fluorescent , or fluorescent tube light, is a low-pressure mercury gas-discharge lamp that uses fluorescence to produce visible light. The electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light which then causes the phosphor coating on the inside of the lamp to glow. Fluorescent lamps convert electrical energy into useful light much more efficiently than incandescent lamps. The typical luminous efficacy of a fluorescent lighting system is 50-100 lumens per watt, several times the efficacy of incandescent lamps with comparable light output.
Fluorescent lighting fixtures are more expensive than incandescent lamps because they require ballasts to regulate the current through the lamps, but lower energy costs usually offset the higher initial cost. Compact fluorescent lamps are now available in the same popular size as incandescents and are used as an energy-efficient alternative in homes.
Because it contains mercury, many fluorescent lamps are classified as hazardous waste. The US Environmental Protection Agency recommends that fluorescent lamps be separated from common waste for recycling or safe disposal, and some jurisdictions require recycling.
Video Fluorescent lamp
History
Physical discovery
Fluorescence of certain rocks and other substances has been observed for hundreds of years before its properties are understood. By the mid-19th century, researchers had observed the glow of light emanating from a glass vessel that was evacuated partly through an electric current through which it was passed. One of the first to explain it was the Irish scientist Sir George Stokes of the University of Cambridge in 1852, who named the phenomenon of "fluorescence" after fluorite, a mineral that many of its samples are luminous because of impurities. The explanation depends on the electrical properties and phenomena of light as developed by British scientist Michael Faraday in the 1840s and James Clerk Maxwell in the 1860s.
A little more was done with this phenomenon until 1856 when German glassmaker Heinrich Geissler invented a mercury vacuum pump that emptied the glass tube to a level previously unlikely. Geissler invented the first gas discharge lamp, a Geissler tube, consisting of a glass tube partially evacuated with metal electrodes at both ends. When a high voltage is applied between the electrodes, the inside of the tube lights up with the discharge of light. By incorporating different chemicals inside, tubes can be made to produce a variety of colors, and an elaborate Geissler tube is sold for entertainment. More important, however, is its contribution to scientific research. One of the first scientists to experiment with Geissler tubes was Julius PlÃÆ'¼cker which was systematically described in 1858 luminous effects that occurred in the Geissler tube. He also made an important observation that the light in the tube shifted position when near the electromagnetic field. Alexandre Edmond Becquerel observed in 1859 that certain substances emit light when they are placed in a Geissler tube. He proceeded by applying a thin layer of luminescent material to the surface of these tubes. Fluorescence occurs, but the tube is very inefficient and has a short operating life.
Questions that begin with the Geissler tube are continued because the vacuums are better produced. The most famous is the evacuated tube used for scientific research by William Crookes. The tube was evacuated by a highly effective mercury vacuum pump manufactured by Hermann Sprengel. Research conducted by Crookes and others eventually led to the discovery of electrons in 1897 by J. J. Thomson and X-ray in 1895 by Wilhelm Roentgen. But the Crookes tube, which is then known, produces little light because the vacuum inside is too good and thus does not have the amount of trace gas required for the luminescence of electric arousal.
Early release light
While Becquerel was particularly interested in conducting scientific research on fluorescence, Thomas Edison briefly pursued fluorescent lamps for his commercial potential. He invented the fluorescent lamp in 1896 that used the calcium tungstate layer as a fluorescence substance, attracted to X-rays, but despite receiving a patent in 1907, it was not put into production. Like several other attempts to use Geissler tubes for illumination, it has a short operating life, and considering the success of incandescent lamps, Edison has little reason to pursue alternative ways of electric lighting. Nikola Tesla conducted similar experiments in the 1890s, designing fluorescent high-powered lights that gave greenish green light, but like the Edison device, no commercial success was achieved.
Although Edison has lost interest in fluorescent lighting, one of its former employees was able to create gas-based lamps that achieved a measure of commercial success. In 1895, Daniel McFarlan Moore demonstrated a 2 to 3 meter (6.6 to 9.8 ft) long light bulb that used carbon dioxide or nitrogen to emit white or pink light. Like future fluorescent lamps, they are much more complicated than incandescent bulbs.
After years of work, Moore was able to extend the life of the lamp by creating a controlled electromagnetic valve that maintains constant gas pressure in the tube. Although the Moore lights are complicated, expensive to install, and require very high voltages, they are much more efficient than incandescent lamps, and produce closer estimates to natural daylight than contemporary incandescent lighting. From 1904 onwards the Moore lighting system is installed in a number of stores and offices. His success contributed to General Electric's motivation to improve incandescent lamps, especially the filaments. GE's efforts began to bear fruit with the discovery of tungsten-based filaments. Extended lifespan and increased incandescent light bulbs negate one of the main advantages of Moore's lights, but GE purchased the relevant patent in 1912. These patents and inventive efforts that support it will be valuable when the company takes fluorescent lighting over two decades later.
At about the same time that Moore developed his lighting system, other Americans created a lighting device that could also be seen as the predecessor of modern fluorescent lamps. This is a mercury vapor lamp, created by Peter Cooper Hewitt and patented in 1901 ( US 682692 ; this patent number is often misquoted as US 889.692 ). The Hewitt lamp shines when an electric current is passed through mercury vapor at low pressure. Unlike Moore lights, Hewitt is manufactured in standard sizes and operated at low voltage. Mercury vapor lamps are superior to incandescent time lamps in terms of energy efficiency, but the blue-green light produces limited applications. It was, however, used for photography and some industrial processes.
Mercury vapor lamps continued to develop at a slower pace, especially in Europe, and by the early 1930s they received limited use for large-scale lighting. Some of them use fluorescent coating, but these are used primarily for color correction and not for enhanced light output. The mercury vapor lamp also anticipates fluorescent lamps in ballast mounting to maintain constant current.
