| 摘要 |
A circuit breaker includes a current detector for generator analog voltage signals in accordance with load current of respective phases and a control circuit for executing a tripping operation in response to the analog voltage signals. The control circuit includes an analog switch repeating a time division selecting operation that one of the analog phase voltage signals generated by the current detector is selectively allowed to pass through the same in a predetermined order, an analog-to-digital (A/D) converter for converting the analog voltage signal having passed through the analog switch to a corresponding digital signal, and a microcomputer receiving the digital voltage signal from the A/D converter and obtaining the effective load current value based on the digital voltage signals. The microcomputer generates a tripping order when the effective load current value exceeds a predetermined value. The control circuit may include an amplifier for amplifying low level analog voltage signals and supplying the amplified signals to the A/D converter.
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