| 摘要 |
PURPOSE:To prevent insulation breakdown, by removing a capacitor from a system when an electrostatic capacity obtained based on the voltage applied onto a self-recovery capacitor and the current flowing at that time and converted to a capacity corresponding to a standard temperature is lower than a predetermined level. CONSTITUTION:A self-recovery capacitor 1 is connected in parallel with a power source system L through a switch 3, a CT4 and a power factor improvement/surge current prevention reactor 2. Capacitance of the capacitor 1 is calculated 10 based on the voltage V of an output voltmeter 8 for a PT5 connected in parallel with the capacitor 1 and the current A of an ammeter 7 connected with the CT4. Temperature of that time is obtained through a thermometer 6 arranged closely to the capacitor 1, and the calculated capacitance is corrected to a value corresponding to a standard temperature through a reference temperature correcting section 11. The corrected capacitance is fed to a comparison output section 12, and when the capacitance is dropped below a predetermined level the switch 3 is opened to disconnect the capacitor 1 from the system. By such arrangement, insulation breakdown can be prevented. |
