Power supply of lighting circuits

The quality of the lighting

A source of comfort and productivity, lighting represents 15% of the quantity of electricity consumed in industry and 40% in buildings. The quality of the lighting (light stability and continuity of service) depends on the quality of the electrical energy thus consumed. The supply of electrical power to lighting networks has therefore assumed great importance.

To help with their design and simplify the selection of appropriate protection devices, the authors present in this document an analysis of the different lamp technologies and the main technological developments in progress. After summarizing the distinguishing features of lighting circuits and their impact on control and protection devices, they discuss the options concerning which equipment to use.

Artificial light

Artificial luminous radiation can be produced from electrical energy according to two principles: incandescence and electroluminescence.

Incandescence

This is the production of light via temperature elevation. The energy levels are plentiful, and in consequence, the emitted radiation spectrum is continuous. The most common example is a filament heated to white state by the circulation of an electrical current. The energy supplied is transformed into the Joule effect and into luminous flux.

Luminescence

This is the phenomenon of emission by a material of visible or almost visible luminous radiation.

• Electroluminescence of gases
  A gas (or vapors) subjected to an electrical discharge emits luminous radiation. Since this gas does not conduct at ordinary temperature and pressure, the discharge is produced by generating charged particles which permit ionization of the gas. The spectrum, in the form of stripes, depends on the energy levels specific to the gas or vapor used. The pressure and temperature of the gas determine the length of the emitted rays and the nature of the spectrum.
• Photoluminescence
  This is the luminescence of a material exposed to visible or almost visible radiation (ultraviolet, infrared).

When the substance absorbs ultraviolet radiationand emits visible radiation which stops a short time after energization, this is fluorescence. Not all the photons received are transformed into emitted photons. The best efficiency rating for existing fluorescent materials is 0.9. When the light emission persists after energization has stopped, it is phosphorescence.

AUTHOR: Schneider Electric experts | Jacques SCHONEK, Marc VERNAY