Cooper-Hewitt was not the first to use mercury vapor for illumination, because previous attempts had been installed by Way, Rapieff, Arons, and Bastian and Salisbury. The most important is the mercury vapor lamp created by KÃÆ'¼ch in Germany. These lights are used quartz in place of glass to allow higher operating temperatures, and hence greater efficiency. Although its light output relative to electricity consumption is better than other light sources, the resulting light is similar to a Cooper-Hewitt lamp because it lacks the red part of the spectrum, making it unsuitable for ordinary lighting.
Neon Lamp
The next step in gas-based lighting takes advantage of the quality of luminescent neon, an inert gas that has been discovered in 1898 by isolation from the atmosphere. Neon glows bright red when used in a Geissler tube. In 1910, Georges Claude, a Frenchman who had developed successful technology and business for liquefaction, acquired enough neon as a by-product to support the fluorescent lighting industry. While fluorescent lights were used around 1930 in France for general lighting, it was no more energy efficient than conventional incandescent lamps. Neon tube lighting, which also includes the use of argon and mercury vapor as an alternative gas, is ultimately used primarily for visible signs and advertisements. Neon lighting was relevant for the development of fluorescent lamps; however, as Claude's improved electrode (patented in 1915) overcame "sputtering", the main source of degradation of the electrode. Sputtering occurs when the ionized particles hit the electrode and tear off pieces of metal. Although Claude's invention requires electrodes with many surface areas, it suggests that the main obstacles to gas-based lighting can be overcome.
The development of neon light is also significant for the last key element of the fluorescent lamp, its fluorescent coating. In 1926, Jacques Risler received a French patent for the application of fluorescent coatings to fluorescent tubes. The main use of this lamp, which can be considered the first commercially successful fluorescent lamp, is for advertising, not general lighting. This, however, is not the first use of fluorescent coatings; Becquerel had previously used the idea and Edison used calcium tungstate for failed lights. Other efforts have been made, but all are distracted by low efficiency and various technical issues. The most important was the invention in 1927 from the "low voltage metal vapor" by Friedrich Meyer, Hans-Joachim Spanner, and Edmund Germer, who was an employee of a German company in Berlin. German patents are given but the lights never go into commercial production.
Commercialization of fluorescent lamps
All the major features of fluorescent lighting existed in the late 1920s. The decade of discovery and development has provided a key component of fluorescent lamps: economically produced glass tubes, inert gas for tube filling, electric shock, durable electrodes, mercury vapor as a source of luminescence, an effective means for generating reliable electrical release, and fluorescent coatings which can be energized by ultraviolet light. At this point, intensive development is more important than basic research.
In 1934, Arthur Compton, a renowned physicist and consultant GE, reported to the GE lighting department in a successful experiment with fluorescent lighting at General Electric Co., Ltd. in the UK (not related to General Electric in the United States). Stimulated by this report, and with all the key elements available, a team led by George E. Inman built a prototype fluorescent light in 1934 at the General Electric engineering laboratory Nela Park (Ohio). This is not a trivial exercise; as noted by Arthur A. Bright, "Many experiments have to be done on the size and shape of lights, cathode construction, gas pressure both argon and mercury vapor, fluorescent powder color, method of attaching it to the inside of the tube, and other details of lamps and aids before the new device is ready for public. "
In addition to having engineers and technicians along with facilities for R & D work on fluorescent lamps, General Electric controls what are considered key patents that include fluorescent lighting, including patents originally issued to Hewitt, Moore, and KÃÆ'¼ch. More important than this is a patent covering an electrode that is not crushed at the gas pressure which is ultimately used in fluorescent lamps. Albert W. Hull of GE's Schenectady Research Laboratory filed a patent on this invention in 1927, issued in 1931. General Electric uses its control of patents to prevent competition with its flashlights and may delay the introduction of fluorescent lighting by 20 years. Finally, war production requires a 24-hour factory with economical lighting and fluorescent lamps available.
While Hull patents gave GE the basis for claiming legal rights over fluorescent lights, a few months after the lights went into production the company noticed a US patent application that had been filed in 1927 for the above mentioned "metal steam lamp" found in Germany by Meyer , Spanner, and Germer. The patent application indicates that the lamp has been made as a superior means to produce ultraviolet light, but this application also contains several statements referring to fluorescent illumination. Attempts to obtain a US patent have experienced many delays, but whether it should be granted, the patent may have caused serious difficulties for GE. At first, GE attempted to block the issuance of a patent by claiming that priority should be given to one of their employees, Leroy J. Buttolph, who, according to claims they had invented the fluorescent lamp in 1919 and whose patent application was pending. GE has also filed a patent application in 1936 under the name Inman to cover the "repairs" made by his group. In 1939 GE decided that Meyer, Spanner, and Germer's claims had some advantages, and in any case long interference procedures did not suit their interests. Therefore they dropped Buttolph's claim and paid $ 180,000 to acquire Meyer, et al. application, which was then owned by a company known as Electrons, Inc. The patent was granted in December 1939. This patent, together with Hull's patent, places GE on what appears to be a strong legal basis, although he faces many years of legal challenges from Sylvania Electric Products, Inc., which claims patent infringement that he held.
Although the patent problem was not fully resolved for years, General Electric's strengths in manufacturing and marketing gave it a superior position in the emerging fluorescent lighting market. The sale of "fluorescent luminaire lamps" began in 1938 when four different tube sizes were placed on the market. They are used in equipment manufactured by three leading companies, Lightolier, Artcraft Fluorescent Lighting Corporation, and Globe Lighting. The introduction of the Slimline public neonator in 1946 was by Westinghouse and General Electric and Showcase/Display Case fixtures introduced by Artcraft Fluorescent Lighting Corporation in 1946. Over the next year, GE and Westinghouse published new lights through exhibitions at New York World's Fair and Golden Gate International Exposition in San Francisco. The fluorescent lighting system spread rapidly during World War II because wartime manufacturing increased lighting demand. With 1951 more light is produced in the United States by fluorescent lamps than by incandescent lamps.
