LIGHT SOURCES.pdf

LIGHT SOURCES TOPIC OUTLINE INCANDESCENT LAMPS FLUORESCENT LAMPS COMPACT FLUORESCENT LAMP (CFL) INCANDESCENT LAMPS INCANDESCENT LAMPS The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence, (a general term for heat-driven...

LIGHT SOURCES TOPIC OUTLINE INCANDESCENT LAMPS FLUORESCENT LAMPS COMPACT FLUORESCENT LAMP (CFL) INCANDESCENT LAMPS INCANDESCENT LAMPS The incandescent light bulb, incandescent lamp or incandescent light globe is a source of electric light that works by incandescence, (a general term for heat-driven light emissions which includes the simple case of black body radiation). An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb prevents the oxygen in air from reaching the hot filament, which otherwise would be destroyed rapidly by oxidation. Incandescent bulbs are also sometimes called electric lamps, a term also applied to the original arc lamps. Incandescent bulbs are made in a wide range of sizes and voltages, from 1.5 volts to about 300 volts. They require no external regulating equipment and have a low manufacturing cost, and work well on either alternating current or direct current. As a result the incandescent lamp is widely used in household and commercial lighting, for portable lighting, such as table lamps, some car headlamps and electric flashlights, and for decorative and advertising lighting. INCANDESCENT LAMPS Illustration from U.S. Patent #223898: ElectricLamp. Issued January 27, 1880 to Thomas Edison. Incandescent light bulbs are gradually being replaced in many applications by (compact) fluorescent lamps, high-intensity discharge lamps, light-emitting diodes (LEDs), and other devices, which give more visible light for the same amount of electrical energy input. Some jurisdictions are attempting to ban the use of incandescent light bulb in favour of more energy-efficient lighting. INCANDESCENT LAMPS Early evolution of the light bulb Original carbon-filament bulb from Thomas Edison In addressing the question "Who invented the incandescent lamp?" historians Robert Friedel and Paul Israel list 22 inventors of incandescent lamps prior to Joseph Wilson Swan and Thomas Edison. They conclude that Edison's version was able to outstrip the others because of a combination of three factors: an effective incandescent material, a higher vacuum than others were able to achieve and a high resistance lamp that made power distribution from a centralized source economically viable. INCANDESCENT LAMPS 1.Outline of Glass bulb 2.Low pressure inert gas (argon, neon, nitrogen) 3.Tungsten filament 4.Contact wire (goes out of stem) 5.Contact wire (goes into stem) 6.Support wires 7.Stem (glass mount) 8.Contact wire (goes out of stem) 9.Cap (sleeve) 10.Insulation (vitrite) 11.Electrical contact INCANDESCENT LAMPS INCANDESCENT LAMPS Halogen lamps The halogen lamp reduces uneven evaporation of the filament and darkening of the envelope by filling the lamp with a halogen gas at low pressure, rather than an inert gas. These lamps can operate at a higher filament temperature with acceptable loss of life, giving them a higher luminous efficiency. Incandescent arc lamps Close-up of a tungsten filament inside a halogen lamp. The two ring-shaped structures left and right are filament supports. A variation of the incandescent lamp did not use a heated filament of wire to produce light but instead used an arc struck between bead-shaped electrodes to produce heat; the electrodes then became incandescent, with the arc contributing little to the light produced. Such lamps were used for projection or illumination for scientific instruments. These arc lamps ran on relatively low voltages and incorporated tungsten filaments to start ionization within the envelope. They provided the intense concentrated light of an arc lamp but were easier to operate. Developed around 1915, these lamps were displaced by mercury and xenon arc lamps. INCANDESCENT LAMPS Electrical characteristics Incandescent lamps are nearly pure resistive loads with a power factor of 1. This means the actual power consumed (in watts) and the apparent power (in volt-amperes) are equal. The actual resistance of the filament is temperature-dependent. The cold resistance of tungsten-filament lamps is about 1/15 the hot-filament resistance when the lamp is operating. For example, a 100-watt, 120-volt lamp has a resistance of 144 ohms when lit, but the cold resistance