Analysis of the interruption process of selective miniature circuit breaker with permanent magnet release

The interruption process of the new-type selective miniature circuit breaker (SMCB) is different from the traditional low-voltage circuit breaker (LVCB). According to the operating principle of the SMCB, its interruption process can be divided into three stages; the corresponding mathematical model and calculation method are proposed as well. The calculation of the static characteristic of the magnetic release equipped with the permanent magnet shows that the influence of the current direction on the electromagnetic force cannot be ignored, which lead to the minimum tripping current of the release is equal to -315 and 490 A, respectively, when the armature is close to the permanent magnet. With the simulation and experimental results when the effective value of the prospective short-circuit current is 644 A and 1.5 kA, it indicates that the bigger the closing phase angle is, the quicker the arc ignition between the main contacts and the less arcing time will be. Moreover, the typical interruption parameters of the simulation and experimental results are comparable, and it demonstrates that the proposed method can be used for the optimization design of the SMCB.