Construction and Working of sodium Vapour Discharge Lamp

Sodium Vapour Discharge Lamp

1. Principle Sodium Vapour Discharge Lamp

Electrons are emitted from cathode subjecting the surface of the cathode to very good high electric stress so thay electrons are forcibly ejected from orbits of atom against nuclear centripetal force".

2. Construction and Working Of Sodium Vapour Discharge Lamp

It consists of inner tube of U shape fitted with neon gas and globules of sodium. For good performance 300°C temperature is to maintained.

To protect discharge tube it is contained in evacuated double walled glass jacket this prevents heat loss.

Sodium Vapour Lamp

•At starting, electric discharge is to be established through neon gas till sodium gas vapourized, so at start for 10-15 min. discharge through lamp will be pink and then as sodium vapourizes, it will turn to yellow.

• For this voltage of about 410 is required white normal voltage is about 165. Supply is given through a leak transformer which has high leak reactance.

• As soon as discharge through the tube starts, heavy voltage drop takes place in the transformer so that required operating voltage is automatically impressed across cathodes.

• P.F. there are lamps is 0.3 lagging and there condenser can be used for P.F. connected.