The Siemens 3RT1044-1AL26 is a SIRIUS power contactor in size S3, designed for switching motor loads in industrial control panels. It carries a 37 kW rating at 500 V AC-3, which means it handles the inrush and running current of a 37 kW induction motor under AC-3 duty (starting, plugging, inching). The contactor mounts via screw and snap-on onto 35 mm or 75 mm standard DIN rail, fitting into a standard enclosure layout.
Ratings and what they mean for fit
The AC-3 motor rating is 37 kW at 500 V, 50/60 Hz. At 690 V the same contactor is rated 18.6 kW — that derating reflects the higher voltage stress on the arc chamber. For resistive loads (AC-1), the contactor can switch at up to 1,000 operations per hour; for AC-3 motor duty the maximum is also 1,000 per hour, while AC-4 (plugging/reversing) drops to 300 per hour. The auxiliary contact block on the front is rated for 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for PLC inputs or small relay coils. The contactor is rated for a pollution degree of 3, meaning it's suitable for industrial environments where conductive pollution or dry non-conductive pollution that becomes conductive due to condensation can occur. The front face carries IP20 protection; the terminals themselves are IP00, so the panel builder must maintain creepage distances and provide finger-safe shrouding if required.
Termination and wiring
Main current circuit terminals are screw-type, accepting solid conductors from 2x (0.5... 1.5 mm²) up to max. 2x (0.75... 4 mm²) for the control circuit, and stranded conductors from 2x (10... 50 mm²) for the power circuit. The solid/stranded range for the main terminals is 2x (2.5... 16 mm²). That covers most motor feeder cables up to 50 mm² stranded. Side-by-side mounting is permitted, which saves panel width when grouping multiple contactors.