Arc resistant shutters

A switchgear cabinet, comprising:

• a circuit breaker with clusters of cluster fingers, each of the clusters having a plurality of cluster fingers enclosed in part within a cluster shield;
• bus bar extensions attached to a back-mold, respective bus bar extensions being engaged with respective clusters when the circuit breaker is in a connected position, the bus bar extensions being disengaged from the clusters when the circuit breaker is in a disconnected position, each bus bar extension having an insulator cap covering a free end of the bus bar extension;
• and
• an independently movable shutter moveable along a bus bar extension, the shutter for covering access to the bus bar extension in the disconnected position and allowing access to the bus bar extension in the connected position, the movable shutter including
• a spring biased support mounted in a fixed position with respect to the bus bar extension,
• the moveable shutter being mounted to the support, the shutter having an opening through which the bus bar extension passes, the shutter being slideable along the bus bar extension away from the insulator cap, in response to a force applied by a leading edge of the cluster shield when in the connected position, and
• the shutter being slideable along the bus bar extension toward the insulator cap, in response to a force applied by the spring biased support, when in the disconnected position, the insulator cap fitting closely within the opening in the shutter, to thereby prevent access to the bus bar extension when in the disconnected position.

A switchgear cabinet, comprising:

• a motor control unit configured to be inserted into a motor control center, the motor control unit including a circuit breaker, the motor control unit further having an exterior face of a back wall of the motor control unit being configured to be located adjacent to bus bars of a power bus when the motor control unit has been inserted into the motor control center;
• connector assemblies moveably mounted in the motor control unit, each of the connector assemblies being electrically connected to a respective phase of the circuit breaker, each of the connector assemblies being configured to project from the back wall of the motor control unit, to mechanically and electrically engage a respective bus bar for electrical connection therewith in a connected position, when the connector assembly is moved toward the power bus;
• the respective bus bar being disengaged from the connector assembly in a disconnected position, when the connector assembly is moved away from the power bus, each bus bar having an insulator cap covering a free end of the bus bar;
• and
• an independently movable shutter moveable along a bus bar, the shutter for covering access to the bus bar in the disconnected position and allowing access to the bus bar in the connected position, the movable shutter including
• a spring biased support mounted in a fixed position with respect to the bus bar,
• the moveable shutter mounted to the support, the shutter having an opening through which the bus bar passes, the shutter being slideable along the bus bar away from the insulator cap, in response to a force applied by a leading edge of the connector assembly when in the connected position, and
• the shutter being slideable along the bus bar toward the insulator cap, in response to a force applied by the spring biased support, when in the disconnected position, the insulator cap fitting closely within the opening in the shutter, to thereby prevent access to the bus bar when in the disconnected position.