There are many different sources of light used in various areas of our life. Starting from the usual incandescent lamp, which illuminates the apartment in most cases, and ending with the latest LED technologies widely available on the market. But there are also intermediate lamps that can become the same “golden mean” between quality and price for a similar product. One of such devices is, of course, a metal halide gas discharge lamp.
These lamps are distinguished by their high color rendering and decent service life, compared to the same incandescent lamps. Being a fairly young invention, metal halide devices are gradually finding their buyer, who values above all efficiency and quality in matters of lighting a particular room.
Metal halide lamps began to be produced about 40 years ago, as a way to get away from the use of conventional lamps with a tungsten filament, which were extremely short-lived. In part, manufacturers succeeded in this, because metal halide devices are now used in many areas of life and for lighting many objects and structures.
Main areas of application:
- for lighting large industrial facilities, gas stations, etc.;
- in the lighting of street avenues and squares;
- in spot lighting of various administrative, cultural and architectural buildings;
- in the lighting of aquariums, greenhouses, etc.;
- in the lighting of large sports facilities, football and hockey stadiums, etc.;
- in the lighting of shopping centers and halls, various showcases and advertising signs;
- in the coverage of various earthworks, pits and geological excavations;
- in the cinematographic environment and in television work.
Separately, it is worth mentioning the possibility of using such lamps in the lighting of the apartment, or when lighting the area around the house. Contrary to some considerations, about the impracticality of use in lighting the house, due to the possible danger of their operation, a standard lamp with a power of 150W is able to illuminate a fairly large room or a small yard of a private house.
Like any light source, they have their own classification and types of performance.
- Lamps of the single-base type without an external bulb. Small in size, used in small-sized lamps. However, the dimensions do not affect the color rendering indicators in any way – this type of lamps has decent efficiency indicators.
- Lamps of the single-base type with an external bulb. One of the most common types, intended for use in everyday life and in industrial areas. They show stable performance in all positions.
- Two-socket type lamps. Depending on the configuration, they can have a contact and threaded base. Recently, GS-type devices have become very popular, which show extremely high efficiency indicators due to their design features.
- Metal halide lamp with a reflector. It is hardly appropriate to talk about it as a separate category of such lamps, because such a lamp is represented by only one name – HMI 1200 PAR. They are used in lighting devices, where a light flux of a long spectrum of action is used.
Metal halide lamps are produced by many well-known companies that have launched the production of this type of lamps. However, when choosing, you should pay attention not only to the manufacturer, but also to certain technical characteristics.
- Power. This indicator is extremely important, because the brightness of the glow and the strength of its light flow will depend on this indicator. It is worth noting that with similar power indicators, compared to an incandescent lamp, a metal halide lamp will shine almost four times brighter.
- Base type. When choosing a base, you need to find out in advance the supported type for your lighting device. Currently, several types are produced: threaded – E27, E40; bilateral base – Rx7S; contact – G12.
- Light flux. This indicator will talk about the intensity of the glow that will be produced by the metal halide lamp. It is worth noting that they tend to lose a certain percentage of their flow. Simply put, metal halide lamps will not shine as brightly after a certain number of months.
- Color temperature. Here we are talking about different shades of light emitted by the lamp. They can be cold, warm and neutral.
- The service life is about 9000 hours, but there are also longer service lives.
The principle of action
Mercury and gas vapors are present in metal halide lamps. An electric discharge occurs between the mercury vapor and the halide elements, and the light bulb lights up. Light is generated and controlled by a burning arc formed between pairs of electrodes. In addition to mercury vapor, metal halide lamps can use impurities of metals or rare earth elements: thulium, dysprosium, holmium, and others. As a result of the work, the connections of these elements disintegrate under the action of an electric arc, forming some kind of light emission.
Long-term operation of the metal halide lamp is achieved thanks to the halogen cycle illuminated in the bulb of the lamp. This cycle arises from the evaporation of tungsten iodides, which settle on the electrodes of the lamp.
As we can see, the operation of a metal halide lamp is based not only on mercury vapor, but also on various additional elements that ensure the stable glow of such lamps.
A metal halide lamp is a kind of construction based on a glass bulb and various internal components. As a rule, there is an electric burner and various electrodes inside. It is the burner that is responsible for the appearance of light radiation, because it is in it that the electric discharge of mercury vapor and additional elements takes place.
In addition, there are other characteristics:
- Metal plinth of various types (contact or threaded).
- The glass bulb, as a rule, is treated with a special composition that helps to increase the color rendering index of the lamp.
- Inside there are numerous wires that support the internal burner and other elements of the lamp.
Scheme of inclusion
By the types of inclusion, metal halide lamps are practically no different from gas-discharge lamps of their kind. The only difference is the mandatory presence of an additional ignition device that provides ignition of several thousand watts.
Recently, a trend has emerged when manufacturers produce additional electronic devices, stabilizing inclusions and the operation of metal halide lamps. These devices are fed with a rectangular voltage with a frequency of about 150 Hz. These devices play the role of an ignition device, an additional ballast and a capacitor.