| 摘要 |
PROBLEM TO BE SOLVED: To protect a self-arc-distinguishing element from an abrupt electric current change which occurs when the element is turned on or off, by respectively connecting current suppressing reactors to the anode and cathode terminals of the element. SOLUTION: One terminal of a current reactor La1 is connected to a terminal 1 and the other terminal of the reactor La1 is connected to the anode terminal of a self-arc-distinguishing element Q1. One terminal of another current suppressing reactor La2 is connected to the cathode terminal of the element Q1 and the other terminal of the reactor La2 is connected to the another terminal of another self-arc-distinguishing element Q2. In addition, serial circuits of resistors for consuming energy and diodes are connected in antiparallel with current suppressing reactors La1-La(n-1). A positive-side arm and a negative- side arm, namely, the cathode terminal of a self-arc-extinguishing element Qn and the anode terminal of another self-arc-extinguishing element Q(n+1) are connected to each other and the connecting point is used as the output terminal of a K-level output inverter (K: an integer of >=4). Therefore, the number of the current suppressing reactors can be minimized. |
