VS - Lighting Systems - Lighting - 998542

11. Gas-discharge lamps

The ignition and ballast operation proceeds in several stages: 1. Turn-on Before ignition, the lamp’s equivalent impedance (resistance) is considered as infinite. In this stage, the voltage generated by the ballast is fed to ignite the lamp.

2. Ignition During this stage, the ignition circuitry generates a high voltage pulse across the lamp, as a result an arc is established in the tube and visible light is generated.

Phase 0

Phase 1

Off state

Ignition 20 kV between electrodes

Electrodes

The required ignition voltage for a lamp when it is cold is around 10 kV. For a lamp when it is hot the voltage is around 25 kV. A conducting tunnel between the Tungsten electrodes is created and current flows between the electrodes. Initial phase/take over: After successful ignition, the lamp requires a large current (takeover current) to sustain the arc. Because the arc is operated at high power, the temperature in the capsule rises quickly. The metallic salts vaporize; the arc is intensified and made spectrally more complete. The resistance between the electrodes also falls; the electronic ballast control unit registers this and automatically switches to continuous operation.

Metal salts

Xenon gas

4.5 mm

Before ignition, the operation frequency is 1 kHz.

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