Electrodeless lamp
Encyclopedia
An electrodeless lamp is a light source in which the power required to generate light is transferred from outside the lamp envelope to inside via electromagnetic field
s, in contrast with a typical electrical lamp that uses electrical connections through the lamp envelope to transfer power. There are three advantages of eliminating electrodes:
Two systems are described below – one, plasma lamps, based on the use of radio waves energizing a bulb filled with sulfur
or metal halides, the other, fluorescent induction lamps, based upon conventional fluorescent lamp
phosphor
s.
demonstrated wired and wireless transfer of power to electrodeless fluorescent and incandescent lamps in his lectures and articles in the 1890s, and subsequently patented a system of light and power distribution on those principles. In the lecture before the AIEE, May 20, 1891, titled Experiments with Alternating Currents of Very High Frequency and Their Application to Methods of Artificial Illumination
and US patent 454622, among many other references in the technical and popular press are found countless records for Tesla's priority in this field. A suit filed by Tesla against J. J. Thomson
for priority on the patent was subsequently granted in Tesla's favor. As of 2011, the transcripts of the case languish in archives, awaiting processing, and eventual publishing. Noting the diagrams in Tesla's lectures and patents, a striking similarity of construction to electrodeless lamps that are available on the market currently is readily apparent. Further, a statement in 1929 by Tesla, published in The World:
In 1967 and 1968, John Anderson of General Electric
applied for patents for electrodeless lamps.
Philips
introduced their QL induction lighting systems, operating at 2.65 MHz, 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 13.6 MHz, it was to be available on the US market in 1993.
In 1990, Michael Ury, Charles Wood and colleagues, formulated the concept of the sulphur 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 ballast, operating at 2.65 MHz. In 1996, Osram
started selling their Endura induction light system, operating at 250 kHz. 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.
Since 2005, Amko Solara in Taiwan introduced induction lamps that can dim and use IP based controls. Their lamps have a range from 12 to 400 watts and operate at 250 kHz.
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 dielectric
waveguide
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 lamps. 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. Recently a number of the core patents were assigned to Ceravision
.
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 used in earlier lamps with an optically clear quartz waveguide giving greatly increased efficiency. In previous lamps, though the burner, or bulb, was very efficient, the opaque ceramic waveguide severely obstructed the collection of light. A quartz waveguide allows all of the light from the plasma to be collected.
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 the development of the sulfur lamp
, a bulb filled with argon and sulfur which is bombarded with microwaves through a hollow waveguide
.
In the past, the reliability of the technology was limited by the magnetron used to generate the microwaves. Solid state RF generation can be used and gives long life. However, using solid state chips to generate RF is approximately fifty times more expensive currently than using a magnetron and so only appropriate for high value lighting niches. It has recently been shown by Dipolar http://www.dipolar.se/ of Sweden to be possible to greatly extend the life of magnetrons to over 40,000 hours 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 allowing all the light from the plasma to be collected. The small source also allows the luminaire to utilize more than 90% of the available light compared with 55% for typical HID fittings. Ceravision claims the highest Luminaire Efficacy Rating (LER) 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 claim a life of 20,000 hours.
Luxim
's LIFI, or light fidelity lamp, claims 120 lumens per RF watt (ie before taking into account electrical losses). The lamp has been used in Robe lighting's ROBIN 300 Plasma Spot moving headlight. It was also used in a line of, now discontinued, Panasonic
rear projection TV's.
Aside from the method of coupling
energy into the mercury
vapour, these lamps are very similar to conventional fluorescent lamp
s. Mercury vapour in the discharge vessel is electrically excited to produce short-wave ultraviolet
light, which then excites the phosphor
s to produce visible light. While still relatively unknown to the public, these lamps have been available since 1990. The first type introduced had the shape of an incandescent light bulb
. 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 lamp, external inductor lamps and internal inductor lamps. The original, and still widely used form of induction lamps are the internal inductor types. A more recent development is the external inductor types which have a wider range of applications and which are available in round, rectangular and "olive" shaped form factors.
