Sodium Vapour Lamp

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Sodium Vapour Lamp consists of a discharge tube made from a heat resistant glass, containing a modest quantity of metallic sodium, neon gas and two electrodes, Neon gas is added to begin the discharge and to develop enough heat to vaporize the sodium. Because of law pressure inside the tube, a sufficiently long tube required to acquire much more light. To www reduce the general dimension of the lamp, this tube is usually bent into U-shape.

The light made by this lamp is yellowish which is made at its optimum pressure of about .004mm of mercury. This pressure is obtained at a temperature of about 280 C and so it becomes essential to preserve this temperature. For this objective the U-tube is enclosed in a double walled flask to prevent lose of heat. The double walled flask is interchangeable and can be fitted on to an additional U-tube. Although replacing the inner U-tube one have to be extremely careful due to the fact if it is broken and sodium comes in make contact with with moisture, it might result in fire.

All electric discharge lamps demand a larger voltage at the time of starting and low voltage during operation. Generally, sodium vapour lamps are operated by a high leakage reactance transformer. At beginning a high voltage of about 450 volts is applied across the lamp which is sufficient to start the discharge. When the lamp is completely operative following 10 - 15 minutes, the voltage across it falls to about 150 volts. Because of the high reactance of circuit, the power element is low and therefore a p.f coops for chickens information 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 specific wavelength possessing yellow color. Sodium lamps are primarily employed for street, high way backyard chicken coops and airfield lighting exactly where color distinction is not so required.