Gas-discharge lamp in which an electric or magnetic field transfers energy to the gas inside.
A round Induction lamp
The internal electrodeless lamp, induction lamp, or electrodeless induction lamp is a gas-discharge lamp in which an electric or magnetic field transfers the power required to generate light from outside the lamp envelope to the gas inside. This is in contrast to a typical gas discharge lamp that uses internal electrodes connected to the power supply by conductors that pass through the lamp envelope. Eliminating the internal electrodes provides two advantages:
Extended lamp life (internal electrodes are the most limiting factor in lamp life, since their metal content will get sputtered onto the lamp ends every time they are turned on)[citation needed]
Ability to use higher-efficiency light-generating substances that would react with internal metal electrodes in conventional fluorescent lamps[citation needed]
Nikola Tesla demonstrated wireless transfer of power to electrodeless lamps in his lectures and articles in the 1890s, and subsequently patented a system of light and power distribution on those principles.[2]
Example of a round 150 W magnetic induction lamp
In 1967 and 1968, John Anderson[3] of General Electric[4][5] applied for patents for electrodeless lamps. In 1971, Fusion UV Systems installed a 300-watt electrodeless microwave plasma UV lamp on a Coorscanproduction line.[6]Philips introduced their QL induction lighting systems, operating at 2.65MHz, in 1990 in Europe and in 1992 in the US. Matsushita had induction light systems available in 1992. Intersource Technologies also announced one in 1992, called the E-lamp. Operating at 13.6MHz, it was available on the US market in 1993.
In 1990, Michael Ury, Charles Wood and colleagues formulated the concept of the sulfur lamp. With support from the United States Department of Energy, it was further developed in 1994 by Fusion Lighting of Rockville, Maryland, a spinoff of the Fusion UV division of Fusion Systems Corporation. Its origins are in microwave discharge light sources used for ultraviolet curing in the semiconductor and printing industries.
Since 1994, General Electric has produced its induction lamp Genura with an integrated high frequency driver, operating at 2.65MHz. In 1996, Osram started selling their Endura induction light system, operating at 250kHz. It is available in the US as the Sylvania Icetron. In 1997, PQL Lighting introduced in the US the Superior Life Brand induction lighting systems. Most induction lighting systems are rated for 100,000 hours of use before requiring absolute component replacements.
In 2005, Amko Solara in Taiwan introduced induction lamps that can dim and use IP (Internet Protocol) based controls. Their lamps have a range from 12 to 400 watts and operate at 250kHz.
From 1995, the former distributors of Fusion, Jenton / Jenact, expanded on the fact that energised UV-emitting plasmas act as lossy conductors to create a number of patents regarding electrodeless UV lamps for sterilising and germicidal uses.
Around 2000, a system was developed that concentrated radio frequency waves into a solid dielectricwaveguide made of ceramic which energized a light-emitting plasma in a bulb positioned inside. This system, for the first time, permitted an extremely bright and compact electrodeless lamp. The invention has been a matter of dispute. Claimed by Frederick Espiau (then of Luxim, now of Topanga Technologies), Chandrashekhar Joshi and Yian Chang, these claims were disputed by Ceravision Limited.[7] A number of the core patents were assigned to Ceravision.[8][9]
In 2006, Luxim introduced a projector lamp product trade-named LIFI. The company further extended the technology with light source products in instrument, entertainment, street, area, and architectural lighting applications among others throughout 2007 and 2008.
In 2009, Ceravision Limited introduced the first high-efficiency plasma (HEP) lamp under the trade name Alvara. This lamp replaces the opaque ceramic waveguide in earlier lamps with an optically clear quartz waveguide that increases efficiency. In previous lamps, the burner, or bulb, was very efficient—but the opaque ceramic waveguide severely obstructed the projection of light. A quartz waveguide passes all the light from the plasma.
In 2012, Topanga Technologies introduced a line of advanced plasma lamps (APL), driven by a solid stateradio frequency (RF) driver,[10] thereby circumventing the limited life of magnetron-based drivers, with system power of 127 and 230 volts and system efficacies of 96 and 87 lumen/watt, with a CRI of about 70.