In the first years zinc orthosilicate with various beryllium content was used as a greenish phosphorus. The small addition of magnesium tungstate fixes the blue part of the spectrum that results in acceptable white color. Once it was discovered that beryllium was toxic, phosphorus-based halophosphate took over.
Maps Fluorescent lamp
Principles of operation
The basic means for converting electrical energy into radiation energy in a fluorescent lamp depends on an inelastic electron scattering when an incident electron collides with atoms in mercury gas. If the free electron (incident) has sufficient kinetic energy, it will transfer energy to the outer electron of the atom, causing the electron to temporarily jump to a higher energy level. Collisions are 'inelastic' because the loss of kinetic energy occurs.
This higher energy state is unstable, and the atoms emit ultraviolet photons when atomic electrons return to lower and more stable energy levels. Most photons released from mercury atoms have wavelengths in the ultraviolet (UV) spectrum region, particularly at wavelengths 253.7 and 185 nanometers (nm). It is invisible to human eyes, so they have to be transformed into visible light. This is done by utilizing fluorescence. The ultraviolet photons are absorbed by the electrons in the atoms of fluorescent coating interior lights, causing the same energy jump, then falling, with further photon emissions. The photons emanating from this second interaction have less energy than the cause. The chemicals forming the phosphorus are selected so that the photons emitted are at the wavelength seen by the human eye. The energy difference between the absorbed ultra-violet photon and the photon light of the light emitted into the warming of phosphorus layers.
When the light is turned on, electric power heats the cathode enough to emit an electron (thermionic emission). These electrons collide with and ionize the noble gas atoms in the sphere around the filaments to form the plasma by the impact ionization process. As a result of the avalanche ionization, the ionized gas conductivity rapidly rises, allowing higher currents to flow through the lamp.
The filling gas helps determine the electrical characteristics of the operation of the lamp, but not the light itself. The gas field effectively increases the distance the electrons travel through the tube, allowing the electrons to have a greater chance of interacting with the mercury atoms. The argon atoms, which are excited to a metastable state by the effects of electrons, can impart this energy to neutral and ionizing mercury atoms, which are described as the Penning effect. It has the benefit of lowering the disturbance and operating voltage of the lamp, compared to other gas filling that may be like krypton.
Construction
The fluorescent lamp tube is filled with a gas containing low-pressure mercury vapor and argon, xenon, neon, or krypton. The pressure inside the lamp is about 0.3% of the atmospheric pressure. The inner surface of the lamp is coated with a fluorescent (and often slightly fluorescent) layer made of various mixtures of metal phosphorus and rare-earth salts. Light electrodes are usually made of circular tungsten and are usually referred to as cathodes because their primary functions emit electrons. For this, they are coated with a mixture of barium, strontium and calcium oxide selected to have a low thermionic emission temperature.
The fluorescent lamp tube is usually straight and in length ranges from about 100 millimeters (3.9 inches) to a miniature lamp, up to 2.43 meters (8.0 ft) for high output lamps. Some lamps have tubes that are bent into circles, used for table lamps or elsewhere where a more compact light source is desired. Larger U-shaped lights are used to provide the same amount of light in denser areas, and are used for special architectural purposes. Compact fluorescent lamps have several small diameter tubes incorporated in a bunch of two, four, or six, or a small diameter tube that is rolled into a helix, to provide large amounts of light output in a small volume.
The emitting phosphor glow is applied as a paint-like layer to the inside of the tube. The organic solvent is allowed to evaporate, then the tube is heated to almost the melting point of the glass to dissipate the remaining organic compound and merge the coating into the lamp tube. Careful control of the grain size of suspended phosphorus is required; large grains, 35 micrometers or larger, lead to weak granular coating, whereas too many small particles of 1 or 2 micrometers or smaller lead to poor maintenance and light efficiency. Most phosphors perform best with particle sizes of about 10 micrometers. The layer must be thick enough to capture all the ultraviolet rays produced by the mercury arc, but not so thick that the phosphor layer absorbs too much visible light. The first phosphorus is a synthetic version of a natural fluorescent mineral, with a small amount of metal added as an activator. Later other compounds were found, allowing different colored lights to be made.
Electrical operating aspects
The fluorescent lamp is a negative differential resistance device, so the more current flowing through it, the electrical resistance of the fluorescent lamp decreases, allowing more current to flow. Connected directly to the constant voltage power supply, the fluorescent lamp will rapidly self-destruct due to uncontrolled current flow. To prevent this, the fluorescent lamp must use an enhancement, reply, to regulate the current flow through the lamp.
The terminal voltage in the operating lamp varies depending on arc current, tube diameter, temperature, and gas content. The fixed part of the voltage drop is due to the electrode. The general lighting service of the 48-inch T12 lamp (1,219 mm) operates at 430 mA, with a drop of 100 volts. High output lamps operate at 800 mA, and some operate at up to 1.5 A A. Power levels vary from 33 to 82 watts per meter tube length (10 to 25 W/ft) for T12 lamps.
The simplest ballast for alternating current (AC) used is an inductor placed in series, consisting of windings on a laminated magnetic core. The inductance of this winding limits the AC current flow. This type is still used, for example, in a 120 volt operated desk lamp using a relatively short lamp. Ballasts are rated for lamp size and power frequency. When the AC voltage is insufficient to start a long fluorescent lamp, the ballast often becomes an autotransformer with substantial leak inductance (thus limiting the flow of current). One form of inductive ballast may also include a capacitor for power factor correction.
Many different circuits have been used to operate fluorescent lamps. The circuit selection is based on AC voltage, tube length, start-up cost, long-term cost, instant versus non-instant start, temperature range and parts availability, etc.
The fluorescent lamp can run directly from a direct current supply (DC) voltage sufficient to attack the arc. Ballasts must be resistive, and will consume as much power as a lamp. When operated from DC, the initial switch is often set to reverse the polarity of the supply to the lamp each time it starts; otherwise, mercury accumulates at one end of the tube. The fluorescent lamp (almost) never operated directly from DC for that reason. Instead, the inverter converts the DC into AC and provides a current limiting function as described below for electronic ballasts.
