| 摘要 |
PROBLEM TO BE SOLVED: To prevent the damaging of an inverter even if energizing time is lengthened by actuating an alarm device when the energizing time of the output current of the inverter exceeds a first specified time and a protecting device when it exceeds a second specified time so as to stop an elevator. SOLUTION: The rotational speed of a motor 8 for hoist-driving an elevator is detected by a speed detector 14, the output current of an inverter 7 composed of a semiconductor element is detected by current detectors 15 and 16, and these output signals are inputted to a monitoring circuit 17 and a voltage command generation circuit 27. When the energizing time of the output current of the inverter 7 exceeds a first specified value, an alarm device is actuated, and when the energizing time exceeds a second specified value larger than the first specified value, the elevator is stopped by a protecting device. Modulated wave generation circuits 29 and 30 selectively output a first modulated wave and a second modulated wave having a frequency lower than that of the first modulated wave, and the alarm and protecting devices are actuated when the second modulated wave is selected. |
