| 摘要 |
PURPOSE:To utilize a mill motor to its maximum capacity by setting the optimum speed of the motor so that a load current becomes substantially equal to the rated current of the motor. CONSTITUTION:The difference between a load current IF detected by a current transformer 9 and acceleration/deceleration current Ialpha calculated by an acceleration/deceleration current calculator 25 is obtained to attain a real load current IF', the difference DELTAI between the rated currents IR set by a rated current setter 24 and IF' is input to an overload detector 26, and if the difference DELTAI is smaller than the certain set value, a relay coil 23c is energized to turn ON or OFF contacts 23a, 23b. Thus, when a load current is smaller than the rated current, it is operated at the preset maximum speed, and when the load current becomes substantially the same as the rated current, its speed is used as a limit speed. |
