Time-dependent simulation of plasma and electrodes in mercury-free high-intensity discharge lamps

A numerical simulation model for dc or ac operation of HID lamps is applied to mercury-free lamps for automotive lighting applications. The model includes a reaction-diffusion equation for the non-LTE electrical conductivity of the plasma. It takes into account interactions of plasma and electrodes considering heat conduction, cooling and heating due to electron / ion cur-rent and radiative loss of energy. We report on case studies for the geometry of the electrodes at dc operation and on transient processes which occur, when control of lamps is switched from dc to rectangular ac of 400 Hz. One main point of the investigation is obtaining temperature dependent constitutive functions describing the multi-component plasma for realistic fillings of lamps.