A fusion welding isolation mechanism for an operating mechanism of a circuit breaker is provided. The operating mechanism of circuit breaker includes: a tripping component, a left side, a right side plate, a latch, a half shaft, a lever, and a main shaft. The tripping component, the latch, and the lever are mounted between the left side plate and the right side plate. The half shaft and the main shaft penetrate through the left side plate and the right side plate, and extend out of the left side plate and the right side plate. The tripping component, the latch, the half shaft, the lever, and the main shaft move in linkage. The lever and the main shaft are provided with isolation devices for preventing an operation handle from an opening operation when a moving contact is subject to fusion welding.

A fusion welding isolation mechanism for an operating mechanism of a circuit breaker is provided. The operating mechanism of circuit breaker includes: a tripping component, a left side, a right side plate, a latch, a half shaft, a lever, and a main shaft. The tripping component, the latch, and the lever are mounted between the left side plate and the right side plate. The half shaft and the main shaft penetrate through the left side plate and the right side plate, and extend out of the left side plate and the right side plate. The tripping component, the latch, the half shaft, the lever, and the main shaft move in linkage. The lever and the main shaft are provided with isolation devices for preventing an operation handle from an opening operation when a moving contact is subject to fusion welding.

An off-stop mechanism for a circuit breaker. Off-stop mechanism includes a handle moveable to an OFF configuration, the handle including a blocking engagement portion, a blocking member pivotally coupled at a pivot location, a linkage coupled between a cross bar housing and a linkage attachment location of the blocking member, the linkage being configured to: position the blocking member in an unblocked orientation when the main contacts are not fused together, and in a blocked orientation when the main contacts are fused together, wherein blocking member in the blocked orientation engages the blocking engagement portion as the operating handle is moved to the OFF configuration wherein the engagement places the blocking member in compression between the pivot location and the blocking contact portion. Circuit breakers including the off-stop mechanism and methods of operating a circuit breaker are also provided, as are other aspects.