is much lower (about 9.5 ohms). Since incandescent lamps are resistive loads, simple triac dimmers can be used to control brightness. Electrical contacts may carry a "T" rating symbol indicating that they are designed to control circuits with the high inrush current characteristic of tungsten lamps. For a 100-watt, 120 volt generalservice lamp, the current stabilizes in about 0.10 seconds, and the lamp reaches 90% of its full brightness after about 0.13 seconds. INCANDESCENT LAMPS Power Incandescent light bulbs are usually marketed according to the electrical power consumed. This is measured in watts and depends mainly on the resistance of the filament, which in turn depends mainly on the filament's length, thickness, and material. For two bulbs of the same voltage, type, color, and clarity, the higherpowered bulb gives more light. The table shows the approximate typical output, in lumens, of standard incandescent light bulbs at various powers. Note that the lumen values for "soft white" bulbs will generally be slightly lower than for standard bulbs at the same power, while clear bulbs will usually emit a slightly brighter light than correspondinglypowered standard bulbs. Comparison of efficacy by power (120 Volt lamps) Power (W) Output (lm) Efficacy (lm/W) 5 25 5 15 110 7.3 25 200 8.0 35 350 10.0 40 500 12.5 50 700 14.0 55 800 14.2 60 850 14.5 65 1000 15.4 70 1100 15.7 75 1200 16.0 90 1450 16.1 95 1600 16.8 100 1700 17.0 135 2350 17.4 150 2850 19.0 200 3900 19.5 300 6200 20.7 INCANDESCENT LAMPS Physical characteristics Bulb shapes, sizes, and terms Incandescent light bulbs come in a range of shapes and sizes. The names of the shapes may be slightly different in some regions. Many of these shapes have a designation consisting of one or more letters followed by one or more numbers, e.g. A55 or PAR38. The letters represent the shape of the bulb. The numbers represent the maximum diameter, either in eighths of an inch, or in millimetres, depending on the shape and the region. For example, in Europe, Australia and elsewhere, 63 mm reflectors are known as R63, whereas in the U.S. they are known as R20 (2.5 inches). However, in both regions, a PAR38 reflector is known as PAR38. These designations may also apply to non-incandescent lamps, such as compact fluorescent lamps or LEDs. INCANDESCENT LAMPS Common shapes: General Service: Light emitted in (nearly) all directions. Available in either clear or frosted. Types: General (A), Mushroom High Wattage General Service: Lamps greater than 200 watts. Types: Pear-shaped (PS) Decorative: lamps used in chandeliers, etc. Types: Candle (B), Twisted Candle, Bent-tip Candle (CA & BA), Flame (F), Fancy Round (P), Globe (G) Reflector (R) : Reflective coating inside the bulb directs light forward. Flood types (FL) spread light. Spot types (SP) concentrate the light. Reflector (R) bulbs put approximately double the amount of light (foot-candles) on the front central area as General Service (A) of same wattage. Types: Standard Reflector (R), Elliptical Reflector (ER), Crown Silvered Parabolic Aluminized Reflector (PAR): Parabolic Aluminized Reflector (PAR) bulbs control light more precisely. They produce about four times the concentrated light intensity of General Service (A), and are used in recessed and track lighting. Weatherproof casings are available for outdoor spot and flood fixtures. 120V Sizes:PAR 16, 20, 30, 38, 56 and 64 230V Sizes:Par 38, 56 and 64 Available in numerous spot and flood beam spreads. Like all light bulbs, the number represents the diameter of the bulb in 1/8s of an inch. Therefore, a PAR 16 is 2" in diameter, a PAR 20 is 2.5" in diameter, PAR 30 is 3.75" and a PAR 38 is 4.75" in diameter. Multifaceted Reflector (MR) : HIR "HIR" means that the bulb has a special coating that reflects infrared back onto the filament. Therefore, less heat escapes, so the filament burns hotter and more efficiently. INCANDESCENT LAMPS Lamp bases Most domestic and industrial light bulbs have a metal fitting (or lamp base) compatible with standard sockets. The lamp base must carry current to the lamp, provide physical support, and resist heat. Lamp bases may be secured to the bulb with a cement, or by mechanical crimping to indentations molded into the glass bulb. Some miniature lamps have no metal bases at all and have only wire leads molded into the bulb. General Electric introduced standard base sizes for