Several companies licensed this technology and it became the viable energy saving solution for lighting retrofit and upgrades before LED lighting reached a viable efficacy solution point. It was widely utilized in roadway and high mast applications around the world replacing 400 watt, 750 watt and 1000 watt metal halide and high pressure sodium systems. The light emitting plasma (LEP) solution was great as it offered a much higher lumen density than its HID counterparts, approximately 50% power reduction and could be at full intensity in around 45-60 seconds from either a cold or hot strike, unlike its HID predecessors.
A 5 KW Soviet plasma xenon lamp made in 1981. The inner white spiral tube is for cooling.
Plasma lamps are a family of light sources that generate light by exciting a plasma inside a closed transparent burner or bulb using radio frequency (RF) power. Typically, such lamps use a noble gas or a mixture of these gases and additional materials such as metal halides, sodium, mercury, or sulfur. A waveguide is used to constrain and focus the electrical field into the plasma. In operation the gas is ionized and free electrons, accelerated by the electrical field, collide with gas and metal atoms. Some electrons circling around the gas and metal atoms are excited by these collisions, bringing them to a higher energy state. When the electron falls back to its original state, it emits a photon, resulting in visible light or ultraviolet radiation depending on the fill materials.
The first plasma lamp was an ultraviolet curing lamp with a bulb filled with argon and mercury vapor, developed by Fusion UV. That lamp led Fusion Systems to develop the sulfur lamp, which concentrates microwaves through a hollow waveguide to bombard a bulb filled with argon and sulfur.
In the past, the magnetron that generates the microwaves limited the reliability of electrodeless lamps. Solid-state RF generation works and gives long life. However, using solid-state chips to generate RF is currently around fifty times more expensive than using a magnetron, and so only appropriate for high-value lighting niches. Dipolar of Sweden has showed that it is possible to greatly extend the life of magnetrons[clarification needed] to over 40,000 hours[12] making low-cost plasma lamps possible. Plasma lamps are currently produced by Ceravision and Luxim and in development by Topanga Technologies.
Ceravision has introduced a combined lamp and luminaire under the trade name Alvara for use in high bay and street lighting applications. It uses an optically clear quartz waveguide with an integral burner so all the light from the plasma passes through. The small source also lets the luminaire use more than 90% of the available light compared with 55% for typical HID fittings. Ceravision claims the highest Luminaire Efficacy Rating (LER)[13] of any light fitting on the market, and to have created the first high-efficiency plasma (HEP) lamp. Ceravision uses a magnetron to generate the required RF power and claims a life of 20,000 hours.
Luxim's LIFI lamp, claims 120 lumens per RF watt (i.e. before taking into account electrical losses).[14] The lamp has been used in Robe lighting's ROBIN 300 Plasma Spotmoving-head light.[15] It was also used in a line of, now discontinued, Panasonic rear-projection TVs.[16]
Magnetic induction lamps
External closed core induction lamp with two turn primaryA Philips QL induction lighting system, where (A) Discharge vessel, (B) Tube with power coupler and (C) Electronic high frequency driver.
Aside from the method of coupling energy into the mercury vapor, these lamps are very similar to conventional fluorescent lamps. Mercury vapor in the discharge vessel is electrically excited to produce short-wave ultraviolet light, which then excites internal phosphors to produce visible light. While still relatively unknown to the public, these lamps have been available since 1990. Unlike an incandescent lamp or conventional fluorescent lamps, there is no electrical connection going inside the glass bulb; the energy is transferred through the glass envelope solely by electromagnetic induction. There are two main types of magnetic induction lamps: external core lamps and internal core lamps. The first commercially available and still widely used form of induction lamp is the internal core type. The external core type, which was commercialized later, has a wider range of applications and is available in round, rectangular and "olive" shaped form factors.
External core lamps are basically fluorescent lamps with magnetic cores wrapped around a part of the discharge tube. The core is usually made of ferrite, a ceramic material containing iron oxide and other metals. In external core lamps, high-frequency energy from a special power supply passes through wires that are wrapped in a coil around a toroidal ferrite core placed around the outside of a portion of the glass tube. This creates a high-frequency magnetic field within the ferrite core. Since the magnetic permeability of the ferrite is hundreds or thousands of times higher than that of the surrounding air or glass, and the ferrite core provides a closed path for the magnetic field, the ferrite core contains virtually all of the magnetic field.
