ppt 8.electrical lighting - large fonts.pptx

8/10/2019 ppt 8.Electrical Lighting - Large fonts.pptx

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Electrical Lighting

EE 2802Applied Electricity

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Contents

1. Introduction

2. Basic Principles

3. Characteristics of Light4. Lamps and Luminaires

5. Lighting Calculations

6. Energy Consumption

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1. Introduction

Lighting or Illumination

Natural illumination

OR

Artificial light sources

Artificial Lighting

- Account for a significant part of allenergy consumed worldwide

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2. Basic Principles

Radiate only heat waves

Radiate heat & light waves

Body becomes luminousColor of light changes

Bright Red

Orange

Yellow

White

4

Te

mperature


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Definitions

Radiant efficiency

= Energy radiated in form of light /

Total energy radiated

Solid anglein steradian (sr)

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Definitions

Candela (cd)

Lumen per steradian

Unit of luminous intensity

Luminous Flux Rate of flow of light energy

Unitlumen (lm)

1 lm = 0.0016 W approx.

Lumen Hour

Quantity of light delivered in one hour by a flux of 1 lm

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3. Characteristics of Light

Travels its path through space

Reflectswhen it hits a smooth surface

Bends when travels from one medium to anotherrefraction

When the medium bends the lightcan seeseparate colors

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4. Lamps and Luminaires

Lamps

Replaceable portion of the luminaire

Luminaries Connecting the lamp to the electricity supply

Controlling the light emitted by the lamp

Protecting the lamp from a hostile environment

Providing a fixture of satisfactory appearance

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Lamps

Production of Light

By heating

Resulting in thermal radiation

By collision

Passing an electric current through a gas orvapour

Ex : Fluorescence

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Types of Lamps

1. Incandescent lamps

2. Discharge lamps

3. LEDs

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Incandescent Lamps

Cheep to install

Expensive to run

Heating a thin metal wire to very high

temperatures (around 2200C)

WireFilamentis almost universally made

from Tungsten 11


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Incandescent Lamps

Tungsten Halogen

Filled with a halogen gas (bromide or iodine)Tungsten atoms that evaporate from the

filament surface combine chemically with

iodine atoms

In this state, they cannot form a black coating

on the inside of the bulb

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Discharge Lamps

Electric current is passed through a low

pressure gas

Electrons flowing between the two electrodes

collide with gas atoms

- Increase their energy

These atoms quickly decay to their stable state

- Releasing photons of ultraviolet

radiation

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Discharge Lamps

Phosphor coatings on the inside of the bulbabsorb most of this energy

- Re-radiate it as visible light

At high pressure:

Gas itself absorbs some of this radiation

Re-emits it as visible light

Ex: FluorescentLow / High pressure sodium lamps

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LEDs

Light Emitting Diodes

Used for indicating purposes for several

decades

Recent developments:

Larger diodes Range of colours including white

Extremely long life 15


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For a well designed lighting scheme:

Provide adequate illumination

Avoid glare and hard shadows

Provide uniform distribution of light

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Space Height Ratio

Horizontal distance between two lamps / Mounting heightof lamps

In indoor lighting this ratio lies between 1 and 2

Utilization Factor (UF)

UF= lumens received on working pane / lumensemitted by the light source

Light Loss Factor (LLF)

LLF = illumination under actual conditions /illumination under perfect condition

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Gross Lumens required

= (E*A)/(UF*LLF)

E = desired illumination (lm/m2)

A = area of working plane (m2)UF = Utilization factor

LLF = Light loss factor18


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Desired Illumination

Ex. Office

Place Desired

Illumination

(lm/m2or lux)

Filing, copying etc 300Writing, typing, reading, data processing 500

Technical drawing 750

CAD work stations 500

Conference and meeting rooms 500

Reception desk 300

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Example:

The illumination in a drawing office 30m x

10m is to have a value of 250 lux and is to be

provided by a number of 300W filament

lamps.

If the coefficient of utilization is 0.4 and the

depreciation factor is 0.9, determine the

number of lamps required. The luminousefficiency of each lamp is 14 lm/W.

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6. Energy Consumption In homes and offices, 20% ~ 50% of total energy

consumed is due to lighting

Ways to minimize:

Study illumination requirement for use area

Analysis of lighting quality (ex. no glare)

Integration of space planning and interior

architecture to lighting design

Select fixture and lamp typesbest energyconservation

Maintenance of lighting systems

Use of natural light 21


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Automated Lighting Control

Building automationand lighting control

solutions are now available to help reduce

energy usage and cost by eliminating over-

illumination

Daylight-linkedautomated response systems

have been developed to further reduce energy

consumption

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References

A TEXTBOOK OF

ELECTRICAL TECHNOLOGY

VOLUME IIITRANSMISSION, DISTRIBUTION & UTILIZATION

B.L. THERAJA

A.K. THERAJA

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