What it is and what it does
The Siemens 3RT1025-1XB40-0LA2 is a SIRIUS S0 power contactor with a 24 V DC coil and an integrated varistor surge suppressor. It switches motor loads in control panels and industrial machinery, rated for AC-4 duty at 15.5 A at 400 V — meaning it handles reversing or inching applications where the contactor makes and breaks the motor at full load. Coil draws 10 A at 24 V DC. Holds in at 0.7 of rated voltage.
Mounting and integration
This contactor snaps onto a 35 mm DIN rail per EN 50022, or you can screw-mount it. At 45 mm wide and 116 mm tall, it fits a standard panel layout. Clearance needs: 10 mm upwards, forwards, and downwards, and 10 mm at the side — tight enough for side-by-side mounting, which is supported. Main circuit terminals are screw-type, accepting 2x (0.5 to 1.5 mm²) solid or 2x (0.75 to 2.5 mm²) stranded, up to 2x 4 mm² max. Auxiliary terminals handle 2x (1 to 2.5 mm²) solid or 2x (2.5 to 6 mm²) stranded, max 2x 10 mm². That covers most panel wiring without needing ferrules.
Sourcing and lifecycle
RoHS compliance date is 01.05.2012.