| 摘要 |
<p>An apparatus monitors an a.c. motor (12), a door (14) operated by the motor, a frequency converter (16) for supplying electric power to the motor (12), and a control and signal-processing means (32) which causes the frequency converter (16) to control the door in accordance with a desired movement. The movement of the door is continously detected. The control and signal-processing means (32) compares the desired movement of the door with the detected movement, in order to emit an alarm signal (L) when the difference is too considerable. A switch means (28) thus blocks the power supply to the motor (12). A sensing means (31) senses whether the power supply to the motor (12) is blocked. The alarm signal (L) is repeatedly emitted in order to establish a possible malfunction of the switch means (28).</p> |
