Editing Induction lamp

{{Short description|Gas-discharge lamp using electric and magnetic fields to transfer energy to the gas inside}}
[[File:Lampe à induction.jpg|thumb|150x150px|A round Induction fluorescent lamp]]

The '''induction lamp''', '''electrodeless lamp''', or '''electrodeless induction lamp''' is a [[gas-discharge lamp]] in which an [[electromagnetic field|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]]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){{citation needed|date=May 2014}}
* Ability to use higher-efficiency light-generating substances that would react with internal metal electrodes in conventional fluorescent lamps{{citation needed|date=October 2015}}

Two systems are common: [[plasma lamp]]s, in which [[microwave]]s or [[radio wave]]s, energizes a bulb filled with [[sulfur]] vapor<ref name=":0">{{Cite web |last=Institution |first=Smithsonian |title=Experimental Sulfur Lamp {{!}} Smithsonian Institution |url=https://www.si.edu/object/experimental-sulfur-lamp:nmah_995200 |access-date=2025-01-17 |website=Smithsonian Institution |language=en}}</ref> or [[metal halide]]s, and fluorescent induction lamps, which are like a conventional [[fluorescent lamp]] bulb that induces current with an external or an internal coil of wire via [[electromagnetic induction]].

==History==
In 1882, [[Philip Diehl (inventor)]] was awarded a patent for a kind of induction incandescent lamp.<ref>{{US patent|255497}}, Incandescent Electric Lamp, March 28, 1882</ref>

[[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.<ref>[http://www.tfcbooks.com/tesla/1891-05-20.htm "Experiments with Alternate Currents of Very High Frequency and Their Application to Methods of Artificial Illumination", AIEE, Columbia College, N.Y., May 20, 1891]</ref>
[[File:150W Magnetic Induction Lamp & Ballast.png|thumb|Example of a round 150 W magnetic induction fluorescent lamp]]

In 1967 and 1968, John Anderson<ref>[http://www.lamptech.co.uk/Documents/People%20-%20Anderson%20JM.htm John Anderson Biography at the Museum of Electric Lamp Technology]</ref> of [[General Electric]]<ref>[https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=3500118# Electrodeless gaseous electric discharge devices utilizing ferrite cores]</ref><ref>[https://worldwide.espacenet.com/publicationDetails/originalDocument?CC=US&NR=3521120# High frequency electrodeless fluorescent lamp assembly]</ref> applied for patents for electrodeless lamps. In 1971, [[Fusion UV Systems]] installed a 300-[[watt]] electrodeless microwave plasma [[UV]] lamp on a [[Coors Brewing Company|Coors]] [[Beverage can|can]] [[production line]].<ref>[http://www.fusionuv.com/history.aspx A History of Heraeus Noblelight Fusion UV and its Industry Leadership in UV Curing Equipment and Products<!-- Bot generated title -->] {{webarchive|url=https://web.archive.org/web/20120905045533/http://www.fusionuv.com/history.aspx |date=2012-09-05 }}</ref><ref>{{Cite web |title=Microwave-powered ultraviolet lamp |url=https://americanhistory.si.edu/collections/object/nmah_751059 |access-date=2025-01-17 |website=americanhistory.si.edu}}</ref> [[Philips]] introduced their ''QL'' induction lighting systems, operating at 2.65&nbsp;MHz, in 1990 in Europe and in 1992 in the US. [[Panasonic Corporation|Matsushita]] had induction light systems available in 1992.  Intersource Technologies also announced one in 1992, called the ''E-lamp''. Operating at 13.6&nbsp;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]]. 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.<ref name=":0" />

Since 1994, [[General Electric]] has produced its induction lamp ''Genura'' with an integrated [[Power supply|high frequency driver]], operating at 2.65&nbsp;MHz. In 1996, [[Osram]] started selling their ''Endura'' induction light system, operating at 250&nbsp;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&nbsp;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 (physics)|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.<ref>[http://www.prnewswire.co.uk/cgi/news/release?id=223764 Ceravision Steps up Legal Action Against Luxim to Recover IP]</ref> A number of the core patents were assigned to Ceravision.<ref>[https://archive.today/20120707161416/http://assignments.uspto.gov/assignments/q?db=pat&reel=022562&frame=0386 Microwave Energized Plasma Lamp with Solid Dielectric Waveguide]</ref><ref>[https://archive.today/20121220215656/https://register.epoline.org/espacenet/application;jsessionid=C1CBEEC558B6B0FBE3305A5D76DECA36.RegisterPlus_prod_0?number=EP01957305&tab=main Plasma Lamp with Dielectric Waveguide]</ref>

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 design|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-state electronics|solid state]] [[radio frequency]] (RF) [[driver circuit|driver]],<ref>{{Cite web |url=https://www.topangatech.com/ |title=Topanga technologies |access-date=2021-03-24 |archive-date=2021-03-14 |archive-url=https://web.archive.org/web/20210314091331/https://www.topangatech.com/ |url-status=dead }}</ref> 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 (unit)|lumen]]/watt, with a [[color rendering index|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.

