Application of Fully Digital Speed Regulators to Tandem Cold Mills

A fully digital speed regulator has been developed for industrial applications mainly in the steel industry. The benefits obtained when the digital speed regulator was used in two different tandem cold rolling mill control systems are described. As compared with conventional analog control, fully digital speed control permitted more stable rolling mill operation, reducing both threading and accelerating times by 50 and 27 percent, respectively, and leading to increased productivity. With the off-gauge length reduced by about 40 percent, the yield was improved accordingly. In addition, with the fully digital speed regulator which employs LSI devices having reduced failure rates, the tandem cold rolling mill control system was entirely computerized from supervisory process computers to motor drive regulators. With easier trouble-shooting capability, the system failure rate was decreased to 50 percent.