The induction lamp, electrodeless 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

electrode An electrode is an electrical conductor used to make contact with a nonmetallic part of a circuit (e.g. a semiconductor, an electrolyte, a vacuum or air). Electrodes are essential parts of batteries that can consist of a variety of materials d ...

s 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) * Ability to use higher-efficiency light-generating substances that would react with internal metal electrodes in conventional fluorescent lamps Two systems are common: plasma lamps, in which

microwaves Microwave is a form of electromagnetic radiation with wavelengths ranging from about one meter to one millimeter corresponding to frequencies between 300 MHz and 300 GHz respectively. Different sources define different frequency rang ...

radio waves Radio waves are a type of electromagnetic radiation with the longest wavelengths in the electromagnetic spectrum, typically with frequencies of 300 gigahertz ( GHz) and below. At 300 GHz, the corresponding wavelength is 1 mm (s ...

, energizes a bulb filled with sulfur vapor or

metal halide Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, ...

s, and fluorescent induction lamps, which are like a conventional

fluorescent lamp 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 ligh ...

bulb that induces current with an external or an internal coil of wire via electromagnetic induction.

History

In 1882,

Philip Diehl (inventor) Philip H. Diehl (January 29, 1847 – April 7, 1913) was a German-American mechanical engineer and inventor who held several U.S. patents, including electric incandescent lamps, electric motors for sewing machines and other uses, and ceiling f ...

was awarded a patent for a kind of induction incandescent lamp.

Nikola Tesla Nikola Tesla ( ; ,"Tesla"
''

In 1967 and 1968, John Anderson of

General Electric General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable en ...

applied for patents for electrodeless lamps. In 1971, Fusion UV Systems installed a 300-

watt The watt (symbol: W) is the unit of power or radiant flux in the International System of Units (SI), equal to 1 joule per second or 1 kg⋅m2⋅s−3. It is used to quantify the rate of energy transfer. The watt is named after James ...

electrodeless microwave plasma UV lamp on a Coors can

production line A production line is a set of sequential operations established in a factory where components are assembled to make a finished article or where materials are put through a refining process to produce an end-product that is suitable for onward c ...

Philips Koninklijke Philips N.V. (), commonly shortened to Philips, is a Dutch multinational conglomerate corporation that was founded in Eindhoven in 1891. Since 1997, it has been mostly headquartered in Amsterdam, though the Benelux headquarters i ...

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 available on the US market in 1993. In 1990, Michael Ury, Charles Wood and colleagues formulated the concept of the

sulfur lamp The sulfur lamp (also sulphur 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 ...

. With support from the

United States Department of Energy The United States Department of Energy (DOE) is an executive department of the U.S. federal government that oversees U.S. national energy policy and manages the research and development of nuclear power and nuclear weapons in the United Stat ...

, 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,

has produced its induction lamp ''Genura'' with an integrated high frequency driver, 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. 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 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 (RF) is the oscillation rate of an alternating electric current or voltage or of a magnetic, electric or electromagnetic field or mechanical system in the frequency range from around to around . This is roughly between the ...

waves into a solid

dielectric In electromagnetism, a dielectric (or dielectric medium) is an electrical insulator that can be polarised by an applied electric field. When a dielectric material is placed in an electric field, electric charges do not flow through the mate ...

waveguide A waveguide is a structure that guides waves, such as electromagnetic waves or sound, with minimal loss of energy by restricting the transmission of energy to one direction. Without the physical constraint of a waveguide, wave intensities de ...

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 Luxim 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. Luxim technology is used in general lighting, entertainment lighting, i ...

, now of Topanga Technologies), Chandrashekhar Joshi and Yian Chang, these claims were disputed by

Ceravision 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 partic ...

Limited. A number of the core patents were assigned to Ceravision. In 2006,

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 is a field of work or study that is concerned with the design of lighting systems within the built environment, both interior and exterior. It can include manipulation and design of both daylight and electr ...

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 state

(RF) driver, thereby circumventing the limited life of

magnetron The cavity magnetron is a high-power vacuum tube used in early radar systems and currently in microwave ovens and linear particle accelerators. It generates microwaves using the interaction of a stream of electrons with a magnetic field while ...