==Plasma lamps==
{{Main|Plasma lamp}}
[[File:Induction Lamp FB 5000 W Soviet Union 1981.jpg|thumb|A 5 KW Soviet plasma xenon lamp made in 1981. The inner white spiral tube is for cooling.<ref>{{cite web |url=http://www.lamptech.co.uk/Spec%20Sheets/D%20ED%20Stella%20FB-3000.htm |title = Stella Electrodeless Xenon ФБ-3000 (FB-3000)}}</ref>]]

Plasma lamps are a family of light sources that generate light by exciting a [[plasma (physics)|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 (element)|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 [[electron excitation|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 (chemistry)|curing]] lamp with a bulb filled with argon and mercury vapor, developed by [https://web.archive.org/web/20150223042237/http://www.fusionuv.com/ 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{{clarify|reason=magnetrons, for instance in radar systems, have very very long lifetimes. Explain why this is not what is being discussed.|date=May 2020}} to over 40,000 hours<ref>[http://www.prnewswire.com/news-releases/ceravision--dipolar-form-global-alliance-to-take-ultra-efficient-lighting-technology-to-market-61908532.html Ceravision & Dipolar Form Global Alliance to Take Ultra-Efficient Lighting Technology to... - MILTON KEYNES, England, May 19 /PRNewswire/<!-- Bot generated title -->]</ref> 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)<ref>[http://www.nema.org/stds/LE5B.cfm Procedure for Determining Luminaire Efficacy Ratings for High-Intensity Discharge (HID) Industrial Luminaires] {{webarchive |url=https://web.archive.org/web/20090501182025/http://www.nema.org/stds/LE5B.cfm |date=May 1, 2009 }}</ref> 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).<ref>{{Cite web|url=https://www.ledsmagazine.com/company-newsfeed/article/16683678/luxim-launches-lifi-sta40-series-solidstate-plasma-light-sources|title=Luxim launches LIFI STA-40 series solid-state plasma light sources|date=2008-11-13|website=LEDs Magazine|language=en-us|access-date=2019-10-30}}</ref> It was also used in a line of, now discontinued, [[Panasonic]] rear-projection TVs.<ref>{{cite news|url=http://news.cnet.com/8301-17938_105-9675567-1.html|title=The gift of LIFI: Panasonic projection TVs don't burn out|date=2007-01-09|publisher=cnet}}</ref>

== Magnetic induction lamps ==
[[File:External Closed Core Induction Lamp with Two Turn Primary.svg|thumb|External closed core induction lamp with two turn primary]]
[[File:QL system components.svg|thumb|A 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 (electronics)|coupling]] energy into the [[mercury (element)|mercury]] vapor, these lamps are very similar to conventional [[fluorescent lamp]]s. Mercury vapor in the discharge vessel is electrically excited to produce short-wave [[ultraviolet]] light, which then excites internal [[phosphor]]s 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 (magnet)|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.

[[File:Internal Inductor-type Induction Lamp.svg|thumb|left|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.

[[File:2023-08-23 13 35 10 Induction florescent street light activated during daylight on utility pole 63424EW along Montague Avenue in the Mountainview section of Ewing Township, Mercer County, New Jersey.jpg|thumb|right|Induction street light]]
[[File:2023-08-23 13 35 20 Induction florescent street light activated during daylight on utility pole 63424EW along Montague Avenue in the Mountainview section of Ewing Township, Mercer County, New Jersey.jpg|thumb|right|Closer view of light]]
The discharge tube contains a low pressure of a rare gas such as [[argon]] and [[mercury (element)|mercury]] vapor. The mercury atoms are provided by a drop of liquid mercury, or by a semi-solid [[amalgam (chemistry)|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 253.7&nbsp;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 (radio)|antenna]] called a ''power coupler'', which consists of a [[electromagnetic coil|coil]] wound over a cylindrical [[ferrite (magnet)|ferrite]] [[magnetic core|core]].  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 [[hertz|MHz]], 2.65&nbsp;MHz and 250&nbsp;kHz. A special [[electrical resonance|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 discharge]] [[electric arc|arc]] in the bulb forming the one-turn secondary coil and the [[electrical load|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 60&nbsp;Hz, or on a voltage between 100 and 400 VDC for [[electric battery|battery]]-fed [[emergency light]] systems. Many drivers are available in low voltage models so can also be connected to [[direct current|DC voltage sources]] like [[lead-acid battery|batteries]] for emergency lighting purposes or for use with renewable energy ([[solar power|solar]] and [[wind power|wind]]) powered systems.

In other conventional gas discharge lamps, the [[electrode]]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 circuit]]s 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===
[[File:BigBenAtDusk.jpg|thumb|right|upright=0.6|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);

===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 [[Federal Communications Commission|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.

==See also==
* [[List of light sources]]
* [[Induction cooker]]

==References==
{{Reflist}}

==External links==
* [http://www.lamptech.co.uk/Electrodeless.htm Electrodeless Induction Lamps], Museum of Electric Lamp Technology

{{Artificial light sources}}

[[Category:Gas discharge lamps]]