External inductor lamps are basically fluorescent lamps with electromagnets wrapped around a part of the tube. In the external inductor lamps, high frequency energy, from the electronic ballast, is sent through wires, which are wrapped in a coil around a ferrite inductor on the outside of the glass tube, creating a powerful electromagnet
called an inductor. The induction coil (inductor) produces a very strong magnetic field which travels through the glass and excites the mercury atoms in the interior. The mercury atoms are provided by the amalgam
(a solid form of mercury). The excited mercury atoms emit UV light and, just as in a fluorescent tube, the UV light 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 light as ordinary glass blocks UV radiation at the 253.7 nm and 185 nm range.
In the internal inductor form (see diagram), a glass tube (B) protrudes bulb-wards 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 tubular ferrite
core
. The coil and ferrite forms the inductor which couples the energy into the lamp interior
The antenna coils receive electric power
from the electronic ballast (C) that generates a high frequency
. The exact frequency varies with lamp design, but popular examples include 13.6 MHz
, 2.65 MHz and 250 kHz. A special resonant
circuit in the ballast 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 discharge arc
in the bulb forming the one-turn secondary coil and the load of the transformer. The ballast is connected to mains electricity
, and is generally designed to operate on voltages between 100 and 277 VAC at a frequency of 50 or 60 Hz. Many ballasts are available in low voltage models so can also be connected to DC voltage sources
like batteries
for emergency lighting purposes of for use with renewable energy (solar
& wind
) powered systems.
In other conventional gas discharge lamps, the electrode
s are the part with the shortest life, limiting the lamp lifespan severely. Since an induction lamp has no electrodes, it can have a very long service life. For induction lamp systems with a separate ballast, the service life can be as long as 100,000 hours, which is 11.4 years continuous operation. For induction lamps with integrated ballast, the lifespan is in the 15,000 to 50,000 hours range. Extremely high-quality electronic circuit
s are needed for the ballast 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.
These benefits offer a considerable cost savings of between 35% and 55% in energy and maintenance costs for induction lamps compared to other types of commercial and industrial lamps which they replace.
Electromagnetic field
An electromagnetic field is a physical field produced by moving electrically charged objects. It affects the behavior of charged objects in the vicinity of the field. The electromagnetic field extends indefinitely throughout space and describes the electromagnetic interaction...
s, in contrast with a typical electrical lamp that uses electrical connections through the lamp envelope to transfer power. There are three advantages of eliminating electrodes:
- Extended lamp life, because the electrodes are usually the limiting factor in lamp life.
- The ability to use light-generating substances of higher efficiency that would react with metal electrodes in normal lamps.
- Improved collection efficiency because the source can be made very small without shortening life, a problem in electroded lamps
Two systems are described below – one, plasma lamps, based on the use of radio waves energizing a bulb filled with sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
or metal halides, the other, fluorescent induction lamps, based upon conventional fluorescent lamp
Fluorescent lamp
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
s.
History
Nikola TeslaNikola Tesla
Nikola Tesla was a Serbian-American inventor, mechanical engineer, and electrical engineer...
demonstrated wired and wireless transfer of power to electrodeless fluorescent and incandescent lamps in his lectures and articles in the 1890s, and subsequently patented a system of light and power distribution on those principles. In the lecture before the AIEE, May 20, 1891, titled Experiments with Alternating Currents of Very High Frequency and Their Application to Methods of Artificial Illumination
and US patent 454622, among many other references in the technical and popular press are found countless records for Tesla's priority in this field. A suit filed by Tesla against J. J. Thomson
J. J. Thomson
Sir Joseph John "J. J." Thomson, OM, FRS was a British physicist and Nobel laureate. He is credited for the discovery of the electron and of isotopes, and the invention of the mass spectrometer...
for priority on the patent was subsequently granted in Tesla's favor. As of 2011, the transcripts of the case languish in archives, awaiting processing, and eventual publishing. Noting the diagrams in Tesla's lectures and patents, a striking similarity of construction to electrodeless lamps that are available on the market currently is readily apparent. Further, a statement in 1929 by Tesla, published in The World:
In 1967 and 1968, John Anderson of General Electric
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
applied for patents for electrodeless lamps.
