The LK3 is Schneider Electric's switch-disconnector kit - the manual isolation point for a feeder or a machine, built to give a visible, lockable break rather than to trip on a fault.

Why a disconnector and not a breaker?

A circuit breaker protects a circuit; a disconnector isolates it. The LK3 carries no trip coil, so it won't open on overload - its job is the off point a technician padlocks before touching the gear. Rated for load-break (AC-22/AC-23) up to 1250 A at 690 V, it switches a feeder safely under load and then locks in the off position for maintenance - the alternative is a breaker used only as a switch, with no clear, lockable isolation indication.

How does the kit scale across a plant?

The LK3 comes as kits from 32 A to 1250 A in 3- and 4-pole versions, with red/yellow padlockable handles and shaft or door mounting, so one disconnect family covers a small control panel and a main incoming feeder. Note the range is discontinued and replaced by the INS series - but the LK3 still appears in legacy panels and spares, which is why a clear isolation device matters more than ever during retrofit.