The Siemens SIRIUS 3RT1045-1AC00 is a size S3 power contactor rated for 45 kW at 400 V in AC-3 duty, which is the standard motor-switching category for squirrel-cage induction motors — so it directly handles starting and stopping loads up to that power without derating. It also carries a 37 kW rating at 400 V for AC-2 duty (slip-ring motors, reversing starts) and a 66 A rating for AC-4 duty (plugging, inching, jogging).
Solid wire capacity is 2x (0.5...1.5 mm²), 2x (0.75...2.5 mm²), or max 2x (0.75...4 mm²). Stranded wire takes 2x (10...50 mm²). The auxiliary circuit accepts 2x (2.5...16 mm²) solid or stranded. That range covers everything from control wiring up to the motor feeder cable for a 45 kW load. Dimensions are 146 mm high, 70 mm wide, 139 mm deep — the S3 frame occupies about the same footprint as a standard 3-pole breaker, so panel layout is straightforward.
RoHS compliance date is 05/01/2012, so the part meets the EU substance restrictions that have been in force for over a decade.
Switching performance
The coil operates at 50 Hz with a voltage tolerance of 0.8 to 1.1 times the rated value. Maximum switching frequency varies by duty: 900 cycles/hour for AC-1 (resistive), 400/h for AC-2, 1000/h for AC-3, and 300/h for AC-4.