Page 339 - Electrician - TT (Volume 1)

ELECTRICIAN - CITS

Fig 5

Ballast equipments designed for use with the 8¼ inch 22 watt, 12-inch 32 watts. circle line include two single
lamp ballasts, one with uncorrected power factor. The other with high power factor. Many of the portable lighting
equipments - dressing table, desk lamp, vanity mirror, tie rack, display unit and boudoir lamps such as Fig 6 and
7 - in which the 8¼ inch circline will be used which have small thin bases and slender stems.
There are varieties of goods which are being displayed in showcases of different colours, size, shape, fineness
etc. Hence Different shades and colour layers will be used to get the proper colour of goods or fineness of detail
or both by proper illumination.

Precaution should be taken while putting the merchandise in showcases so that wiring will not be damaged. Also
the wiring and merchandise should not get damaged due to the excessive heat of lamps.
Luminous Efficiency Calculation

Luminous Efficiency: Luminous efficiency is a measure of how will a light source produces a visible light. It is
a quantity of measurement for light source and it is defined as the ratio of luminous flux to power of the lamp in
watts. It’s unit is lumen/watt in SI unit.
Luminous flux in lumen
Luminous efficiency =
Power in watt
This is important, it describes how much light is being given compare to the amount of electricity is used.

Purpose of calculating luminous efficiency
Typical house hold spends 30% of the electricity bill in lighting. Money can be saved by bringing the most cost
efficient lighting option in home needs.

For example: A 60w light bulb usually produces 860 lumens. Calculate the luminous efficiency.
Luminous flux in lumen
So, efficiency =
Power in watt
860
= = 14.3 lumen/watt
60

Fig 6 Fig 7

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CITS : Power - Electrician & Wireman - Lesson 54-59