Operating mechanism of a circuit breaker with a locking system disengageable on a short circuit

An operating mechanism of a low voltage multipole circuit breaker with high electrodynamic strength, comprising an electrical power circuit having per pole a pair of compensated contacts kept in a closed position by electrodynamic compensation effect of repulsion forces, said mechanism being supported by a frame and comprising:

• a toggle device associated to a trip hook and to an opening spring to move a movable contact of the compensated contacts to an open position when the hook is actuated from a loaded position to a tripped position,
• a switching bar made of insulating material coupled to the toggle device and extending transversely to the frame, and comprising a rotary shaft supporting the movable contacts of the compensated contacts of all the poles,
• an opening ratchet cooperating with the trip hook to perform loading or tripping of the mechanism respectively in a locked or unlocked position of said ratchet, and a catch controlled by a tripping component to actuate the opening ratchet to the unlocked position,
• wherein the opening ratchet comprises disengageable actuating means causing self-unlocking of the catch due to a short-circuit current exceeding a calibration threshold defined by flexible means, said self-unlocking being commanded from a mechanical reaction generated by the electrodynamic compensation effect and causing an ultra-fast rotation of the catch to unlock the opening ratchet before the tripping component operates.