| 摘要 |
A circuit breaker includes an insulative case and three first current transformers for detecting load currents. Each first current transformer has a U-shaped core with a gap and is disposed so that a movable contact arm is positioned in the gap. Three second current transformers for control power source are disposed between main contacts for opening and closing power feed path to loads and power-supply side terminals. An output of each second current transformer is supplied to a power source circuit of a control circuit. A zero-phase-sequence transformer for detection of an earth fault current is disposed between the movable contact arms and load side terminals in the case. A control circuit generates an overcurrent trip signal based on an detection output of each first current transformer and an earth leakage trip signal based on an detection output of the zero-phase-sequence current transformer. A tripping device opens main contacts in response to the overcurrent trip signal and the earth leakage trip signal. The control circuit and the tripping device are disposed in the space at the zero-phase-sequence current transformer side in the case.
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