Large voltage source inverter for Hot Strip Mill

The rolling mill of metal industry is one of large markets of the large capacity motor drive system. The DC motor and thyristor Leonard was long used because rolling mill required the speed control accuracy, speed control response and torque control accuracy and the AC drive lacked enough capability. Then the vector control was developed and the control performance was improved and the vector control type cycloconverter was applied. The control performance was better than that of the DC drive, but the cycloconverter generated large harmonics and large amount of reactive power.