Study of HID Lamps with Reduced Acoustic Resonances

Abstract

There is much interest in operating HID lamps at frequencies in the several tens k Hz range, since the reduction can be expected in the weight, the size, and the power dissipation of the ballast, and also some of features will be added.
The problems made by the acoustic resonances are the change of colour, the unstable arcs, which causes fluctuations in the intensity and distribution of emitted light, the extinguished arc caused by rising the voltage, and/or, the tube cracking.
There have been many studies in this field, but only a few studies which reduced the acoustic reasonances have been done. Therefore, the high frequency operation with a full-electronic ballast has never been applied for HID lamps on the market.
The purpose of this work is to find the method of reducing the acoustic resonances. And, from view points of the shape of arc tube, we have analysed the pressure distribution by method of using the finite element method, and made several experiments of the arc behavior by changing the tube shaphs. As the result of the study, we found that the specific shape of end portion of the arc tube is very effective to reduce the acoustic resonancesunder the condition of the high frequency operation with the frequency modulated wave. This method is useful to operate higher wattage HID lamps than 250 W.