The Siemens 3RT1045-3KF44-0LA0 is a SIRIUS S3 power contactor with a 110 V coil, rated for motor switching at 45 kW at 500 V in AC-3 duty and 21.1 kW at 690 V. The AC-3 maximum operating rate is 1 000 switching cycles per hour, while the AC-4 rate — for reversing or inching duty — drops to 300 1/h, reflecting the heavier arc stress on the contacts. Auxiliary contact ratings cover the low-voltage control side: 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for pilot-duty loads like indicator lamps or small relay coils.
Dimensions are 145 mm high, 95 mm wide, 191 mm deep — the S3 frame size fits standard panel layouts; check gland-plate clearance for the 191 mm depth, especially in shallow enclosures. Main-circuit terminals are screw-type, accepting 2x (10... 50 mm²) stranded and 2x (0.25... 2.5 mm²) solid; auxiliary terminals take 2x (2.5... 16 mm²) solid or stranded.