Inverter-fed AC drive systems for steel rolling mills

In the steel rolling industry, steel rolling plants with inverterfed drive systems have been applied for small to large capacity motors. The power devices supporting the inverter drive continue to gain in capacity, as represented by the 6 kV, 6 kA gate turn-off thyristor (GTO). The large capacity ofthese elements makes it possible to reduce the size ofmedium- and large-capacity inverter drive systems. The application range affected by power line needs has also expanded accordingly. To satisfy these needs, Hitachi, Ltd. provides a large-capacity GTO inverter drive system for steel rolling mills. A large-capacity GTO inverter drive system (motor capacity: 5000-6400 kW class) using the latest large-capacity GTO (6 kV, 6 kA) was developed along with a medium-capacity insulated gate bipolar transistor (IGBT) inverter drive system (motor capacity: about 2000 kW) using a large-capacity lGBT. These drive systems satisfy power line needs with high power factor and minimum harmonics.