| 摘要 |
A static trip unit for automatic electric circuit breakers includes an analog to digital converter for converting an analog signal proportional to the magnitude of current flowing in a distribution circuit to a digital signal having a pulse frequency proportional to the second power of the analog signal. When the analog signal exceeds a preselected threshold level, a binary counter is conditioned to accumulate the digital signal pulse. A decoder monitors the pulse count accumulating in the counter and issues a trip signal when the pulse count reaches a preselected total.
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