Embed Size (px)
DESCRIPTION
training
Citation preview
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
WELCOME
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Slide No. 2
LIGHT
From the view point of physics, light is regarded as that portion of the electromagnetic
spectrum which lie between the wavelength limit of 380 nanometers and 770
nanometers. Visually there is some individual variation in these limits.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Slide No. 3
Some Basic Parameters
Luminous flux
Luminous flux or luminous power is the measure of the perceived power of light. It differs from radiant flux, the measure of the total power of light emitted, in that luminous flux is adjusted to reflect the varying sensitivity of the human eye to different wavelengths of light.The SI unit of luminous flux is the lumen (lm). One lumen is defined as the luminous flux of light produced by a light source that emits one candela of luminous intensity over a solid angle of one steradian.
Luminous Intensity
Quotient of the luminous flux leaving the source propagated in an element of solid angle containing the given direction, by the element of a solid angle. The SI unit of luminous intensity is Candela (cd)Is the expression of light lumen emitted by light source in a given direction per unit solid angle
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Slide No. 4
Luminous efficacy
The luminous efficacy of a source of light is the quotient of the total lumen luminous flux emitted divided by the total lamp power input .
Illuminance
In photometry, illuminance is the total luminous flux incident on a surface, per unit area. The SI unit of illuminance is Lux.Is the quantity of light emitted by a light source at a distance of 1 m on a surface having area of 1 sq.m
Coefficient of utilization
A coefficient of utilization (CU) is a measure of the efficiency of a luminaire in transferring luminous energy to the working plane in a particular area.The CU is the ratio of lumens from a luminaire, incident upon a work plane relative to the lumens emitted by the lamps within the luminaire
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Slide No. 5
Maintenance Factor
It takes into account the reduction of luminous flux lumen due to the soiling of the luminaire. It is the ratio of the average illuminance on the working plane after a specified period of use of a lighting installation to the average illuminance obtained under the same conditions for a new installation.
Correlated Colour Temperature
Temperature of a black body which emits radiation having chromaticity nearest to that of the light source under consideration.
CRI
The color rendering index (CRI) is a quantitative measure of the ability of a light source to reproduce the colors of various objects faithfully in comparison with an ideal or natural light source. Light sources with a high CRI are desirable in color-critical applications.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
Glare
This is defined as a condition of vision in which there is discomfort or a reduction in the ability to see significant objects, or both. This may occur due to an unsuitable distribution or range of luminance or due to extreme contrasts in space or time.
Generally two types of glares are discussed – Disability and Discomfort Glare. Disability glare impairs the vision of objects without necessarily causing discomfort. This generally happens due to scattering of light, either directly from a light source or due to internal properties of eye. Discomfort glare takes place due to extreme contrast of a light source either in respect of background illuminance or due to variable luminance with respect to time. Lack of proper shielding, improper positioning or improper direction may cause glare of a light source.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Slide No. 8
Sources of light
Incandescent lamps
Incandescent lamp is a source of electric light that works by incandescence. An electric current passes through a thin filament, heating it until it produces light. The enclosing glass bulb prevents the oxygen in air from reaching the hot filament, which otherwise would be destroyed rapidly by oxidation.
Highly magnified photo of a 200 watt light bulb filament
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Gas discharge lamps
Gas-discharge lamps are a family of artificial light sources that generate light by sending an electrical discharge through an ionized gas, i.e. a plasma. The character of the gas discharge critically depends on the frequency or modulation of the current. Typically, such lamps use a noble gas (argon, neon, krypton and xenon) or a mixture of these gases. Most lamps are filled with additional materials, like mercury, sodium, and/or metal halides. In operation the gas is ionized, and free electrons, accelerated by the electrical field in the tube, collide with gas and metal atoms. Some electrons circling around the gas and metal atoms are 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. Ultraviolet radiation is converted to visible light by a fluorescent coating on the inside of the lamp's glass surface for some lamp types. The fluorescent lamp is perhaps the best known gas-discharge lamp.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Low pressure discharge lamps
Fluorescent lamps, the most common lamp in office lighting and many other applications, produce up to 100 lumens/watt
Low pressure sodium vapor lamps, the most efficient gas-discharge lamp type, producing up to 200 lumens/watt, but at the expense of very poor color rendering. The almost monochromatic yellow light is only acceptable for street lighting and similar applications.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
High pressure discharge lamps
Metal halide lamps: These lamps produce almost white light, and attain 100 lumen/watt light output. Applications include indoor lighting of high buildings, parking lots, shops, sport terrains.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
High pressure sodium vapour lamps: producing up to 150 lumens/watt. These lamps produce a broader light spectrum than the low pressure sodium lamps. Also used for street lighting, and for artificial photo assimilation for growing plants.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
High pressure mercury-vapor lamps: This lamp type is the oldest high pressure lamp type, being replaced in most applications by the metal halide lamp and the high pressure sodium lamp.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
Type of Lamp Luminous efficacy(lumen/watt)
CRI
Incandescent 10-15 100
Fluorescent 80-90 75-85
Compact Fluorescent 70-80 80-85
Standard Metal Halide 80 65
Standard High Pressure Sodium
90-100 20-25
Standard High Pressure Mercury Vapor
50-60 40-50
Daylight 100
Average life expectancy (Hrs)
1000
24000
12000
20000
15000- 20000
15000- 20000
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Objectives of Lighting Installation
• To provide a specified average intensity of illumination at working level (depending on the requirement for the respective nature of application)
•To maintain a proper luminance illuminance distribution , i.e., to maintain a reasonable Uniformity Ratio
•To minimize the glare for the persons involved
•To Provide a good colour rendering for the objects
•Maintaining proper direction of incidence of light and optimize the shadow effectMaintain proper direction of incidence light and minimize shadow effect
•To provide an arrangement of the fixtures, that is in line with the application requirement as well as conforms to aesthetic requirement.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
Lighting Calculation
• Decide upon the level of illumination required.
• Decide upon the height of the working plane and the fixture mounting height.
• Based on the room dimensions, calculate the Room Index ( R.I) as follows
R.I =
)( blh
bl
m
l = Room Lengthb = Room Widthhm = Mounting Height over the work plane
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
Decide upon the type of fixture to be used Using the manufacturer’s catalogue for the fixture,
calculate the Coefficient of Utilization(CU) corresponding to the calculated room index and taking into account the reflectance factor. Commonly, reflectance factor of 20%, 70% and 50% is considered for working plane, ceiling and walls respectively.
Decide upon the maintenance factor, M.F – commonly taken as 0.8, which accounts for the reduced output from the fixture due to ageing and dust formation.
Calculate No. of fixture required as follows
N = MFCU
blE
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
Point by Point Illumination Level is calculated based on the photometric curve of the fixture provided by the manufacturer
A Typical photometric curve for an industrial tube fixture:
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
Luminous Intensity in any direction is determined from Photometric Curve
Then Intensity of illumination ( Lux) is calculated by well known equation
E = 2r
CosI
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
Module III B – Session 3
Induction programme for GETS – June 2007
Demonstration of a lighting calculation software ( CGLUX)
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
La
hm
eye
r In
tern
atio
na
l (In
dia
) P
vt.
Ltd
.