Cross section through internal inductor lamp
Following Faraday's law of induction, the time varying magnetic field in the core generates a time varying electric voltage in any closed path that encloses the time varying magnetic field. The discharge tube forms one such closed path around the ferrite core, and in that manner the time varying magnetic field in the core generates a time varying electric field in the discharge tube, There is no need for the magnetic field to penetrate the discharge tube. The electric field generated by the time varying magnetic field drives the mercury-rare gas discharge in the same way the discharge is driven by the electric field in a conventional fluorescent lamp. The primary winding on the ferrite core, the core, and the discharge form a transformer, with the discharge being a one-turn secondary on that transformer.
The discharge tube contains a low pressure of a rare gas such as argon and mercury vapor. The mercury atoms are provided by a drop of liquid mercury, or by a semi-solid amalgam of mercury and other metals such as bismuth, lead, or tin. Some of the liquid mercury or the mercury in the amalgam vaporizes to provide the mercury vapor. The electric field ionizes some of the mercury atoms to produce free electrons, and then accelerates those free electrons. When the free electrons collide with mercury atoms, some of those atoms absorb energy from the electrons and are "excited" to higher energy levels. After a short delay, the excited mercury atoms spontaneously relax to their original lower energy state and emit a UV photon with the excess energy. As in a conventional fluorescent tube, the UV photon diffuses through the gas to the inside of the outer bulb, and is absorbed by the phosphor coating that surface, transferring its energy to the phosphor. When the phosphor then relaxes to its original, lower energy state, it emits visible light. In this way the UV photon is down-converted to visible light by the phosphor coating on the inside of the tube. The glass walls of the lamp prevent the emission of the UV photons because ordinary glass blocks UV radiation at the 253.7nm and shorter wavelengths.
In the internal core form (see diagram), a glass tube (B) protrudes bulb-ward from the bottom of the discharge vessel (A), forming a re-entrant cavity. This tube contains an antenna called a power coupler, which consists of a coil wound over a cylindrical ferritecore. The coil and ferrite form the inductor that couples the energy into the lamp interior
The antenna coils receive electric power from the electronic high frequency driver (C) that generates a high frequency. The exact frequency varies with lamp design, but popular examples include 13.6 MHz, 2.65MHz and 250kHz. A special resonant circuit in the driver produces an initial high voltage on the coil to start a gas discharge; thereafter the voltage is reduced to normal running level.
The system can be seen as a type of transformer, with the power coupler (inductor) forming the primary coil and the gas dischargearc in the bulb forming the one-turn secondary coil and the load of the transformer. The driver is connected to mains electricity, and is generally designed to operate on voltages between 100 and 277 VAC at a frequency of 50 or 60Hz, or on a voltage between 100 and 400 VDC for battery-fed emergency light systems. Many drivers are available in low voltage models so can also be connected to DC voltage sources like batteries for emergency lighting purposes or for use with renewable energy (solar and wind) powered systems.
In other conventional gas discharge lamps, the electrodes are the part with the shortest life, limiting lamp lifespan severely. Since an induction lamp has no electrodes, it can have a longer service life. For induction lamp systems with a separate driver, the service life can be as long as 100,000 hours, which is 11.4 years of continuous operation. For induction lamps with integrated drivers, the lifespan is in the 15,000 to 50,000 hours range. Extremely high-quality electronic circuits are needed for the driver to attain such a long service life. Such lamps are typically used in commercial or industrial applications. Typically operations and maintenance costs are significantly lower with induction lighting systems due to their industry average 100,000 hour life cycle and five to ten year warranty.
Advantages
The London landmark clock tower containing Big Ben. The clock face is lit by electrodeless lamps.
Long lifespan due to the lack of electrodes – strictly speaking, almost indefinite on the lamp but between 25,000 and 100,000 hours, depending on lamp model and quality of electronics used;
High energy conversion efficiency of between 62 and 90 lumens/watt (higher power lamps are more energy efficient);
Minimal lumen depreciation (declining light output with age) compared to other lamp types, as there is no filament evaporation and depletion;
Environmentally friendly, as induction lamps use less energy, and less mercury per hour of operation than most conventional lighting due to their long lifespan. The mercury is in a solid form that is easily recovered if the lamp is broken or recycled at end-of-life.[citation needed]
Disadvantages
Some internal inductor lamps that use high-frequency drivers can produce radio frequency interference (RFI) that can interfere with radio communications. Newer external-inductor type lamps use low-frequency drivers that usually have FCC or other certification, thus suggesting compliance with RFI regulations.
