Ryoichi Kurosawa

An Approach to Flux Control of Induction Motors Operated with Variable-Frequency Power Supply

A new speed control system for induction motors has been developed which is capable of controlling with quick field weakening and superior response and stability. This method is to control the stator current as a vector quantity on the basis of slip frequency control. More specifically, it is designed to calculate the commanded stator current of the induction motor by corresponding to flux and torque commands on the basis of motor constants and use the calculated commands to control the stator current.

A high-performance cross-current type cycloconverter-fed induction motor drive system

Making use of the latest techniques, the authors have successfully developed a cross-current-type cycloconverter-fed, squirrel-cage induction motor drive system, which far exceeds DC drive systems over a wide range from zero speed to high speed. It is best suited for tandem cold mill main and various other large-scale rolling mills. >

Application of New Drive Systems for Plate Mill Drives

Recently, certain plans have been made to replace existing motors with the objective of achieving controlled rolling in Japanese plate mills. Application of ac drive systems, which are making rapid progress, can be considered for these plans. A comparison of conventional dc motors, brushless dc motors, and vector-controlled induction motors fed by cycloconverters (cycloconverter IMs) is introduced from the viewpoint of their characteristics such as power-torque curve, efficiency, and influence of harmonic current on the power system. As a result of comparison it is found that the cycloconverter IMs can be satisfactorily applied to the plate mills.

Parallel operation of active and passive filters for variable speed cycloconverter drive systems

The authors prepared a digital simulation program consisting of a passive filter, active filter, cycloconverter, and power supply system, and they studied a variety of combinations of passive and active filters in terms of harmonic compensation, parallel resonance suppression, and series resonance suppression. It is shown that the harmonic compensation equipment with a combined use of active and passive filters can effectively compensate a variable-frequency harmonic current generated by the cycloconverter over a wide operation range and can suppress the parallel and series resonance phenomena. The authors analyze the characteristics of three types of arrangement of the active and passive filters. The total harmonic current compensation and total current feedback compensation show good characteristics in terms of harmonic compensation and resonance suppression.<<ETX>>

Development of strip tension stabilization by decentralized control strategy based on Advanced mill drive system suppressing resonant vibrations in hot strip finisher mill

Abstract Recently, Steel Industry has faced serious demands of products quality improvement and drastic competition of cost reduction in production. Hot strip finisher mill, in particular, is the important process in steel industry, and has to satisfy product quality and reduction of production cost as the users demand. Now as for the products quality, thickness accuracy at head end and tail end remains open area to be improved by advanced control methods. And the operation support system at strip threading of strip is necessary to reduce the production cost. So this paper shows that AC drive system performance is successfully combined to decentralized method and that strip tension control has realized quicker response, and thai as the results, thickness accuracy has been improved drastically.