tungsten incandescent lamps under the Mazda trademark in 1909. This standard was soon adopted across the United States, and the Mazda name was used by many manufacturers under license through 1945. INCANDESCENT LAMPS Lamp bases: A light bulb with a standard E27 Edison screw base Screw thread Bayonet Pin base Special lamp bases The double-contact bayonet cap on an incandescent bulb INCANDESCENT LAMPS Bayonet designation alternative designation dimension, etc. Ba5s 5 mm Ba7s 7 mm Bax9s 9 mm Ba9s MBC Ba15d SBC Bax15s Ba15s Bayonet 9 mm Miniature Bayonet Cap 15 mm Small Bayonet Cap 15 mm SCC 15 mm Single Centre Contact Ba20s 20 mm Ba20d 20 mm Ba21d 21 mm B21-4 21 mm 4 Pin Ba22d BC 22 mm Bayonet Cap BC-3 BC3 22 mm Bayonet Cap 3 Pin B22d-3 22 mm Double Ended (Railway) Bx22d 22 mm Of these, only the BC (Ba22d) is commonly sold in supermarkets. INCANDESCENT LAMPS Voltage, light output, and lifetime Incandescent lamps are very sensitive to changes in the supply voltage. These characteristics are of great practical and economic importance. 5% reduction in operating voltage will more than double the life of the bulb, at the expense of reducing its light output by about 20%. a lamp operated at much lower than rated voltage could last for hundreds of times longer than at rated conditions, albeit with greatly reduced light output. INCANDESCENT LAMPS Voltage, light output, and lifetime Lamps designed for different voltages have different luminous efficacy. Lamps also vary in the number of support wires used for the tungsten filament. Very low voltages are inefficient since the lead wires would conduct too much heat away from the filament, so the practical lower limit for incandescent lamps is 1.5 volts. INCANDESCENT LAMPS Luminous efficacy and efficiency Type Overall luminous efficiency Overall luminous efficacy (lm/W) 40 W tungsten incandescent 1.9% 12.6 60 W tungsten incandescent 2.1% 14.5 100 W tungsten incandescent 2.6% 17.5 glass halogen 2.3% 16 quartz halogen 3.5% 24 high-temperature incandescent 5.1% 35 ideal black-body radiator at 4000 K 7.0% 47.5 ideal black-body radiator at 7000 K 14% 95 ideal monochromatic 555 nm (green) source 100% 683 The chart lists values of overall luminous efficacy and efficiency for several types of general service, 120 volt, 1000-hour lifespan incandescent bulb, and several idealized light sources. INCANDESCENT LAMPS Luminous efficacy and efficiency For a given quantity of light, an incandescent light bulb produces more heat (and consumes more power) than a fluorescent lamp. Quality halogen incandescent lamps have higher efficacy, which will allow a 60 W bulb to provide nearly as much light as a non-halogen 100 W. Alternatives to standard incandescent lamps for general lighting purposes include: Fluorescent lamps, and Compact fluorescent lamps High-intensity discharge lamps LED lamps INCANDESCENT LAMPS Measures to discontinue use Due to the higher energy usage of incandescent light bulbs in comparison to more energy efficient alternatives, such as compact fluorescent lamps and LED lamps, some governments have passed laws and regulations that have started to phase out their usage. Efforts to improve efficiency Various efforts to improve the efficiency of incandescent lamps have been made recently, due to legislation and other movements to ban incandescent lamps. FLUORESCENT LAMPS FLUORESCENT LAMPS A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce shortwave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. Fluorescent lamps Assorted types of fluorescent lamps. Top, two Compact fluorescent lamps, bottom, two regular tubes. Matchstick shown for scale. FLUORESCENT LAMPS Inside the lamp end of a bi-pin lamp Typical F71T12HO 100W bi-pin lamp used in tanning beds. Note (Hg) symbol indicating it contains mercury. In the US this symbol is now required on all fluorescent bulbs that contain mercury. FLUORESCENT LAMPS History The history of the fluorescent lamp begins with early research into electrical phenomena. By the beginning of the 18th century, experimenters had observed a radiant glow emanating from partially evacuated glass vessels through which an electrical current passed. Little more could be done with this phenomenon until 1856 when a German glassblower named Heinrich Geissler (1815–1879) created a mercury vacuum pump that evacuated a glass tube to an extent not previously possible. When an electrical current