Effect of temperature
The light output and fluorescent lamp performance are strongly influenced by the temperature of the bulb walls and their effect on the partial pressure of mercury vapor in the lamp. Each lamp contains a small amount of mercury, which must evaporate to support the lamp current and produce light. At low temperatures, mercury in the form of liquid dispersed droplets. When the lights heat up, more mercury in the form of steam. At higher temperatures, self-absorption in the vapor reduces UV and visible light. Since mercury condenses in the coolest place in the lamp, a careful design is required to keep the point at an optimum temperature, about 40 ° C (104 ° F).
Using amalgam with some other metals reduces the vapor pressure and extends the optimum upward temperature range; However, the "freezing" temperature of the bulb wall remains to be controlled to prevent mercury migration out of amalgam and condensation at cold point. Fluorescent lamps intended for higher output will have structural features such as defective tubes or internal heat-sinks to control cold point temperature and mercury distribution. Small, heavy loaded lights, such as compact fluorescent lamps, also include a heat-sink area inside the tube to keep the mercury vapor pressure at optimum value.
Losses
Only a small part of the electrical energy input to the lamp is converted into useful light. Ballasts eliminate some heat; Electronic ballasts may be about 90% efficient. The voltage drop still occurs on the electrode, which also produces heat. Some of the energy in the mercury vapor column is also lost, but about 85% turns into visible light and ultraviolet.
UV rays are absorbed by fluorescent lamp layers, which radiate energy back at a longer wavelength to emit visible light. Not all of the UV energy that attacks phosphorus is converted into visible light. In modern lamps, for every 100 photons incident of UV light that affect phosphor, only 86 emitted visible light photons (86% quantum efficiency). The biggest single disadvantage in modern lights is because of the lower energy of every visible light photon, compared to the UV photon energy that produces them (a phenomenon called Stokes shift). The incidence of photons has an energy of 5.5 volts of electrons but produces visible light photons with an energy of about 2.5 volts of electrons, so that only 45% of the UV energy is used; the rest is dissipated as heat. If "two-photon" phosphors can be developed, this will improve efficiency but many studies have not found such a system.
Cold Cathode fluorescent lamp
Most fluorescent lamps use electrodes that operate with thermionic emissions, which means they are operated at temperatures high enough for the electrode material (usually aided by a special coating) to radiate electrons into the tube by heat.
However, there are also tubes operating in cold cathode mode, where the electrons are released into the tube only by a large potential difference (voltage) between the electrodes. This does not mean the electrodes are cold (it can be very hot), but that means they operate under their thermionic emission temperature. Because cold cathode lamps do not have thermionic emission coatings for wear, they can have a much longer life than hot cathode tubes. These qualities make them desirable for care free longevity applications (such as backlights in liquid crystal display). Sputtering electrodes may still occur, but electrodes can be formed (eg into internal cylinders) to capture most of the material sputtered so as not to be lost from the electrode.
Cold cathode lamps are generally less efficient than thermionic emission lamps because the voltage drops the cathode is much higher. Increased falling voltages result in more power dissipation at the end of the tube, which does not contribute to the light output. However, this is less significant with longer tubes. Increased power dissipation at the end of the tube also usually means that the cold cathode tube must be run at a lower loading than the thermionic emission equivalent. Given the higher tube voltage required, these tubes can easily be made long, and even run as string strings. They are better suited for bending into special shapes for letters and marks, and can also be directly enabled or disabled.
Start
The noble gases used in fluorescent tubes (generally argon) must be ionized before the arc can "attack" inside the tube. For small lights, it does not take much stress to attack the arc and start the lights no problem, but larger tubes require large voltages (in the range of a thousand volts).
Preheating
This technique uses a combination of cathode-filaments at each end of a lamp together with a mechanical or automatic (bi-metal) switch (see right-side circuit diagram) which initially connects the filament in series with the ballast to heat it; when the arc is struck, the filament is disconnected. This system is described as hot in some countries and switch-start in other countries. This system is standard equipment in countries V 200-240 (and for 100-120 V lamps up to about 30 watts).
Before the 1960s, four-pin thermal starters and manual switches were used. The widely used mechanism for preheating, still commonly used, is a light switch starter (illustrated). It consists of a bi-metal switch normally open in a small enclosed gas-discharge lamp containing inert gas (neon or argon).
When power is first applied to the circuit, there will be light discharge across the electrodes in the starter light. This heats the gas in the starter and causes one of the bi-metal contacts to bend in the other direction. When the contact is touched, two filaments of fluorescent lamps and ballasts will effectively be diverted to the supply voltage. The current through the filaments causes them to heat up and emit electrons into the gas cylinders by thermionic emissions. In the starter, the touching contact shortens the voltage that keeps the beam of light, extinguishes it so that the gas cools and no longer heats the bi-metal switch, which opens in a second or two. The current through the inductive filament and ballast is suddenly disrupted, leaving the full line voltage applied between the filaments at the end of the tube and producing an inductive kick which provides the high voltage required to start the lamp. The lamp will fail to crash if the filament is not hot enough, in this case the cycle repeats; some cycles are usually required, which causes flickering and clicking on startup (older thermal starters behave better in this case). A power factor correction capacitor (PFC) draws the main current from the parent to compensate for the lagging current drawn by the lamp circuit.
After a collision impinges, the overriding spike causes the cathode to remain hot, allowing continuous electron emissions without the need for filaments to continue to be heated. The starter switch does not close again because the tension on the flashing tube is not enough to start the light discharge in the starter.
