Induction lamps operate without electrodes, instead using an alternating magnetic field to induce current in mercury vapor which produces light. They have advantages over fluorescent lamps like longer lifespan up to 100,000 hours. Different types of induction lamps exist including cavity lamps with internal coils and external-coil lamps resembling transformers. Induction lamps open new possibilities for lighting design and performance.

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FLUORESCENT INDUCTION
Electrodeless Lamp

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OPENING NEW FRONTIERS FOR LIGHTING
l IT IS IMPOSSIBLE TO IMAGINE MODERN LIFE
WITHOUT ELECTRIC LIGHTING. WITH THE WIDE
AVAILABILITY AND AFFORDABILITY OF TODAY’S
LIGHTING, PEOPLE THROUGHOUT THE WORLD
ARE FREE TO PLAY, AND LEARN VIRTUALLY
ANYWHERE, ANYTIME.
Continued innovation in lamps and other system components, as
well as in design practices, have made lighting progressively more
effective, efficient, and economical since Edison’s time.
Electrodeless Lamps continue to make breakthrough innovations in
design and affordability.

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Introduction to Induction Lighting
Induction lamps are high frequency (HF) light sources, which follow the same basic
principles of converting electrical power into visible radiation as conventional fluorescent
lamps. Fig. 1 below shows the operating principle of a fluorescent lamp.
The fundamental difference between induction lamps and conventional lamps is that
the Induction Lamps operate without electrodes. Conventional fluorescent lamps
require electrodes to connect the discharge plasma to an electrical circuit and inject
electrons into the plasma. Fluorescent lamps normally operate on ac current at a
frequency of 50 Hz or at HF of 40 to 100 kHz when driven by electronic ballasts.
Thus, each electrode operates for one-half period as a cathode and the other half
period as an anode. The production of electrons from electrodes is due to
thermionic emission. The presence of electrodes in fluorescent lamps has imposed
many restrictions on lamp design and performance and is a major factor limiting
lamp life.

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Introduction to Induction Lighting
Induction lighting is based on the well-known principles of induction and light generation via a gas
discharge. Induction is the energy transportation through magnetism. Practical examples are
transformers, which consist of ferrite cores or rings with primary coils and secondary rings via the
mercury vapour inside the lamps. Fig. 2 and Fig. 3 show two typical induction lamp types, and their
principle of operation, which are commercially available today. An alternative current Ip? through the
primary coil induces an alternative magnetic field in the ferrite core or coil. The alternative magnetic
field in turn induces an alternative secondary current in the secondary coil or ring (Is). The efficiency of
the lamp is proportional to the operating frequency of the driving alternative current.
Fig. 3: External-coil Type Induction Lamp
The mercury vapor inside the induction lamp can be regarded as the secondary coil of the
system and the induced current circulate through the vapor causing acceleration of free
electrons, which collide with the mercury atoms and bring electrons to a higher orbit.
Fig. 2: Cavity Type Induction Lamp Electrons from these excited atoms fall back from this higher energy state to the lower
stable level and consequently emit ultraviolet radiations. The UV radiations interact with the
fluorescent powder coated inside the lamp and convert to visible light.

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Advantages of Induction Lighting
The loss of cathode emission materials, due to evaporation and sputtering caused by ion
bombardment, limits the life of fluorescent lamps to between 5,000 to 20,000 hours, while
the life of induction lamps on the market today reaches 100,000 hours. This makes it
beneficial to use such lamps in applications where lamp maintenance is expensive
(e.g. High Ceiling Applications where accessibility is costly for building owners or Locations where accessibility for safety reasons are a
concern (Fig. 4 & 5)).

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Advantages of Induction Lighting
The elimination of electrodes and their power losses opens up
unlimited possibilities in the variety of possible lamp shapes and
increases their efficiency respectively. The presence of hot electrodes
limits the fill gas pressure and its composition to avoid chemical and
physical reactions that destroy the electrodes. There is no such
restriction in induction lamps, where gas pressure is optimized for
maximum efficiency.
As far as lamp rating of fluorescent lamp is concerned, cathode
emission takes place from a tiny spot heated by the discharge current,
which cannot be over 1.5A – this limits the maximum power rating and
light output of these lamps (e.g. the highest rating of high output T5
lamp is 80W).