passed through a Geissler tube, a strong green glow on the walls of the tube at the cathode end could be observed. FLUORESCENT LAMPS Principles of operation The fundamental means for conversion of electrical energy into radiant energy in a fluorescent lamp relies on inelastic scattering of electrons. Incident free electron transfers energy to the atom's outer electron, causing that electron to temporarily jump up to a higher energy level. This higher energy state is unstable, and the atom will emit an ultraviolet photon as the atom's electron reverts to a lower, more stable, energy level. Ultraviolet photons are absorbed by electrons in the atoms of the lamp's fluorescent coating, causing a similar energy jump, then drop, with emission of a further photon. The difference in energy between the absorbed ultra-violet photon and the emitted visible light photon goes to heat up the phosphor coating. The UV light is absorbed by the bulb's fluorescent coating, which re-radiates the energy at longer wavelengths to emit visible light. The blend of phosphors controls the color of the light, and along with the bulb's glass prevents the harmful UV light from escaping. FLUORESCENT LAMPS Components of a Fluorescent Lamp A fluorescent lamp consists of a phosphor-coated tube, starter, and ballast. The tube is filled with an inert gas (argon) plus a small amount of mercury vapor. The starter energizes the two filaments when the lamp is first turned on. The filaments supply electrons to ionize the argon, forming a plasma that conducts electricity. The ballast limits the amount of current that can flow through the tube. The plasma excites the mercury atoms, which then emit red, green, blue, and ultraviolet light. The light strikes the phosphor coating on the inside of the lamp, which converts the ultraviolet light into other colors. Different phosphors produce warmer or cooler colors. FLUORESCENT LAMPS Construction Close-up of the cathodes and anodes of a germicidal lamp (an essentially-similar design that uses no fluorescent phosphor, allowing the electrodes to be seen.) The unfiltered ultraviolet glow of a germicidal lamp is produced by a low pressure mercury vapor discharge (identical to that in a fluorescent lamp) in an uncoated fused quartz envelope. FLUORESCENT LAMPS Electrical aspects of operation ballast, to regulate the current flow through the tube. capacitor for power factor correction transistors or other semiconductor components to alter mains voltage frequency into high-frequency AC while also regulating the current flow in the lamp. ("Variable frequency electronic ballasts" ) FLUORESCENT LAMPS Starting The mercury atoms in the fluorescent tube must be ionized before the arc can "strike" within the tube. For small lamps, it does not take much voltage to strike the arc and starting the lamp presents no problem, but larger tubes require a substantial voltage (in the range of a thousand volts). FLUORESCENT LAMPS Preheat lamps Preheat lamps use a combination filament/cathode at each end of the lamp in conjunction with a mechanical or automatic switch that initially connect the filaments in series with the ballast and thereby preheat the filaments prior to striking the arc. FLUORESCENT LAMPS Instant start In some cases, a high voltage is applied directly: instant start fluorescent tubes simply use a high enough voltage to break down the gas and mercury column and thereby start arc conduction. These tubes can be identified by 1. a single pin at each end of the tube, and 2. the lampholders that they fit into having a "disconnect" socket at the lowvoltage end to ensure that the mains current is automatically removed so that a person replacing the lamp cannot receive a high-voltage electric shock. FLUORESCENT LAMPS Rapid start Newer rapid start ballast designs provide filament power windings within the ballast; these rapidly and continuously warm the filaments/cathodes using low-voltage AC. No inductive voltage spike is produced for starting, so the lamps must be mounted near a grounded (earthed) reflector to allow the glow discharge to propagate through the tube and initiate the arc discharge. In some lamps a "starting aid" strip of grounded metal is attached to the outside of the lamp glass. FLUORESCENT LAMPS Electronic ballasts Electronic ballasts often revert to a style in-between the preheat and rapid-start styles: a capacitor (or sometimes an autodisconnecting