With automatic start-ups such as light beginnings, the failed tube will spin endlessly, blinking when the light goes out quickly because the emission mix is ​​not sufficient to keep the lamp current high enough to keep the starter open. It runs the ballast at higher temperatures. Some start times are more sophisticated in this situation, and do not try to start over until the power is reset. Some older systems use a thermal over-current trip to detect repetitive early attempts and turn the circuit off until it is reset manually. The switch contact at the beginning of light is subject to wear and ultimately fails, so the starter is created as a plug-in replaceable unit.
Recently introduced electronic beginners use different methods to heat the cathode. They may be designed for interchangeable plug-ins with light starter for use in standard fittings. They typically use specially designed semiconductor switches and "soft start" lights with preheating the cathode before applying a controlled initial pulse that attacks the first light without blinking; this releases a small amount of material from the cathode during start, giving the lamp life a longer time than is possible with an uncontrolled impulse in which the lamp is worn in the switchstart. It is claimed to extend lamp life by a factor typically 3 to 4 times for frequently-lit lamps such as domestic usage, and to reduce typical blackening of the tip lamps from the fluorescent tubes. This circuit is usually complex, but its complexity is built into the IC. Electronic starters can be optimized to start quickly (typical start time of 0.3 seconds), or to start most reliably even at low temperatures and with low supply voltages, with a start time of 2-4 seconds. A faster start unit can produce audible sounds during start-up.
The electronic starter only tries to turn on the light for a short time when power is initially applied, and does not repeatedly attempt to muffle a dead light and can not maintain the arc; some automatically turn off failed lights. This eliminates light strikes and continuous flickering of lights that fail with flame starters. Electronic starter is not worn and does not need to be replaced regularly, although they may fail like other electronic circuits. Manufacturers usually cite the life of 20 years, or during lamp installation. Beginners are inexpensive, usually less than 50 Ã, Â ¢ for short-term light types (depending on the power of the lamp), and maybe ten times as much for electronic types as of 2013.
Instant Start
Other types of tubes have no filament to start at all. Instant Start the fluorescent tube simply uses a high enough voltage to break down the gas and the mercury column and thus start the conduction of the arc. These tubes can be identified with one pin at each end of the tube. The lamp holder has a "disconnect" socket on the low-voltage end that breaks the ballast when the tube is released, to prevent electrical shock. In North America, cheap lighting fixtures with integrated electronic ballasts use an instant start on lamps originally designed for preheating, even though it shortens the lamp life. This reply technology is not common outside North America.
Quick start
Newer ballast design quick start gives the filament power reel in reply; this quickly and continuously warms the filaments/cathodes using low voltage AC. It usually operates at a lower arc voltage than the instant start design; no inductive voltage spikes are generated to start, so the lamp should be installed near the earthed (earthed) reflector to allow the release of the incandescent to propagate through the tube and initiate the release of the arc. In some lights, the installed "aid" strip is attached to the outside of the glass lamp. This ballast technology is not used outside North America, where line voltage 220-240V is common, and is incompatible with the T8 European energy saving lamps because these lamps require a higher initial voltage than the fast open ballast circuit voltage.
Start quickly
Quick start ballast uses a small automatic transformer to heat the filament when power is first applied. When the arc strikes, the filament heater's power is reduced and the tube will start in half a second. The automatic transformer is combined with a ballast or perhaps a separate unit. The tubes should be installed near an earthed metal reflector so they can attack. Fast-starting ballasts are more commonly used in commercial installations because of lower maintenance costs. Fast-start ballast eliminates the need for a starter switch, a common source of lamp failure. However, Quick-start ballasts are also used in home installations because of the desired feature that fast light bulbs start to fire almost immediately after power is applied (when the switch is turned on). Fast starting ballasts are only used on 240 V circuits and are designed for use with older and less efficient T12 tubes.
Start semi-resonance
The semi-resonance start circuit is created by Thorn Lighting for use with T12 fluorescent tubes. This method uses a double wound transformer and a capacitor. Without the arc current, the transformer and capacitor resonate at the line frequency and produce about twice the supply voltage across the tube, and the heating current of the electrode is small. The voltage of the tube is too low to attack the arc with the cold electrode, but as the electrodes heat up to the thermionic emission temperature, the striking voltage of the tube falls below the ringing voltage, and the arc strike. When the electrode is hot, the light is slow, more than three to five seconds, reaching full brightness. As the arc current increases and the voltage drops the tube, this circuit provides a current limitation.
The initial semi-resonant circuit is mainly limited for use in commercial installations due to the higher initial cost of the circuit components. However, there is no starters switch that should be replaced and less cathode damage when starting to make longer lights, reducing maintenance costs. Due to the high open circuit circuit voltage, this initial method is very good for starting the tubes in cold locations. In addition, the power factor circuit is nearly 1.0, and no additional power factor correction is required in the lighting installation. Since the design requires that twice the supply voltage must be lower than the cold cathode striking voltage (or the tube will be incorrectly started instantly), this design can not be used with 240 volt AC power unless the tube has a length of at least 1, 2 m (3 ft 11 inches). Semi-resonance devices are generally incompatible with T8 retrofit energy-saving tubes, since such tubes have a higher initial voltage than T12 lamps and may not start reliably, especially at low temperatures. Recent proposals in some countries to eliminate T12 tubes will reduce the adoption of this initial method.
Start programmed
These are used with electronic ballasts shown below. This ballast applies power to the first filament, then after a short delay to allow the cathode to heat up, apply the voltage to the lamp to attack the arc. This ballast provides the best life and mostly starts from the lamp, and is preferred for applications with very frequent power cycles such as visual inspection rooms and toilets with motion detector switches.
Electronic ballast
Electronic ballasts use transistors to convert the supply frequency into high frequency AC while also regulating the flow of current in the lamp. Some still use inductance to limit the current, but higher frequencies allow a much smaller inductance to use. Others use a combination of capacitor-transistor to replace the inductor, because the transistors and capacitors work together can simulate the inductor action. This ballast utilizes a higher efficacy than the current higher frequency operated lamps, which are up nearly 10% at 10 kHz , compared to efficacy at normal power frequencies. When the AC period is shorter than the relaxation time to deionize the mercury atoms in the exhaust column, the discharge remains closer to the optimum operating conditions. Electronic ballasts are generally supplied with AC power, which is internally converted to DC and then returned to variable frequency AC waveforms. Depending on the capacitance and quality of current-constant pulse width modulation, this can largely eliminate modulation at 100 or 120 Hz.
