NF series Mitsubishi Molded-Case Circuit Breakers

Trip with the power of bimetal and electromagnet.

1. An overcurrent heats and warps the bimetal to trip by rotate the trip bar.
2. If the overcurrent is excessive, movable core rotates clockwise and the armature is attracted and to trip by rotate the trip bar.

Trip with the power of electromagnet.

1. At an overcurrent flow, the magnetic force of the coil overcomes the spring, the core closes to the pole piece, attracts the armature, and actuates the trip bar. The delay is obtained by the viscosity of silicon oil.
2. If the overcurrent is excessive, the armature is instantly attracted, without the influence of the moving core.

Trip with the calculation of electronic circuit.

1. The current flowing in each phase is detected by a current transformer (CT). Each phase of the transformed current undergoes full-phase rectification in the rectifier circuit. After rectification, each of the currents are converted by a peak-conversion and an effective-value conversion circuit.
2. When over current or short circuit current flows, each time-delay circuit generates a time delay corresponding to the largest phase. The trigger circuit outputs a trigger signal. The trip coil is excited, operating the switching mechanism to trip.