A digital controller based cycloconverter-fed drive

The first China-developed digital controller based cycloconverter-fed main drive of a rolling mill has been in operation since the end of 1995. The squirrel-cage motor drive has rating values of 2500 kW, 1300 V, 1230 A, 13.3/16.7 Hz and 400/500 RPM. The hardware of the controller is a general purpose programmable multiprocessor controller, SEMADYN-D, made by Siemens, and the vector control system of the drive is self-programmed. The motor drive controller has the following features: (1) sampling time assignation and delay time compensation; (2) VFD-type actual value evaluation; (3) motor current model and voltage model; and (4) rotor time constant correction. Test results are also shown at the end of the paper.