The Schneider Electric TeSys LA9FK4F4F is a mechanical interlock accessory designed to prevent simultaneous closure of two contactors in a reversing or bypass configuration. It physically blocks the armature of one contactor from closing when the other is engaged, which is the standard method for ensuring a break-before-make sequence in motor-reversing and star-delta starters. The interlocking type is purely mechanical — no electrical connections, no auxiliary contacts to wire. It is a passive safety device that sits between the contactor yokes.
Which Contactors It Fits
The LA9FK4F4F interlocks bottom-position LC1F115 through LC1F150 (3P or 4P) or CR1F150 (3P or 4P), middle-position LC1F115 through LC1F150 (3P or 4P) or CR1F150 (3P or 4P), and top-position LC1F500 (2P, 3P, or 4P) or CR1F500 (3P or 4P). This covers the F-frame contactor range from 115 A up to 500 A, including both power and control-circuit (CR1F) variants. Mounting position is specified as three vertical — the contactors sit one above the other on the panel. This is the standard layout for a two-speed or reversing starter where the contactors share a common bus. The interlock bar engages the contactor yokes through the front face; no rear-panel access is needed for installation.
The active status means no forced alternate search — the same order code lands the same mechanical interlock as the original design.