Abstract: The tension of a strip can be controlled with high responsiveness and high accuracy despite its drastic external variation by threading the strip (1) between a transportation roll (2) and a movable transportation roll (10) and moving the movable transportation roll (10). The movable transportation roll (10) is mounted on one end of an arm (11), which is mounted for a swing motion around a supporting shaft (12), a torque around the supporting shaft (12) is generated in the arm (11) by an arm driving motor (14) connected directly to the supporting shaft (12), thereby applying a tension to the strip (1). The angle of swing motion of the arm (11) is detected by an arm angle sensor (16), and the tension of the strip (1) is detected by a tension sensor (15). The torque to be generated in the arm (11) is corrected in accordance with the detected angle and tension, whereby the strip tension is controlled for a target tension.

Abstract: A speed control method and apparatus for a motor driven by output of a power conversion unit, wherein a first current command value is inputted to derive a drooping variable, a deviation between a detected speed value of the motor and a speed command value is derived, the first current command value is derived on the basis of a value obtained by compensating the deviation with the drooping variable, the speed command value is inputted to derive an acceleration or deceleration current value for accelerating or decelerating the motor, and the first current command value and the acceleration or deceleration current value are added together to derive a second current command value and control the output current of the power conversion unit on the basis of the second current command value.