-based drivers, with system power of 127 and 230 volts and system efficacies of 96 and 87 lumen/watt, with a

CRI CRI or CRi may refer to: Organizations * Canadian Rivers Institute, for river sciences, University of New Brunswick * Cancer Research Institute, New York, US * Centro de Relaciones Internacionales (International Relations Center), Universidad N ...

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.

Plasma lamps

Induction Lamp FB 5000 W Soviet Union 1981

Plasma lamps are a family of light sources that generate light by exciting a plasma inside a closed transparent burner or bulb using

(RF) power. Typically, such lamps use a

noble gas The noble gases (historically also the inert gases; sometimes referred to as aerogens) make up a class of chemical elements with similar properties; under standard conditions, they are all odorless, colorless, monatomic gases with very low ch ...

or a mixture of these gases and additional materials such as

metal halides Metal halides are compounds between metals and halogens. Some, such as sodium chloride are ionic, while others are covalently bonded. A few metal halides are discrete molecules, such as uranium hexafluoride, but most adopt polymeric structures, su ...

sodium Sodium is a chemical element with the symbol Na (from Latin ''natrium'') and atomic number 11. It is a soft, silvery-white, highly reactive metal. Sodium is an alkali metal, being in group 1 of the periodic table. Its only stable ...

, mercury, or sulfur. A

is used to constrain and focus the

electrical field An electric field (sometimes E-field) is the physical field that surrounds electrically charged particles and exerts force on all other charged particles in the field, either attracting or repelling them. It also refers to the physical field f ...

into the plasma. In operation the gas is ionized and free electrons, accelerated by the

, 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 A photon () is an elementary particle that is a quantum of the electromagnetic field, including electromagnetic radiation such as light and radio waves, and the force carrier for the electromagnetic force. Photons are massless, so they a ...

, resulting in visible light or

ultraviolet Ultraviolet (UV) is a form of electromagnetic radiation with wavelength from 10 nm (with a corresponding frequency around 30 PHz) to 400 nm (750 THz), shorter than that of visible light, but longer than X-rays. UV radiation ...

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 b
Fusion UV
That lamp led Fusion Systems to develop the

, which concentrates microwaves through a hollow

to bombard a bulb filled with argon and sulfur. In the past, the

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 to over 40,000 hours making low-cost plasma lamps possible. Plasma lamps are currently produced by

and

and in development by Topanga Technologies.

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) of any light fitting on the market, and to have created the first high-efficiency plasma (HEP) lamp.

uses a

to generate the required RF power and claims a life of 20,000 hours.

's LIFI lamp, claims 120 lumens per RF watt (i.e. before taking into account electrical losses). The lamp has been used in Robe lighting's ''ROBIN 300 Plasma Spot'' moving-head light. It was also used in a line of, now discontinued,

Panasonic formerly between 1935 and 2008 and the first incarnation of between 2008 and 2022, is a major Japanese multinational conglomerate corporation, headquartered in Kadoma, Osaka. It was founded by Kōnosuke Matsushita in 1918 as a lightbulb ...

rear-projection TVs.

Magnetic induction lamps

External Closed Core Induction Lamp with Two Turn Primary

Aside from the method of

coupling A coupling is a device used to connect two shafts together at their ends for the purpose of transmitting power. The primary purpose of couplings is to join two pieces of rotating equipment while permitting some degree of misalignment or end mov ...

energy into the mercury vapor, these lamps are very similar to conventional

s. Mercury vapor in the discharge vessel is electrically excited to produce short-wave

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 Components of an electrical circuit are electrically connected if an electric current can run between them through an electrical conductor. An electrical connector is an electromechanical device used to create an electrical connection between ...

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 In electronics, a ferrite core is a type of magnetic core made of ferrite on which the windings of electric transformers and other wound components such as inductors are formed. It is used for its properties of high magnetic permeability couple ...