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Advantages of Induction Lighting
For induction lamps, there is no such restriction and rating of lamp
could be up to 200W (e.g. 200W AES Saturn long life lamp as shown in
Fig. 6). Theoretically, induction lamps have instant and harmless
starting and are more convenient for dimming, as maintenance of high
cathode temperatures during dimming are no longer required.

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Benefits of Induction Lighting
l 100,000 Hour Life
l .99 Power Factor
l Wide range of Color Temperatures 2700K~6400K
l Instant Start at –35•‹
C
l Instant Re-Strike
l Wide Operating Temperature –35•‹ C~90•‹C
l System 80-90 Lumens per Watt
l Excellent Lumen Maintenance
l 100% Flicker Free
l Excellent CRI (Color Rendering Index) 80-95

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TYPES OF INDUCTION LIGHT SOURCES
There are several commercial available induction lamps in the lighting
market currently. The development of induction lamps involve decades of
effort in researches on relevant gas discharge physics, solid-state physics,
material science and electronic ballasts. The outcome is to bring the
induction lighting concepts to engineering and to products in the
commercial markets today. Advances in diverse technology fronts promise
to drive down the cost and multiply the capabilities of microchips and
photovoltaics, opening the way to new levels of performance and freedom
of standard design practices.

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TYPES OF INDUCTION LIGHT SOURCES
The cavity design has the advantage of reassembling the shape of an incandescent lamp. The
cavity at the centre of the lamp is used to accommodate the induction core and coils (Fig. 7).
This electrodeless fluorescent induction lamp operates at 2.65 MHz with system power 55W and an
efficacy of about 70 lm/W. The 2.65 MHz is specifically allocated in according to IEC regulations, for
industrial application as radio frequency lighting devices. Lamps having the higher rating of 85W and
165W are also available for application where high intensity lighting is required. The lamp is filled with
argon at 0.25 Torr. Mercury pressure is controlled by two amalgams: one is for lamp starting and the
other maintain optimal mercury pressure over a wide range of ambient temperature. The induction
coil of the lamp is wound on a ferrite core and is housed within the lamp cavity. The ferrite core has
an internal copper conductor rod connected to the lamp base for cooling of the induction cool and
cavity. These lamps are driven by remote ballasts connected to the lamps by coaxial cables.

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TYPES OF INDUCTION LIGHT SOURCES
Another version of cavity induction lamp is designed to
integrate the RF generating ballast into the lamp (Fig. 8). This
kind of induction lamp looks similar to a compact fluorescent
lamp and could be used to directly replace an incandescent
reflector lamp with much higher efficacy and longer service
life. The lamps operate at the same frequency of 2.65 MHz
but have lower lamp power of 23W at 48 lm/W efficacy, and
the lamp life is rated up to 15,000 hours. EMI is the major
restriction of using these lamps in sensitive areas and
significant efforts have been made for suppressing magnetic
and electric components to comply with existing EMC
regulations. The cost of the lamp is over $50.00 at the
moment and is relatively much higher than those of tungsten
and compact fluorescent lamps. Fig. 8: Self-ballasted Cavity
Induction Lamp

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TYPES OF INDUCTION LIGHT SOURCES
The external-coil induction lighting system is shown in
Fig. Fig. 9. The likeness to a standard transformer of
this lamp is more apparent than for any other induction
lamps. The lamp is made from a 54 mm diameter tube
encircled by two closed ferrite cores. The lamp rating
available are 15W~200W at an efficacy of up to 95
lm/W. The designed operating frequency is 250 kHz
only, which is not governed by the radio frequencies
allocated for industrial applications such as 2.65, 13.56,
27.12 and 40.68 MHz. The decrease in working
frequency has virtually eliminated EMI problems, ballast
complexity, and cost as compared to other induction
lamps working at 2.65 MHz.
Due to the closed magnetic path of the ferrite cores, the
power-transfer efficiency and efficacy of this lamp are
extremely high; they are 98% and 95 lm/W respectively.
The rated life of this induction lighting system is
100,000 hours, which is determined by the life of
electronic ballast but not the lamp. The high system
efficiency is achieved by the distributed power
deposition along the lamp in contrast with the cavity
induction lamp where power transfer is localized around Fig. 9: External-coil induction lamp
the coupling induction coil, causing local thermal stress
and overheating that limits maximum lamp power.