Transcript incandescant lamps

History and Evolution
PLATINUM AND IRIDIUM FILAMENTS: 1802 -1880'S
• Humphry Davy created the first incandescent light by
passing current through a platinum strip. It caused a
glow and did not last long, but marked the beginning of
incandescent light development. Experimenters
continued over the next 70 years to use platinum and
iridium. Frederick used a platinum filament in an
evacuated glass tube to make a light bulb.
• Early inventors knew that making a vacuum in a bulb
would help reduce blackening and lengthen bulb life,
the problem was ways to better create a vacuum had
to be developed.
CARBONIZED THREADS AND PAPER: 1860'S - 1883
Edison first used carbonized sewing thread as a
filament, he managed to get it inside a vacuum.
This made his first practical lightbulb. He used
carbonized sewing threads until 1880. Then he used
paper bristol board. (Carbonized paper) This move
increased lamp life to 600 hours.
Edison figured out how to create a pure vacuum in
his bulbs. He did this by heating up the bulb at the
same time that he pumped out the air. He used a
Sprengle pump.
SINTERED TUNGSTEN FILAMENTS: 1904 -1911
• In 1904 sintered tungsten is developed by
Alexander Just and Franz Hanaman
(Austria). Tungsten improves the lamps
efficiency by 100 % and is used by GE in
1907 after it buys the rights for it.
• Tungsten and Molybdenum filaments were
used by A.N. Lodygin (Russia) in a 1900
"Exposition Universelle" in Paris
DUCTILE TUNGSTEN FILAMENTS: 1908 - TODAY
• William D. Coolidge had been working with
tungsten which proved to be a superior material for
a long lasting lightbulb over any other material to
date. Previous tungsten filaments had been
efficient, but brittle and not practical. Coolidge
figured out how to heat tungsten and draw it out
through heated dies of decreasing diameter. The
result of his work was a workable, bendable
(ductile) wire that was high strength and made a
great filament material. The new material was used
in bulbs in 1911 and this is still used today.
CONSTRUCTION
• Incandescent light bulbs consist of an air-tight glass
enclosure (the envelope, or bulb) with a filament
of tungsten wire inside the bulb, through which
an electric current is passed. Contact wires and a base
with two (or more) conductors provide electrical
connections to the filament. Incandescent light bulbs
usually contain a stem or glass mount anchored to the
bulb's base that allows the electrical contacts to run
through the envelope without air or gas leaks. Small
wires embedded in the stem in turn support the
filament and its lead wires.
• Most light bulbs have either clear or coated glass.
The coated glass bulbs have a white powdery
substance electrostatically deposited on the
inside called kaolin. It diffuses the light emitted
from the filament, producing a more gentle and
evenly distributed light. Manufacturers may add
pigments to the kaolin to adjust the characteristics
of the final light emitted from the bulb. Kaolin
diffused bulbs are used extensively in interior
lighting because of their comparatively gentle
light.
1- Outline of Glass bulb
2- Low pressure inert gas
- (argon, nitrogen, krypton, xenon)
3- Tungsten filament
4- Contact wire (goes out of stem)
5- Contact wire (goes into stem)
6- Support wires (one end
embedded in stem; - conduct no
current)
7- Stem (glass mount)
8- Contact wire (goes out of stem)
9- Cap (sleeve)
10- Insulation (vitrite)
11- Electrical contact
WORKING
• Incandescent bulbs work by sending electric current through a
resistive material. Filaments are made from materials that have a
high melting point. The electric current heats the filament to
typically 2,000 to 3,300 K (3,140 to 5,480 °F), well below tungsten's
melting point of 3,695 K (6,191 °F). Filament temperatures
depend on the filament type, shape, size, and amount of
current drawn. The heated filament emits light that
approximates a continuous spectrum. The useful part of the
emitted energy is visible light, but most energy is given off as
heat in the near-infrared wavelengths. Other materials have
made good filaments or parts of filaments including tantalum,
molybdenum, and carbon.
When current flows through the filament, atoms in the
material absorb energy and electrons around the atoms are
excited They temporarily reach an orbital which is further
from the nucleus. When the electron orbit collapses to a
lower orbital it ejects the extra energy in the form of a
photon and heat.
