Siemens SIRIUS 3RT1044-3AL20 — S3 Power Contactor
The Siemens 3RT1044-3AL20 is a SIRIUS S3-frame power contactor rated for motor switching up to 37 kW at 500 V and 18.6 kW at 690 V, making it a fit for medium-horsepower induction motors on 400–690 V three-phase lines. The coil accepts 50 or 60 Hz at 230 V, with an operating range factor of 0.8–1.1 at 50 Hz and 0.85–1.1 at 60 Hz — meaning the coil holds in across a sag down to roughly 184 V and overvoltage up to 253 V. Mounting is screw-and-snap-on onto 35 mm or 75 mm standard DIN rail, with side-by-side mounting permitted — no derating gap required between units in a row. The IP20 front enclosure (IP00 at the terminals) suits panel-mount installations where the contactor is behind a cabinet door. Maximum switching rates vary by duty: 1,000 cycles/hour for AC-1 (resistive) and AC-3 (motor start/run), 400 cycles/hour for AC-2 (slip-ring motor), and 300 cycles/hour for AC-4 (plugging/inching). The arcing time spans 10–19 ms at AC, with a tighter 10–15 ms window typical.
Main current circuit uses screw-type terminals accepting solid conductors 2x (0.25–2.5 mm²) and stranded 2x (10–50 mm²), plus a mid-range 2x (2.5–16 mm²) for both solid and stranded. The auxiliary contact block is rated for 10 A at 24 V, 6 A at 230 V, and 3 A at 400 V — enough for PLC-level pilot duty or small relay loads.