not contain a starting electrode, it strikes the arc, and requires an igniter to generate a high voltage kV cold strike, 30 kV used in thermal reignition pulse to start the arc. The electronic ballast includes the igniter circuit in a package.

The American National Standards Institute ANSI lamp ballast system standard establishes the parameters of all metal halide components except for some newer products. Self-ballasted lamps As of , several companies have begun to provide self-ballasted metal halide lamps to directly replace incandescent lamps and self-ballasted mercury lamps. These lamps include an arc tube with a starting electrode, and a tubular halogen lamp, which is connected in series and used to regulate the current in the arc tube.

The resistance provides a limited starting electrode current. Like self-ballasted mercury vapor lamps, self-ballasted metal halide lamps are directly connected to the main power source and do not require an external ballast. In contrast to this, these lamps usually have a clear outer bulb without coating, so that the arc tube and halogen tube are clearly visible from the outside.

Due to the whiter and more natural light produced, the metal halide lamp was originally the blue mercury lamp of choice. With the introduction of specialized metal halide mixtures, metal halide lamps are now associated with a correlated color temperature from K to K. The color temperature can vary slightly from lamp to lamp, and this effect is obvious where many lamps are used.

Because the color characteristics of the lamp tend to change during the life of the lamp, according to the ANSI standard that the color after hours flavoring is measured after the bulb has been burned.

The color temperature of the metal halide lamp can also be affected by the electrical characteristics of the bulb and the manufacturing difference of the bulb itself through the power supply of the electrical system. This phenomenon can be seen during the heating period, when the arc tube has not reached the full working temperature and the halide has not yet completely evaporated. It is also very obvious with dimming ballasts. The inverse is true that a light bulb is too powerful, but this condition may be dangerous and may cause the arc tube to explode due to overheating and overvoltage.

It sometimes takes a few seconds to start the initial argon arc welding or xenon car , and depending on the bulb type the warm-up period can be as long as five minutes. During this period, the lamp showed that various metal halides of different colors vaporized in the arc chamber. If the power supply is interrupted, or even simply, the arc in the lamp is extinguished, and the high pressure present in the thermoluminescent tube will prevent the arc from re-starting; the minute cooling period with the normal igniter will be required before the lamp can be restarted , But with a specially designed lamp with a special igniter, the arc can be re-established immediately.

In lamps without the ability to reignite instantaneously, a momentary loss of power may mean that there is no light for several minutes.

For safety reasons, many metal halide lamps have incandescent lamps that work as backup tungsten halogen lamps during cooling and restriking. Once the metal halide restrikes and heats up, the incandescent light is safely turned off. A warm lamp also often takes more time than a lamp that begins to cool completely to fully exert its brightness. The strength of all HID arc tubes reduces their lifetime due to various factors such as chemical corrosion, thermal stress and mechanical vibration.

As the lamp ages, the arc tube changes color, absorbs light and gets hotter. Lamp current crest factor CCF is defined by ANSI as the ratio of the peak value of lamp current to the root-mean-square value of the current.

A low CCF between 1. Volume 7 Issue 1. January revised March Why do metal halide lamps require a ballast?