| 摘要 |
<p>1,089,796. Control of A.C. motors. ENGLISH ELECTRIC CO. Ltd. Sept. 4, 1964 [June 5, 1963], No. 22458/63. Heading H2J. A valve 3 is opened by actuating push-button 25 to energize relay 9 which closes contacts 9A in series with motor 1, so driving the valve when the lost-motion in device 5 is taken up. The relay 9 has self-holding contacts 9C. Normally the motor will continue to operate until either stop push-button 15 is opened or limit switch 32 is actuated. If the motor torque exceeds a predetermined value, however, switch 17 closes to energize relay 19 which opens contacts 19A to stop the motor. The valve is closed when relay 11 is energized by operation of push-button 27, so closing reverse contacts 11A. The relay 11 has self-holding contacts 11C. Normally, the motor will continue to run until either the switch 15 is opened or limit switch 36 is actuated. Excessive motor torque closes contacts 21 to energize relay 23 and open contacts 23A. If, during the opening operation of the valve, the lost-motion is taken up and the motor stops due to resistance imposed by jamming, the motor is disconnected by closure of switch 17. To free the valve, push-buttons'25, 29 are operated simultaneously, relay 11 being energized to drive the valve in the closing direction, taking up the lost motion in device 5. As the motor starts, switch 17 opens to deenergize relay 19. After a predetermined time delay, contacts 19A close and contacts 19B open to de-energize relay 11. The time delay is such that the motor stops before all the lost-motion is taken up, thereby preventing any closing force being applied to the valve. Closure of contacts 19A drives the valve in the opening direction to apply an unjamming force. This cycle is repeated until the valve is freed. Similar operation is obtained when the valve is jammed in the fully-opened position and push-button 27 is actuated to close the valve.</p> |