Most low cost ballasts contain only simple oscillators and series resonant LC circuits. When turned on, the oscillator starts, and the resonant current excites the LC circuit. This resonant current directly drives the switching transistor through the ring core transformer. This principle is called current resonant inverter circuit. After a while, the voltage in the lamp reaches about 1 kV and the light turns on. The process is too fast to heat the cathode, so the instant light starts in cold cathode mode. The cathode filament is still used to protect the ballast from overheating if the lamp is not on. Some manufacturers use positive temperature coefficients (PTC) thermistors to disable instant start and give some time to heat the filament.
More complex electronic ballast using programmed start. The output frequency starts above the resonant frequency of the ballast output circuit; and after the filament is heated, its frequency decreases rapidly. If the frequency is close to the ballast resonance frequency, the output voltage will increase so that the lamp will light up. If the light is not lit, the electronic circuit terminates the operation of the ballast.
Many electronic ballasts are controlled by a microcontroller or similar, and these are sometimes called digital ballasts. Digital ballasts can apply quite complex logic to start and operate lights. This allows functions such as testing for damaged electrodes and missing tubes before attempting to start, automatic detection of tube replacements, and automatic detection of tube types, so that single ballast can be used with several different tubes, even those operating on different arc currents. , etc. Once fine-grained controls over the start and arc currents can be achieved, features such as dimming, and having the ballast maintaining a constant light level against the contribution changes of the sun are all easily incorporated in embedded microcontroller software, and can be found in many manufacturers' products.
Since its introduction in the 1990s, high-frequency ballasts have been used in general lighting fixtures with fast or pre-heat start lamps. This ballast converts incoming power to output frequency over 20 kHz . This improves lamp efficiency. It is used in several applications, including a new generation tanning lamp system, where a 100 watt lamp (for example, F71T12BP) can be powered using 90 watts of actual power while getting the same luminous flux (measured in lumens) as a magnetic ballast. The ballast operates with a voltage that can reach nearly 600 volts, requiring some consideration in the design of the housing, and can cause small limitations on the length of the cable leading from the ballast to the end of the lamp.
End of life
The ultimate failure mode for fluorescent lamps varies depending on how they are used and the type of control of their teeth. Often the light will turn pink (see Loss of mercury), with black burns at the end of the lamp due to the stirring of emission mix (see below). The light may also blink at a noticeable level (see Flicker Problems).
Emission mix
The "emission mix" on the filament/lamp cathode is required to allow the electrons to enter the gas through the thermionic emission at the operating voltage of the lamp used. The mixture is slowly sputtered by the bombardment of electrons and mercury ions during operation, but larger amounts sputter each time the lamp starts with a cold cathode. The light start method has a significant impact on this. The lights are operated for typically less than 3 hours each switch-on will usually run out of emission mixture before other parts of the lamp fail. The emission mix stuttered into dark marks at the end of the lights seen in the old lights. When all the emission mixture is gone, the cathode can not miss enough electrons into the gas filling to maintain the gas discharge at the designed lamp operating voltage. Ideally, the control gear must turn off the light when this happens. However, some control teeth will provide sufficient voltage to continue operating the lamp in cold cathode mode, which will cause excessive heat at the end of the lamp and rapid disintegration of the electrode (filaments running open circuit) and filamentary filament wire until completely lost. or cracked glass, destroys low-pressure gas and stops gas flow.
Electronic ballast
This can occur in compact fluorescent lamps with integral electric ballasts or in linear lamps. Electronic ballast damage is a rather random process that follows a standard failure profile for every electronic device. There was a small early peak of initial failure, followed by a steady decline and a steady increase in lamp life. Electronic life depends heavily on operating temperature - usually twice for every temperature rise of 10 Â ° C. The average life of the lamps quoted is usually at 25 ° C, (77 ° F) (this may vary by country). The average electronic life at this temperature is usually larger than this, so at this temperature, not many lights will fail because electronics fail. In some fittings, the ambient temperature can be far above this, in which case electronic failure can be the dominant failure mechanism. Similarly, running a compact fluorescent lamp base will produce more electronics, which can lead to shorter average life (especially with higher powered ones). Electronic ballasts should be designed to turn off the tube when the emission mixture runs out as described above. In the case of integral electronic ballasts, since they do not need to work anymore, this is sometimes done by asking them to accidentally burn some components to stop the operation permanently.
In most CFLs the filaments are connected in series, with small capacitors between them. The discharge, once illuminated, is parallel to the capacitor and presents a lower-resistance path, effectively shortening the capacitor.
Phosphor
Phosphorus decreases in efficiency when used. With about 25,000 hours of operation, it will usually be half the brightness of the new lamp (although some manufacturers claim a longer half-life for their lamps). Unsuccessful lamps from an integrated emissions or electronics ballast mixture will eventually develop this failure mode. They are still working, but become dim and inefficient. The process is slow, and often becomes clear only when new lights are operating next to the old ones.
Loss of mercury
As in all tubes containing mercury-containing gases, mercury is slowly absorbed into the glass, phosphorus, and tube electrodes over the lifetime of the lamp, until it no longer functions. The loss of mercury will take over from the failure of phosphors in some lights. The failure symptoms are similar, except that the loss of mercury initially causes a long extra time to the full light output, and ultimately causes the red glowing light to dim when mercury runs out and the argon base gas takes over as primary discharge. Drain the tube to an asymmetrical waveform, where the total current flow through the tube does not cancel and the tube operates effectively under DC bias, causing asymmetric distribution of mercury ions along the tube due to the kataphoresis. The depletion of localized mercury vapor pressure manifests as a pink glow from an alkaline gas around one of the electrodes, and the operating life of the lamp can be dramatically reduced. This can be a problem with some poorly designed inverters.