Philips
Philips
Koninklijke Philips Electronics N.V. , more commonly known as Philips, is a multinational Dutch electronics company....
introduced their QL induction lighting systems, operating at 2.65 MHz, 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 13.6 MHz, it was to be available on the US market in 1993.
In 1990, Michael Ury, Charles Wood and colleagues, formulated the concept of the sulphur lamp. With support from the United States Department of Energy
United States Department of Energy
The United States Department of Energy is a Cabinet-level department of the United States government concerned with the United States' policies regarding energy and safety in handling nuclear material...
, 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
General Electric
General Electric Company , or GE, is an American multinational conglomerate corporation incorporated in Schenectady, New York and headquartered in Fairfield, Connecticut, United States...
has produced its induction lamp Genura with an integrated ballast, operating at 2.65 MHz. In 1996, Osram
Osram
Osram, founded 1919, is part of the industry sector of Siemens AG and one of the two leading lighting manufacturers in the world. The name is derived from osmium and Wolfram , as both these elements were commonly used for lighting filaments at the time the company was founded...
started selling their Endura induction light system, operating at 250 kHz. 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.
Since 2005, Amko Solara in Taiwan introduced induction lamps that can dim and use IP based controls. Their lamps have a range from 12 to 400 watts and operate at 250 kHz.
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
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
waves into a solid dielectric
Dielectric
A dielectric is an electrical insulator that can be polarized by an applied electric field. When a dielectric is placed in an electric field, electric charges do not flow through the material, as in a conductor, but only slightly shift from their average equilibrium positions causing dielectric...
waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
made of ceramic which energized a light emitting plasma
Plasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
in a bulb positioned inside. This system, for the first time, permitted an extremely bright and compact electrodeless lamps. The invention has been a matter of dispute. Claimed by Frederick Espiau (then of Luxim
Luxim
LUXIM, the world leader in Light Emitting Plasma technology, is a privately owned clean tech company based in Sunnyvale, California, which was founded in 2000.LUXIM manufactures a solid state electrodeless lamp lighting system...
now of Topanga Technologies), Chandrashekhar Joshi and Yian Chang, these claims were disputed by Ceravision
Ceravision
Ceravision is a privately owned lighting company based in Bletchley Park, UK. Ceravision is the inventor of a range of electrodeless lamps and integrated luminaires under the trade name Alvara, the world's first High Efficiency Plasma lamp...
Limited. Recently a number of the core patents were assigned to Ceravision
Ceravision
Ceravision is a privately owned lighting company based in Bletchley Park, UK. Ceravision is the inventor of a range of electrodeless lamps and integrated luminaires under the trade name Alvara, the world's first High Efficiency Plasma lamp...
.
In 2006 Luxim
Luxim
LUXIM, the world leader in Light Emitting Plasma technology, is a privately owned clean tech company based in Sunnyvale, California, which was founded in 2000.LUXIM manufactures a solid state electrodeless lamp lighting system...
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
Architectural lighting design
Architectural lighting design is a field within architecture and architectural engineering that concerns itself primarily with the illumination of buildings. The objective of architectural lighting design is to obtain sufficient light for the purposes of the building, balancing factors of initial...
applications among others throughout 2007 and 2008.
In 2009 Ceravision
Ceravision
Ceravision is a privately owned lighting company based in Bletchley Park, UK. Ceravision is the inventor of a range of electrodeless lamps and integrated luminaires under the trade name Alvara, the world's first High Efficiency Plasma lamp...
Limited introduced the first High Efficiency Plasma (HEP) lamp under the trade name Alvara. This lamp replaces the opaque ceramic waveguide used in earlier lamps with an optically clear quartz waveguide giving greatly increased efficiency. In previous lamps, though the burner, or bulb, was very efficient, the opaque ceramic waveguide severely obstructed the collection of light. A quartz waveguide allows all of the light from the plasma to be collected.
