What
is Fluorescent Lamp | The Fluorescent tube consists of a
glass tube 25mm in diameter and 0.6mt, 1.2mt and 1.5 mt in length. The tube
contains argon gas at a low pressure of 2.5 mt and one or two drops of mercury and
inside surface of the tube is coated with a thin layer of Fluorescent material
in the form of a powder.
The
coating material used depends upon the color effect desired and may consist of zinc
silicate, cadmium silicate or calcium tungsten. These organic chemicals are
known as phosphorous which transformers short waves invisible radiation into
visible light. At the start, a current is passed through filaments which get
heated up and emit electrons. This is achieved by the use of choke with a starter.
The
choke is connected in series with the tube which acts as ballasts in running
conditions and provides a high voltage impulse or surge for starting. At the
time when the switch is operated the starter is provided and the electrodes get
heated and start emitting sufficient electrons. The switches or starters are of
two types:
a)
Thermal type starter b) Glow type starter
The
bimetallic strips of the starter are normally open. When the supply is switched
ON, full voltage is available across the bimetallic strips of the starter. This
discharge heats the bimetallic strips of the starter causing them to bend and
make contact. Now the tube filaments get heated and emit electrons inside the
tube due to the flow of current.
Now
the voltage across the strips of the starter is reduced to zero. Hence the
bimetallic strips cool down and the contacts open. Due to the change of
current, high voltage is induced in the choke e=L di/dt. The high voltage
produces an arc between the filaments of the tube. Hence the mercury in the
tube discharges and the tube emit light.
After
the establishment of light in the tube, the voltage maintains light is reduced
to 110V. As the tube current flows through the choke, sufficient voltage drop
occurs in the choke. Thereby allowing only the required voltage to be applied
across the tube. Also, the choke limits the current in the lamp circuit. Due to
the choke, the power factor of the circuit is low. Hence to improve the power
factor a capacitor is connected across the supply.
![]() |
Fluorescent Lamp |
Advantages
- Efficiency and life under normal conditions are three times of those for filament lamp.
- The quality of the light obtained is much superior.
Since
the stroboscopic effect is present, they are suitable for semi-direct lighting,
domestic, industrial, commercial, roads and halls, etc.
What is Compact Fluorescent Lamp?
A
CFL is a fluorescent lamp designed to replace an incandescent light bulb. The
Compact fluorescent lamp is also called compact fluorescent light,
energy-saving light, and compact fluorescent tube. Some types of CFL fit into
light fixtures designed for incandescent bulbs. Compact fluorescent light use a
tube which is curved or folded to fit into the space of an incandescent bulb. A
compact electronic ballast in the base of the CFL.
Compact Fluorescent Lamp Working Principle
The
electrons that are bound to mercury atoms are excited to states where they will
radiate ultraviolet light as they return to a lower energy level. This emitted
ultraviolet light is converted into visible light as it strikes the fluorescent
coating as well as into heat when absorbed by other materials.
![]() |
Compact Fluorescent Lamp - CFL |
Two Main Components of Compact Fluorescent Lamp
ballast and a gas-filled tube where ballasts
contain a small circuit board with a bridge rectifier, a filter capacitor and
usually two switching transistors, which are often insulated-gate bipolar
transistors. The incoming alternating current is first rectified to direct
current and then converted to high-frequency AC by the transistors, connected
as a resonant series DC to AC inverter. The resulting high frequency is applied
to the CFL tube.
Since
the resonant converter tends to stabilize lamp current over a range of input
voltages. Lamps emit light from a mix of phosphors, each emitting one band of
color with some bands still in the ultraviolet range as can be seen on the
light spectrum. This is the reason why additional UV filtering, is required to
reduce damage to the retina.
Compact
fluorescent lamp output is roughly proportional to the phosphor surface area.
Typical shapes of CFL light tubes are a helix with one or more turns, multiple
parallel tubes, circular arc, or a butterfly. Lamps use three or four phosphors
to achieve a pure white light with a color rendering index of about 80, where
the maximum 100 represents the appearance of colors under daylight or other
sources of black-body radiation such as an incandescent light bulb.
Types of Compact Fluorescent Lamp
1.
Integrated
2.
Non-integrated CFL
Integrated CFL
The
type of lamps combines a ballast and the tube in a single unit. Integrated
lamps allow peoples to replace incandescent lamps easily with CFLs. This type
of CFLs works well in any standards. Incandescent lights, reducing the cost of
converting to fluorescent. Dimmable models with three-way lamps with standard
bases are available easily.
Non-integrated CFL
The
lamps have the ballast permanently installed in the luminaries. This type of
CFL housings can be both more expensive and sophisticated. There are two types
of tubes available in the Non-integrated CFL are
1.
A bi-pin tube designed for conventional ballast,
2.
A quad-pin tube designed for electronic ballast or conventional ballast with an
external starter.
Comparison of Compact Fluorescent Lamp with Incandescent Lamp
If
incandescent lamps are replaced by CFLs, the heat produced due to lighting is significantly
reduced. In office or buildings where A/c (air conditioning) is often required,
CFLs reduce the load on the cooling system when compared to the use of
incandescent lamps, resulting in savings in electricity in addition to the
energy efficiency savings of the lamps themselves.
Compact Fluorescent Lamp
|
Incandescent Lamp
|
Typically have a rated service life of 6000 –
15000 hours.
|
750 to 1000 hours of service life.
|
Incandescent lamps giving the same amount of
visible light, CFLs use one-fifth to one-third the electric power and last
eight to fifteen times longer.
|
Electric power consumption is high while
comparing CFLs
|
Its purchase price is higher than the
incandescent lamp, but less electric bill charge.
|
Electric bill charge is the high but purchasing
price is low.
|
Its radiate a spectral power distribution that
is different from that of incandescent lamps
|
Improved phosphor formulations have improved
the perceived color of the light emitted by CFLs, such that some sources rate
the best "soft white" CFLs as subjectively similar in color to
standard incandescent lamps
|
Limitations of Compact Fluorescent Lamp
- The lamps, like all fluorescent lamps, contain mercury as vapor inside the glass tubing.
- CFLs contain toxic mercury which complicates their disposal. In many countries, governments have banned the disposal of CFLs together with the regular garbage.
- Most CFLs contain 3–5 mg per bulb, with the bulbs labeled "Eco-friendly" containing as little as 1 mg.
- Because mercury is poisonous, even these small amounts are a concern for landfills and waste incinerators where the mercury from lamps may be released and contribute to air and water pollution.
- Health and environmental concerns about mercury have prompted many jurisdictions to require spent lamps to be properly disposed of or recycled, rather than being included in the general waste stream sent to landfills.
Final Word
Hope you understand this article
about the What is Fluorescent
Lamp and CFL. In case of any doubt please comment
below. Please follow our website for future updates. Thank you for visiting our
website @Electrical2z.
Thanks for sharing your knowledge!
ReplyDeletePost a comment