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. Internal Inductor-type Induction 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 A transformer is a passive component that transfers electrical energy from one electrical circuit to another circuit, or multiple circuits. A varying current in any coil of the transformer produces a varying magnetic flux in the 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 Argon is a chemical element with the symbol Ar and atomic number 18. It is in group 18 of the periodic table and is a noble gas. Argon is the third-most abundant gas in Earth's atmosphere, at 0.934% (9340 ppmv). It is more than twice as ...

and mercury vapor. The mercury atoms are provided by a drop of liquid mercury, or by a semi-solid

amalgam Amalgam most commonly refers to: * Amalgam (chemistry), mercury alloy * Amalgam (dentistry), material of silver tooth fillings ** Bonded amalgam, used in dentistry Amalgam may also refer to: * Amalgam Comics, a publisher * Amalgam Digital ...

of mercury and other metals such as

bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...

lead Lead is a chemical element with the symbol Pb (from the Latin ) and atomic number 82. It is a heavy metal that is denser than most common materials. Lead is soft and malleable, and also has a relatively low melting point. When freshly cu ...

, or

tin Tin is a chemical element with the symbol Sn (from la, stannum) and atomic number 50. Tin is a silvery-coloured metal. Tin is soft enough to be cut with little force and a bar of tin can be bent by hand with little effort. When bent, t ...

. 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

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 253.7 nm 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 ferrite

core Core or cores may refer to: Science and technology * Core (anatomy), everything except the appendages * Core (manufacturing), used in casting and molding * Core (optical fiber), the signal-carrying portion of an optical fiber * Core, the centra ...

. 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 Frequency is the number of occurrences of a repeating event per unit of time. It is also occasionally referred to as ''temporal frequency'' for clarity, and is distinct from ''angular frequency''. Frequency is measured in hertz (Hz) which is eq ...

. The exact frequency varies with lamp design, but popular examples include 13.6

MHz The hertz (symbol: Hz) is the unit of frequency in the International System of Units (SI), equivalent to one event (or cycle) per second. The hertz is an SI derived unit whose expression in terms of SI base units is s−1, meaning that one he ...

, 2.65 MHz and 250 kHz. A special

resonant Resonance describes the phenomenon of increased amplitude that occurs when the frequency of an applied periodic force (or a Fourier component of it) is equal or close to a natural frequency of the system on which it acts. When an oscilla ...

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

, with the power coupler (inductor) forming the primary coil and the

gas discharge Electric discharge in gases occurs when electric current flows through a gaseous medium due to ionization of the gas. Depending on several factors, the discharge may radiate visible light. The properties of electric discharges in gases are studied ...

arc in the bulb forming the one-turn secondary coil and the load of the transformer. The driver is connected to

mains electricity Mains electricity or utility power, power grid, domestic power, and wall power, or in some parts of Canada as hydro, is a general-purpose alternating-current (AC) electric power supply. It is the form of electrical power that is delivered to h ...

, and is generally designed to operate on voltages between 100 and 277 VAC at a frequency of 50 or 60 Hz, or on a voltage between 100 and 400 VDC for battery-fed

emergency light An emergency light is a battery-backed lighting device that switches on automatically when a building experiences a power outage. In the United States, emergency lights are standard in new commercial and high occupancy residential buildings, ...

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 Wind is the natural movement of air or other gases relative to a planet's surface. Winds occur on a range of scales, from thunderstorm flows lasting tens of minutes, to local breezes generated by heating of land surfaces and lasting a few ho ...

) powered systems. In other conventional gas discharge lamps, the

s 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 A product's service life is its period of use in service. Several related terms describe more precisely a product's life, from the point of manufacture, storage, and distribution, and eventual use. Service life has been defined as "a product li ...

. 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 – 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);

Disadvantages

* Some internal inductor lamps that use high-frequency drivers can produce

radio frequency interference Electromagnetic interference (EMI), also called radio-frequency interference (RFI) when in the radio frequency spectrum, is a disturbance generated by an external source that affects an electrical circuit by electromagnetic induction, electrost ...

(RFI) that can interfere with radio communications. Newer external-inductor type lamps use low-frequency drivers that usually have

FCC The Federal Communications Commission (FCC) is an independent agency of the United States federal government that regulates communications by radio, television, wire, satellite, and cable across the United States. The FCC maintains jurisdictio ...

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.

References

External links

Electrodeless Induction Lamps
Museum of Electric Lamp Technology {{Artificial light sources Gas discharge lamps