Siemens 3RT1044-3AN20 — SIRIUS Size S3 Power Contactor
The Siemens 3RT1044-3AN20 is a SIRIUS-brand power contactor in the Size S3 frame, rated for motor switching up to 37 kW at 500 V and 18.6 kW at 690 V. Front protection is IP20 with the cover and box terminal in place; the terminal body itself is IP00, so the panel enclosure provides the real ingress barrier.
The 37 kW at 500 V and 18.6 kW at 690 V are AC-3 motor-duty ratings — that's the current the contactor can break under full-load motor starts. If your motor plate says 37 kW at 500 V three-phase, this contactor is sized correctly. The AC-1 resistive rating governs heater or lighting loads; the maximum switching rate at AC-1 and AC-3 is 1000 operations per hour, which covers most pump and conveyor cycles. At AC-4 (plugging, inching) the rate drops to 300 per hour — the contactor takes more thermal stress during reversing or jogging duty. Side-by-side mounting is allowed, which saves rail space when you're stacking multiple contactors in a motor control center. The auxiliary contact ratings cover common control voltages: 10 A at 24 V, 6 A at 230 V, 3 A at 400 V. That's enough for direct PLC output driving or interposing relay coils. The main circuit uses screw-type terminals accepting 2x (10...50 mm²) stranded or 2x (0.25...2.5 mm²) solid — the larger range handles motor feeder cables up to 50 mm².