What it is and what it does
The Siemens 3RB1066-2LG0 is a solid-state overload relay from the 3RB10 series, rated for motor protection from 300 to 630 A with a Class 20 trip curve. It comes with mounting rails for direct attachment to a 3TF68 or 3TF69 contactor, or for separate mounting on a DIN rail or panel. Class 20 means it allows a 20-second overload before tripping at 600% of the set current — standard for general-purpose motor starting where the inrush transient needs to ride through without nuisance trips.
Integration notes
The relay includes mounting rails for contactor mounting on 3TF68 or 3TF69 frames, or separate mounting on a DIN rail. In a panel, this means it can be ganged directly to the contactor to save rail space, or positioned remotely if heat dissipation or access for reset is a concern. The solid-state design eliminates the mechanical wear of bimetallic relays, which matters in high-cycle applications like conveyors or pumps.