Light years [cathode heating effect on lamp life in dimming use]

The aim of the work described in this article is to find out the effect of cathode-heating voltage during continuous burning to the lamp life in dimming use. In order to find out the effect of cathode heating voltage to the lamp life, a lamp-life test was made. In addition to the nominal cathode heating voltage, three different cathode heating levels were chosen, namely -10, +10, and +20% of the nominal. Some of the test groups were burned undimmed and others dimmed. The cathode heating currents and voltages were measured at the same dimming level that was used when they were burning in a test rack. Differences up to -10% from the acquired optimum in the measured cathode heating voltages had about 2 % difference in lamp life. When the measured cathode voltage differed by -50% from the optimum, lamp life was less than half the maximum. With a proper cathode heating level, the lamp will reach nominal lamp life even if the lamp is dimmed according to daylight.