Overview
The LA9FL4G is a Schneider TeSys F mechanical interlock, order code LA9FL4G, in a PCE package with 2 vertical mounting. It provides mechanical interlocking between two contactors to prevent simultaneous closure, essential for reversing or changeover motor starter assemblies. This interlock is designed for use with bottom-mounted contactors in the 185–225 A frame and top-mounted contactors in the 630–800 A frame.
The LA9FL4G mounts between two vertical contactors and uses a mechanical linkage to block the armature of one contactor from closing when the other is already closed. This prevents a direct short circuit across the supply that would occur if both contactors in a reversing pair were to close simultaneously. The interlock is a passive mechanical device — no electrical connections or power supply are needed. It relies on the physical travel of the contactor armatures; the interlock rod transfers motion between the two contactors, ensuring that only one can be in the closed position at any time.
Applications
This mechanical interlock is used in reversing contactor assemblies for motor direction control — for example, in conveyor drives, hoists, winches, and pump reversing stations where a three-phase motor must run forward and reverse. It is also used in changeover schemes for dual-power supplies or standby generator transfer. Within the TeSys F range, the LA9FL4G fits assemblies that pair a smaller bottom contactor (up to 225 A frame) with a larger top contactor (up to 800 A frame), a common configuration for high-inertia loads where the reversing contactor must handle the full motor current while the forward contactor is smaller.