circuit) may complete the circuit between the two filaments, providing filament preheating. When the tube lights, the voltage and frequency across the tube and capacitor typically both drop, thus capacitor current falls to a low but non-zero value. Generally this capacitor and the inductor, which provides current limiting in normal operation, form a resonant circuit, increasing the voltage across the lamp so it can easily start. FLUORESCENT LAMPS Advantages Luminous efficacy Fluorescent lamps convert more of the input power to visible light than incandescent lamps. A typical 100 watt tungsten filament incandescent lamp may convert only 10% of its power input to visible white light, whereas typical fluorescent lamps convert about 22% of the power input to visible white light Life Typically a fluorescent lamp will last between 10 to 20 times as long as an equivalent incandescent lamp when operated several hours at a time. FLUORESCENT LAMPS Advantages Lower luminosity Compared with an incandescent lamp, a fluorescent tube is a more diffuse and physically larger light source. Lower heat About two-thirds to three-quarters less heat is given off by fluorescent lamps compared to an equivalent installation of incandescent lamps. FLUORESCENT LAMPS Disadvantages Health and safety issues If a fluorescent lamp is broken, mercury can contaminate the surrounding environment. Ballast Fluorescent lamps require a ballast to stabilize the current through the lamp, and to provide the initial striking voltage required to start the arc discharge. This increases the cost of fluorescent light fixtures. FLUORESCENT LAMPS Disadvantages Power quality and radio interference Simple inductive fluorescent lamp ballasts have a power factor of less than unity. Fluorescent lamps are a non-linear load and generate harmonic currents in the electrical power supply Operating temperature Fluorescent lamps operate best around room temperature. At much lower or higher temperatures, efficiency decreases. Lamp shape Fluorescent tubes are long, low-luminance sources compared with high pressure arc lamps and incandescent lamps. FLUORESCENT LAMPS Disadvantages Flicker problems Fluorescent lamps using a magnetic mains frequency ballast do not give out a steady light; instead, they flicker at twice the supply frequency. While this is not easily discernible by the human eye, it can cause a strobe effect, where something spinning at just the right speed may appear stationary if illuminated solely by a single fluorescent lamp. Dimming Fluorescent light fixtures cannot be connected to the same dimmer switch used for incandescent lamps. FLUORESCENT LAMPS Disadvantages Disposal and recycling The disposal of phosphor and particularly the toxic mercury in the tubes is an environmental issue. FLUORESCENT LAMPS Tube designations Lamps are typically identified by a code such as F##T##, where F is for fluorescent, the first number indicates the power in watts (or where lamps can be operated at different power levels, the length in inches), the T indicates that the shape of the bulb is tubular, and the last number is the diameter in eighths of an inch (sometimes in millimeters, rounded to the nearest millimeter). Typical diameters are T12 or T38 (11/2" Ø or 38.1 mm Ø) for residential bulbs with old magnetic ballasts, T8 or T26 (1" Ø or 25.4 mm Ø) for commercial energy-saving lamps with electronic ballasts, and T5 or T16 (5/8" Ø or 15.875 mm Ø) for very small lamps which may even operate from a battery powered device. FLUORESCENT LAMPS Light outputs High-output lamps are brighter and draw more electrical current, have different ends on the pins so they cannot be used in the wrong fixture, and are labeled F##T##HO, or F##T##VHO for very high output. Since about the early to mid 1950s to today, General Electric developed and improved the Power Groove lamp with the label F##PG17. These lamps are recognizable by their large diameter (17/8" or 21/8"), grooved tube shape and an R17d cap on each end of them. FLUORESCENT LAMPS Other tube shapes U-shaped tubes are FB##T##, with the B meaning "bent". Most commonly, these have the same designations as linear tubes. Circular bulbs are FC##T#, with the diameter of the circle (not circumference or watts) being the first number, and the second number usually being 9 (29 mm) for standard fixtures. FLUORESCENT LAMPS Colors Color is usually indicated by WW for