Pulse, dc and ac breakdown in high pressure gas discharge lamps

Abstract

An optical study of pulse, dc, and ac (50–400 kHz) ignition of metal halide lamps has been performed by investigating intensified CCD camera images of the discharges. The ceramic lamp burners were filled with xenon gas at pressures of 300 and 700 mbar. In comparison with dc and pulse ignition, igniting with an ac voltage decreases the ignition voltage by up to 56% and the breakdown time scales get much longer (∼10−3 s compared with ∼10−7 s for pulse ignition). Increasing the ac frequency decreases the ignition voltages and changes the ionization channel shapes. External irradiation of UV light can have either an increasing or a decreasing effect on ignition voltages.

Ac breakdown in near-atmospheric pressure noble gases: I. Experiment

“…Later observations of the lowering of the threshold voltage when switching to highfrequency AC voltage [1][2][3][4][5][6][7], and also as the frequency was increased, brought on again the same theories and possible explanations afore proposed by Meek and Craggs [8]. For high frequencies it was argued that the electron drift losses were lowered, which caused a more favourable ratio between electron production and loss [2,4].…”

“…We adapted the experimental setup used by Beckers et al and described in [7]. The experiments were performed on HID lamps filled with near-atmospheric pressure noble gas.…”

“…Also, both volume and surface AC discharges that occur in partial vacuum are of particular interest for aerospace insulating technology and power devices operating in space [5]. The lighting industry focuses on AC discharges in near-atmospheric pressure noble gasses with an admixture of mercury when trying to achieve two important goals: one, to design ignition concepts for high-frequency operated lamps [6], and two, to lower the ignition voltage of lamps [7].…”

Note: Measuring breakdown characteristics during the hot re-ignition of high intensity discharge lamps using high frequency alternating current voltage

“…2,4,5 From previous research on cold HID lamps it is already known that the ignition voltage can be lowered by roughly 50% if a high frequency AC voltage is applied instead of a pulsed or DC voltage. 6 Therefore is decided to implement a high frequency voltage between 60 and 220 kHz in the setup discussed here. a) Author to whom correspondence should be addressed.…”

“…In this configuration the lamp is burnt horizontally. Built on the base of work published earlier by Beckers et al 6 on high frequency AC breakdown in HID lamps a ramped sinusoidal voltage pulse of frequency f pulse between 60 kHz and 220 kHz with a set repetition time, t rep , of 10 s is generated in our setup. The repetition time between subsequent voltage pulses is set much longer than the time of the voltage pulse itself (t rep t pulse ) to minimize the influence of previous ignition attempts on the breakdown voltage and to still have a reasonable time resolution during a hot re-ignition measurement.…”