| 摘要 |
PROBLEM TO BE SOLVED: To reduce control force of an operation mechanism of an auxiliary circuit breaker serially connected to a main circuit breaker. SOLUTION: This D.C. circuit breaker is provided with: the main circuit breaker 1 and the auxiliary circuit breaker 2 serially connected to a D.C. circuit; a commutation circuit 6 having a capacitor 4 and a commutation switch 3 connected in parallel with the circuit breaker 1 for superposing a reverse commutation current on the D.C. circuit; a first operation mechanism 11 for switching the circuit breaker 1; and a second operation mechanism 12 for switching the circuit breaker 2. The D.C. circuit breaker is characterized by that the circuit breaker 1 and the circuit breaker 2 start to open and the commutation current is carried from the commutation circuit 6; control force of the operation mechanism 11 is so set that the electrodes of the circuit breaker 1 reach open positions with respect to each other by the time a D.C. current comes to a current zero point between the electrodes of the circuit breaker 1; and control force of the operation mechanism 12 is so set that the electrodes of the circuit breaker 2 reach open positions with respect to each other by the time the D.C. current of the D.C. circuit is attenuated to come to a current zero point. COPYRIGHT: (C)2005,JPO&NCIPI
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