Plasma lamps
Plasma lamps are a family of light sources that generate light by exciting a plasmaPlasma (physics)
In physics and chemistry, plasma is a state of matter similar to gas in which a certain portion of the particles are ionized. Heating a gas may ionize its molecules or atoms , thus turning it into a plasma, which contains charged particles: positive ions and negative electrons or ions...
inside a closed transparent burner or bulb using radio frequency
Radio frequency
Radio frequency is a rate of oscillation in the range of about 3 kHz to 300 GHz, which corresponds to the frequency of radio waves, and the alternating currents which carry radio signals...
(RF) power. Typically, such lamps use a noble gas
Noble gas
The noble gases are a group of chemical elements with very similar properties: under standard conditions, they are all odorless, colorless, monatomic gases, with very low chemical reactivity...
or a mixture of these gases and additional materials such as metal halides, sodium
Sodium
Sodium is a chemical element with the symbol Na and atomic number 11. It is a soft, silvery-white, highly reactive metal and is a member of the alkali metals; its only stable isotope is 23Na. It is an abundant element that exists in numerous minerals, most commonly as sodium chloride...
, mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
or sulfur
Sulfur
Sulfur or sulphur is the chemical element with atomic number 16. In the periodic table it is represented by the symbol S. It is an abundant, multivalent non-metal. Under normal conditions, sulfur atoms form cyclic octatomic molecules with chemical formula S8. Elemental sulfur is a bright yellow...
. A waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
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
Electron excitation
Electron excitation is the movement of an electron to a higher energy state. This can either be done by photoexcitation , where the original electron absorbs the photon and gains all the photon's energy or by electrical excitation , where the original electron absorbs the energy of another,...
by these collisions, bringing them to a higher energy state. When the electron falls back to its original state, it emits a photon
Photon
In physics, a photon is an elementary particle, the quantum of the electromagnetic interaction and the basic unit of light and all other forms of electromagnetic radiation. It is also the force carrier for the electromagnetic force...
, resulting in visible light or ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
radiation depending on the fill materials.
The first plasma lamp was an ultraviolet curing
Curing (chemistry)
Curing is a term in polymer chemistry and process engineering that refers to the toughening or hardening of a polymer material by cross-linking of polymer chains, brought about by chemical additives, ultraviolet radiation, electron beam or heat...
lamp with a bulb filled with argon and mercury vapor developed by Fusion UV. That lamp led Fusion Systems to the development of the sulfur lamp
Sulfur lamp
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. The technology was developed in the early 1990s, but, although it appeared initially to be very promising, sulfur lighting was...
, a bulb filled with argon and sulfur which is bombarded with microwaves through a hollow waveguide
Waveguide
A waveguide is a structure which guides waves, such as electromagnetic waves or sound waves. There are different types of waveguides for each type of wave...
.
In the past, the reliability of the technology was limited by the magnetron used to generate the microwaves. Solid state RF generation can be used and gives long life. However, using solid state chips to generate RF is approximately fifty times more expensive currently than using a magnetron and so only appropriate for high value lighting niches. It has recently been shown by Dipolar http://www.dipolar.se/ of Sweden to be possible to greatly extend the life of magnetrons to over 40,000 hours making low cost plasma lamps possible. Plasma lamps are currently produced by Ceravision
Ceravision
Ceravision is a privately owned lighting company based in Bletchley Park, UK. Ceravision is the inventor of a range of electrodeless lamps and integrated luminaires under the trade name Alvara, the world's first High Efficiency Plasma lamp...
and Luxim
Luxim
LUXIM, the world leader in Light Emitting Plasma technology, is a privately owned clean tech company based in Sunnyvale, California, which was founded in 2000.LUXIM manufactures a solid state electrodeless lamp lighting system...
and in development by Topanga Technologies.
