What it is and what it does
The Siemens SIRIUS 3RT1045-1BP40 is a power contactor in the S3 frame size, designed for switching motor loads and resistive loads in industrial control panels. Its AC-2 rating of 37 kW at 400 V means it handles slip-ring motor duty cycles reliably, while the AC-4 rating of 66 A at 400 V covers reversing and inching applications where the contactor makes and breaks full motor current.
Mounting and integration
Mounts via screw or snap-on onto 35 mm and 75 mm standard DIN rails — side-by-side mounting is permitted, so you can pack multiple units without spacing gaps. The screw-type terminals on the main current circuit accept solid conductors from 0.5 mm² up to 4 mm² (double ferruled) and stranded conductors up to 50 mm², covering most motor feeder sizes through the S3 frame.
Switching performance and coil data
Arcing time runs 10 to 15 ms, dropout time at DC is 14 to 20 ms. Mechanical life is typical 10 million operations. Maximum switching rates vary by duty: 900 cycles/hour at AC-1, 400 at AC-2, 1,000 at AC-3, and 300 at AC-4. The coil pickup and dropout thresholds are 0.8 x Uc and 1.1 x Uc respectively.