What it is and what it does
The Siemens 3RT1044-3XP00-0GA0 is a SIRIUS power contactor in size S3, rated for motor switching at 37 kW at 500 V AC-3 and 30 kW at 400 V AC-2. It uses screw-type terminals on the main current circuit and mounts via screw or snap-on onto 35 mm or 75 mm standard DIN rails — the snap-on feature speeds panel assembly when you're populating a row of contactors.
Ratings that matter for fit
The AC-3 rating of 37 kW at 500 V is the one that governs motor switching for most pump, fan, and conveyor loads — that's the duty cycle where the contactor makes and breaks the motor under full load. The AC-2 rating of 30 kW at 400 V covers slip-ring motor starting, which sees higher inrush and longer arcing times (10 to 15 ms typical for this unit). Mechanical life is rated at 10,000,000 operations typical, so for a line running at 1000 cycles per hour in AC-3 duty, the contactor body itself will outlast most application refreshes. The operating temperature range of -25 to +60 °C and storage range of -55 to +80 °C cover unheated plant floors and warehouse extremes. Pollution degree 3 means it's rated for industrial environments with conductive pollution or dry non-conductive pollution that becomes conductive due to condensation — standard for an open panel installation. The front carries IP20 with the cover or box terminal fitted; the terminal area itself is IP00, so finger-safe only once the cover is on.
Mounting and wiring
The contactor occupies 70 mm width, 176 mm height, and 152 mm depth — size S3 footprint. It accepts solid conductors from 0.25 to 2.5 mm² (two per terminal) and stranded from 10 to 50 mm² (two per terminal), with an intermediate range of 2.5 to 16 mm² for stranded. Side-by-side mounting is supported, so you can gang multiple contactors on the same DIN rail without spacing — useful for compact motor control centers.