Some types of induction lamps contain mercury, which is highly toxic if released to the environment.
An electric light, lamp, or colloquially called light bulb is an electrical device that produces light. It is the most common form of artificial lighting. Lamps usually have a base made of ceramic, metal, glass, or plastic, which secures the lamp in the socket of a light fixture. The electrical connection to the socket may be made with a screw-thread base, two metal pins, two metal caps or a bayonet cap.
Artificial lighting technology began to be developed tens of thousands of years ago and continues to be refined in the present day.
A fluorescent lamp, or fluorescent tube, is a low-pressure mercury-vapor gas-discharge lamp that uses fluorescence to produce visible light. An electric current in the gas excites mercury vapor, which produces short-wave ultraviolet light that then causes a phosphor coating on the inside of the lamp to glow. A fluorescent lamp converts electrical energy into useful light much more efficiently than an incandescent lamp. The typical luminous efficacy of fluorescent lighting systems is 50–100 lumens per watt, several times the efficacy of incandescent bulbs with comparable light output. For comparison, the luminous efficacy of an incandescent bulb may only be 16 lumens per watt.
A cold cathode is a cathode that is not electrically heated by a filament. A cathode may be considered "cold" if it emits more electrons than can be supplied by thermionic emission alone. It is used in gas-discharge lamps, such as neon lamps, discharge tubes, and some types of vacuum tube. The other type of cathode is a hot cathode, which is heated by electric current passing through a filament. A cold cathode does not necessarily operate at a low temperature: it is often heated to its operating temperature by other methods, such as the current passing from the cathode into the gas.
A neon lamp is a miniature gas discharge lamp. The lamp typically consists of a small glass capsule that contains a mixture of neon and other gases at a low pressure and two electrodes. When sufficient voltage is applied and sufficient current is supplied between the electrodes, the lamp produces an orange glow discharge. The glowing portion in the lamp is a thin region near the cathode; the larger and much longer neon signs are also glow discharges, but they use the positive column which is not present in the ordinary neon lamp. Neon glow lamps were widely used as indicator lamps in the displays of electronic instruments and appliances. They are still sometimes used for their electrical simplicity in high-voltage circuits.
In the signage industry, neon signs are electric signs lighted by long luminous gas-discharge tubes that contain rarefied neon or other gases. They are the most common use for neon lighting, which was first demonstrated in a modern form in December 1910 by Georges Claude at the Paris Motor Show. While they are used worldwide, neon signs were popular in the United States from about the 1920s to 1950s. The installations in Times Square, many originally designed by Douglas Leigh, were famed, and there were nearly 2,000 small shops producing neon signs by 1940. In addition to signage, neon lighting is used frequently by artists and architects, and in plasma display panels and televisions. The signage industry has declined in the past several decades, and cities are now concerned with preserving and restoring their antique neon signs.
A gas-filled tube, also commonly known as a discharge tube or formerly as a Plücker tube, is an arrangement of electrodes in a gas within an insulating, temperature-resistant envelope. Gas-filled tubes exploit phenomena related to electric discharge in gases, and operate by ionizing the gas with an applied voltage sufficient to cause electrical conduction by the underlying phenomena of the Townsend discharge. A gas-discharge lamp is an electric light using a gas-filled tube; these include fluorescent lamps, metal-halide lamps, sodium-vapor lamps, and neon lights. Specialized gas-filled tubes such as krytrons, thyratrons, and ignitrons are used as switching devices in electric devices.
A plasma globe or plasma lamp is a clear glass container filled with a mixture of various noble gases with a high-voltage electrode in the center of the container.
High-intensity discharge lamps are a type of electrical gas-discharge lamp which produces light by means of an electric arc between tungsten electrodes housed inside a translucent or transparent fused quartz or fused alumina arc tube. This tube is filled with noble gas and often also contains suitable metal or metal salts. The noble gas enables the arc's initial strike. Once the arc is started, it heats and evaporates the metallic admixture. Its presence in the arc plasma greatly increases the intensity of visible light produced by the arc for a given power input, as the metals have many emission spectral lines in the visible part of the spectrum. High-intensity discharge lamps are a type of arc lamp.