warm white, EW for enhanced (neutral) white, CW for cool white (the most common), and DW for the bluish daylight white. BLB is used for blacklight-blue lamps commonly used in bug zappers. BL is used for blacklight lamps commonly used in nightclubs. Other non-standard designations apply for plant lights or grow lights. COMPACT FLUORESCENT LAMP A compact fluorescent lamp (CFL), also known as a compact fluorescent light or energy saving light (or less commonly as a compact fluorescent tube [CFT]), is a type of fluorescent lamp. Many CFLs are designed to replace an incandescent lamp and can fit into existing light fixtures formerly used for incandescents. COMPACT FLUORESCENT LAMP COMPACT FLUORESCENT LAMP A spiral-type integrated compact fluorescent lamp, with combined tube and electronic ballast. This style has slightly reduced efficiency compared to tubular fluorescent lamps, due to the excessively thick layer of phosphor on the lower side of the twist. Despite this, it has become one of the most popular types among North American consumers since its introduction in the mid 1990s. COMPACT FLUORESCENT LAMP History The parent to the modern compact fluorescent lamp (CFL) was invented in the late 1890s by Peter Cooper Hewitt. The Cooper Hewitt lamps were used for photographic studios and industries. Edmund Germer, Friedrich Meyer, and Hans Spanner then patented a high pressure vapor lamp in 1927. George Inman later teamed with General Electric to create a practical fluorescent lamp, sold in 1938 and patented in 1941.The modern CFL was invented by Ed Hammer, an engineer with General Electric, in response to the 1973 oil crisis. While it met its design goals, it would have cost GE about US$25 million to build new factories to produce them and the invention was shelved. The design was eventually leaked out and copied by others. CFLs have steadily increased in sales volume. COMPACT FLUORESCENT LAMP Construction A compact fluorescent lamp used outside of a building. The most important technical advance has been the gradual replacement of electromagnetic ballasts with electronic ballasts; this has removed most of the flickering and slow starting traditionally associated with fluorescent lighting. There are two types of CFLs: integrated and nonintegrated lamps. COMPACT FLUORESCENT LAMP Parts Electronic ballast of a compact fluorescent lamp There are two main parts in a CFL: the gas-filled tube (also called bulb or burner) and the magnetic or electronic ballast. An electrical current from the ballast flows through the gas, causing it to emit ultraviolet light. The ultraviolet light then excites a phosphor coating on the inside of the tube. This coating emits visible light (see Fluorescent lamp). Electronic ballasts contain a small circuit board with rectifiers, a filter capacitor and usually two switching transistors connected as a high-frequency resonant series DC to AC inverter. The resulting high frequency, around 40 kHz or higher, is applied to the lamp tube. Since the resonant converter tends to stabilize lamp current (and light produced) over a range of input voltages, standard CFLs do not respond well in dimming applications and special lamps are required for dimming service. CFLs that flicker when they start have magnetic ballasts; CFLs with electronic ballasts are now much more common. COMPACT FLUORESCENT LAMP Integrated CFLs Integrated lamps combine a tube, an electronic ballast and either an Edison screw or bayonet fitting in a single CFL unit. These lamps allow consumers to replace incandescent lamps easily with CFLs. Integrated CFLs work well in standard incandescent light fixtures. This lowers the cost of CFL use, since they can reuse the existing infrastructure. COMPACT FLUORESCENT LAMP Non-integrated CFLs Non-integrated CFLs have a separate, replaceable bulb and a permanently installed ballast. These ballasts are typically of the magnetic type, and the starter is housed in the base of the replaceable bulb. Since the ballasts are placed in the light fixture they are larger and last longer, compared to the integrated ones. Non-integrated CFL housings can be both more expensive and sophisticated, providing options such as dimming, less flicker, faster starts, etc. COMPACT FLUORESCENT LAMP CFL power sources CFLs are produced for both alternating current (AC) and direct current (DC) input. DC CFLs are popular for use in recreational vehicles and