The following are the most widely used types of lighting equipment used in commercial buildings. Characteristics such as energy efficiency, light quality, and lifetime vary by lamp type.
A fluorescent lamp consists of a sealed gas-filled tube. The gas in the tube consists of a mixture of low pressure mercury vapor and an inert gas such as argon. The inner surface of the tube has a coating of phosphor powder. When an electrical current is applied to electrodes in the tube, the mercury vapor emits ultraviolet radiation which then causes the phosphor coating to emit visible light (the process is termed fluorescence).
A ballast is required to regulate and control the current and voltage. Two types of ballasts are used, magnetic and electronic. Electronic ballasts have several characteristics that make them attractive. They are more energy efficient, they permit lamps to start quickly, and they eliminate lamp flicker.
A compact fluorescent lamp (CFL) produces light the same way as a standard fluorescent lamp. A CFL has a small diameter tube that is arranged in a shape and style that is more compact than a standard fluorescent lamp. A CFL with a built-in ballast may have a screw-base and can replace a screw-in incandescent bulb. Other CFLs have a pin base that fit into fixtures with built-in ballasts.
An incandescent lamp produces light by applying electrical current to a tungsten filament. The filament is mounted in a glass bulb that is filled with an inert gas such as nitrogen and/or argon. The filament when heated by the current emits visible light. Incandescent lamps are energy inefficient and only convert five to ten percent of the input energy into visible light with the rest converted to heat.
High Intensity Discharge
A high intensity discharge (HID) lamp produces light by an electrical arc discharge between two tungsten electrodes in a sealed arc tube mounted within an outer bulb. This lamp requires a ballast to start and regulate the arc. There are several types of HID lamps, including mercury vapor, metal halide, and high pressure sodium lamps.
A halogen lamp is a type of incandescent lamp, but they are longer lasting than standard incandescent lamps. This lamp also uses a tungsten filament; however it is enclosed in a halogen gas-filled (iodine or bromine) quartz capsule and is operated at a higher temperature than an incandescent lamp.
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