Ceravision
Ceravision
Ceravision is a privately owned lighting company based in Bletchley Park, UK. Ceravision is the inventor of a range of electrodeless lamps and integrated luminaires under the trade name Alvara, the world's first High Efficiency Plasma lamp...
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 allowing all the light from the plasma to be collected. The small source also allows the luminaire to utilize more than 90% of the available light compared with 55% for typical HID fittings. Ceravision claims the highest Luminaire Efficacy Rating (LER) of any light fitting on the market and to have created the first High Efficiency Plasma (HEP) lamp. Ceravision
Ceravision
Ceravision is a privately owned lighting company based in Bletchley Park, UK. Ceravision is the inventor of a range of electrodeless lamps and integrated luminaires under the trade name Alvara, the world's first High Efficiency Plasma lamp...
uses a magnetron to generate the required RF power and claim a life of 20,000 hours.
Luxim
Luxim
LUXIM, the world leader in Light Emitting Plasma technology, is a privately owned clean tech company based in Sunnyvale, California, which was founded in 2000.LUXIM manufactures a solid state electrodeless lamp lighting system...
's LIFI, or light fidelity lamp, claims 120 lumens per RF watt (ie before taking into account electrical losses). The lamp has been used in Robe lighting's ROBIN 300 Plasma Spot moving headlight. It was also used in a line of, now discontinued, Panasonic
Panasonic
Panasonic is an international brand name for Japanese electric products manufacturer Panasonic Corporation, which was formerly known as Matsushita Electric Industrial Co., Ltd...
rear projection TV's.
Magnetic induction lamps
Coupling (electronics)
In electronics and telecommunication, coupling is the desirable or undesirable transfer of energy from one medium, such as a metallic wire or an optical fiber, to another medium, including fortuitous transfer....
energy into the mercury
Mercury (element)
Mercury is a chemical element with the symbol Hg and atomic number 80. It is also known as quicksilver or hydrargyrum...
vapour, these lamps are very similar to conventional fluorescent lamp
Fluorescent lamp
A fluorescent lamp or fluorescent tube is a gas-discharge lamp that uses electricity to excite mercury vapor. The excited mercury atoms produce short-wave ultraviolet light that then causes a phosphor to fluoresce, producing visible light. A fluorescent lamp converts electrical power into useful...
s. Mercury vapour in the discharge vessel is electrically excited to produce short-wave ultraviolet
Ultraviolet
Ultraviolet light is electromagnetic radiation with a wavelength shorter than that of visible light, but longer than X-rays, in the range 10 nm to 400 nm, and energies from 3 eV to 124 eV...
light, which then excites the phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
s to produce visible light. While still relatively unknown to the public, these lamps have been available since 1990. The first type introduced had the shape of an incandescent light bulb
Incandescent light bulb
The incandescent light bulb, incandescent lamp or incandescent light globe makes light by heating a metal filament wire to a high temperature until it glows. The hot filament is protected from air by a glass bulb that is filled with inert gas or evacuated. In a halogen lamp, a chemical process...
. Unlike an incandescent lamp or conventional fluorescent lamps, there is no electrical connection
Electrical connection
An electrical connection between discrete points allows the flow of electrons . A pair of connections is needed for a circuit.Between points with a low voltage difference, direct current can be controlled by a switch...
going inside the glass bulb; the energy is transferred through the glass envelope solely by electromagnetic induction
Electromagnetic induction
Electromagnetic induction is the production of an electric current across a conductor moving through a magnetic field. It underlies the operation of generators, transformers, induction motors, electric motors, synchronous motors, and solenoids....
.
There are two main types of magnetic induction lamp, external inductor lamps and internal inductor lamps. The original, and still widely used form of induction lamps are the internal inductor types. A more recent development is the external inductor types which have a wider range of applications and which are available in round, rectangular and "olive" shaped form factors.
