The Siemens 3RB1066-1KG0 is a solid-state overload relay from the 3RB10 series, rated for motor protection in the 200 to 540 A range. The MOD.S10/S12 designation indicates the relay includes both standard and selectable trip classes, giving the panel builder flexibility to match the motor's starting profile.
This relay ships with mounting rails for direct attachment to a Siemens 3RT106 contactor, or it can be mounted separately on a DIN rail. The separate-mounting option is useful when the contactor and overload need to be physically spaced apart in the panel — for thermal separation or to fit the enclosure layout. The 200-540 A current range covers large motor loads typical of pumps, compressors, and conveyors in industrial plants.