Basic Terms in Lighting System and Features

Basic Terms in Lighting System and Features

Lamps : Lamp is equipment, which produces light . The most commonly used lamps are described briefly as follows :

Incandescent lamps : Incandescent lamps produce light by means of a filament heated to incandescence by the flow of electric current through it. The principal parts of an incandescent lamp, also known as GLS (General Lighting Service) lamp include the filament the bulb, the fill gas and the cap.
Reflector lamps : Reflector lamps are basically incandescent provided with a high quality internal mirror, which follows exactly the parabolic shape of the lamp. The reflector is resistant to corrosion, thus making the lamp maintenance free and output efficient.
Gas discharge lamps : The light from a gas discharge lamp is produced by the excitation of gas contained in either a tabular or elliptical outer bulb.

The most commonly used discharge lamps are as follows :

Luminaire :

Luminaire is a device that distributes, filters or transforms the light emitted from one or more lamps. The luminaire includes, all the parts necessary for fixing and protecting the lamps, except the lamps themselves.
In some cases, luminaires also include the necessary circuit auxiliaries, together with the means for connecting them to the electric supply.
The basic physical principles used in optical luminaire are reflection, absorption, transmission and refraction.

Control gear :

Ballast :

A current limiting device, to counter negative resistance characteristics of any discharge lamps . In case of fluorescent lamps, it helps the initial voltage build-up, required for starting.

Ignitors :

These are used for starting high intensity Metal Halide and Sodium vapour lamps.

Illuminance :

This is the quotient of the illuminous flux incident on an element of the surface at a point of surface containing the point by the area of that element.
The lighting level produced by a lighting installation is usually qualified by the illuminance produced on a specified plane.
In most cases, this plane is the major plane of the tasks in the interior and is commonly called the working plane.
The illuminance provided by an installation affects both the performance of the tasks and the appearance of the space.

Lux (lx) :

This is the illuminance produced by a luminous flux of one lumen, uniformly distributed over a surface area of one square metre. One lux is equal to one lumen per square metre.

Luminous efficacy (Im/w) :

This is the ratio of luminous flux emitted by a lamp to the power consumed by the lamp. It is a reflection of efficiency of energy conversion from electricity to light form.

Colour Rendering Index (RI) :

It is a measure of the degree to which the colours of surfaces illuminated by a given light source confirm to those of the same surfaces under a reference iluminent suitable allowance have been made for the state of Chromatic adaptation.

Lamp Types and their Features

Luminous performance characteristics of commonly used luminaries

Types of lamp	Lumens/Watt		Colour	Typical application	Typical life (hours)
Types of lamp	Range	Average	Colour	Typical application	Typical life (hours)
Incandescent	8-18	14	Excellent	Homes, restaurant, general lighting, emergency lighting.	1000
Flourescent lamps	40-60	50	Good w.r.t. Coating	Offices, shops, hospitals, homes	5000
Compact fluorescent lamps(CFL)	40-70	60	Very good	Hotels, shops, homes, offices	8000-10000
High pressure mercury (HPMV)	44-57	50	Fair	General lighting in factories, garages, car parking, flood lighting	5000
Halogen lamps	18-24	20	Excellent	Display, food lighting, stadium exhibition grounds, constructions area	2000-4000
High pressure sodium (HPSV) SON	67-121	00	Fair	General lighting factories, warehouses, steel lighting	6000-12000
Low pressure sodium (LPSV) SOX	101-175	150	Poor	Roadways, tunnels, canals, street lighting	6000-12000