| 摘要 |
PURPOSE:To reduce the cost by intermittently supplying power to a motor in response to the amplitude relation between the load current and the set value of a motor, thereby eliminating a torque sensor or a limit switch. CONSTITUTION:When a contact 3 is closed, a flip-flop 5 is set, and a flip-flop 6 is reset. Then, a switching element 7 is ON, a switching element 8 is OFF, a motor 9 is normally rotated to open a valve. When the valve arrives at the opening end position, the load torque of the motor 9 abrupting increases to rapidly increase the load current of the motor. A load current monitor 11 compares the load current with the set value, and when the load current increases larger than the set value, a timer circuit 15 operates. When the counting of the timer 15 is completed, if the load current is still larger than the set value, the output of an AND gate 16 becomes 'H', and the flip-flop 5 is reset by a signal from the gate 2, and the element 7 is turned OFF. |