External inductor lamps are basically fluorescent lamps with electromagnets wrapped around a part of the tube. In the external inductor lamps, high frequency energy, from the electronic ballast, is sent through wires, which are wrapped in a coil around a ferrite inductor on the outside of the glass tube, creating a powerful electromagnet
Electromagnet
An electromagnet is a type of magnet in which the magnetic field is produced by the flow of electric current. The magnetic field disappears when the current is turned off...
called an inductor. The induction coil (inductor) produces a very strong magnetic field which travels through the glass and excites the mercury atoms in the interior. The mercury atoms are provided by the amalgam
Amalgam (chemistry)
An amalgam is a substance formed by the reaction of mercury with another metal. Almost all metals can form amalgams with mercury, notable exceptions being iron and platinum. Silver-mercury amalgams are important in dentistry, and gold-mercury amalgam is used in the extraction of gold from ore.The...
(a solid form of mercury). The excited mercury atoms emit UV light and, just as in a fluorescent tube, the UV light is down-converted to visible light by the phosphor
Phosphor
A phosphor, most generally, is a substance that exhibits the phenomenon of luminescence. Somewhat confusingly, this includes both phosphorescent materials, which show a slow decay in brightness , and fluorescent materials, where the emission decay takes place over tens of nanoseconds...
coating on the inside of the tube. The glass walls of the lamp prevent the emission of the UV light as ordinary glass blocks UV radiation at the 253.7 nm and 185 nm range.
In the internal inductor form (see diagram), a glass tube (B) protrudes bulb-wards from the bottom of the discharge vessel (A), forming a re-entrant cavity. This tube contains an antenna
Antenna (radio)
An antenna is an electrical device which converts electric currents into radio waves, and vice versa. It is usually used with a radio transmitter or radio receiver...
called a power coupler, which consists of a coil
Coil
A coil is a series of loops. A coiled coil is a structure in which the coil itself is in turn also looping.-Electromagnetic coils:An electromagnetic coil is formed when a conductor is wound around a core or form to create an inductor or electromagnet...
wound over a tubular ferrite
Ferrite (magnet)
Ferrites are chemical compounds consisting of ceramic materials with iron oxide as their principal component. Many of them are magnetic materials and they are used to make permanent magnets, ferrite cores for transformers, and in various other applications.Many ferrites are spinels with the...
core
Magnetic core
A magnetic core is a piece of magnetic material with a high permeability used to confine and guide magnetic fields in electrical, electromechanical and magnetic devices such as electromagnets, transformers, electric motors, inductors and magnetic assemblies. It is made of ferromagnetic metal such...
. The coil and ferrite forms the inductor which couples the energy into the lamp interior
The antenna coils receive electric power
Electric power
Electric power is the rate at which electric energy is transferred by an electric circuit. The SI unit of power is the watt.-Circuits:Electric power, like mechanical power, is represented by the letter P in electrical equations...
from the electronic ballast (C) that generates a high frequency
Frequency
Frequency is the number of occurrences of a repeating event per unit time. It is also referred to as temporal frequency.The period is the duration of one cycle in a repeating event, so the period is the reciprocal of the frequency...
. The exact frequency varies with lamp design, but popular examples include 13.6 MHz
Hertz
The hertz is the SI unit of frequency defined as the number of cycles per second of a periodic phenomenon. One of its most common uses is the description of the sine wave, particularly those used in radio and audio applications....
, 2.65 MHz and 250 kHz. A special resonant
Resonance
In physics, resonance is the tendency of a system to oscillate at a greater amplitude at some frequencies than at others. These are known as the system's resonant frequencies...
circuit in the ballast produces an initial high voltage on the coil to start a gas discharge; thereafter the voltage is reduced to normal running level.
The system
System
System is a set of interacting or interdependent components forming an integrated whole....
can be seen as a type of transformer
Transformer
A transformer is a device that transfers electrical energy from one circuit to another through inductively coupled conductors—the transformer's coils. A varying current in the first or primary winding creates a varying magnetic flux in the transformer's core and thus a varying magnetic field...