A Geissler tube is an early gas discharge tube used to demonstrate the principles of electrical glow discharge, similar to modern neon lighting. The tube was invented by the German physicist and glassblower Heinrich Geissler in 1857. It consists of a sealed, partially evacuated glass cylinder of various shapes with a metal electrode at each end, containing rarefied gasses such as neon, argon, or air; mercury vapor or other conductive fluids; or ionizable minerals or metals, such as sodium. When a high voltage is applied between the electrodes, an electrical current flows through the tube. The current dissociates electrons from the gas molecules, creating ions, and when the electrons recombine with the ions, the gas emits light by fluorescence. The color of light emitted is characteristic of the material within the tube, and many different colors and lighting effects can be achieved. The first gas-discharge lamps, Geissler tubes were novelty items, made in many artistic shapes and colors to demonstrate the new science of electricity. In the early 20th century, the technology was commercialized and evolved into neon lighting.
A mercury-vapor lamp is a gas-discharge lamp that uses an electric arc through vaporized mercury to produce light. The arc discharge is generally confined to a small fused quartz arc tube mounted within a larger borosilicate glass bulb. The outer bulb may be clear or coated with a phosphor; in either case, the outer bulb provides thermal insulation, protection from the ultraviolet radiation the light produces, and a convenient mounting for the fused quartz arc tube.
A metal-halide lamp is an electrical lamp that produces light by an electric arc through a gaseous mixture of vaporized mercury and metal halides. It is a type of high-intensity discharge (HID) gas discharge lamp. Developed in the 1960s, they are similar to mercury vapor lamps, but contain additional metal halide compounds in the quartz arc tube, which improve the efficiency and color rendition of the light. The most common metal halide compound used is sodium iodide. Once the arc tube reaches its running temperature, the sodium dissociates from the iodine, adding orange and reds to the lamp's spectrum from the sodium D line as the metal ionizes. As a result, metal-halide lamps have high luminous efficacy of around 75–100 lumens per watt, which is about twice that of mercury vapor lights and 3 to 5 times that of incandescent lights and produce an intense white light. Lamp life is 6,000 to 15,000 hours. As one of the most efficient sources of high CRI white light, metal halides as of 2005 were the fastest growing segment of the lighting industry. They are used for wide area overhead lighting of commercial, industrial, and public places, such as parking lots, sports arenas, factories, and retail stores, as well as residential security lighting, automotive headlamps and indoor cannabis grow operations.
Hydrargyrum medium-arc iodide (HMI) is the trademark name of Osram's brand of metal-halide gas discharge medium arc-length lamp, made specifically for film and entertainment applications. Hydrargyrum comes from the Greek name for the element mercury.
A xenon arc lamp is a highly specialized type of gas discharge lamp, an electric light that produces light by passing electricity through ionized xenon gas at high pressure. It produces a bright white light to simulate sunlight, with applications in movie projectors in theaters, in searchlights, and for specialized uses in industry and research. For instance, Xenon arc lamps with mercury lamps are the two most common lamps used in wide-field fluorescence microscopes.
The sulfur lamp is a highly efficient full-spectrum electrodeless lighting system whose light is generated by sulfur plasma that has been excited by microwave radiation. They are a particular type of plasma lamp, and one of the most modern. The technology was developed in the early 1990s, but, although it appeared initially to be very promising, sulfur lighting was a commercial failure by the late 1990s. Since 2005, lamps are again being manufactured for commercial use.
Gas-discharge lamps are a family of artificial light sources that generate light by sending an electric discharge through an ionized gas, a plasma.
Ceravision is a privately owned lighting company based in Milton Keynes, UK. Ceravision is the inventor of High Efficiency Plasma (HEP) lighting technology, a new and unique genre of electrodeless lamps, driven by radio frequency (RF) and particularly suited to medium and high power commercial applications.
Plasma lamps are a type of electrodeless gas-discharge lamp energized by radio frequency (RF) power. They are distinct from the novelty plasma lamps that were popular in the 1980s.
UV curing is the process by which ultraviolet light is used to initiate a photochemical reaction that generates a crosslinked network of polymers. UV curing is adaptable to printing, coating, decorating, stereolithography, and in the assembly of a variety of products and materials. In comparison to other technologies, curing with UV energy may be considered a low-temperature process, a high-speed process, and is a solventless process, as cure occurs via direct polymerization rather than by evaporation. Originally introduced in the 1960s, this technology has streamlined and increased automation in many industries in the manufacturing sector.
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