| 摘要 |
PURPOSE:To detect the defect of an element without affected by the increase or decrease in a load current by detecting the currents of parallel arms by arm current detectors, and informing a malfunction of the element when the difference of the currents of the parallel arms exceeds a threshold value. CONSTITUTION:DC current transformers 21-24 are respectively provided at parallel arms 2-4 of a power converter 1, output signals are input through signal converters 24-26 to difference detectors 27-29 to obtain the difference of currents of the arms 2-4. The difference signals are input to discriminators 30- 32, and whether the threshold value exceeds the difference signal or not is judged with the signal proportional to the load current as a threshold value. The outputs of the discriminators 30-32 are led through a logic sum circuit 37 to inform the malfunction of the element. |
