Optimization of electronic ballast drive for the high power sodium vapor lamps based on two-dimensional plasma finite element modeling

Summary form only given. High power sodium vapor lamps (up to 2-kW) are widely used for illuminative purposes. Foremost application of these lamps is in the large scale environment lighting such as highways. These lamps are used with appropriate reflectors control the light propagation direction and pattern. Accomplishment of proper characteristics of such lamps, e.g., ignition and continuity of the lamp operation requires a drive circuit, known as ballast, which generates the applied voltage to the plasma tube. Two types of ballasts are mainly used in the industries: electric (conventional circuit using chuck) and electronic ballasts. Different characteristics of these two types of ballasts affect the plasma behavior and consequently the emitted light properties. In this paper, the effects of electronic ballast, such as high frequency harmonics, controlled power factor, have been investigated and compared with conventional approaches. A typical plasma tube which is commonly used in high power sodium vapor lamp structures has been considered without any reflectors. Plasma channel of the lamp has been modeled by a finite element method, solving particle continuity, momentum conservation and thermal balance equations in gaseous medium, in 2-D geometry. Cylindrical symmetry of the lamp structure has been applied. As a result of the simulations, light spectrum distribution is achieved by use of electron and ion density and velocity distribution along the plasma channel. These parameters have been compared at two different cases: conventional electric and electronic ballasts.