The Siemens SIRIUS 3RT1044-1AJ60 is a size S3 power contactor, rated for switching motor loads up to 37 kW at 500 V AC and 18.6 kW at 690 V AC.
The 37 kW rating at 500 V AC is the AC-3 motor-switching figure — that's the one that governs real motor duty, not the higher resistive-load number. At 690 V it still handles 18.6 kW, so it covers 400 V and 480 V systems with headroom. The contactor measures 146 mm tall, 70 mm wide, and 139 mm deep — a compact S3 footprint that fits a standard DIN-rail layout without crowding adjacent devices. Wire capacity is generous: stranded cable up to 2x 50 mm² on the main terminals, and solid or stranded control wiring from 0.5 to 4 mm². The screw terminals accept two conductors per clamp, which simplifies daisy-chaining in a motor control center.
Switching frequency and coil data
Electrical switching frequency depends on duty: up to 1,000 cycles per hour at AC-1 (resistive) and AC-3 (motor), 400 at AC-2, and 300 at AC-4 (plugging/inching). The coil operates at 50/60 Hz with a voltage tolerance of 0.8 to 1.1 times rated, and the arcing time runs 10 to 15 ms.