The induction lamp is a promising technology which features good efficiency
and long life. The induction lamp was conceived early on by Nobel laureate
J.J Thomson. It was not until the 1960s-1970s when patents for a practical
induction lamp were filed by both General Electric and Philips (more
on inventors at the bottom of this page). Even
then it was not until the 1990s that induction lamps began to see use
on a wider scale. They still have not reached full market potential
yet and there is still work to do to improve the lamp. All
credits and sources are located at the bottom of each lighting page
-Longer life: no electrodes, electrodes
fail in normal fluorescent lamps shortening life, the tungsten
thins and brakes.
-Longer life: sealed tube, by not having electrodes the
tube can be perfectly sealed, when seals go bad in regular fluorescent
lamps gas escapes through the weakness and the lamp fails.
-Energy efficient, often 80+ lumens per watt
-Dimmable 30 -100%
-Can light both small and large areas depending on which type
of induction lamp one uses
-Bulky design for large area lighting, the discharge
tube is large compared with HID lamps.
-New and Old technology: it is new: it is still expensive to buy
the lamps. It is old: most companies that make the lamps are using
20 year old ballast technology copied from OSRAM and Philips.
The ballasts have a high failure rate.
- The technology is under commercialized.
-Radio interference is a major problem to be worked out.
The lamps are limited in use due to this issue.
A video on induction
lamps will be added here soon.
Lamps create light by using an electromagnetic field to excite
mercury particles mixed in an inert gas like argon or krypton. The mercury
creates a UV light and a phosphor on the inside of the bulb or tube
filters the energy into visible light. This is a type of fluorescent
light. Unlike a standard fluorescent light this does not use electrodes
in the tube.
lamp has three parts: frequency generator (ballast), discharge tube
and electromagnet (aka: inductor, energy coupling coils or energizing
First the ballast creates high frequency
current (between 2.51-3 MHz or 250 kHz for closed ferrite toroid(external lamps)).
2. The current is sent through the electromagnet and an electric field
is produced. The number of turns (times the wire is wrapped around the
iron core) is determined by how each product is designed (so it is not
consistent among different lamps).
3. Energy is transferred from the magnet to the mercury in the tube
in the same way that a transformer works... induction.
4. The mercury vapor emits UV light which strikes the phosphor and makes
light. GE Genura and Philips QL lamps have a conductive coating to contain electromagnetic
Note on mercury use: Induction lamps use a mercury amalgam, amalgams consist of mercury
chemically combined with other metals. The mercury amalgam is in a chemically stable state
and is not harmful in the way that pure mercury vapor is.
Mercury amalgams have been used in dental fillings for over 1000 years.
The HEP induction lamp works differently, it uses a nobel gas
with metal halide salts to create a high intensity light. The
HEP also uses a magnetron to create microwave frequencies, it
is described later on.
ballast is made of four parts. First is an EMI filter to
reduce harmonics from the supply of alternating current. The
next part is a bridge rectifier, this converts AC to DC power.
After that is the PFC circuit which boosts the DC voltage to
a constant 400 V value and increases the power factor to 0.95+.
The final part of the ballast is an inverter which converts
the DC power to high frequency AC. For a more advanced discussion
of the ballast and control read here.
John Anderson at GE developed the first commercial induction
lamp, building upon earlier work by Peter Cooper Hewitt. Mr. Anderson's
breakthrough prototype used a frequency of 13.56 MHz with air core coupler.
The induction lamp can potentially have the longest life of any light source if the ballasts
are made with quality in mind. External Induction Lamp:
external induction lamp lasts the longest due to its design which allows
waste heat to escape directly into the air from the coil. Internal Induction Lamp: 60,000-75,000
The internal induction lamp has the coil buried in the glass envelope
bulb. The waste heat eventually damages the induction assembly, see
below to learn more about the types of induction lamps.
are three kinds of induction lamps: external, internal and HEP
External Induction Lamp - this uses
an induction coil mounted outside of the bulb or tube. The metal coil
which is covered by a sheath is clearly visible. A soft or rubberized
material is used to prevent the metal ring from coming in direct contact
with the glass tube.
High frequency energy is sent from the ballast to the electromagnet.
This creates a powerful magnetic field, this excites the mercury amalgam
in the protruding small tub (see diagram below). It is normal for mercury
when it cools from a vapor form to escape to the coolest part of a bulb
or tube, this is usually on the ends of a standard fluorescent tube
or HID discharge tube. The small tube is designed to consistently capture
the mercury after the lamp is turned off. The tube is located close
to the inductor so that the powerful magnetic field easily excites the
mercury. The mercury vaporizes and spreads throughout the rest of the
tube. It continues to be excited since the magnetic field reaches more
than 6 inches in the examples below. If the lamp is large enough two
inductors are needed to keep the entire tube area excited. Just as in
a standard fluorescent lamp, the mercury vapor creates UV and this is
converted into visible light via the phosphor.
There may be more than one
mercury amalgam, others are called assistant amalgams and are located
close to the induction assembly.
there are two coils on the lamp (above) than both coils are wired
in parallel, not in series.
Left: Some external induction lamps are small with a single electromagnet. The
electrical field follows a loop within the discharge tube, flowing from positive
to the negative side of the electromagnet.
Internal Induction Lamp - this works
on the same principle as the external induction lamp except that the
electromagnet is placed inside of the glass bulb. This is typically
used when you need a small lamp in a normal household socket.
is not likely to be 70,000 hours as low cost ballast electronics will likely fail
induction lamps for household use start at 7 USD as of 2012.
Prices will drop and the light may become more popular as an
alternative to higher priced LED bulbs. At the time of writing LED units were more
expensive to produce than induction lamps, that could change however.
High Efficiency Plasma (HEP)
new type of induction
lamp has been developed called the high efficiency plasma or HEP.
