Sodium Vapour Lamp

出典: くみこみックス

Sodium Vapour Lamp consists of a discharge tube made from a heat resistant glass, containing a small quantity of metallic sodium, neon gas and two electrodes, Neon gas is added to commence the discharge and to create sufficient heat to vaporize the chickencoop discussion sodium. Due to the fact of law pressure inside the tube, movable chicken coop talk a sufficiently long tube essential to acquire far more light. To decrease the general dimension of the lamp, this tube is typically bent into U-shape.

The light produced by this lamp www is yellowish which is created at its optimum pressure of about .004mm of mercury. This pressure is obtained at a temperature of about 280 C and so it becomes necessary to maintain this temperature. For this objective the U-tube is enclosed in a double walled flask to stop lose of heat. The double walled flask is interchangeable and can be fitted on to another U-tube. Although replacing the inner U-tube a single have to be very cautious since if it is broken and sodium comes in contact with moisture, it may possibly outcome in fire.

All electric discharge lamps require a greater voltage at the time of starting and low voltage for the duration of operation. Generally, sodium vapour lamps are operated by a high leakage reactance transformer. At starting a high voltage of about 450 volts is applied across the lamp which is adequate to begin the discharge. When the lamp is completely operative after ten - 15 minutes, the voltage across it falls to about 150 volts. Simply because of the high reactance of circuit, the power factor is low and hence a p.f improvement capacitor is connected.

The efficiency of a low pressure sodium vapour lamp is quite high (about 40 - 50 lumens/watt) and it produces a light of certain wavelength obtaining yellow color. Sodium lamps are primarily employed for street, high way and airfield lighting where color distinction is not so required.