Incandescent and Halogen
What is Incandescence?
Incandescent lamps were the original electric light sources and, with some refinements, they still employ basic technology that is over one hundred years old: a tungsten wire filament is placed inside a glass bulb, an electric current is passed through the filament, and resistance in the filament causes it to heat and “incandesce” or glow. Most modern lamps feature a coiled filament that improves efficacy and reduces heat loss. Whereas early bulbs contained a vacuum to prevent the filament from combining with oxygen and “burning out,” most of today’s lamps use various mixtures of inert gases for the same purpose.
The Characteristics of Incandescent Lamps
Incandescent light is the most commonly used electric light source in the home, which means that people consider it to be “normal.” The low color temperature and high CRI of incandescent casts a warm light which provides excellent color rendition of human skin tones. In addition, incandescent lamps are affordable, can be controlled by inexpensive dimming circuits, and are available in a wide range of sizes, configurations and wattages. Unfortunately, incandescent lamps are inefficient. Because they produce light by heating a solid material until it glows, most of the energy they consume is given off as heat, resulting in low LPW performance. Other more energy efficient lamp types can therefore offer substantially lower operating costs.
Halogen–Superior Incandescent Technology
Tungsten halogen lamps are a refinement of incandescent technology that offer up to 20 percent greater energy efficiency, longer service life and improved light quality. In a standard incandescent lamp, tungsten from the filament evaporates over time and is deposited on the walls of the bulb, thus reducing light output. The filament gets thinner and thinner and eventually breaks, causing the lamp to fail. The halogen gas inside a halogen lamp causes the evaporated tungsten to redeposit on the filament. This process, along with high pressure inside the capsule, slows down deterioration of the filament, improves lumen maintenance and extends the lamp’s service life.
Whiter, Brighter Light
Halogen lamps have higher color temperatures than standard incandescent lamps—their light output contains more blue and green. Halogen lamps therefore appear whiter and brighter. Although both types of lamp essentially have a CRI of 100, the higher color temperature of halogen lamps provides more pleasing and vibrant color rendition across a wider range of colors.
Low Voltage– an Almost Perfect Point Source
Special halogen lamps are available for low voltage configurations and they offer a number of advantages. Low voltage systems, which can be designed to operate efficiently at lower wattages than line voltage systems, allow the use of lamps that are extremely compact and still provide high lumen output. The relatively short, thick filaments in MR16 and MR11 halogen lamps, for example, produce large amounts of light from a very small area and permit excellent beam control. Low voltage halogen lamps have therefore become the preferred choice for accent, display and decor .
A Wide Range of Lamp Shapes
Halogen lamps are available in many sizes, shapes and wattages. Reflector types include PAR, AR and MR configurations in a wide range of wattages and beam angles, from narrow spot to wide flood. Midbreak versions provide long lasting, energy efficient alternatives to standard incandescent lamps. Other lamp configurations allow fixture designers to take full advantage of the special attributes that halogen technology offers.