offthe-grid housing. Some families in developing countries are using DC CFLs (with car batteries and small solar panels) and/or wind generators, to replace kerosene lanterns. CFLs can also be operated with solar powered street lights, using solar panels located on the top or sides of a pole and luminaires that are specially wired to use the lamps. COMPACT FLUORESCENT LAMP Comparison with incandescent lamps Lifespan The average rated life of a CFL is between 8 and 15 times that of incandescents. CFLs typically have a rated lifespan of between 6,000 and 15,000 hours, whereas incandescent lamps are usually manufactured to have a lifespan of 750 hours or 1,000 hours COMPACT FLUORESCENT LAMP Energy efficiency The chart shows the energy usage for different types of light bulbs operating at different light outputs. Points lower on the graph correspond to lower energy use. COMPACT FLUORESCENT LAMP Efficacy and efficiency A typical CFL is in the range of 17 to 21% efficient at converting electric power to radiant power. Because the eye's sensitivity changes with the wavelength, however, the output of lamps is more commonly measured in lumens, a measure that accounts for the effect of the source's spectrum on the eye. The luminous efficacy of CFL sources is typically 60 to 72 lumens per watt, versus 8 to 17 lm/W for incandescent lamps. COMPACT FLUORESCENT LAMP Cost While the purchase price of an integrated CFL is typically 3 to 10 times greater than that of an equivalent incandescent lamp, the extended lifetime and lower energy use will compensate for the higher initial cost CFLs are extremely cost-effective in commercial buildings when used to replace incandescent lamps. COMPACT FLUORESCENT LAMP Starting time Incandescents give light almost immediately upon the application of voltage. CFLs take a perceptible time to achieve full brightness, and can take much longer in very cold temperatures. Certain styles of lamp using a mercury amalgam can take up to three minutes to reach full output. Coupling this with the shorter life of CFLs when turned on and off for short amounts of time may make incandescent bulbs more attractive for applications such as outdoor or motion-activated lighting. COMPACT FLUORESCENT LAMP Other CFL technologies Another type of fluorescent lamp is the electrodeless lamp, known as a radiofluorescent lamp or fluorescent induction lamp. These lamps have no wire conductors penetrating their envelopes, and instead excite mercury vapor using a radio-frequency oscillator. The Cold Cathode Fluorescent Lamp (CCFL) is one of the newest forms of CFL. CCFLs use electrodes without a filament. The voltage of CCFLs is about 5 times higher than CFLs and the current is about 10 times lower. CCFLs have a diameter of about 3 millimeters. CCFLs were initially used for backlighting LCD displays, but they are now also manufactured for use as lamps. COMPACT FLUORESCENT LAMP Spectrum of light The light of CFLs is emitted by a mix of phosphors on the inside of the tube, which each emit one color. Modern phosphor designs are a compromise between the shade of the emitted light, energy efficiency, and cost. A photograph of various lamps illustrates the effect of color temperature differences (left to right): (1) Compact Fluorescent: General Electric, 13 watt, 6500 K (2) Incandescent: Sylvania 60-Watt Extra Soft White (3) Compact Fluorescent: Bright Effects, 15 watts, 2644 K (4) Compact Fluorescent: Sylvania, 14 watts, 3000 K COMPACT FLUORESCENT LAMP Spectrum of light Color temperature can be indicated in kelvins or mireds (1 million divided by the color temperature in kelvins). A blacklight CFL. Color temperature kelvin mired 'Warm white' or 'Soft white' ≤ 3000 K ≥ 333 M 'White' or 'Bright White' 3500 K 286 M 'Cool white' 4000 K 250 M 'Daylight' ≥ 5000 K ≤ 200 M Color temperature is a quantitative measure. The higher the number in kelvins, the 'cooler', i.e., bluer, the shade. Color names associated with a particular color temperature are not standardized for modern CFLs and other triphosphor lamps like they were for the older-style halophosphate fluorescent lamps. COMPACT FLUORESCENT LAMP Environmental issues Energy savings Since fluorescent lamps use less power to supply the same amount of light as an incandescent lamp, they decrease energy consumption and the environmental effects of electric power generation. Where electricity is largely produced from burning