Investigation of the effect of the slot and shunt on the transient and steady state current response of a commercially available lighting ballast

Shunts and slots in electromagnetic ballasts control starting and steady state currents. Conventional methods of analysis fall short in an accurate qualitative and quantitative description of the effect of these important design parameters because their function can be explained only when steel saturation and material nonlinearity are considered. Because of the existence of the shunts, parallel paths for the flux lines exist, thus making conventional methods of analysis extremely difficult when nonlinear material characteristics have to be taken into account. As a result, this kind of electromagnetic ballast has traditionally been designed using more empirical rules and trial and error (build-test) methods than theoretical methods. This study tries to give a comprehensive understanding of the function of the shunts and slots in an electromagnetic ballast. The commercially available finite element package MSC/EMAS was used in this study. MKS units are used throughout the analysis.