Metal halide lamp belongs to the class of discharge lamps. In their work, such devices use a gas discharge rather than the thermal glow of an incandescent filament. Such lamps can be called relatively young light sources, the history of which lasts no more than fifty years. Their birth is associated with a number of experiments by scientists to improve gas discharge mercury lamps. From the point of view of the filling, their distinctive feature is the use as a working mixture of mercury vapor, a composition of salts and gases. The composition of the salt mixture affects the shade of the emitted light. A metal halide lamp can emit light bluish or reddish hues. Inside the flask, the gas is under very high pressure.
Features of the devices
Metal halide lamps are turned on in the same way as fluorescent, as well as other gas discharge. For ignition, they require connecting to the network through special ballasts. When it is turned on in the lamp, a discharge in argon first starts, triggering an electric arc between the electrodes of the lamp bulb. When the lamp is off, mercury and salts settle in the form of particles on the walls of the bulb. After starting, the electric arc instantly heats the flask, evaporating solid particles, after which the discharge continues in pairs of salts and mercury. The first minutes, the temperature rises very much, as does the brightness of the radiation. The metal halide lamp during operation is heated to a temperature that exceeds a thousand degrees, which is why the spotlights in which such devices are used are so large. To cool them, a large metal surface of the searchlight is needed.
Philips metal halide lamp works much more efficient than fluorescent, since almost 24 percent of the energy consumed in this case is converted into light. Such products are available in a fairly wide range of capacities - 20-20000 watts, which allows us to find it everywhere. Design features vary according to lamp power.
Fields of application
A small metal halide lamp can be used in the same place as a traditional halogen lamp - in devices for office, home, advertising, inside museum displays and shops. It is much more economical and more effective than halogen, however, it needs to install additional ballasts.
A 150w metal halide lamp is useful for lighting a large room or for a lamp in the courtyard of a private home. High-power devices are suitable for professional lighting equipment - powerful spotlights, theater spotlights, photo and film lighting equipment, as well as for some types of projectors.
An interesting area of use of metal halide lamps can be the lighting of greenhouses and aquariums. They have a radiation spectrum favorable for the growth of plants and corals.
Such devices can be produced with two flasks - external and internal. It is believed that this option has improved color characteristics.