The HEP lamp performs at 90 lumens per system watt.
Components: It uses a quartz RF resonator and integral plasma
burner with a transition unit and magnetron. The integrated burner
use metal halide salts and an inert gas. Microwave energy within
the lamp resonates and ionizes the gas, this combines with metal
halides to make an intense white light. Read more from its manufacturer
The HEP lamp is a "Plasma
Lamp" just like the LEP. The LEPwas developed earlier in 2001, it uses a dielectric waveguide made
of ceramic. Much of the light was lost in the ceramic waveguide resulting
in loss of efficiency. Ceravision changed the design using a clear quartz
waveguide which improved the lamp and forms what we call the HEP.
The sulfur lamp is
also a plasma lamp. It uses microwave radiation to excite sulfur
vapor mixed with argon to create light. 2.45 GHz radiation hits
a electrodeless bulb that contains a sulfur powder. You can identify
the lamp by a metal screen on the outside of the lamp. The bulb
operates at a very high temperature and most models needs a fan
The lamp was developed
in the 1990s and failed to be a commercial success. It may come
back into the public eye as it is improved. Improvements include
eliminating the fan. Today the lamp is sold in limited numbers
by LG under the name Plasma Lighting System (PLS).
3. Inventors and Developments
Above: J.J. Thomson built various induction lamps to study the
electromagnetic field, however his work did not focus on creating consumer
products. He is more well known for the discovery of the electron and
developments in x-ray/cathode ray tubes.
1884Johann Wilhelm Hittorf discovers the electrodeless
discharge lamp. Hittorf is also known for the discovery of the
cathode-ray tube in 1869 Munster, Germany
1880sJ. J. Thomson thoroughly studies the phenomena
of the electrodeless discharge lamp after initial discovery
by Johann Wilhelm Hittorf (1884). Thomson like Hittorf is an
established physicist. Cambridge,
1893Nikola Tesla first demonstrates
his electrodeless lamp at the 1893 World Columbian Exposition
in Chicago. His lamp looked like a large lightbulb and had strange
greenish phosphors. His lamp was powered by the electromagnetic
field of a nearby large "Tesla Coil". Tesla brought
the lamp into the public eye and further improved the lamp.
The industrialist later sued academian J.J. Thomson in order
to secure rights to try to make money from it. A practical consumer
lamp was never developed. New York, NY
Peter Cooper Hewitt developed an induction lamp that
used mercury vapor (like today's lamps). He already had
expertise as the inventor of the first commercial mercury
vapor lamps. He worked on induction lamps with a sphere
shape and double sphere shape, with external induction coils
wrapped around the sphere or "waist" of the double
sphere. PC Hewitt also developed internal induction lamps. General
Electric, New York, NY
1967John Anderson develops the
first reliable electrodeless lamp. The induction lamp moves
out of experimental stages and the commercial era of the lamp
begins. Later his compact GENURA lamp was released in 1994.
Anderson was a professor at Rensselaer Polytechnic Institute
and employee of General Electric with 27 patents related to
lamp technology. He also advanced regular
fluorescent lamps. Read
more on Anderson's work. Schenectady,
1990sPhilips Corporation (no names available)
develops the QL induction lamp series. The lamps operated at
2.65 Mz. Nederlands
1990Michael Ury, Charles Wood develop
the sulfur lamp, the first form of "plasma lamp" which
uses microwave energy to energize sulfur in a sealed bulb. The
US Department of Energy and Fusion Lighting developed this lamp.
The sulfur lamp led to the LEP and HEP lamp later on. Rockville,
Neate developes the HEP lamp (High Efficiency Plasma).
This lamp is a cross between the induction lamp and a metal
halide lamp. Ceravision. Also see LEP
lamps listed on our metal halide page. Neate developed a
quartz waveguide that increases efficiency.
Keynes, United Kingdom
2005? at Amko Solara develops
the dimmable fluorescent induction lamp which operates at 250
Help us complete this history if you know who was the inventor.
has its own line called the Endura which operates at 250 kHz
1891: J.J. Thomson's induction lamp was used to study electromagnetic
fields and there was no phosphor on the bulb. Only the circular part
of the glass bulb glowed with an arc discharge. Thomson's work set the
stage for later inventors like Tesla and Peter Cooper Hewitt. Learn
more about J.J. Thomson from the book: J.J.
Thomson and the Discovery of the Electron by E.A. Davis and Isobel
1893: Tesla demonstrating wireless power transferred through the air
by electromagnetic fields created by the Tesla coil in Chicago. His
demonstration attracted a lot of attention, however the invention needed
a lot of work to become practical. RFI/EMI and severe safety issues
were the major problems with wireless lamp power. His use of phosphors
in the induction lamp are a lasting contribution to the modern incandescent
lamp. Phosphors were first used in regular electrode lamps as early
as the 1859 by Alexandre-Edmond Becquerel
1904 Peter Cooper Hewitt develops both internal and external
induction lamps which are the first to use mercury vapor. Mercury is
inserted into the spheres, then impurities are removed before sealing
the vessel. Below are four different configurations.
Help us edit and add to this page by becoming a ETC volunteer! Give us feedback
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by M.Whelan with additional research by Rick DeLair and Dr. Victor Roberts
Please contact us if you are a historian and wish to correct or improve
"A Consideration on the electrodeless fluorescent lamp and its
radio interference characteristics". Jin-Dam Mok, Sang-Bong Jeon,
Seun-Keun Park. IEEE Xplore Digital Library.
www.Electriciansforum.co.uk Induction Lighting
Environmental Aspects of Magnetic Induction Lamps by L. Michael Roberts
and Jim Morelli
JJ Thomson and the Discovery of the Electron by I.J. Falconer
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