SIRIUS S3 power contactor for motor and resistive loads
The Siemens SIRIUS S3 power contactor 3RT1044-3XF40-0LA2 is a Size S3 frame unit rated for motor switching at 37 kW at 500 V and 18.6 kW at 690 V. Screw-type terminals on the main circuit accept up to 35 mm² conductors. The contactor mounts via screw or snap-on onto standard 35 mm or 75 mm DIN rail, fitting into a 70 mm wide by 176 mm tall by 152 mm deep envelope.
What the ratings mean for panel fit
The 37 kW at 500 V and 18.6 kW at 690 V ratings define the maximum three-phase motor load this contactor can switch under AC-3 duty (starting/running squirrel-cage motors). The screw-type main terminals handle up to 35 mm² — sufficient for the supply and motor leads at these power levels. Operating temperature range of -40 to +70 °C covers most indoor industrial enclosures without derating.
Mounting and wiring integration
Mounts on 35 mm or 75 mm DIN rail via screw or snap-on fastening. Side-by-side mounting is permitted. Control circuit wiring accepts 2x (0.25 to 2.5 mm²) solid or stranded conductors; main circuit terminals accept 2x (10 to 50 mm²) stranded. Clearance requirements: 10 mm upwards, 20 mm forwards, 10 mm downwards, 10 mm at the side.