Tripping mechanism for air circuit breaker

The invention relates to the technical field of circuit protection, and discloses a tripping mechanism for an air circuit breaker, the tripping mechanism comprises a second coil and a strong magnetic iron core, the output end and the input end of the second coil are both in contact with a stroke device, the bottom of the strong magnetic iron core is sleeved with a holder, the holder is sleeved with a top hole, and the top hole is provided with an opening. The strong magnetic iron core is integrally located in the second coil, the spiral direction of the first coil is opposite to that of the second coil, and the input end and the output end of the second coil penetrate through the stroke frame to be connected with the upper contact piece and the lower contact piece respectively. After the second coil is short-circuited and loses magnetism, the magnetized strong magnet core does not lose magnetism immediately and is gradually lowered, so that the strong magnet core does not release the energy storage block imme