, with the power coupler (inductor) forming the primary coil and the gas discharge arc
Electric arc
An electric arc is an electrical breakdown of a gas which produces an ongoing plasma discharge, resulting from a current flowing through normally nonconductive media such as air. A synonym is arc discharge. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on...
in the bulb forming the one-turn secondary coil and the load of the transformer. The ballast is connected to mains electricity
Mains electricity
Mains is the general-purpose alternating current electric power supply. In the US, electric power is referred to by several names including household power, household electricity, powerline, domestic power, wall power, line power, AC power, city power, street power, and grid power...
, and is generally designed to operate on voltages between 100 and 277 VAC at a frequency of 50 or 60 Hz. Many ballasts are available in low voltage models so can also be connected to DC voltage sources
Direct current
Direct current is the unidirectional flow of electric charge. Direct current is produced by such sources as batteries, thermocouples, solar cells, and commutator-type electric machines of the dynamo type. Direct current may flow in a conductor such as a wire, but can also flow through...
like batteries
Lead-acid battery
Lead–acid batteries, invented in 1859 by French physicist Gaston Planté, are the oldest type of rechargeable battery. Despite having a very low energy-to-weight ratio and a low energy-to-volume ratio, their ability to supply high surge currents means that the cells maintain a relatively large...
for emergency lighting purposes of for use with renewable energy (solar
Solar power
Solar energy, radiant light and heat from the sun, has been harnessed by humans since ancient times using a range of ever-evolving technologies. Solar radiation, along with secondary solar-powered resources such as wind and wave power, hydroelectricity and biomass, account for most of the available...
& wind
Wind power
Wind power is the conversion of wind energy into a useful form of energy, such as using wind turbines to make electricity, windmills for mechanical power, windpumps for water pumping or drainage, or sails to propel ships....
) powered systems.
In other conventional gas discharge lamps, the electrode
Electrode
An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit...
s are the part with the shortest life, limiting the lamp lifespan severely. Since an induction lamp has no electrodes, it can have a very long service life. For induction lamp systems with a separate ballast, the service life can be as long as 100,000 hours, which is 11.4 years continuous operation. For induction lamps with integrated ballast, the lifespan is in the 15,000 to 50,000 hours range. Extremely high-quality electronic circuit
Electronic circuit
An electronic circuit is composed of individual electronic components, such as resistors, transistors, capacitors, inductors and diodes, connected by conductive wires or traces through which electric current can flow...
s are needed for the ballast to attain such a long service life
Service life
A product's service life is its expected lifetime, or the acceptable period of use in service. It is the time that any manufactured item can be expected to be 'serviceable' or supported by its manufacturer....
. 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
- Long lifespan due to the lack of electrodes – between 65,000 and 100,000 hours depending on lamp model;
- Very high energy conversion efficiency of between 62 and 90 Lumens/Watt [higher power lamps are more energy efficient];
- High power factorPower factorThe power factor of an AC electric power system is defined as the ratio of the real power flowing to the load over the apparent power in the circuit, and is a dimensionless number between 0 and 1 . Real power is the capacity of the circuit for performing work in a particular time...
due to the low loss of the high frequency electronic ballasts which are typically between 95% and 98% efficient; - Minimal Lumen depreciation (declining light output with age) compared to other lamp types as filament evaporation and depletion is absent;
- “Instant-on” and hot re-strike, unlike most conventional lamps used in commercial-industrial lighting applications (such as mercury-vapor lampMercury-vapor lampA 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...
, sodium-vapor lamp and metal halide lampMetal halide lampMetal-halide lamps, a member of the high-intensity discharge family of lamps, produce high light output for their size, making them a compact, powerful, and efficient light source. By adding rare earth metal salts to the mercury vapor lamp, improved luminous efficacy and light color is obtained...
); - Environmentally friendly as induction lamps use less energy, and use less mercury per hour of operation than conventional lighting due to their long lifespan. The mercury is in a solid form and can be easily recovered if the lamp is broken, or for recycling at end-of-life.
These benefits offer a considerable cost savings of between 35% and 55% in energy and maintenance costs for induction lamps compared to other types of commercial and industrial lamps which they replace.