Disclosed embodiments include an instant trip mechanism for a molded case circuit breaker. In some embodiments, the mechanism includes an adjustment dial to set a current for an instant trip operation; an instant bar provided with an upper portion contactable with the adjustment dial, a shaft portion serving as a rotation shaft, and a lower extending portion downwardly extending from the shaft portion; an electromagnet unit to generate a magnetic attraction force that is proportional to an amount of current flowing on the circuit; an armature rotatable with a lower end portion supported by a shaft, and attracted toward the electromagnet unit by the magnetic attraction force; and a spring for applying to the armature a load varying in a direction of the armature getting away from the electromagnet unit.

A circuit breaker tripping mechanism providing relatively low instantaneous level tripping is disclosed. Circuit breaker tripping mechanism includes an armature with a first portion extending in a first direction from an armature pivot and a second portion extending in a second direction from the armature pivot, and a magnetic field generator configured as part of a line conductor. Magnetic field generator is operable to produce a magnetic field acting upon the second portion during a short circuit. Circuit breakers including the circuit breaker tripping mechanism and methods of tripping a circuit breaker are provided, as are other aspects.

An interrupter system includes a first coil and an interrupter electrically connected to the first coil. The interrupter includes: a first terminal; a second terminal electrically connected to the first terminal; a third terminal electrically separated from the first terminal and the second terminal; a heat generating element electrically connected to the third terminal; and an explosive configured to be ignited by the heat generating element to produce a gas for interrupting an electrical connection between the first terminal and the second terminal. The first coil is electrically connected to the heat generating element via the third terminal. Moreover, the first coil is configured to, when an abnormal current flows between the first terminal and the second terminal, generate an electric power for igniting the explosive from the abnormal current.

An interrupter system includes a first coil and an interrupter electrically connected to the first coil. The interrupter includes: a first terminal; a second terminal electrically connected to the first terminal; a third terminal electrically separated from the first terminal and the second terminal; a heat generating element electrically connected to the third terminal; and an explosive configured to be ignited by the heat generating element to produce a gas for interrupting an electrical connection between the first terminal and the second terminal. The first coil is electrically connected to the heat generating element via the third terminal. Moreover, the first coil is configured to, when an abnormal current flows between the first terminal and the second terminal, generate an electric power for igniting the explosive from the abnormal current.