Comparison of controlled rectifier and chopper power supplies for DC smelting furnace applications

Abstract

High power electric are furnaces are used in the metals industry for smelting various ore types and melting scrap steel. To a power system an arc furnace represents an erratic load, which a leading cause of voltage flicker, harmonic distortion, and low power factor. In an attempt to reduce the impact on the power system and to reduce production cost new electric arc furnaces have been constructed with DC power supplies. DC electric arc furnaces have been proven to be superior to AC furnaces with regard to reducing voltage flicker and lowering production cost. -- Traditionally DC furnaces have been supplied from thyristor-controlled rectifiers. However, as transistor rating increase alternative configurations become available. Namely active rectifiers, and uncontrolled rectifier chopper combinations. To date only the uncontrolled rectifier chopper power supply has been used as an alternative to the controlled rectifier power supply. The purpose of this thesis is to describe each configuration in detail and investigate their suitability to DC smelting furnace applications. The comparison will investigate the line side power quality, rectifier performance, and reliability.