fossil fuels, the savings reduces emission of greenhouse gases and other pollutants. While CFLs require more energy in manufacturing than incandescent lamps, this is offset by the fact that they last longer and use less energy than equivalent incandescent lamps during their lifespan. COMPACT FLUORESCENT LAMP Mercury emissions Mercury use of compact fluorescent lamp vs. incandescent lamp if powered by electricity generated completely from coal, though coal accounts for about half of the power production in the United States. COMPACT FLUORESCENT LAMP Design and application issues The primary objectives of CFL design are high electrical efficiency and durability. However, there are some other areas of CFL design and operation that are problematic: Size CFL light output is roughly proportional to phosphor surface area, and high output CFLs are often larger than their incandescent equivalents. This means that the CFL may not fit well in existing light fixtures. End of life The electronic ballast may fail since it has a number of component parts; such failures may be accompanied by discoloration or distortion of the ballast enclosure, odors, or smoke. COMPACT FLUORESCENT LAMP Design and application issues Dimming Only a few CL lamps are labeled for dimming control. Using regular CFLs with a dimmer can shorten bulb life and will void the warranty of certain manufacturers Perceived Coldness of Low Intensity CFL When a CFL is dimmed the colour temperature (warmth) stays the same. Heat Some CFLs are labeled not to be run base up, since heat will shorten the ballast's life. Such CFLs are unsuitable for use in pendant lamps and especially unsuitable for Recessed light fixtures. COMPACT FLUORESCENT LAMP Design and application issues Power quality The introduction of CFLs may affect power quality appreciably, particularly in large-scale installations Time to achieve full brightness Compact fluorescent lamps may provide as little as 50-80% of their rated light output at initial switch on and can take up to three minutes to warm up, and color cast may be slightly different immediately after being turned on. Infrared signals Electronic devices operated by infrared remote control can interpret the infrared light emitted by CFLs as a signal limiting the use of CFLs near televisions, radios, remote controls, or mobile phones COMPACT FLUORESCENT LAMP Design and application issues Audible noise CFLs, much as other fluorescent lights, may emit a buzzing sound, where incandescents normally do not. Iridescence Fluorescent lamps can cause window film to exhibit iridescence. This phenomenon usually occurs at night. Use with timers and other electronic controls Electronic (but not mechanical) timers can interfere with the electronic ballast in CFLs and can shorten their lifespan. COMPACT FLUORESCENT LAMP Design and application issues Fire hazard Inferior quality electronic components used in some CFLs can cause excessive heat or fire. Outdoor use CFLs not designed for outdoor use will not start in cold weather. Differences among manufacturers There are large differences among quality of light, cost, and turn-on time among different manufacturers, even for lamps that appear identical and have the same color temperature. COMPACT FLUORESCENT LAMP Design and application issues Lifetime brightness Fluorescent lamps get dimmer over their lifetime, so what starts out as an adequate luminosity may become inadequate. UV emissions Fluorescent bulbs can damage paintings and textile fabrics which are composed of light-sensitive dyes and pigments. They can also initiate polymer degradation. COMPACT FLUORESCENT LAMP Efforts to encourage adoption Due to the potential to reduce electric consumption and pollution, various organizations have encouraged the adoption of CFLs and other efficient lighting. Efforts range from publicity to encourage awareness, to direct handouts of CFLs to the public. Some electric utilities and local governments have subsidized CFLs or provided them free to customers as a means of reducing electric demand (and so delaying additional investments in generation). More controversially, some governments are considering stronger measures to entirely displace incandescents. These measures include taxation, or bans on production of incandescent light bulbs. Australia, Canada, and the US have already announced nationwide bans on incandescent bulbs End of Presentation