AC_CIRCUIT_BREAKER

Published:2009/7/9 21:19:00 Author:May | From:SeekIC

The adjustable circuit breaker responds in 0.02 s under all conditions-provided you select a fast relay for K1. For moderate overload conditions, it's preferable to use the fuse or the fast-acting breaker. Toroid transformer T1 senses ac load current and produces an ac signal at the wiper of R1, when switch S3 is closed. Diode D1 rectifies this signal to produce a positive voltage at test point TP1. Because R1 allows you to calibrate this voltage, the circuit accommodates a variety of current-sense transformers. To calibrate the trip threshold, apply the maximum expected overload and adjust R1 until the TP1 voltage is 0.7 V below the positive saturation level for IC1. Then adjust R4 for the desired trip point. To reset the circuit breaker after it has tripped, open S1 or S2.



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