# Prebake - smaller Si-metal furnaces, aluminum - Carbon cylinders threaded together # Söderberg - FeSi, other ferroalloy furnaces, aluminum - Continuously baked - Electrode paste placed into steel casing - Steel consumed to provide Fe for FeSi # Composite - larger Si-metal furnaces - Prebake + Söderberg - Extrude electrode through steel casing # Control mechanisms ### Power control - change transformer tapping ### Electrode control - move electrodes up (resistance↑) and down (resistance↓) - movement of one affects others $P = RI^2$ - Three phase AC current - skin effect - nonuniform current distribution due to induced magnetic field