| 摘要 |
PROBLEM TO BE SOLVED: To provide a direct current breaker which can shut off even a small current in a short time and isolate a direct current power source from a load surely without influencing the breaking operation of a large current in an accident. SOLUTION: This direct current breaker comprising a vacuum switch 1 inserted in serial in a main circuit connecting the direct current power source with the load and a commutation circuit 4 connected in parallel with the vacuum switch 1 shuts off the current while making a current-zero point superimposing a current discharged through a commutation reactor 3 from a commutation capacitor preliminarily charged by switching a commutation switch 4 when the contact of the vacuum switch 1 opens, on the current flowing the vacuum switch 1. Additionally, this breaker comprises a sub-commutation circuit 11 which is connected in parallel with the commutation circuit 5 and flows a current only in one direction. The discharge current from the commutation capacitor 2 is commutated to the sub-commutation circuit 11 after the vacuum switch 1 is extinguished and opened.
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