POWER SUPPLY SYSTEM FOR THREE-PHASE ARC FURNACE WITH HIGH-VOLTAGE MULTILEVEL FREQUENCY CONVERTER

摘要

) A power-supply system for three-phase arc furnace comprises a high-voltage multi-level frequency converter installed on primary side of an arc transformer, the secondary winding of which supplies the three-phase arc furnace. The high-voltage multi-level frequency converter comprises a high-voltage multi-winding frequency converter, secondary windings of which power supply power units of a rectifier-inverter, which are in series connected by their output terminals. An arc furnace control system is connected to a low-voltage network through series connected a no-break power supply and a first power unit. Also, the power-supply system comprises a second unit for power supply of control circuits, connected by the input terminals to output terminals of the no-break power supply, by output terminals it is connected to a closed current-conducting stage formed by in series connected primary windings of current transformers, quantity of which is equal to number of rectifier-inverter power units; moreover, each power unit comprises a local power unit, which comprises two input and one output stages. The control local unit for each power unit rectifier-inverter has two independent stage, with every stage being connected to local unit using independent power supply lines.