To provide a circuit breaker aiming at averaging of the number of opening and closing times of each phase contact and capable of improving contact life and durability for opening and closing.
The circuit breaker is provided with a current detection means 3 installed in a plurality of electric paths 1 for detecting current flowing in each electric path, a calculating means 6 calculating a current actual value for each electric path on the basis of a detected signal of the current detection means, a variability period detection means 7 detecting a variability period of current in each electric path on the basis of an actual current value calculated by the calculating means, a switch 2 opening each electric path, and an opening and closing history information storage means 8 memorizing the opening and closing history information obtained for each electric path on the basis of the current actual value of the calculating means when the switch opens, a tripping means 9 opening the switch at the time when the current actual value of the calculating means is more than a predetermined value, by finding it from the variability period of the variability period detection means, at which the current actual value of the electric path having maximum opening and closing history information of the opening and closing history information storage means turns to a lower value.
Toshihide Kodama
Takenaka Ikuo
Keigo Murakami
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