SIRIUS S3 power contactor for motor loads
The Siemens 3RT2045-1AF00 is a SIRIUS S3-size power contactor rated for 77 A at 400 V in AC-3 duty, which is the standard category for squirrel-cage motor switching — making it the figure that governs real motor load sizing, not the higher AC-1 resistive rating. Screw-type terminals on the magnet coil and main contacts accept solid conductors from 2.5 to 16 mm² and stranded from 6 to 70 mm², covering the full range of motor feeder cables for this frame. The contactor mounts via screw or snap-on onto 35 mm DIN rail per DIN EN 60715, and the mounting position allows ±180° rotation on a vertical surface plus ±22.5° forward/backward tilt, giving panel builders flexibility in tight enclosures.
DIN-rail integration and panel space
At 70 mm wide, 140 mm tall, and 152 mm deep, the S3 frame occupies a defined footprint on the DIN rail.
Switching frequency and contact configuration
Maximum switching rates: 900 cycles/hour at AC-1 (resistive), 400 at AC-2 (slip-ring motors), 1,000 at AC-3 (squirrel-cage motors), and 300 at AC-4 (plugging/inching). The AC-3e rating also tops at 1,000 cycles/hour. The main contact arrangement is 10 normally open and 2 normally closed — a 10-pole NO block for power switching plus a 2-pole NC block typically used for auxiliary or interlock circuits. Auxiliary contacts are present and rated for DC switching: 10 A at 24 V, 2 A at 48 V and 60 V, 1 A at 110 V, 0.9 A at 125 V, 0.3 A at 220 V, 3 A at 400 V, and 0.8 A at 440 V.