Westinghouse Electric M331B Mechanical Interlock

The Westinghouse M331B Mechanical Interlock prevents two paired contactors or motor starters from closing simultaneously in reversing and transfer control circuits, delivering reliable mechanical interlock for safe switching in automation systems. Designed for contactor-mounted installation in commercial and industrial motor control environments, it is compatible with Westinghouse A200 and A900 starters and contactors and supports 3x3 and 5x5 pole configurations across NEMA sizes 00, 0, and 1. Commonly installed in motor control centers, reversing starter assemblies, conveyors, pumps, and manufacturing automation equipment to ensure interlock integrity and prevent misoperation. Part number M331B with alternate M33-1B nomenclature, this industrial interlock assembly provides a robust mechanical interlock function essential for reversing starters and interlocked control circuits.