Such type of circuit breaker is designed to instantly trip when the operating current is 3 to 5 times its rated current. Their tripping time falls between 0. In this 2025 guide, we explain type B vs type C vs type D characteristics, show how a thermal magnetic trip curve works, and provide a practical trip curve chart plus. The main objective of circuit breaker tripping units and protective functions in general is to detect faults and to selectively isolate faulted parts of the system. It must also permit short clearance times to limit the fault power and the effect of arcing faults. The fault currents generated due to these fault conditions can damage the electrical devices as well as cause fire in a. A trip curve is a logarithmic graph that displays the time-to-trip relationship for a circuit breaker at various overcurrent levels.