Filaments burned
Filaments can burn (fail) at the end of the lamp life, open the circuit and lose the ability to heat. Both filaments lose their function because they are connected in series, with only a simple initial switch circuit, a damaged filament will make the lamp completely useless. Filaments rarely burn or fail to open the circuit unless the filament becomes exhausted and the control gear is capable of supplying sufficiently high voltages in the tube to operate it in cold cathode mode. Some digital electronic ballasts capable of detecting filaments are damaged and can still attack the arc with one or both broken filaments providing there are still enough emitters. Filaments damaged in lights attached to magnetic ballasts often cause both lights to burn or blink.
Phosphor and emitted light spectrum
The spectrum of light emitted from a fluorescent lamp is a combination of light directly emitted by mercury vapor, and the light emitted by the phosphor layer. The spectral lines of mercury emissions and the fluorescent effect, provide a uniform distribution of light spectrum different from that produced by an incandescent source. The relative intensity of the light emitted in each narrow wave in the spectrum is seen in different proportions compared to the incandescent source. Colored objects are perceived differently under light sources with different spectrum distributions. For example, some people find the color appearance produced by some fluorescent lights to be loud and unpleasant. Healthy people sometimes appear to have unhealthy skin tone under fluorescent lighting. The extent to which this phenomenon occurs is related to the composition of the light spectrum, and can be measured by color rendering index (CRI).
Color temperature
Correlative color temperature (CCT) is a white "shade" measure of light sources compared to blackbody. The usual incandescent lamp is 2700 K, which is yellowish white. Halogen lighting is 3000 K. A fluorescent lamp is produced to select CCT by converting the phosphorus mixture inside the tube. Warm-white fluorescents have CCT 2700 K and are popular for residential lighting. The neutral-white fluorescent has a CCT of 3000 K or 3500 K. The white-cold fluorescent has CCT 4100 K and is popular for office lighting. Daylight fluorescents have CCT 5000 K to 6500 K, which is bluish-white in color.
High CCT lighting generally requires a higher level of light. At the dim illumination level, the human eye views the lower color temperature as more pleasing, as it is linked through the Kruithof curve. So, the dimly lit 2700 K lamp looks comfortable and the bright 5000 K lamp also looks natural, but the 5000 K fluorescent lamp that looks too pale. Daylight-type fluorescents look natural only if they are very bright.
Color rendering index
The color rendering index (CRI) is a measure of how well a color can be felt by using light from the source, relative to light from reference sources such as daylight or black with the same color temperature. By definition, incandescent lamps have a CRI of 100. Real-life fluorescent tubes reach CRI anywhere from 50 to 98. Low fluorescent fluorescent lamps have phosphors that emit too little red light. The skin appears less pink, and therefore "unhealthy" compared to incandescent bulbs. Colored objects appear muted. For example, a low CRI 6800 K halophosphate tube (extreme example) will make the red color look dull red or even brown. Because the eye is relatively inefficient in detecting red light, an increase in color rendering index, with increased energy in the red part of the spectrum, can reduce overall glowing properties.
The lighting settings use fluorescent tubes in various white colors. Mixing the type of tube inside the fittings can improve the color reproduction of lower quality tubes.
Phosphor composition
Some of the most unpleasant lights come from tubes containing the older, phosphorus halophosphate type (chemical formula Ca 5 (PO 4 ) 3 ( F, Cl): Sb 3 , Mn 2 ). These phosphors primarily emit yellow and blue light, and are relatively little green and red. In the absence of a reference, this mixture looks white to the eye, but the light has an incomplete spectrum. The color rendering index (CRI) of the lamp is about 60.
Since the 1990s, high-quality fluorescent lamps use higher CRI halophosphate layers, or triphosphor mixtures, based on europium and TB ions, which have more evenly emission bands above the visible light spectrum.. The high-CRI halophosphate and triphosphor tubes provide more natural color reproduction to the human eye. CRI lamps like that are usually 82-100.
Apps
Fluorescent lamps are available in various shapes and sizes. Compact fluorescent lamps (CFLs) are becoming more popular. Many compact fluorescent lamps integrate additional electronics into the lamp base, allowing them to fit into regular light bulb sockets.
In homes of US residents, fluorescent lights are mostly found in kitchens, dungeons, or garages, but schools and businesses find the cost savings of fluorescent lamps to be significant and rarely use incandescent lamps. Tax incentives and building codes result in higher usage in places like California.
In other countries, the use of home fluorescent lighting varies depending on the energy, financial and environmental costs of the local population, and the acceptance of light output. In East and Southeast Asia, it is rare to see incandescent lights in buildings anywhere.
Some countries encourage the removal of incandescent bulbs and fluorescent lamp replacements with fluorescent lamps or other types of energy-saving lamps.
In addition to general illumination, special fluorescent lamps are often used in stage lighting for film and video production. They are cooler than traditional halogen light sources, and use high frequency ballasts to prevent video flashes and high color rendition index lights to approach daytime color temperatures.
Benefits
Luminous efficacy
Fluorescent lamps convert more input power to visible light than incandescent bulbs, although in 2013 LEDs are sometimes even more efficient and improve efficiency faster. A 100-watt tungsten filament lamp typically can only convert 5% of its input power to visible white light (wavelength 400-700 μm), whereas ordinary fluorescent lamps convert about 22% of the input power to visible white light.
The efficacy of fluorescent tubes ranges from about 16 lumens per watt to 4 watt tubes with regular ballasts up to over 100 lumens per watt with modern electronic ballasts, generally averaging 50 to 67 lm/W overall. Most compact fluorescent above 13 watts with an integral electronic ballast reaches about 60 Âμm/W. The lamp is rated by lumens after 100 hours of operation. For certain fluorescent tubes, high-frequency electronic ballasts provide about 10% increase in efficacy over inductive ballasts. It is necessary to include ballast losses when evaluating the efficacy of fluorescent lighting systems; this can be about 25% of the power of the lamp with a magnetic ballast, and about 10% with an electronic ballast.
