Study of the movable contact fallback phenomenon in MCCB

Movable contact fallback may have disadvantageous effect on the interruption performance of low voltage molded case circuit breaker (MCCB). Based on short circuit experiments of one MCCB product, the occurrence of movable contact fallback phenomenon was predicted. In order to analyze the phenomenon more detailed, a multi-physical coupled model was proposed to simulate the interruption process. The model included three parts: firstly, the dynamic model of the operation mechanism was developed by ADAMS software, and its validity was verified by measuring the angular displacement of the main axis; secondly, the electro-magnetic forces acting on the movable contact and the armature of the magnetic release were calculated based on finite element method; finally, by embedding some self-programmed codes into ADAMS software to consider the above-mentioned electro-magnetic forces, the whole interruption process could be simulated. It demonstrates that the proposed model could be used to evaluate the interruption performance of MCCB qualitatively, especially for the movable contact fallback phenomenon.