The Siemens SIRIUS 3RT1044-3AL20-ZX95 is a size S3 power contactor rated for motor switching up to 37 kW at 500 V under AC-3 duty, meaning it handles the inrush and break current of a standard three-phase induction motor at that load point. The main power circuit uses screw-type terminals, with a solid-wire capacity of 2x (0.25 to 2.5 mm²) and a stranded-wire capacity of 2x (10 to 50 mm²), covering the range from control-circuit pilot wiring to motor feeder cables.
The AC-3 motor rating of 37 kW at 500 V is the headline figure for sizing this contactor to a motor load; at 690 V the same contactor is rated 18.6 kW, reflecting the higher voltage stress on the switching gap. Mechanical life is rated at 10 million operations typical, with maximum switching frequencies of 1000 cycles per hour under AC-3 and AC-1, and 400 cycles per hour under AC-2 — the AC-2 limit governs applications with frequent jogging or inching. Operating temperature range of -25 to +60 °C and storage range of -55 to +80 °C cover most indoor industrial environments; the IP20 rating on the front (with cover or box terminal) and IP00 at the terminal itself means the panel enclosure provides the touch protection.
Side-by-side mounting is permitted, which saves DIN-rail space when grouping multiple contactors in a motor control centre. Dimensions of 146 mm height, 70 mm width, and 139 mm depth fit the S3 footprint; verify gland-plate clearance for the 139 mm depth when the contactor is mounted near the back wall of a shallow enclosure.