Incandescence is thermal radiation. Heat is constantly
emitted from objects around us, we just can't see it. When
heat gets intense enough it reaches wavelengths that we
can see. It starts with red and goes up the spectrum. The
wavelength/colour of the light depends on how much
energy is being released and what kind of atom is doing the
release. In an incandescent bulb most of the heat energy
(90%) is emitted in the infrared spectrum which is just below
visible light. This is also what makes the lamp inefficient.
1884 Johann Wilhelm Hittorf discovers the electrodeless discharge lamp.
Hittorf is also known for the discovery of the cathode-ray tube in 1869.
1891: J.J. Thomson made induction lamp to study electromagnetic fields
but there was no phosphor on the bulb. Only the circular part of the
glass bulb glowed with an arc discharge. His work did not focus on
creating consumer product.
1893: Tesla demonstrating wireless power transferred through the air by
electromagnetic fields created by the Tesla coil . 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.
1904 Peter Cooper Hewitt develops both internal and external induction
lamp designs which are the first to use mercury vapor. Mercury is
inserted into the spheres, then impurities are removed before sealing the
vessel.
1967 John 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.
1990s Philips Corporation develops the QL induction lamp series. The
lamps operated at 2.65 MHz
(Osram has its own line called the Endura which operates at 250 kHz)
1990 Michael 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.
2000s Andrew Neate develops the HEP lamp (High Efficiency Plasma).
This lamp is a cross between the induction lamp and a metal halide
lamp.
CONSTRUCTION:
1)The lamp has three parts: frequency generator (ballast),
discharge tube or bulb and electromagnet (i.e.: inductor, energy
coupling coils or energizing coils).
2)The ballast is present in series with the discharge tube or the
bulb.
3)The tube or the bulb has a small projection in which the mercury
amalgam is filled.
4)There is an layer of phosphor present on the in side of the wall
of the discharge tube or the bulb.
5)The electromagnet can be present inside or out side of the
discharge tube or the bulb. Depending on which the induction
lamps are of two types
TYPES
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 type
INTERNAL CORE TYPE
MAIN DIFFERENCE:
• 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
• In the internal core form, a
glass tube contains an
antenna called a power
coupler, which consists of a
coil wound over a
cylindrical ferrite core.
HOW IT WORKS:
• Induction 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.
• First the ballast creates high frequency current
(between 2.51-3 MHz or 250 kHz for closed ferrite
toroid(external lamps)).
• 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).
• Energy is transferred from the magnet to the
mercury in the tube through induction.
PRODUCTION OF UV RAYS
1) The discharge tube contains a low pressure of a rare gas
such as argon and mercury vapor.
2) The mercury atoms are provided by a drop of liquid
mercury or by a semi-solid amalgam of mercury and other
metals such as bismuth, lead or tin.
3) 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.
4) 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.
• This UV photon strikes inner coating of induction
lamp to cause fluorescence.
INCANDESCENT LAMP Advantages
• Inexpensive and have low initial cost.
• easy to use, small and does not need auxiliary equipment
choke(ballast).
• easy to dim by changing the voltage.
• excellent color rendering properties.
• directly work at power supplies with fixed voltage.
• free of toxic components.
• instant switching.
• used in desk lamps, table lamps, hallway lighting.
• these lamps have low initial cost.
INCANDESCENT LAMP
DISADVANTAGES
• short lamp life (1000 hrs).
• low luminous efficacy(60-80 l/W).
• heat generation is high.
• lamp life and other characteristics are strongly
dependent on the supply voltage.
• the total costs are high due to high operation cost.
• Least efficient lamps on the market.
INDUCTION LAMP
ADVANTAGES
• Very long life(60,000-100,000hrs)
• Have high energy conversion efficiency 60 l/w -90 l/w.
• Provide incredible energy savings
• They are environment friendly containing solid amalgam
mercury which is easily recyclable, some other commercial
lamps contain hazards liquid or gas type mercury.
• They use least amount of hg compared to other lamps
INDUCTION LAMP
DISADVANTAGES
• Induction bulbs are physically larger than some other
lightening technology which makes them unsuitable for
some application where a compact light source is
required.
• Induction bulbs are available in a limited range of colors
and cannot produce color change lightening.