Cycloconverter Drives for Rolling Mills

Following a brief review of the problems arising in the design of dc machines for maximum ratings, the cycloconverter-fed synchronous and asynchronous rotating-field machines with field-oriented control as interesting alternatives to the dc drives will be described. The mode of operation of the cycloconverter is discussed in brief, followed by a description of the principle of field orientation by way of example of the synchronous machine. Oscilloscope records are presented to prove that the dynamic properties of a 1.2 MW drive using this control principle are fully equivalent to those of a dc drive. The drive variant described does not require special motors or motors fitted with internal flux sensing devices. It was originally developed for rolling mill applications but can also be used advantageously in hoists and comparable high-capacity drives running at slow speed.