The efficacy of a fluorescent lamp depends on the temperature of the lamp in the coldest part of the lamp. In this T8 lamp is in the center of the tube. In this T5 lamp is at the end of the tube with the text printed on it. The ideal temperature for the T8 lamp is 25 Â ° C (77 Â ° F) while the ideal T5 lamp at 35 Â ° C (95 Â ° F).
Life
Usually a fluorescent lamp will last 10 to 20 times during an incandescent incandescent lamp when it is operated several hours at a time. Under standard test conditions general illumination lamps have 9000 hours or longer service life.
The higher initial cost of a fluorescent lamp compared to an incandescent bulb is usually more than compensated by lower energy consumption during its lifetime.
Some manufacturers produce T8 lamps with 90,000 hours of live light, rival the life of LED lights.
Lower lighting
Compared with incandescent lamps, fluorescent tubes are a more diffuse and physically larger source of light. In suitable lights designed, light can be distributed more evenly without the source point of glare as seen from incandescent incandescent filaments; a large lamp compared to the typical distance between the lamp and the illuminated surface.
Lower heat
The fluorescent lamps remove about one-fifth of the heat from equivalent incandescent bulbs. This greatly reduces the size, cost, and energy consumption that is reserved for air conditioning for office buildings that usually have multiple lights and multiple windows.
Disadvantages
Frequent switching
If the light is installed where it is often switched on and off, the lamp will quickly get old. In extreme conditions, the lifespan may be much shorter than a cheap incandescent lamp. Each cycle begins to slightly erode the surface of the cathode that emits an electron; when all the emission material is gone, the lamp can not start with the available reply voltage. Equipment intended to light a lamp (such as for an ad) will use a ballast that maintains the cathode temperature when the arc dies, maintaining the lamp life.
The extra energy used to start a fluorescent lamp is equivalent to a few seconds of normal operation; it is more energy efficient to turn off the lights when not needed for a few minutes.
Health and safety issues
If the fluorescent lamp is damaged, a small amount of mercury can contaminate the surrounding environment. Approximately 99% of mercury is usually contained in phosphorus, especially in lights nearing the end of their lives. Broken glass is usually considered a greater danger than the small amount of mercury spilled. The EPA recommends displaying the location of the fluorescent tube break and using a wet paper towel to help remove broken glass and fine particles. Any used glass and towel should be thrown away in a sealed plastic bag. Vacuum cleaners can cause particles to become air, and should not be used.
Fluorescent lamps with magnetic ballasts flicker at frequent unheard frequencies of 100 or 120 Hz and this flicker can cause problems for some individuals with light sensitivity; they are listed as problematic for some individuals with autism, epilepsy, lupus, chronic fatigue syndrome, Lyme disease, and vertigo. Newer fluorescent lamps without magnetic ballasts have essentially eliminated flicker.
Ultraviolet emission
Fluorescent lamps emit small amounts of ultraviolet (UV) rays. A 1993 study in the US found that ultraviolet exposure from sitting under fluorescent lights for eight hours was equivalent to one minute of sun exposure. Ultraviolet radiation from compact fluorescent lamps can exacerbate symptoms in light-sensitive individuals.
Ultraviolet light from fluorescent lamps can lower the pigment in the painting (especially the watercolor pigment) and whiten the dye used in textiles and some printing. Valuable artworks should be protected from ultraviolet light by placing additional glass or transparent acrylic sheets between lamps and artwork.
Ballast
The fluorescent lamp requires a ballast to stabilize the current through the lamp, and to provide the initial striking voltage required to initiate the discharge of the arc. This increases the cost of fluorescent lighting fixtures, although often one ballast is split between two or more lights. Electromagnetic ballasts with small errors can produce humming sounds or audible buzz. Magnetic ballasts are usually filled with pot compounds such as tar to reduce the emitted noise. Hum is removed in lamps with high frequency electronic ballasts. The energy lost in magnetic ballasts is about 10% of lamp input power according to GE literature from 1978. Electronic ballasts reduce this loss.
Power quality and radio interruption
Simple inductive fluorescent lamp bulbs have less than one power factor. Inductive ballasts include power factor correction capacitors. Simple electronic ballasts can also have low power factor due to the input stage of their rectifier.
The fluorescent lamp is a non-linear load and generates harmonic current in the power supply. The bow in the lamp can generate radio frequency noise, which can be done through the power cord. Radio disturbance suppression is possible. Excellent oppression is possible, but adds to the cost of neon fixtures.
Operating temperature
Fluorescent lamps operate best around room temperature. At much lower or higher temperatures, efficacy decreases. Below standard freezing temperatures may not start. Special lights may be required for reliable outside services in cold weather. In applications such as road and rail signals, fluorescent lamps that do not generate as much heat as incandescent lamps may not melt snow and ice accumulate around the lamp, leading to reduced visibility.
Light shapes
Long fluorescent tubes, low-source lighting compared to high-pressure arc lamps, incandescent bulbs and LEDs. However, the low luminous intensity of emitting surfaces is useful because it reduces glare. The design of the fixture lamp should control the light from the long tube, not the solid globe.
Compact fluorescent lamps (CFLs) replace ordinary incandescent lamps. However, some CFLs will not match some lights, because the lute (heavy wire bracket) is formed for the narrow neck of the incandescent lamp, while the CFL tends to have a wide house for their electronic ballast close to the base of the lamp.
Flicker issues
Fluorescent lamps using electric channel frequency ballasts do not provide stable light; instead, they blink twice the supply frequency. This produces fluctuations not only with the light output but also the color temperature, which can cause problems for photography and sensitive people
Source of the article : Wikipedia
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