Arc instability

Arc instability

The narrow spacing between the electrode tips, along with the optimized electrode and envelope designs, provide LTI lamps with extremely stable arcs. However, several factors may contribute to arc instability:

Lamp current: Operating a lamp at low current causes the cathode tip to run to cold. This results in not enough electrons being supplied by the cathode tip, which causes the arc to move over the cathode tip surface searching for electrons. If the current is too high, the cathode tip runs too hot, which results in the evaporation of the thorium. The causes too few electrons to be emitted from the cathode, with resulting arc instability.

In-rush current: High in-rush currents on a repeated basis cause the erosion of the cathode tip, which leads to arc instability.

Start-up time: Immediately after lamp ignition, some instability occurs as the lamp components are heating up. This effect passes after a few minutes of operation as the mercury vaporizes.

Burning position: As specified in the section describing burning position, the closer to vertical a lamp is operated, the better its stability.

Lamp life: As a lamp progresses through its lifetime, one of the normal changes is the structure of the electrodes and a gradual decrease in light output.



		Arc instability The narrow spacing between the electrode tips, along with the optimized electrode and envelope designs, provide LTI lamps with extremely stable arcs. However, several factors may contribute to arc instability: Lamp current: Operating a lamp at low current causes the cathode tip to run to cold. This results in not enough electrons being supplied by the cathode tip, which causes the arc to move over the cathode tip surface searching for electrons. If the current is too high, the cathode tip runs too hot, which results in the evaporation of the thorium. The causes too few electrons to be emitted from the cathode, with resulting arc instability. In-rush current: High in-rush currents on a repeated basis cause the erosion of the cathode tip, which leads to arc instability. Start-up time: Immediately after lamp ignition, some instability occurs as the lamp components are heating up. This effect passes after a few minutes of operation as the mercury vaporizes. Burning position: As specified in the section describing burning position, the closer to vertical a lamp is operated, the better its stability. Lamp life: As a lamp progresses through its lifetime, one of the normal changes is the structure of the electrodes and a gradual decrease in light output.