| 摘要 |
PURPOSE:To stop the inverter automatically by detecting system service interruption, by monitoring voltage and frequencies. CONSTITUTION:The noises included in the system voltage signal from a signal transformer 6 is removed by a filter 7, and said signal is inputted to a frequency decrease detector 8, a frequency increase detector 9, a voltage decrease detector 10. and a voltage increase detector 11. The outputs of said detectors 8-11 are inputted to a flip-flop 13 via an OR gate 12. When either the magnitutude of the system voltage or the frequency exceeds a preset allowance of each rating, the flip-flop 13 is set. Then, the inverter 1 is automatically stopped based on a pulse off command (a) from said flip-flop 13 via a control device 4. Since the inverter 1 is automatically stopped at the time of system service interruption in this way, the abnormal voltage is not applied to load equipment connected to the system service interruption. |
