AC drives in metal industries

Today all variable speed drives (VSDs) in the metallurgical industry are AC drives. These range from simple Volts/Hertz (V/Hz) to vector controlled drives. Insulated gate bipolar transistor pulse-width modulated (IGBT PWM) inverters offer power ratings up to a few megawatts. Cycloconverters, multi-level gate turn-off (ML-GTO) inverters, and load commutated inverters (LCI) cover the upper range. Up to about 1000 kW (<10 kNm) is the domain of squirrel cage induction motors. Synchronous motors dominate the high power range. AC drives have not just achieved but also excelled the performance and power ratings which were once exclusive to DC drives. Apart from the intrinsic benefits of lower maintenance and size, AC drives offer energy efficient and clean power operation.