What it is and what it does
The Siemens 3RT1044-1BP40 is a SIRIUS power contactor in size S3, built for switching motor loads in industrial control panels. It handles 55 A in AC-4 duty at 400 V — that's the rugged reversing or inching profile — and delivers 37 kW at 500 V in AC-2 duty, which covers slip-ring motor starting. The coil pulls 230 V rated value, and the contactor carries a full set of voltage-dependent current ratings: 10 A at 24 V, 2 A at 60 V, 1 A at 110 V, 0.3 A at 220 V, 6 A at 230 V, 3 A at 400 V, and 30 W at 1000 V.
Mounting and wiring reality
Snaps onto 35 mm or 75 mm standard DIN rail — screw and snap-on fastening method. Side-by-side mounting is allowed, so you can pack them tight in a row. Main circuit wiring uses screw-type terminals; solid wire accepts 2x (0.5…1.5 mm²), 2x (0.75…2.5 mm²), max 2x (0.75…4 mm²), and stranded goes up to 2x (10…50 mm²). The front face carries IP20 with the cover or box terminal; the terminal body itself is IP00. Degree of pollution 3 means it's rated for industrial environments with conductive dust or condensation.
Thermal and mechanical endurance
Rated for 10 million typical mechanical operations. Operating temperature range is -25 to +60 °C; storage goes from -55 to +80 °C. Maximum switching rates: 1 000 cycles/hour at AC-1 and AC-3, 400 at AC-2, and 300 at AC-4. Arcing time is 10…15 ms, and the DC dropout delay (at DC) is 14…20 ms.