Lighting Research Center Lighting Research Center
    Volume 9 Issue 3
May 2000    
A-lamp - The incandescent lamp most commonly used in North American households. The "A" designation refers to the lamp's bulbous shape. ballast - A device required by electric-discharge light sources such as fluorescent or HID lamps to regulate voltage and current supplied to the lamp during start and throughout operation. bi-level switching - Control of light source intensity at two discrete levels in addition to off. compact fluorescent lamp (CFL) - A family of single-ended fluorescent-discharge light sources with small-diameter [16-millimeter (5/8-inch) or less] tubes. continuous dimming - Control of a light source's intensity to practically any value within a given operating range. lamp - A radiant light source. tri-level switching - Control of light source intensity at three discrete levels in addition to off. indirect lighting - Light arriving at a surface after reflecting from one or more surfaces (usually walls and/or ceilings) that are not part of the luminaire. luminaire - A complete lighting unit consisting of a lamp or lamps and the parts designed to distribute the light, to position and protect the lamp(s), and to connect the lamp(s) to the power supply. (Also referred to as fixture.) correlated color temperature (CCT) - A specification for white light sources used to describe the dominant color tone along the dimension from warm (yellows and reds) to cool (blue). Lamps with a CCT rating below 3200 K are usually considered warm sources, whereas those with a CCT above 4000 K usually considered cool in appearance. Temperatures in between are considered neutral in appearance. Technically, CCT extends the practice of using temperature, in kelvins (K), for specifying the spectrum of light sources other than blackbody radiators. Incandescent lamps and daylight closely approximate the spectra of black body radiators at different temperatures and can be designated by the corresponding temperature of a blackbody radiator. The spectra of fluorescent and LED sources, however, differ substantially from black body radiators yet they can have a color appearance similar to a blackbody radiator of a particular temperature as given by CCT. direct light - Light emitted by a luminaire in the general direction of the task to be illuminated. The term usually refers to light emitted in a downward direction. halogen lamp - An incandescent lamp that uses a halogen fill gas. Halogen lamps have higher rated efficacies and longer lives than standard incandescent A-lamps. active power - the system input power (in watts) for a lamp-ballast combination. color rendering index (CRI) - A rating index commonly used to represent how well a light source renders the colors of objects that it illuminates. For a CRI value of 100, the maximum value, the colors of objects can be expected to be seen as they would appear under an incandescent or daylight spectrum of the same correlated color temperature (CCT). Sources with CRI values less than 50 are generally regarded as rendering colors poorly, that is, colors may appear unnatural. efficacy - The ratio of light output (in lumens) to input power (in watts), expressed as lumens per watt (LPW). illuminance - The density of luminous flux incident upon a surface. Illuminance is measured in footcandles (lumens/square foot) or lux (lumens/square meter). One footcandle equals 10.76 lux. lamp life - The number of hours at which half of a large group of lamps have failed when operated under standard testing conditions. lumen (lm) - A unit measurement of the rate at which a lamp produces light. A lamp's lumen output rating expresses the total amount of light the lamp emits in all directions per unit time. metal halide lamp - A high-intensity discharge (HID) lamp that uses mercury and several halide additives as light-producing elements. Metal halide lamps have better color properties than other HID lamp types because the different additives produce light distributed over more visible wavelengths, resulting in a more complete spectrum. Metal halide lamps are available with CCTs from 2300 to 5400 K and with CRI values from 60 to 93. Efficacies of metal halide lamps typically range from 75 to 125 LPW.
What are the alternatives to halogen torchieres?

Manufacturers have introduced a number of compact-fluorescent-lamp (CFL) torchieres and at least one metal halide torchiere that offer similar light output and better energy efficiency than halogen torchieres and greatly reduce concerns about fire and explosion. Incandescent (A-lamp) torchieres are another alternative to reduce the risk of fire, although they are not necessarily more efficient than halogen torchieres. Alternative products are becoming available at retail outlets, online, and through mail-order catalogs (see "Where are they available?" for more information).

Incandescent-lamp torchieres
Many stores now offer torchieres with 100- or 150-watt (W) incandescent A-lamps. Like halogen lamps, incandescent lamps can be dimmed, and these torchieres are usually available with either continuous or trilevel dimming. Incandescent lamps are cooler than halogen torchieres, but they achieve lower temperatures primarily through reduced light output. They are about as efficacious as halogen lamps. Incandescent lamps are the least expensive of the lamps discussed in this report.
CFL torchieres
CFLs require a ballast to regulate starting voltage and operating current. The ballast increases the weight of the torchiere, although CFL torchieres are still lightweight and compact enough to be moved easily.

Several CFL torchieres include bilevel or trilevel switching, a few offer continuous dimming. Dimming generally increases the correlated color temperature (CCT) of CFLs, making their color appear cooler (unlike halogen and incandescent lamps). CFL torchieres are available in a number of lamp configurations containing the CFLs shown below. These CFLs are available in a range of CCTs with color-rendering indexes (CRIs) of at least 82, with efficacy ranging from 60-86 lumens per watt (LPW).

Figure 4
Metal halide torchieres
Like CFLs, metal halide lamps require a ballast to regulate starting voltage and operating current. The metal halide torchiere tested by NLPIP uses a 68-W metal halide lamp. Two 25-W (or lower wattage) incandescent A-lamps are included in the torchiere to provide light during the time needed for the metal halide lamp to reach full light output. The A-lamps can be turned off separately. The 68-W metal halide lamp has a CCT of 3200 with a CRI of about 75. The metal halide lamp is also more efficacious (at 88 LPW) than CFLs. However, it cannot be dimmed.

Previous
Previous
2000 Rensselaer Polytechnic Institute. All rights reserved. Next Next


Rensselaer Polytechnic Institute
LRC Intranet Web mail Lighting Research Center